An investigation into the role of microRNAs in prostate cancer

• Main Author: Lynch, Seodhna M.
• Published: Ulster University 2016
• Subjects: 616.99
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.697546

In prostate cancer (PCa), abnormal expression of several microRNAs (miRNAs) has been previously reported. Increasing evidence also shows that aberrant epigenetic regulation of miRNAs is a contributing factor to their altered expression in cancer. In this thesis we investigate the expression ofa panel ofmiRNAs (miR-24, miR-200c, miR-141, miR-138, miR- 205 and miR-29a) in PCa and whether their expression is related to DNA methylation status. PCR analysis of the selected miRNAs was performed in PCa cell lines and in archived prostate biopsy specimens. The biological significance of the selected miRNAs expression in prostate cancer cells was assessed by a series of in vitro bioassays and the effect on proposed targets was investigated. CpG methylation analysis was performed by COBRA and pyrosequencing for miR-200c, miR-141, miR-13 8 and miR-205 in PCa cell lines and in clinical specimens. The effect on methylation status in cells treated with demethylating agents including Decitabine (5- aza-2'deoxycytidine), knockdown of DNA methyltransferase 1 (DNMTl) and Genistein was also examined. miR-24 expression was found to be down-regulated in PCa and showed an inverse correlation with p27 (CDKNIB) and p16 (CDK2NA) with results confirming these as targets ofmiR-24 in PCa. miR-200c and miR-141 expression levels across PCa cell lines and prostate biopsy tissue inversely correlated with the methylation status of the miR-200c/miR-141 promoter. Demethylating treatments resulted in restoration of expression suggesting their expression is regulated by methylation with DNMT3A and TETlITET3 identified as target genes of miR- 200c and miR-141 respectively. miR-138 expression was down-regulated in PCa and was identified to target RARA, although no correlation was found between expression and methylation levels. miR-205 was shown to be down-regulated in PCa and showed an inverse correlation between expression and methylation. Demethylation treatments suggested miR-205 expression is under epigenetic control. miR-29a expression was also generally down-regulated in PCa. The findings provide evidence that these miRNAs are abnormally expressed in PCa, which impacts upon cell behaviour through regulation of target genes. Furthermore, some of the selected miRNAs appear to be under epigenetic regulation in PCa cells. The results present evidence that profiling their expression and methylation status may have potential as a novel biomarker or focus of therapeutic intervention in the diagnosis and prognosis of PCa.