Involvement Of MiR-146a And Its Polymorphism In Prostate Cancer Carcinogenesis

Prostate cancer is the most common noncutaneous malignancy and the second leading cause of cancer-related deaths of men in the developed world. To date, the mechanisms of prostate cancer remained largely unknown. Environmental and genetic factors may contribute to prostate cancer carcinogenesis.MircoRNAs (miRNAs) are conserved small (about 17-27 nucleotides in length), endogenous, non-coding molecules that negatively regulate gene expression by suppressing translation or degrading mRNAs. Previous studies have documented that miRNAs affect not only biologic processes such as metabolism, proliferation, tissue differentiation, cell type identity maintenance, apoptosis, cell signal regulation, organ development and aging, but also tumorigenesis. To date, over 50 miRNAs have been found aberrant expressed in prostate cancer including miR-146a. Moreover, it is also suggested that changes in miR-146a expression observed in these solid tumors could be related to a common G/C polymorphism located in the stem-loop of pre-miR-146a (rs2910164). Thus, we suppose that miR-146a and its polymorphism may contribute to prostate cancer carcinogenesis.To test the hypothesis, we conduct a case-control study to evaluate the association of environmental factors and miR-146a polymorphism in prostate cancer susceptibility and moreover, the role and mechanisms of miR-146a in prostate cancer Objective: A G > C polymorphism (rs2910164) which is located in the sequence of miR-146a precursor, results in a change from a G: U pair to a C: U mismatch in its stem region. To explore whether rs2910164 play any role in prostate caner (CaP), we analyzed the association between miR-146a polymorphism and risk of CaP and the expression of miR-146a with different genotypes in CaP tissues in southern Chinese Han population.Materials and Methods: Two hundred and fifty-one CaP and 280 control subjects were included in the cancer association study. Vectors containing either G or C alleles were constructed and the expression of miR-146a was test by real-time quantitative reverse transcription PCR. Moreover, 15 CaP tissue samples were used to test the expression of the miRNA precursors also by real-time quantitative reverse transcription PCR.Results: We found that subjects carrying CC homozygotes had a 0.65-fold reduced risk (95% CI = 0.43-0.99) than those carrying GG/GC genotypes (P < 0.05), and the C allele displayed a lower prevalence of CaP compared with the G allele (OR = 0.73, 95% CI = 0.57-0.94, P < 0.05). Moreover, hsa-miR-146a quantification showed that homozygous carriers of the C-variant had significantly decreased miRNA levels compared to the carriers of the GG/GC genotype.Conclusions: The natural genetic variation in pre-miR-146a affects the amount of mature miR-146a, contributes to the genetic predisposition to CaP. Objective: MicroRNAs have been implicated in regulating diverse cellular pathways. Emerging evidence indicates that miR-146a plays causal roles in cancer tumorigenesis as a tumor suppress gene; however, its role in hormone resistance prostate cancer tumorigenesis remains largely unknown. The aims of this study were to verify the effect of miR-146a on proliferation and migration abilities of hormone resistance prostate cancer cell lines DU145 and PC3.Materials and Methods: Expression of miR-146a in AI prostate cancer tissues and AD prostate cancer tissues were measured by realtime PCR. Effects of miR-146a in DU145 and PC3 cells proliferation, migration and chemosensitivity were evaluated by MTT assay, colony formation assay, transwell migratory assay in vitro and tumorigenicity in vivo. The potential predicted target of miR-146a was identified by systemic bioinformatic analysis (miRanda). A human EGFR 3'-UTR fragment was cloned downstream of luciferase reporter gene in pMir-reoprter vector. Then, after we have cotransfected miR-146a or NC with pMir-reporter-EGFR or pMir-reporter-NC for 48 hours, the luciferases were detected. Western blotting was used to analyisis the expression of EGFR, p-ERK and MMP2 proteins.Results: Expression of miR-146a in AI prostate cancer tissues was dramatically decreased compared to that of AD prostate cancer tissues. Over-expression of miR-146a in hormone resistance prostate cancer cells suppressed their proliferation and migration in vitro and in vivo and increased their sensitivity to Cisplatin. Moreover, when miR-146a was cotransfected, luciferase reporter assay showed that the relative luciferase activity of the pMir-reporter-EGFR was significantly suppressed (P < 0.05). Western blotting showed that miR-146a inhibited EGFR, p-ERK and MMP2 expressions.Conclusions: These findings suggested that miR-146a plays an important role in hormone resistance prostate cancer cells proliferation, migration and chemosenstivity by suppressing EGFR and subsequent inactivation of MAPK pathway, which provides a potential development of a new approach for the treatment of prostate cancer.