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Molecular Cancer - published by BioMed Central -
... is ready to receive a wide range of manuscripts presenting original research and commentary in all areas of cancer-related science.

Molecular Cancer Research - published by The American Association for Cancer Research -
... publishes original, novel, and well-designed studies on the molecular and cellular aspects of cancer biology. Papers should represent significant new information gathered from basic research that has implications for cancer therapeutics in one of the following areas: Angiogenesis, Metastasis, and the Cellular Microenvironment; Cancer Genes and Genomics; Cell Cycle, Cell Death, and Senescence; DNA Damage and Cellular Stress Responses; Model Organisms; and Signaling and Regulation.

Molecular Carcinogenesis - published by Wiley Interscience -
... presents information describing investigations of molecular aspects of the mechanisms involved in chemical, physical, and viral (biological) carcinogenesis. Areas of interest include, but are not limited to, the structure, expression, or function of genes or gene products associated with normal growth and differentiation and alterations in neoplasia; characterization of genes or gene products expressed in preneoplastic or neoplastic cells; molecular studies that define a specific function of a tumor-associated protein or its effects on cellular function; virtually all research on molecular aspects of oncogenes, tumor suppressor genes, and their gene products; carcinogenesis studies in transgenic mice; and research on human tumor viruses.

Aktuelle wissenschaftliche Fachartikel der genannten Journale:

Membrane androgen receptor activation triggers down-regulation of PI-3K/AKT/NF-kapaB activity and induces apoptotic responses via BAD, FasL and cacpase 3 in DU145 prostate cancer cells.

Background: Recently we have reported membrane androgen receptors-induced apoptotic regression of prostate cancer cells regulated by Rho/ROCK/actin signaling. In the present study we explored the specificity of these receptors and we analyzed downstream effectors controlling survival and apoptosis in hormone refractory DU145-prostate cancer cells stimulated with membrane androgen receptor-selective agonists. Results: Using membrane impermeable conjugates of serum albumin covalently linked to testosterone, we show here down-regulation of the activity of pro-survival gene products, namely PI-3K/Akt and NF-kappaBeta, in DU145 cells. Testosterone-albumin conjugates further induced FasL expression. A FasL blocking peptide abrogated membrane androgen receptors-dependent apoptosis. In addition, testosterone-albumin conjugates increased caspase 3 and Bad protein activity. The actin cytoskeleton drug cytochalasin B and the ROCK inhibitor Y-27632 inhibited FasL induction and caspase 3 activation, indicating that the newly identified Rho/Rock/actin signaling may regulate the downstream pro-apoptotic effectors in DU145 cells. Finally, other steroids or steroid-albumin conjugates did not interfere with these receptors indicating testosterone specificity. Conclusions: Collectively, our results provide novel mechanistic insights pointing to specific pro-apoptotic molecules controlling membrane androgen receptors-induced apoptotic regression of prostate cancer cells and corroborate previously published observations on the potential use of membrane androgen receptor-agonists as novel anti-tumor agents in prostate cancer.

Quelle: Molecular Cancer - Latest articles | 3 Dec 2008 | 12:00 am CET

Association between adenomatosis polyposis coli functional status and microsomal prostaglandin E synthase-1 expression in colorectal cancer

Bioactive metabolites downstream of cyclooxygenase-2 (COX-2) generated prostaglandin H2 (PGH2), in particular prostaglandin E2 (PGE2), are thought to play critical roles during the development of colorectal tumors. Previous reports reveal that defects of the tumor suppressor adenomatosis polyposis coli (APC) contribute to COX-2 upregulation in colon tumor cells. We investigated whether a similar relation was present between APC functional status and the expression of microsomal prostaglandin E synthase-1 (mPGES-1), which acts downstream of COX-2 and catalyses the terminal conversion of PGH2 into PGE2. Surprisingly, mPGES-1 mRNA and protein levels were upregulated upon induction of a wild type-APC carrying vector in HT29 colon cancer cells, and downregulated following siRNA silencing of APC in HCT-116 cells. mPGES-1 was overall enhanced in human colorectal tumor specimens versus corresponding non-tumor mucosa and, in accordance with data on HT29 and HCT116 cells, higher levels of mPGES-1 were observed among tumors carrying wild type versus mutant APC. RNAi silencing of [beta]-catenin and luciferase assays regarding the mPGES-1 promoter region did not reveal a role for APC or [beta]-catenin/Tcf in controlling mPGES-1 gene transcription. However, RNA degradation assays in HT29 cells revealed a suppressed degradation of mPGES-1 in the presence of wild type APC, implying that mPGES-1 mRNA is stabilized in the APC wild type state. Collectively, we demonstrate a novel association between APC functional status and mPGES-1 expression in colorectal tumor cells, being most likely related to reduced mPGES-1 mRNA degradation rate in the APC wild type state. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 26 Nov 2008 | 11:27 am CET

ALDH isozymes downregulation affects cell growth, cell motility and gene expression in lung cancer cells

Background: Aldehyde dehydrogenase isozymes ALDH1A1 and ALDH3A1 are highly expressed in non small cell lung cancer. Neither the mechanisms nor the biologic significance for such over expression have been studied. Methods: We have employed oligonucleotide microarrays to analyze changes in gene profiles in A549 lung cancer cell line in which ALDH activity was reduced by up to 95% using lentiviral mediated expression of siRNA against both isozymes (Lenti 1+3). Stringent analysis methods were used to identify gene expression patterns that are specific to the knock down of ALDH activity and significantly different in comparison to wild type A549 cells (WT) or cells similarly transduced with green fluorescent protein (GFP) siRNA. Results: We confirmed significant and specific down regulation of ALDH1A1 and ALDH3A1 in Lenti 1+3 cells and in comparison to 12 other ALDH genes detected. The results of the microarray analysis were validated by real time RT-PCR on RNA obtained from Lenti 1+3 or WT cells treated with ALDH activity inhibitors. Detailed functional analysis was performed on 101 genes that were significantly different (P < 0.001) and their expression changed by [greater than or equal to] 2 folds in the Lenti 1+3 group versus the control groups. There were 75 down regulated and 26 up regulated genes. Protein binding, organ development, signal transduction, transcription, lipid metabolism, and cell migration and adhesion were among the most affected pathways. Conclusions: These molecular effects of the ALDH knock-down are associated with in vitro functional changes in the proliferation and motility of these cells and demonstrate the significance of ALDH enzymes in cell homeostasis with a potentially significant impact on the treatment of lung cancer.

Quelle: Molecular Cancer - Latest articles | 24 Nov 2008 | 12:00 am CET

The problem of choice

Convictions are a driving force for actions. Considering that every individual has a different set of convictions and larger groups act once a consensus decision is reached, one can see that debate is an inherent exercise in decision-making. This requires a sustainably generated surplus to allow time for intellectual exchange, gathering of information and dissemination of findings. It is essential that the full spectrum of options remain treated equally. At the end of this process, a choice has to be made. Looking back at a later time point, a retrospective analysis sometimes reveals that the choice was neither completely free nor a truly conscious one. Leaving the issue of consequences of a once made decision aside, we wish to contribute to the debate of the problem of choice.

Quelle: Molecular Cancer - Latest articles | 23 Nov 2008 | 12:00 am CET

Tissue Inhibitor of Metalloproteinases-4. The road less traveled.

Tissue inhibitors of metalloproteinases (TIMPs) regulate diverse processes, including extracellular matrix (ECM) remodeling, and growth factors and their receptors' activities through the inhibition of matrix metalloproteinases (MMPs). Recent evidence has shown that this family of four members (TIMP-1 to TIMP-4) can also control other important processes, such as proliferation and apoptosis, by a mechanism independent of their MMP inhibitory actions. Of these inhibitors, the most recently identified and least studied is TIMP-4. Initially cloned in human and, later, in mouse, TIMP-4 expression is restricted to heart, kidney, pancreas, colon, testes, brain and adipose tissue. This restricted expression suggests specific and different physiological functions. The present review summarizes the information available for this protein and also provides a putative structural model in order to propose potential relevant directions toward solving its function and role in diseases such as cancer.

Quelle: Molecular Cancer - Latest articles | 21 Nov 2008 | 12:00 am CET

Profiling Human Androgen Receptor Mutations Reveals Treatment Effects in a Mouse Model of Prostate Cancer

Gain-of-function mutations in the androgen receptor (AR) are found in prostate cancer and are implicated in the failure of hormone therapy. Most studies have emphasized the ligand-binding domain (LBD) where mutations can create promiscuous receptors, but mutations in the NH₂-terminal transactivation domain have also been found. To assess AR alteration as a mechanism of treatment resistance, a mouse model (h/mAR-TRAMP) was used in which the murine AR coding region is replaced by human sequence and prostate cancer initiated by a transgenic oncogene. Mice received either no treatment, androgen depletion by castration, or treatment with antiandrogens, and 20 AR transcripts were sequenced per end-stage tumor. All tumors expressed several mutant alleles, although most mutations were low frequency. Some mutations that occurred multiple times within the population were differentially located dependent on treatment. Mutations in castrated or antiandrogen-treated mice were widely dispersed but with a prominent cluster in the LBD (amino acids 736-771), whereas changes in intact mice centered near the NH₂-terminal polymorphic glutamine tract. Functional characterization of selected LBD mutant alleles showed diverse effects on AR activity, with about half of the mutations reducing transactivation in vitro. One receptor, AR-R753Q, behaved in a cell- and promoter-dependent manner, although as a germ-line mutation it causes androgen insensitivity syndrome. This suggests that alleles that are loss of function during development may still activate a subset of AR targets to become gain of function in tumorigenesis. Mutant ARs may thus use multiple mechanisms to evade cancer treatment. (Mol Cancer Res 2008;6(11):1691–701)

Quelle: Molecular Cancer Research current issue | 14 Nov 2008 | 12:00 am CET

Antisense MDM2 Enhances E2F1-Induced Apoptosis and the Combination Sensitizes Androgen-Dependent and Androgen-Independent Prostate Cancer Cells to Radiation

We have previously shown in separate studies that MDM2 knockdown via antisense MDM2 (AS-MDM2) and E2F1 overexpression via adenoviral-mediated E2F1 (Ad-E2F1) sensitized prostate cancer cells to radiation. Because E2F1 and MDM2 affect apoptosis through both common and independent pathways, we hypothesized that coupling these two treatments would result in increased killing of prostate cancer cells. In this study, the effect of Ad-E2F1 and AS-MDM2 in combination with radiation was investigated in three prostate cancer cell lines: LNCaP cells, LNCaP-Res cells [androgen insensitive with functional p53 and androgen receptor (AR)], and PC3 cells (androgen insensitive, p53^null, and AR^null). A supra-additive radiosensitizing effect was observed in terms of clonogenic inhibition and induction of apoptosis (caspase-3 + caspase-7 activity) in response to Ad-E2F1 plus AS-MDM2 treatments in all three cell lines. In LNCaP and LNCaP-Res, these combination treatments elevated the levels of phospho-Ser¹⁵ p53 with significant induction of p21^waf1/cip1, phospho-H2AX, PUMA, and Bax levels and reduction of AR and bcl-2 expression. Similarly, AR^null and p53^null PC-3 cells showed elevated levels of Bax and phospho-H2AX expression. These findings show that the combination of Ad-E2F1 and AS-MDM2 significantly increases cell death in prostate cancer cells exposed to radiation and that this effect occurs in the presence or absence of AR and p53. (Mol Cancer Res 2008;6(11):1742–54)

Quelle: Molecular Cancer Research current issue | 14 Nov 2008 | 12:00 am CET

High-Throughput Hacking of the Methylation Patterns in Breast Cancer by In vitro Transcription and Thymidine-Specific Cleavage Mass Array on MALDI-TOF Silico-Chip

Over the last decade, the rapidly expanding interest in the involvement of DNA methylation in developmental mechanisms, human diseases, and malignancies has highlighted the need for an accurate, quantitative, and high-throughput assay. Existing methods are limited and are often too laborious for high-throughput analysis or inadequate for quantitative analysis of methylation. Recently, a MassCLEAVE assay has been developed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to analyze base-specific methylation patterns after bisulfite conversion. To find an efficient and more cost-effective high-throughput method for analyzing the methylation profile in breast cancer, we developed a method that allows for the simultaneous detection of multiple target CpG residues by using thymidine-specific cleavage mass array on matrix-assisted laser desorption/ionization time-of-flight silicon chips. We used this novel quantitative approach for the analysis of DNA methylation patterns of four tumor suppressor genes in 96 breast tissue samples from 48 patients with breast cancer. Each individual contributed a breast cancer specimen and corresponding adjacent normal tissue. We evaluated the accuracy of the approach and implemented critical improvements in experimental design. (Mol Cancer Res 2008;6(11):1702–9)

Quelle: Molecular Cancer Research current issue | 14 Nov 2008 | 12:00 am CET

17-Allylamino-17-Demethoxygeldanamycin Down-Regulates Hyaluronic Acid-Induced Glioma Invasion by Blocking Matrix Metalloproteinase-9 Secretion

Hyaluronic acid (HA) has been implicated in cell adhesion, motility, and tumor progression in gliomas. We previously reported that HA stimulates secretion of matrix metalloproteinase-9 (MMP-9) and induces glioma invasion. However, the molecular mechanism of HA action and therapeutic strategies for blocking HA-induced MMP-9 secretion remain unknown. Here, we report that the Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) blocks MMP-9 secretion and that HA-induced nuclear factor-B (NF-B) activation is mediated by IB kinase, which phosphorylates the NF-B inhibitor IB and promotes its degradation. In addition, using an RNA interference approach, we show that the focal adhesion kinase plays a critical role in mediating HA-induced NF-B activation, which resulted in increased MMP-9 expression and secretion, cell migration, and invasion. Importantly, we show that 17-AAG acts by blocking focal adhesion kinase activation, thereby inhibiting IB kinase–dependent IB phosphorylation/degradation, NF-B activation, and MMP-9 expression. This leads to suppression of HA-induced cell migration and invasion. Based on our data, we propose that 17-AAG is a candidate drug for treatment of highly invasive gliomas resulting from HA-induced, NF-B–mediated MMP-9 secretion. (Mol Cancer Res 2008;6(11):1657–65)

Quelle: Molecular Cancer Research current issue | 14 Nov 2008 | 12:00 am CET

Luteinizing Hormone-Induced Up-Regulation of ErbB-2 Is Insufficient Stimulant of Growth and Invasion in Ovarian Cancer Cells

The effects of luteinizing hormone (LH), a gonadotropic hormone implicated in the development of ovarian cancer, are mediated by specific binding to its G protein–coupled receptor, the LH receptor (LHR). Activated LHR initiates second messenger responses, including cyclic AMP (cAMP) and inositol phosphate. Because cAMP increases expression of ErbB-2, a receptor tyrosine kinase whose overexpression in cancers correlates with poor survival, we hypothesized that LH may regulate ErbB-2 expression. Cell surface LHR expression in stable transformants of the ErbB-2–overexpressing ovarian cancer cell line SKOV3 was confirmed by PCR and whole-cell ligand binding studies. Second messenger accumulation in the LHR-expressing cells confirmed signaling through Gs and Gq. Western blots of total protein revealed that LHR introduction up-regulated ErbB-2 protein expression 2-fold and this was further up-regulated in a time- and dose-dependent manner in response to LH. Forskolin and 8Br-cAMP also up-regulated ErbB-2 in both LHR-expressing and mock-transfected cells, indicating that regulation of ErbB-2 is a cAMP-mediated event. Kinase inhibitor studies indicated the involvement of protein kinase A–mediated, protein kinase C–mediated, epidermal growth factor receptor–mediated, and ErbB-2–mediated mechanisms. The LH-induced up-regulation of ErbB-2 was insufficient to overcome the negative effects of LH on proliferation, invasion, and migration. A molecular signature for this nonaggressive phenotype was determined by Taqman array to include increased and decreased expression of genes encoding adhesion proteins and metalloproteinases, respectively. These data establish a role for LH and LHR in the regulation of ErbB-2 expression and suggest that, in some systems, ErbB-2 up-regulation alone is insufficient in producing a more aggressive phenotype. (Mol Cancer Res 2008;6(11):1775–85)

Quelle: Molecular Cancer Research current issue | 14 Nov 2008 | 12:00 am CET

Expression of an IFN-Inducible Cellular Senescence Gene, IFI16, Is Up-Regulated by p53

IFN-inducible IFI16 protein (encoded by IFI16 gene at 1q23.1) is the human member of the IFN-inducible structurally related p200 family proteins. Increased expression of the IFI16 protein, a positive modulator of p53-mediated transcription, in normal old human diploid fibroblasts (HDF) is associated with cellular senescence-mediated cell growth arrest. However, the underlying mechanisms that contribute to transcriptional activation of the IFI16 gene in old HDFs remain to be elucidated. Here, we reported that functional activation of p53 in normal young HDFs and p53-null Saos2 cell line resulted in transcriptional activation of the IFI16 gene. We identified a potential p53 DNA-binding site (indicated as IFI16-p53-BS) in the 5'-regulatory region of the IFI16 gene. Importantly, p53 bound to IFI16-p53-BS in a sequence-specific manner in gel-mobility shift assays. Furthermore, p53 associated with the 5'-regulatory region of the IFI16 gene in chromatin immunoprecipitation assays. Interestingly, p53 associated with the regulatory region of the IFI16 gene only on treatment of cells with DNA-damaging agents or in the old, but not in the young, HDFs. Importantly, our promoter-reporter assays, which were coupled with site-directed mutagenesis of IFI16-p53-BS, showed that p53 activates transcription of the IFI16 gene in HDFs through the p53 DNA-binding site. Together, our observations provide support for the idea that up-regulation of IFI16 expression by p53 and functional interactions between IFI16 protein and p53 contribute to cellular senescence. (Mol Cancer Res 2008;6(11):1732–41)

Quelle: Molecular Cancer Research current issue | 14 Nov 2008 | 12:00 am CET

Inhibition of Src Family Kinases with Dasatinib Blocks Migration and Invasion of Human Melanoma Cells

Src family kinases (SFK) are involved in regulating a multitude of biological processes, including cell adhesion, migration, proliferation, and survival, depending on the cellular context. Therefore, although SFKs are currently being investigated as potential targets for treatment strategies in various cancers, the biological responses to inhibition of SFK signaling in any given tumor type are not predictable. Dasatinib (BMS-354825) is a dual Src/Abl kinase inhibitor with potent antiproliferative activity against hematologic malignancies harboring activated BCR-ABL. In this study, we show that dasatinib blocks migration and invasion of human melanoma cells without affecting proliferation and survival. Moreover, dasatinib completely inhibits SFK kinase activity at low nanomolar concentrations in all eight human melanoma cell lines investigated. In addition, two known downstream targets of SFKs, focal adhesion kinase and Crk-associated substrate (p130^CAS), are inhibited with similar concentrations and kinetics. Consistent with inhibition of these signaling pathways and invasion, dasatinib down-regulates expression of matrix metalloproteinase-9. We also provide evidence that dasatinib directly inhibits kinase activity of the EphA2 receptor tyrosine kinase, which is overexpressed and/or overactive in many solid tumors, including melanoma. Thus, SFKs and downstream signaling are implicated as having key roles in migration and invasion of melanoma cells. (Mol Cancer Res 2008;6(11):1766–74)

Quelle: Molecular Cancer Research current issue | 14 Nov 2008 | 12:00 am CET

Enforced Expression of MCAM/MUC18 Increases In vitro Motility and Invasiveness and In vivo Metastasis of Two Mouse Melanoma K1735 Sublines in a Syngeneic Mouse Model

Human MCAM/MUC18 has been shown to increase metastasis of human melanoma cells in xenograft mouse systems. To be more relevant to understanding the progression of clinical melanoma and for designing better preclinical therapeutic trials, it is highly desirable to establish a syngeneic mouse model for studying the mechanisms of MCAM/MUC18-mediated tumorigenesis and metastasis of melanoma cells. To reach this goal, we transfected the mouse MCAM/MUC18 (moMCAM/MUC18) cDNA into two MCAM/MUC18-minus, low-metastatic mouse melanoma K1735 sublines, K1735-10 (tumor^–/met^low) and K1735-3 (tumor⁺/met^low), and selected for G418-resistant clones, which expressed different levels of moMCAM/MUC18, and used for testing the effect of MCAM/MUC18 overexpression on their in vitro growth rate, motility, and invasiveness and in vivo subcutaneous tumor growth and pulmonary metastasis in syngeneic mice. Enforced expression of moMCAM/MUC18 did not significantly affect in vitro growth rate, but it increased the in vitro motility and invasiveness of clones derived from both sublines. Ectopic expression of moMCAM/MUC18 did not alter the nontumorigenicity of the K1735-10 clones per cells nor significantly affect the subcutaneous tumor growth of the K1735-3 clones per cells. The moMCAM/MUC18-expressing K1735-10 clones were able to establish only microscopic lung modules in 86% of the mice. In contrast, the moMCAM/MUC18-expressing K1735-3 clones could induce numerous large lung nodules (3-4 mm in diameter) in all the mice. We concluded that increased moMCAM/MUC18 expression in the two K1735 sublines minimally affected their tumorigenicity, but it augmented their in vitro motility and invasiveness and increased their pulmonary metastasis in the syngeneic C3H mice. (Mol Cancer Res 2008;6(11):1666–77)

Quelle: Molecular Cancer Research current issue | 14 Nov 2008 | 12:00 am CET

Mutation of ERBB2 Provides a Novel Alternative Mechanism for the Ubiquitous Activation of RAS-MAPK in Ovarian Serous Low Malignant Potential Tumors

Approximately, 10% to 15% of serous ovarian tumors fall into the category designated as tumors of low malignant potential (LMP). Like their invasive counterparts, LMP tumors may be associated with extraovarian disease, for example, in the peritoneal cavity and regional lymph nodes. However, unlike typical invasive carcinomas, patients generally have a favorable prognosis. The mutational profile also differs markedly from that seen in most serous carcinomas. Typically, LMP tumors are associated with KRAS and BRAF mutations. Interrogation of expression profiles in serous LMP tumors suggested overall redundancy of RAS-MAPK pathway mutations and a distinct mechanism of oncogenesis compared with high-grade ovarian carcinomas. Our findings indicate that activating mutation of the RAS-MAPK pathway in serous LMP may be present in >70% of cases compared with ~12.5% in serous ovarian carcinomas. In addition to mutations of KRAS (18%) and BRAF (48%) mutations, ERBB2 mutations (6%), but not EGFR, are prevalent among serous LMP tumors. Based on the expression profile signature observed throughout our serous LMP cohort, we propose that RAS-MAPK pathway activation is a requirement of serous LMP tumor development and that other activators of this pathway are yet to be defined. Importantly, as few nonsurgical options exist for treatment of recurrent LMP tumors, therapeutic targeting of this pathway may prove beneficial, especially in younger patients where maintaining fertility is important. (Mol Cancer Res 2008;6(11):1678–90)

Quelle: Molecular Cancer Research current issue | 14 Nov 2008 | 12:00 am CET

Mesothelin-Induced Pancreatic Cancer Cell Proliferation Involves Alteration of Cyclin E via Activation of Signal Transducer and Activator of Transcription Protein 3

Mesothelin (MSLN) is a cell surface glycoprotein that is overexpressed in human pancreatic cancer. Although its value as a tumor marker for diagnosis and prognosis and as a preferred target of immunointervention has been evaluated, there is little information on the growth advantage of MSLN on tumor cells. In this study, we examined the effect of MSLN on pancreatic cancer cell proliferation, cell cycle progression, expression of cell cycle regulatory proteins, and signal transduction pathways in two pancreatic cancer cell lines, MIA-MSLN (overexpressing MSLN in MIA PaCa-2 cells) and BxPC-siMSLN (silencing MSLN in BxPC-3 cells). Increased cyclin E and cyclin-dependent kinase 2 expression found in MIA-MSLN cells correlated with significantly increased cell proliferation and faster cell cycle progression compared with control cells. BxPC-siMSLN cells showed slower proliferation and slower entry into the S phase than control cells. Signal transducer and activator of transcription protein 3 (Stat3) was constitutively activated in MIA-MSLN cells, but not in control cells. Inhibition of Stat3 activation in MIA-MSLN cells by the Janus-activated kinase–selective inhibitor tyrphostin AG490 was followed by a marked decrease in proliferation of the cells. Small interfering RNA against Stat3 significantly reduced the MIA-MSLN cell cycle progression with a concomitant decrease in cyclin E expression. Our data indicate that overexpression of MSLN in pancreatic cancer cells leads to constitutive activation of the transcription factor Stat3, which results in enhanced expression of cyclin E and cyclin E/cyclin-dependent kinase 2 complex formation as well as increased G₁-S transition. (Mol Cancer Res 2008;6(11):1755–65)

Quelle: Molecular Cancer Research current issue | 14 Nov 2008 | 12:00 am CET

Period 2 Mutation Accelerates ApcMin/+ Tumorigenesis

Colorectal cancer risk is increased in shift workers with presumed circadian disruption. Intestinal epithelial cell proliferation is gated throughout each day by the circadian clock. Period 2 (Per2) is a key circadian clock gene. Per2 mutant (Per2^m/m) mice show an increase in lymphomas and deregulated expression of cyclin D and c-Myc genes that are key to proliferation control. We asked whether Per2 clock gene inactivation would accelerate intestinal and colonic tumorigenesis. The effects of PER2 on cell proliferation and β-catenin were studied in colon cancer cell lines by its down-regulation following RNA interference. The effects of Per2 inactivation in vivo on β-catenin and on intestinal and colonic polyp formation were studied in mice with Per2 mutation alone and in combination with an Apc mutation using polyp-prone Apc^Min/+ mice. Down-regulation of PER2 in colon cell lines (HCT116 and SW480) increases β-catenin, cyclin D, and cell proliferation. Down-regulation of β-catenin along with Per2 blocks the increase in cyclin D and cell proliferation. Per2^m/m mice develop colonic polyps and show an increase in small intestinal mucosa β-catenin and cyclin D protein levels compared with wild-type mice. Apc^Min/+Per2^m/m mice develop twice the number of small intestinal and colonic polyps, with more severe anemia and splenomegaly, compared with Apc^Min/+ mice. These data suggest that Per2 gene product suppresses tumorigenesis in the small intestine and colon by down-regulation of β-catenin and β-catenin target genes, and this circadian core clock gene may represent a novel target for colorectal cancer prevention and control. (Mol Cancer Res 2008;6(11):1786–93)

Quelle: Molecular Cancer Research current issue | 14 Nov 2008 | 12:00 am CET

Opposing Roles of c-Jun NH2-Terminal Kinase and p38 Mitogen-Activated Protein Kinase in the Cellular Response to Ionizing Radiation in Human Cervical Cancer Cells

Exposure of cells to ionizing radiation induces activation of multiple signaling pathways that play critical roles in determining cell fate. However, the molecular basis for cell death or survival signaling in response to radiation is unclear at present. Here, we show opposing roles of the c-jun NH₂-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) pathways in the mitochondrial cell death in response to ionizing radiation in human cervical cancer cells. Ionizing radiation triggered Bax and Bak activation, Bcl-2 down-regulation, and subsequent mitochondrial cell death. Inhibition of JNK completely suppressed radiation-induced Bax and Bak activation and Bcl-2 down-regulation. Dominant-negative forms of stress-activated protein kinase/extracellular signal-regulated kinase kinase 1 (SEK-1)/mitogen-activated protein kinase kinase-4 (MKK-4) inhibited JNK activation. Radiation also induced phosphoinositide 3-kinase (PI3K) activation. Interestingly, inhibition of PI3K effectively attenuated radiation-induced mitochondrial cell death and increased clonogenic survival. Inhibition of PI3K also suppressed SEK-1/MKK-4 and JNK activation, Bax and Bak activation, and Bcl-2 down-regulation. In contrast, inhibition of p38 MAPK led to enhanced Bax and Bak activation and mitochondrial cell death. RacN17, a dominant-negative form of Rac1, inhibited p38 MAPK activation and increased Bax and Bak activation. Exposure of cells to radiation also induced selective activation of c-Src among Src family kinases. Inhibition of c-Src by pretreatment with Src family kinase inhibitor PP2 or small interfering RNA targeting of c-Src attenuated radiation-induced p38 MAPK and Rac1 activation and enhanced Bax and Bak activation and cell death. Our results support the notion that the PI3K-SEK-1/MKK-4-JNK pathway is required for the mitochondrial cell death in response to radiation, whereas the c-Src-Rac1-p38 MAPK pathway plays a cytoprotective role against mitochondrial cell death. (Mol Cancer Res 2008;6(11):1718–31)

Quelle: Molecular Cancer Research current issue | 14 Nov 2008 | 12:00 am CET

Overexpression and Hypomethylation of Flap Endonuclease 1 Gene in Breast and Other Cancers

Flap endonuclease 1 (FEN1) is a structure-specific nuclease best known for its critical roles in Okazaki fragment maturation, DNA repair, and apoptosis-induced DNA fragmentation. Functional deficiencies in FEN1, in the forms of somatic mutations and polymorphisms, have recently been shown to lead to autoimmunity, chronic inflammation, and predisposition to and progression of cancer. To explore how FEN1 contributes to cancer progression, we examined FEN1 expression using 241 matched pairs of cancer and corresponding normal tissues on a gene expression profiling array and validated differential expression by quantitative real-time PCR and immunohistochemistry. Furthermore, we defined the minimum promoter of human FEN1 and examined the methylation statuses of the 5' region of the gene in paired breast cancer tissues. We show that FEN1 is significantly up-regulated in multiple cancers and the aberrant expression of FEN1 is associated with hypomethylation of the CpG island within the FEN1 promoter in tumor cells. The overexpression and promoter hypomethylation of FEN1 may serve as biomarkers for monitoring the progression of cancers. (Mol Cancer Res 2008;6(11):1710–7)

Quelle: Molecular Cancer Research current issue | 14 Nov 2008 | 12:00 am CET

Resident hepatocyte fibroblast growth factor receptor 4 limits hepatocarcinogenesis

Fibroblast growth factor (FGF) family signaling mediates cell-to-cell communication in development and organ homeostasis in adults. Of the FGF receptor (FGFR) isotypes, FGFR4 is the sole resident isotype present in mature parenchymal hepatocytes. FGFR1 that is normally associated with activated nonparenchymal cells appears ectopically in hepatoma cells. Ectopic expression and chronic activity of FGFR1 in hepatocytes accelerates diethylnitrosamine (DEN)-initiated hepatocarcinogenesis by driving unrestrained cell proliferation and tumor angiogenesis. Hepatocyte FGFR4 mediates liver's role in systemic cholesterol/bile acid and lipid metabolism and affects proper hepatolobular restoration after damage without effect on cell proliferation. Here we ask whether FGFR4 plays a role in progression of hepatocellular carcinoma (HCC). We report that although spontaneous HCC was not detected in livers of FGFR4-deficient mice, the ablation of FGFR4 accelerated DEN-induced hepatocarcinogenesis. In contrast to FGFR1 that induced a strong mitogenic response and depressed rate of cell death in hepatoma cells, FGFR4 failed to induce a mitogenic response and increased the rate of cell death. FGFR1 but not FGFR4 induced cyclin D1 and repressed p27 expression. Analysis of activation of Erk, JNK, and PI3K-related AKT signaling pathways indicated that in contrast to FGFR1, FGFR4 failed to sustain Erk activation and did not activate AKT. These differences may underlie the opposing effects of FGFR1 and FGFR4. These results suggest that in contrast to ectopic FGFR1 that is a strong promoter of hepatoma, resident FGFR4 that mediates differentiated hepatocyte metabolic functions also serves to suppress hepatoma progression. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 13 Nov 2008 | 11:00 am CET

Common polymorphisms in the vascular endothelial growth factor gene and colorectal cancer development, prognosis, and survival

Angiogenesis plays an important role in growth, progression, and metastasis of tumors. The most important regulator of angiogenesis is vascular endothelial growth factor (VEGF). VEGF expression has been associated with advance stage and poor survival of several cancers. In the present study we evaluated the association of functional polymorphisms in the VEGF gene with colorectal cancer development, prognosis, and survival. Three hundred twelve consecutive patients with surgically treated colorectal adenocarcinoma were enrolled in the present study. The genomic DNA was extracted from paraffin-embedded tissue and five VEGF (-2578C>A, -1154G>A, -634G>C, -460T>C, and +936C>T) gene polymorphisms were determined using a polymerase chain reaction-restriction fragment length polymorphism assay. VEGF -2578C>A, -1154G>A, -634G>C, -460T>C, and +936C>T genotype and allele frequencies were similar among patients and controls. There was a trend showing carriers of the -2578A and +936T alleles more frequent among patients with CRC, but these differences did not reach statistical significance. Furthermore, no correlation was found between all these variants and tumor characteristics like size, histological grading, positive regional lymph node metastases or tumor stage. However, the -2578AA, -634CC, and +936TT genotypes found to be related with a significantly lower overall survival in our study. In conclusion, VEGF gene polymorphisms were found to be an independent prognostic marker for Greek CRC patients. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 13 Nov 2008 | 10:51 am CET

The 23rd Aspen Cancer Conference: Mechanisms of toxicity, carcinogenesis, cancer prevention and cancer therapy 2008

No Abstract.

Quelle: Molecular Carcinogenesis | 13 Nov 2008 | 10:50 am CET

Alterations in candidate genes PHF2, FANCC, PTCH1 and XPA at chromosomal 9q22.3 region: Pathological significance in early- and late-onset breast carcinoma

Background: Younger women with breast carcinoma (BC) exhibits more aggressive pathologic features compared to older women; young age could be an independent predictor of adverse prognosis. To find any existing differences in the molecular pathogenesis of BC in both younger and older women, alterations at chromosomal (chr.) 9q22.32-22.33 region were studied owing to its association in wide variety of tumors. Present work focuses on comparative analysis of alterations of four candidate genes; PHF2, FANCC, PTCH1 and XPA located within 4.4 Mb region of the afore-said locus in two age groups of BC, as well as the interrelation and prognostic significance of alterations of these genes. Methods: Deletion analysis of PHF2, FANCC, PTCH1 and XPA were examined in a subset of 47 early-onset (group-A: [less than or equal to]40 years) and 59 late-onset (group-B: >40 years) breast carcinomas using both microsatellite and exonic markers. Methylation Sensitive Restriction analysis (MSRA) was done to check for promoter methylation. Quantitative real-time polymerase chain reaction (Q-PCR) and immunohistochemisty (IHC) was done in some genes to see their relative mRNA and protein expressions respectively. Clinico-pathological correlation of different parameters as well as patient survival was calculated using different statistical softwares like EpiInfo 6.04b, SPSS 10.0 etc. Results: Either age group exhibited high frequency of overall alterations in PHF2, FANCC and PTCH1 compared to XPA. Samples with alteration (deletion/methylation) in these genes showed reduced level of mRNA expression as seen by Q-PCR. Immunohistochemical analysis of FANCC and PTCH1 also supported this observation. Poor patient survival was noted in both age groups having alterations in FANCC. Similar result was also seen with PTCH1 and XPA alterations in group-A and PHF2 alterations in group-B. This reflected their roles as prognostic tools in the respective groups in which they were altered. Conclusions: Overall alterations of PHF2, FANCC and PTCH1 were comparatively higher than XPA. Differential association of alterations in FANCC and PTCH1 with that of PHF2, XPA and two breast cancer susceptibility genes (BRCA1/BRCA2) in the two age groups suggests differences in their molecular pathogenesis and dysregulation of multiple DNA repair pathways as well as hedgehog dependent stem cell renewal pathway.

Quelle: Molecular Cancer - Latest articles | 6 Nov 2008 | 12:00 am CET

Promoter hypermethylation of the SFRP2 gene is a high-frequent alteration and tumor-specific epigenetic marker in human breast cancer

Background: We have previously reported that expression of the Wnt antagonist genes SFRP1 and SFRP5 is frequently silenced by promoter hypermethylation in breast cancer. SFRP2 is a further Wnt inhibitor whose expression was recently found being downregulated in various malignancies. Here we investigated whether SFRP2 is also implicated in human breast cancer, and if so whether SFRP2 promoter methylation might serve as a potential tumor biomarker. Methods: We analyzed SFRP2 mRNA expression and SFRP2 promoter methylation in 10 breast cell lines, 199 primary breast carcinomas, 20 matched normal breast tissues and 17 cancer-unrelated normal breast tissues using RT-PCR, realtime PCR, methylation-specific PCR and Pyrosequencing, respectively. SFRP2 protein expression was assessed by immunohistochemistry on a tissue microarray. Proliferation assays after transfection with an SFRP2 expression vector were performed with mammary MCF10A cells. Statistical evaluations were accomplished with SPSS 14.0 software. Results: Of the cancerous breast cell lines, 7/8 (88%) lacked SFRP2 mRNA expression due to SFRP2 promoter methylation (P<0.001). SFRP2 expression was substantially restored in most breast cell lines after treatment with 5-aza-2'-deoxycytidine and trichostatin A. In primary breast carcinomas SFRP2 protein expression was strongly reduced in 93 of 125 specimens (74%). SFRP2 promoter methylation was detected in 165/199 primary carcinomas (83%) whereas all cancer-related and unrelated normal breast tissues were not affected by SFRP2 methylation. SFRP2 methylation was not associated with clinicopathological factors or clinical patient outcome. However, loss of SFRP2 protein expression showed a weak association with unfavorable patient overall survival (P=0.071). Forced expression of SFRP2 in mammary MCF10A cells substantially inhibited proliferation rates (P=0.045). Conclusions: The SFRP2 gene is a high-frequent target of epigenetic inactivation in human breast cancer. Its methylation leads to abrogation of SFRP2 expression, conferring a growth advantage to epithelial mammary cells. This altogether supports a tumor suppressive function of SFRP2. Although clinical patient outcome was not associated with SFRP2 methylation, the high frequency of this epimutation and its putative specificity to neoplastic cells may qualify SFRP2 promoter methylation as a potential candidate screening marker helping to improve early breast cancer detection.

Quelle: Molecular Cancer - Latest articles | 6 Nov 2008 | 12:00 am CET

Ursolic acid inhibits IL-1[beta] or TNF-[alpha]-induced C6 glioma invasion through suppressing the association ZIP/p62 with PKC-[zeta] and downregulating the MMP-9 expression

Ursolic acid (UA), a constant constituent of Rosmarinus officinalis extracts, is a triterpenoid compound which has been shown to have antioxidant and anticarcinogenic properties. In the present study, we found that UA was able to reduce interleukin-1 beta (IL-1[beta]) or tumor necrosis-alpha (TNF-[alpha])-induced rat C6 glioma cell invasion, which was examined by a reconstituted basement membrane in a set of transwell chambers. However, the inhibitory effect of UA did not influence cell proliferation or cause cell cytotoxity. The results analyzed by zymography assay and Western blotting revealed that the activity and expression of matrix metalloproteinase-9 (MMP-9) was eliminated by UA in a dose-dependent manner. Because MMP-9 is the target gene of the transcription factor nuclear factor-kappaB (NF-[kappa]B), we further investigated the effect of UA on the activity of NF-[kappa]B. As expected, UA upregulated the levels of IkappaBalpha (I[kappa]B[alpha]) and attenuated the nuclear translocation of p65. Furthermore, UA suppressed the IL-1[beta] or TNF-[alpha]-induced activation of protein kinase C-zeta (PKC-[zeta]). Our data showed UA potently inhibited the association of ZIP/p62 and PKC-[zeta]. Taken together, we demonstrated that UA could efficiently inhibit the interaction of ZIP/p62 and PKC-[zeta]. It also further suppressed the activation of NF-[kappa]B and downregulation of the MMP-9 protein, which in turn contributed to its inhibitory effects on IL-1[beta] or TNF-[alpha]-induced C6 glioma cell invasion. These results all showcase the potential UA has in the chemoprevention and treatment of cancer metastasis and invasion. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 30 Oct 2008 | 1:23 pm CET

Conditional loss of PTEN leads to skeletal abnormalities and lipoma formation

To understand the role of tumor suppressor PTEN in cartilage development, we have generated chondrocyte specific PTEN deletion mice using Col2a1Cre and PTENloxp/loxp mice. PTEN mutant mice are viable and fertile, nonetheless, develop kyphosis over time. Histological analyses show mutant vertebrae and intervertebral discs are larger and therefore the spines are longer than in control mice. In addition, the growth plates are thicker, invading trabecular bone areas are deeper, and marrow adipocyte populations are higher in PTEN mutant mice. Furthermore, the growth plates, not normally fused in mouse long bones, are fused in PTEN mutants. Intriguingly, PTEN mice develop lipomas and show abnormal accumulation of fat tissues along spines. Cell tracking assays have confirmed that lipomas and a portion of fat tissues were derived from Col2a1Cre PTENloxp/loxp cells. Further analyses have suggested that the phenotypes of PTEN mutant likely attribute to PTEN's negatively regulating role in PI3K/Akt pathway. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 30 Oct 2008 | 1:23 pm CET

Polyporenic acid C induces caspase-8-mediated apoptosis in human lung cancer A549 cells

Lung cancer continues to be the leading cause of cancer-related mortality worldwide. This warrants the search for new and effective agents against lung cancer. We and others have recently shown that lanostane-type triterpenoids isolated from the fungal species Poria cocos (P. cocos) can inhibit cancer growth. However, the mechanisms responsible for the anticancer effects of these triterpenoids remain unclear. In this study, we investigated the effect of polyporenic acid C (PPAC), a lanostane-type triterpenoid from P. cocos, on the growth of A549 nonsmall cell lung cancer cells (NSCLC). The results demonstrate that PPAC significantly reduced cell proliferation via induction of apoptosis as evidenced by sub-G1 analysis, annexin V-FITC staining, and increase in cleavage of procaspase-8, -3, and poly(ADP-ribose)-polymerase (PARP). However, unlike our previously reported lanostane-type triterpenoid, pachymic acid, treatment of cells with PPAC was not accompanied by disruption of mitochondrial membrane potential and increase in cleavage of procaspase-9. Further, PPC-induced apoptosis was inhibited by caspase-8 and pan caspase inhibitors but not by a caspase-9 inhibitor. Taken together, the results suggest that PPAC induces apoptosis through the death receptor-mediated apoptotic pathway where the activation of caspase-8 leads to the direct cleavage of execution caspases without the involvement of the mitochondria. Furthermore, suppressed PI3-kinase/Akt signal pathway and enhanced p53 activation after PPAC treatment suggests this to be an additional mechanism for apoptosis induction. Together, these results encourage further studies of PPAC as a promising candidate for lung cancer therapy. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 30 Oct 2008 | 1:22 pm CET

c-Fos accelerates hepatocyte conversion to a fibroblastoid phenotype through ERK-mediated upregulation of paxillin-Serine178 phosphorylation

Transforming growth factor [beta] (TGF-[beta]) exerts an important role in the late steps of carcinogenesis by cooperating with Ras to induce cell motility and tumor invasion. The transcription complex AP-1 has been implicated in the regulation of genes involved in motility and invasion, by mechanisms not yet delineated. We utilized a model of immortalized human hepatocytes (IHH) overexpressing c-Fos (IHH-Fos) or not (IHH-C) to investigate the role of c-Fos on cell motility in response to a prolonged treatment with TGF-[beta], EGF or a combination of both. Cotreatment with EGF and TGF-[beta], but neither cytokine alone, induced the conversion of hepatocytes to a fibroblastoid phenotype and increased their motility in Boyden chambers. EGF/TGF-[beta] cotreatment induced a higher effect on ERK phosphorylation compared to TGF-[beta] treatment alone. It also induced an increase in total and phosphorylated Ser178 paxillin, a protein previously implicated in cell motility. This response was inhibited by two specific MEK inhibitors, indicating the involvement of the ERK pathway in paxillin activation. Overexpression of c-Fos correlated with increased cell scattering and motility, higher levels of ERK activation and phospho Ser178 paxillin, increased levels of EGF receptor (EGF-R) mRNA and higher EGF-R phosphorylation levels following EGF/TGF-[beta] cotreatment. Conversely, siRNA-mediated invalidation of c-Fos delayed the appearance of fibroblastoid cells, decreased EGF-R mRNA and downregulated ERK and Ser178 paxillin phosphorylations, indicating that c-Fos activates hepatocyte motility through an EGF-R/ERK/paxillin pathway. Since c-Fos is frequently overexpressed in hepatocarcinomas, this newly identified mechanism might be involved in the progression of hepatic tumors in vivo. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 30 Oct 2008 | 1:21 pm CET

Transcription destabilizes triplet repeats

Triplet repeat expansion is the molecular basis for several human diseases. Intensive studies using systems in bacteria, yeast, flies, mammalian cells, and mice have provided important insights into the molecular processes that are responsible for mediating repeat instability. The age-dependent, ongoing repeat instability in somatic tissues, especially in terminally differentiated neurons, strongly suggests a robust role for pathways that are independent of DNA replication. Several genetic studies have indicated that transcription can play a critical role in repeat instability, potentially providing a basis for the instability observed in neurons. Transcription-induced repeat instability can be modulated by several DNA repair proteins, including those involved in mismatch repair (MMR) and transcription-coupled nucleotide excision repair (TC-NER). Though the mechanism is unclear, it is likely that transcription facilitates the formation of repeat-specific secondary structures, which act as intermediates to trigger DNA repair, eventually leading to changes in the length of the repeat tract. In addition, other processes associated with transcription can also modulate repeat instability, as shown in a variety of different systems. Overall, the mechanisms underlying repeat instability in humans are unexpectedly complicated. Because repeat-disease genes are widely expressed, transcription undoubtedly contributes to the repeat instability observed in many diseases, but it may be especially important in nondividing cells. Transcription-induced instability is likely to involve an extensive interplay not only of the core transcription machinery and DNA repair proteins, but also of proteins involved in chromatin remodeling, regulation of supercoiling, and removal of stalled RNA polymerases, as well as local DNA sequence effects. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 30 Oct 2008 | 1:12 pm CET

DNA methylation-based biomarkers for early detection of non-small cell lung cancer: an update

Lung cancer is the number one cancer killer in the United States. This disease is clinically divided into two sub-types, small cell lung cancer, (10â€“15% of lung cancer cases), and non-small cell lung cancer (NSCLC; 85â€“90% of cases). Early detection of NSCLC, which is the more common and less aggressive of the two sub-types, has the highest potential for saving lives. As yet, no routine screening method that enables early detection exists, and this is a key factor in the high mortality rate of this disease. Imaging and cytology-based screening strategies have been employed for early detection, and while some are sensitive, none have been demonstrated to reduce lung cancer mortality. However, mortality might be reduced by developing specific molecular markers that can complement imaging techniques. DNA methylation has emerged as a highly promising biomarker and is being actively studied in multiple cancers. The analysis of DNA methylation-based biomarkers is rapidly advancing, and a large number of potential biomarkers have been identified. Here we present a detailed review of the literature, focusing on DNA methylation-based markers developed using primary NSCLC tissue. Viable markers for clinical diagnosis must be detectable in 'remote media' such as blood, sputum, bronchoalveolar lavage, or even exhaled breath condensate. We discuss progress on their detection in such media and the sensitivity and specificity of the molecular marker panels identified to date. Lastly, we look to future advancements that will be made possible with the interrogation of the epigenome.

Quelle: Molecular Cancer - Latest articles | 23 Oct 2008 | 12:00 am CEST

The prince and the pauper: a tale of anticancer targeted agents

Cancer rates are set to increase at an alarming rate, from 10 million new cases globally in 2000 to 15 million in 2020. Regarding the pharmacological treatment of cancer, we currently are in the interphase of two treatment eras. The so-called pregenomic therapy which names the traditional cancer drugs, mainly cytotoxic drug types, and post-genomic era-type drugs referring to rationally-based designed. Although there are successful examples of this newer drug discovery approach, most target-specific agents only provide small gains in symptom control and/or survival, whereas others have consistently failed in the clinical testing. There is however, a characteristic shared by these agents: -their high cost-. This is expected as drug discovery and development is generally carried out within the commercial rather than the academic realm. Given the extraordinarily high therapeutic drug discovery-associated costs and risks, it is highly unlikely that any single public-sector research group will see a novel chemical "probe" become a "drug". An alternative drug development strategy is the exploitation of established drugs that have already been approved for treatment of non-cancerous diseases and whose cancer target has already been discovered. This strategy is also denominated drug repositioning, drug repurposing, or indication switch. Although traditionally development of these drugs was unlikely to be pursued by Big Pharma due to their limited commercial value, biopharmaceutical companies attempting to increase productivity at present are pursuing drug repositioning. More and more companies are scanning the existing pharmacopoeia for repositioning candidates, and the number of repositioning success stories is increasing. Here we provide noteworthy examples of known drugs whose potential anticancer activities have been highlighted, to encourage further research on these known drugs as a means to foster their translation into clinical trials utilizing the more limited public-sector resources. If these drug types eventually result in being effective, it follows that they could be much more affordable for patients with cancer; therefore, their contribution in terms of reducing cancer mortality at the global level would be greater.

Quelle: Molecular Cancer - Latest articles | 23 Oct 2008 | 12:00 am CEST

Bone marrow ectopic expression of a non-coding RNA in childhood T-cell acute lymphoblastic leukemia with a novel t(2;11)(q11.2;p15.1) translocation

Chromosomal translocations play a crucial role in tumorigenesis, often resulting in the formation of chimeric genes or in gene deregulation through position effects. T-cell acute lymphoblastic leukemia (T-ALL) is associated with a large number of such rearrangements. We report the ectopic expression of the 3' portion of EST DA926692 in the bone marrow of a childhood T-ALL case showing a t(2;11)(q11.2;p15.1) translocation as the sole chromosome abnormality. The breakpoints, defined at the sequence level, mapped within HPS5 (Hermansky Pudlak syndrome 5) intron 1 at 11p15.1, and DA926692 exon 2 at 2q11.2. The translocation was accompanied by a submicroscopic inversion that brought the two genes into the same transcriptional orientation. No chimeric trancript was detected. Interestingly, Real-Time Quantitative (RQ)-PCR detected, in the patient's bone marrow, expression of a 173 bp product corresponding to the 3' portion of DA926692. Samples from four T-ALL cases with a normal karyotype and normal bone marrow used as controls were negative. It might be speculated that the juxtaposition of this genomic segment to the CpG island located upstream HPS5 activated DA92669 expression. RQ-PCR analysis showed expression positivity in 6 of 23 human tissues examined. Bioinformatic analysis excluded that this small non-coding RNA is a precursor of micro-RNA, although it is conceivable that it has a different, yet unknown, functional role. To the best of our knowledge, this is the first report, in cancer, of the activation of a small non-coding RNA as a result of a chromosomal translocation.

Quelle: Molecular Cancer - Latest articles | 23 Oct 2008 | 12:00 am CEST

Down-regulation of the microRNAs miR-34a, miR-127, and miR-200b in rat liver during hepatocarcinogenesis induced by a methyl-deficient diet

Altered expression of microRNAs (miRNAs) has been reported in diverse human cancers; however, the down-regulation or up-regulation of any particular miRNAs in cancer is not sufficient to address the role of these changes in carcinogenesis. In this study, using the rat model of liver carcinogenesis induced by a methyl-deficient diet, which is relevant to the hepatocarcinogenesis in humans associated with viral hepatitis C and B infections, alcohol exposure and metabolic liver diseases, we showed that the development of hepatocellular carcinoma (HCC) is characterized by prominent early changes in expression of miRNA genes, specifically by inhibition of expression of microRNAs miR-34a, miR-127, miR-200b, and miR-16a involved in the regulation of apoptosis, cell proliferation, cell-to-cell connection, and epithelial-mesenchymal transition. The mechanistic link between these alterations in miRNAs expression and the development of HCC was confirmed by the corresponding changes in the levels of E2F3, NOTCH1, BCL6, ZFHX1B, and BCL2 proteins targeted by these miRNAs. The significance of miRNAs expression dysregulation in respect to hepatocarcinogenesis was confirmed by the persistence of these miRNAs alterations in the livers of methyl-deficient rats re-fed a methyl-adequate diet. Altogether, the early occurrence of alterations in miRNAs expression and their persistence during the entire process of hepatocarcinogenesis indicate that the dysregulation of microRNAs expression may be an important contributing factor in the development of HCC. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 21 Oct 2008 | 4:47 pm CEST

Enhanced skin carcinogenesis and lack of thymus hyperplasia in transgenic mice expressing human cyclin D1b (CCND1b)

Cyclin D1b is an alternative transcript of the cyclin D1 gene (CCND1) expressed in human tumors. Its abundance is regulated by a single base pair polymorphism at the exon 4/intron 4 boundary (nucleotide 870). Epidemiological studies have shown a correlation between the presence of the G870A allele (that favors the splicing for cyclin D1b) with increased risk and less favorable outcome in several forms of cancer. More recently, it has been shown that, unlike cyclin D1a, the alternative transcript D1b by itself has the capacity to transform fibroblasts in vitro. In order to study the oncogenic potential of cyclin D1b, we developed transgenic mice expressing human cyclin D1b under the control of the bovine K5 promoter (K5D1b mice). Seven founders were obtained and none of them presented any significant phenotype or developed spontaneous tumors. Interestingly, K5D1b mice do not develop the fatal thymic hyperplasia, which is characteristic of the cyclin D1a transgenic mice (K5D1a). Susceptibility to skin carcinogenesis was tested in K5D1b mice using two-stage carcinogenesis protocols. In two independent experiments, K5D1b mice developed higher papilloma multiplicity as compared with wild-type littermates. However, when K5D1b mice were crossed with cyclin D1KO mice, the expression of cyclin D1b was unable to rescue the carcinogenesis-resistant phenotype of the cyclin D1 KO mice. To further explore the role of cyclin D1b in mouse models of carcinogenesis we carried out in silico analysis and in vitro experiments to evaluate the existence of a mouse homologous of the human cyclin D1b transcript. We were unable to find any evidence of an alternatively spliced transcript in mouse Ccnd1. These results show that human cyclin D1b has different biological functions than cyclin D1a and confirm its oncogenic properties. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 21 Oct 2008 | 4:47 pm CEST

Epidermal growth factor receptor and claudin-2 participate in A549 permeability and remodeling: Implications for non-small cell lung cancer tumor colonization

Tumor colonization involves changes in cell permeability and remodeling. Paracellular permeability is regulated by claudins, integrated tight junction (TJ) proteins, located on the apicolateral portion of epithelial cells. Epidermal growth factor (EGF) was reported to modify cellular claudin levels and induce remodeling. To investigate a role for EGF receptor (EGFR) activation in tumor colonization we studied the effect of EGF and claudin-2 overexpression on permeability and cell reorganization in the human A549 non-small cell lung cancer (NSCLC) cell line. Our data demonstrated that A549 cells possess functional TJs and that EGF treatment increased levels of claudin-2 expression by 46%. Furthermore, EGFR signaling reduced monolayer permeability to choline and triggered cellular remodeling. The mitogen-activated protein kinase inhibitor PD98059 blocked the effect on A549 permeability and remodeling. EGF stimulation also exacerbated a fourfold increase in cell colonization elicited by claudin-2 upregulation. Our findings are consistent with the hypothesis that EGFR signaling plays an important role in A549 cell physiology and acts synergistically with claudin-2 to accelerate tumor colonization. Understanding the influence of EGF on A549 cell permeability and reorganization will help shed light on NSCLC tumor colonization and contribute to the development of novel anti-cancer treatments. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 21 Oct 2008 | 4:46 pm CEST

Characterization of an alternatively spliced GADD45[alpha], GADD45[alpha]1 isoform, in arsenic-treated epithelial cells

A new GADD45[alpha] isoform, GADD45[alpha]1, was identified in the cellular response to arsenic. DNA sequencing and biochemical analyses suggested that GADD45[alpha]1 is derived from an alternative splicing of the GADD45[alpha] mRNA by skipping the region corresponding to exon2 of the gadd45[alpha] gene during mRNA maturation. In addition to the size difference due to the lack of 34 amino acids encoded by exon2, GADD45[alpha]1 and GADD45[alpha] proteins differ in their effects on cell proliferation and cell cycle transition. Unlike GADD45[alpha], the GADD45[alpha]1 is unable to attenuate cell growth. In over-expression experiments, the full length GADD45[alpha], but not the GADD45[alpha]1, sensitized cells to arsenic-induced prometaphase arrest of the cell cycle. Furthermore, GADD45[alpha]1 appears to be able to antagonize the function of the GADD45[alpha] on the G2/M phase cell cycle arrest as demonstrated in cotransfection experiment. Thus, these data suggest that the generation of the GADD45[alpha]1 isoform may not only offset but also antagonize the effects of arsenic and GADD45[alpha] on cell growth and cell cycle regulation. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 21 Oct 2008 | 4:46 pm CEST

Tumor suppressor and oncogene actions of TGF[beta]1 occur early in skin carcinogenesis and are mediated by Smad3

Interactions between TGF[beta]1 and ras signaling pathways play an important role in cancer development. Here we show that in primary mouse keratinocytes, v-rasHa does not block the early biochemical events of TGF[beta]1 signal transduction but does alter global TGF[beta]1 mediated gene expression in a gene specific manner. Expression of Smad3 dependent TGF[beta]1 early response genes and the TGF[beta]1 cytostatic gene expression response were not altered by v-rasHa consistent with an intact TGF[beta]1 growth arrest. However, TGF[beta]1 and v-rasHa cause significant alteration in genes regulating matrix remodeling as the TGF[beta]1 induction of extracellular matrix genes was blocked by v-rasHa but specific matrix proteases associated with cancer progression were elevated. Smad3 deletion in keratinocytes repressed normal differentiation maker expression and caused expression of Keratin 8 a simple epithelial keratin and marker of malignant conversion. Smad3 was required for the TGF[beta]1 cytostatic response in v-rasHa keratinocytes, but also for protease induction, keratinocyte attachment and migration. These results show that pro-oncogenic activities of TGF[beta]1 can occur early in carcinogenesis before loss of its tumor suppressive function and that selective regulation rather than complete inactivation of Smad3 function may be crucial for tumor progression. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 21 Oct 2008 | 4:46 pm CEST

Rhabdomyosarcoma cells show an energy producing anabolic metabolic phenotype compared with primary myocytes

Background: The functional status of a cell is expressed in its metabolic activity. We have applied stable isotope tracing methods to determine the differences in metabolic pathways in proliferating Rhabdomysarcoma cells (Rh30) and human primary myocytes in culture. Uniformly 13C-labeled glucose was used as a source molecule to follow the incorporation of 13C into more than 40 marker metabolites using NMR and GC-MS. These include metabolites that report on the activity of glycolysis, Krebs' cycle, pentose phosphate pathway and pyrimidine biosynthesis. Results: The Rh30 cells proliferated faster than the myocytes. Major differences in flux through glycolysis were evident from incorporation of label into secreted lactate, which accounts for a substantial fraction of the glucose carbon utilized by the cells. Krebs' cycle activity as determined by 13C isotopomer distributions in glutamate, aspartate, malate and pyrimidine rings was considerably higher in the cancer cells than in the primary myocytes. Large differences were also evident in de novo biosynthesis of riboses in the free nucleotide pools, as well as entry of glucose carbon into the pyrimidine rings in the free nucleotide pool. Specific labeling patterns in these metabolites show the increased importance of anaplerotic reactions in the cancer cells to maintain the high demand for anabolic and energy metabolism compared with the slower growing primary myocytes. Serum-stimulated Rh30 cells showed higher degrees of labeling than serum starved cells, but they retained their characteristic anabolic metabolism profile. The myocytes showed evidence of de novo synthesis of glycogen, which was absent in the Rh30 cells. Conclusion: The specific 13C isotopomer patterns showed that the major difference between the transformed and the primary cells is the shift from energy and maintenance metabolism in the myocytes toward increased energy and anabolic metabolism for proliferation in the Rh30 cells. The data further show that the mitochondria remain functional in Krebs' cycle activity and respiratory electron transfer that enables continued accelerated glycolysis. This may be a common adaptive strategy in cancer cells.

Quelle: Molecular Cancer - Latest articles | 21 Oct 2008 | 12:00 am CEST

PrLZ expression is associated with the progression of prostate cancer LNCaP cells

PrLZ is a novel recent isolated gene and specific expression in prostate tissues. PrLZ expression was specifically elevated in prostate embryonic tissues and androgen independent prostate cancer cells, suggesting it might be association with the embryonic development and malignancy progression. However, the function and mechanism of PrLZ during the progression of prostate cancer remain blurred. Our present studies showed PrLZ expression might enhance the proliferation and invasion capability in vitro and also increase the tumorigenicity in situ prostate cancer animal model, which is indicated PrLZ expression contributed to the malignancy progression of prostate cancer. In addition, PrLZ also might up regulate androgen receptor (AR) expression and increase the PSA expression, a putative downstream target gene of AR, which indicated PrLZ mediated the malignancy progression of prostate cancer was associated with androgen signals. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 17 Sep 2008 | 10:51 am CEST

Tumor suppressor gene Co-operativity in compound Patched1 and suppressor of fused heterozygous mutant mice

Dysregulation of the Hedgehog signaling pathway is central to the development of certain tumor types, including medulloblastoma and basal cell carcinoma (BCC). Patched1 (Ptch1) and Suppressor of fused (Sufu) are two essential negative regulators of the pathway with tumor suppressor activity. Ptch1+/- mice are predisposed to developing medulloblastoma and rhabdomyosarcoma, while Sufu+/- mice develop a skin phenotype characterized by basaloid epidermal proliferations. Here, we have studied tumor development in Sufu+/-Ptch1+/- mice to determine the effect of compound heterozygosity on the onset, incidence, and spectrum of tumors. We found significantly more (2.3-fold) basaloid proliferations in Sufu+/-Ptch1+/- compared to Sufu+/- female, but not male, mice. For medulloblastoma, the cumulative 1-yr incidence was 1.5-fold higher in Sufu+/-Ptch1+/- compared to Ptch1+/- female mice but this strong trend was not statistically significant. Together this suggests a weak genetic interaction of the two tumor suppressor genes. We noted a few rhabdomyosarcomas and pancreatic cysts in the Sufu+/-Ptch1+/- mice, but the numbers were not significantly different from the single heterozygous mice. Hydrocephalus developed in [sim]20% of the Ptch1+/- and Sufu+/-Ptch1+/- but not in Sufu+/- mice. Interestingly, most of the medulloblastomas from the Sufu+/-Ptch1+/- mice had lost expression of the remaining Ptch1 wild-type allele but not the Sufu wild-type allele. On the contrary, Sufu as well as Gli1 and Gli2 expression was upregulated in the medulloblastomas compared to adult cerebellum in Ptch1+/- and Sufu+/-Ptch1+/- mice. This suggests that Sufu expression may be regulated by Hedgehog pathway activity and could constitute another negative feedback loop in the pathway. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 9 Sep 2008 | 12:02 pm CEST

Apple polyphenol phloretin potentiates the anticancer actions of paclitaxel through induction of apoptosis in human hep G2 cells

Phloretin (Ph), which can be obtained from apples, apple juice, and cider, is a known inhibitor of the type II glucose transporter (GLUT2). In this study, real-time PCR analysis of laser-capture microdissected (LCM) human hepatoma cells showed elevated expression (>5-fold) of GLUT2 mRNA in comparison with nonmalignant hepatocytes. In vitro and in vivo studies were performed to assess Ph antitumor activity when combined with paclitaxel (PTX) for treatment of human liver cancer cells. Inhibition of GLUT2 by Ph potentiated the anticancer effects of PTX, resensitizing human liver cancer cells to drugs. These results demonstrate that 50-150 ÂµM Ph significantly potentiates DNA laddering induced in Hep G2 cells by 10 nM PTX. Activity assays showed that caspases 3, 8, and 9 are involved in this apoptosis. The antitumor therapeutic efficacy of Ph (10 mg/kg body weight) was determined in cells of the SCID mouse model that were treated in parallel with PTX (1 mg/kg body weight). The Hep G2-xenografted tumor volume was reduced more than fivefold in the Ph + PTX-treated mice compared to the PTX-treated group. These results suggest that Ph may be useful for cancer chemotherapy and chemoprevention. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 2 Sep 2008 | 12:12 pm CEST

Association between polymorphisms in the GSTA4 gene and risk of lung cancer: A case-control study in a Southeastern Chinese population

GST Alpha 4 (GSTA4) has an important role in the protection against oxidative stress induced by carcinogens such as tobacco smoke. However, few studies investigated the association between GSTA4 polymorphisms and lung cancer risk. We genotyped three selected GSTA4 SNPs (rs182623 - 1718:T > A, rs3798804 + 5034:G > A and rs316141 + 13984:C > T) in a case-control study of 500 lung cancer patients and 517 cancer-free controls and evaluated the association between these SNPs and risk of lung cancer in this Han Chinese population. We found that there was a significant difference in genotype and allele frequency distributions of GSTA4 -1718 between the cases and the controls (P = 0.006 and P = 0.003, respectively). Compared with the GSTA4 -1718TT genotype, individuals with the TA + AA genotypes had a significantly decreased risk of lung cancer (adjusted OR, 0.63; 95% CI, 0.47-0.84; P = 0.006). Although there were no such statistical differences between the cases and controls at the loci +5034 and +13984, nor for histological types, individuals carrying the genotypes of -1718TA, +5034GG and +13984CT had a significantly decreased lung cancer risk (OR, 0.37; 95% CI, 0.23-0.61; P < 0.0001), especially for those smokers who smoked [le]25 pack-years (P < 0.000001). These results need to be confirmed in larger studies with different ethnic groups. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 2 Sep 2008 | 12:12 pm CEST

Proteomics study of medullary thyroid carcinomas expressing RET germ-line mutations: Identification of new signaling elements

Proteomics may help to elucidate differential signaling networks underlying the effects of compounds and to identify new therapeutic targets. Using a proteomic-multiplexed analysis of the phosphotyrosine signaling together with antibody-based validation techniques, we identified several candidate molecules for RET (rearranged during transfection) tyrosine kinase receptor carrying mutations responsible for the multiple endocrine neoplasia type 2A and 2B (MEN2A and MEN2B) syndromes in two human medullary thyroid carcinoma (MTC) cell lines, TT and MZ-CRC-1, which express the RET-MEN2A and RET-MEN2B oncoproteins, respectively. Signaling elements downstream of these oncoproteins were identified after treating cells with the indolinone tyrosine kinase inhibitor RPI-1 to knock down RET phosphorylation activity. We detected 23 and 18 affinity-purified phosphotyrosine proteins in untreated TT and MZ-CRC-1 cells, respectively, most of which were shared and sensitive to RPI-1 treatment. However, our data clearly point to specific signaling features of the RET-MEN2A and RET-MEN2B oncogenic pathways. Moreover, the detection of high-level expression of minimally phosphorylated epidermal growth factor receptor (EGFR) in both TT and MZ-CRC-1 cells, together with our data on the effects of EGF stimulation on the proteomic profiles and the response to Gefitinib treatment, suggest the relevance of EGFR signaling in these cell lines, especially since analysis of 14 archival MTC specimens revealed EGFR mRNA expression in all samples. Together, our data suggest that RET/EGFR multi-target inhibitors might be beneficial for therapy of MTC. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 28 Aug 2008 | 11:24 am CEST

PKC-mediated secretion of death factors in LNCaP prostate cancer cells is regulated by androgens

Activation of PKC[delta] in androgen-dependent LNCaP prostate cancer cells leads to apoptosis via the activation of p38 MAPK and JNK cascades. We have recently shown that treatment of LNCaP cells with phorbol 12-myristate 13-acetate (PMA) leads to a PKC[delta]-mediated autocrine release of death factors, including the cytokines TNF[alpha] and TRAIL, and that conditioned medium (CM) collected from PMA-treated LNCaP cells promotes the activation of the extrinsic apoptotic cascade. Interfering with this autocrine loop either at the level of factor release or death receptor activation/signaling markedly impaired the PMA apoptotic response. In the present study we show that this PKC[delta]-dependent autocrine mechanism is greatly influenced by androgens. Indeed, upon androgen depletion, which down-regulates PKC[delta] expression, TNF[alpha] and TRAIL mRNA induction and release by PMA are significantly diminished, resulting in a reduced apoptogenic activity of the CM and an impaired ability of the CM to activate p38 MAPK and JNK. These effects can be rescued by addition of the synthetic androgen R1881. Furthermore, RNAi depletion of the androgen-receptor (AR) from LNCaP cells equally impaired PMA responses, suggesting that PKC-mediated induction of death factor secretion and apoptosis in LNCaP prostate cancer cells are highly sensitive to hormonal control. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 28 Aug 2008 | 10:50 am CEST

Delphinidin, an anthocyanidin in pigmented fruits and vegetables, induces apoptosis and cell cycle arrest in human colon cancer HCT116 cells

Because of unsatisfactory treatment options for colon cancer, there is a need to develop novel preventive approaches for this malignancy. One such strategy is through chemoprevention by the use of non-toxic dietary substances and botanical products. Delphinidin, an anthocyanidin in pigmented fruits and vegetables, possesses strong anti-oxidant and anti-inflammatory properties. In the present study, we investigated the antiproliferative and proapoptotic properties of delphinidin in human colon cancer HCT116 cells. We found that treatment of cells with delphinidin (30-240 ÂµM; 48 h) resulted in (i) decrease in cell viability (ii) induction of apoptosis, (iii) cleavage of PARP, (iv) activation of caspases-3, -8, and -9, (v) increase in Bax with a concomitant decrease in Bcl-2 protein, and (vi) G2/M phase cell cycle arrest. NF-[kappa]B provides a mechanistic link between inflammation and cancer, and is a major factor controlling the ability of both pre-neoplastic and malignant cells to resist apoptosis-based tumor surveillance mechanisms. We therefore, determined the effect of delphinidin on NF-[kappa]B signaling pathway. The immunoblot, ELISA and EMSA analysis demonstrated that the treatment of HCT116 cells with delphinidin resulted in the inhibition of (i) IKK[alpha], (ii) phosphorylation and degradation of I[kappa]B[alpha], (iii) phosphorylation of NF-[kappa]B/p65 at Ser536, (iv) nuclear translocation of NF-[kappa]B/p65, (v) NF-[kappa]B/p65 DNA binding activity, and (vi) transcriptional activation of NF-[kappa]B. Our results suggest that delphinidin treatment of HCT116 cells suppressed NF-[kappa]B pathway, resulting in G2/M phase arrest and apoptosis. We suggest that delphinidin could have potential in inhibiting colon cancer growth. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 26 Aug 2008 | 11:02 am CEST

Apigenin suppresses insulin-like growth factor I receptor signaling in human prostate cancer: An in vitro and in vivo study

Deregulation of insulin-like growth factor (IGF)-I/IGF-IR signaling has been implicated in the development and progression of prostate cancer. Agents that can suppress the mitogenic activity of the IGF/IGF-IR growth axis may be of preventive or therapeutic value. We have previously demonstrated that apigenin, a plant flavone, modulates IGF signaling through upregulation of IGFBP-3. In this study, we investigated the mechanism(s) of apigenin action on the IGF/IGF-IR signaling pathway. Exposure of human prostate cancer DU145 cells to apigenin markedly reduced IGF-I-stimulated cell proliferation and induced apoptosis. Apigenin inhibited IGF-I-induced activation of IGF-IR and Akt in DU145 cells. Similar growth inhibitory and apoptotic responses were observed in PC-3 cells, which constitutively overexpress this pathway. This effect of apigenin appears to be due partially to reduced autophosphorylation of IGF-IR. Inhibition of p-Akt by apigenin resulted in decreased phosphorylation of GSK-3[beta] along with decreased expression of cyclin D1 and increased expression of p27/kip1. In vivo administration of apigenin to PC-3 tumor xenografts inhibited tumor growth, resulted in IGF-IR inactivation and dephosphorylation of Akt and its downstream signaling. These results suggest that inhibition of cell proliferation and induction of apoptosis by apigenin are mediated, at least in part, by its ability to inhibit IGF/IGF-IR signaling and the PI3K/Akt pathway. Â© 2008 Wiley-Liss, Inc.

Quelle: Molecular Carcinogenesis | 25 Aug 2008 | 10:43 am CEST

Enhancement of p53 expression in keratinocytes by the bioflavonoid apigenin is associated with RNA-binding protein HuR

We have reported previously that apigenin, a naturally occurring nonmutagenic flavonoid, increased wild-type p53 protein expression in the mouse keratinocyte 308 cell line by a mechanism involving p53 protein stabilization. Here we further demonstrated that the increase in p53 protein level induced by apigenin treatment of 308 keratinoyctes was not the result of enhanced transcription, mRNA stabilization or cytoplasmic export of p53 mRNA. Instead, biosynthetic labeling showed that apigenin increased nascent p53 protein synthesis by enhancing p53 translation. The AU-rich element (ARE) within the 3[prime]-untranslated region (UTR) of p53 mRNA was found to be responsible for apigenin's ability to increase p53 translation, as demonstrated in studies wherein the 3[prime]-UTR of p53 mRNA containing the ARE was fused downstream of a luciferase reporter gene. Furthermore, apigenin