Abstract 4418: Investigation of miR-205 expression and its methylation status in prostate cancer
Authors: Lynch Seodhna M. , O'Neill Karla M. , McKenna Michael M. , Walsh Colum P. , Watson William , Gallagher William M. , McKenna Declan J. 
Published: August 2018

Introduction: In prostate cancer (PCa), abnormal expression of several microRNAs (miRNAs) has been previously reported. Increasing evidence shows that aberrant epigenetic regulation of miRNAs is a contributing factor to their altered expression in cancer. In this study, we investigated whether expression of miR-205 in PCa is related to the DNA methylation status of its promoter and locus region.

Methods: PCR analysis of miR-205 expression was performed in PCa cell lines and in clinical FFPE biopsy and prostatectomy specimens. CpG methylation analysis of the miR-205 promoter and miR-205 locus, was performed in PCa cell lines and in clinical prostate specimens via pyrosequencing. The effect on promoter and locus methylation status in cells treated with demethylating agents including 5-aza-2'deoxycytidine (decitabine), knockdown of DNA methyltransferase 1 (DNMT1) and knockdown of enhancer of zeste homolog 2 (EZH2) was also examined. Finally, the biological significance of miR-205 in PCa cells was assessed by a series of in vitro bioassays.

Results: miR-205 was shown to be significantly down-regulated across PCa cell lines. This correlates inversely with the methylation status of the miR-205 promoter and miR-205 locus, which is hypermethylated across this panel of PCa cell lines in both regions. Interestingly, a trend towards an inverse correlation was evident between miR-205 methylation, for both regions, and miR-205 expression levels in clinical prostatectomy biopsy specimens. Moreover, in PC3 cells, miR-205 expression was subsequently elevated by treatment with the demethylating agents including 5-aza-2 deoxycytidine and knockdown of DNMT1 and EZH2, suggesting its expression is regulated by methylation. miR-205 promoter and locus methylation status, following treatment with 5-aza-2 deoxycytidine in PC3 cells, showed no change in methylation levels in either region. Finally, in vitro over-expression of miR-205 in PC3 cells inhibited growth and clonogenic potential, as well as inducing apoptosis.

Conclusions: Preliminary findings to date provide evidence that miR-205 is abnormally expressed in PCa and appears to have a tumour suppressor role in PCa. This study investigated the role of DNA methylation in regulating miR-205 expression. It is evident that DNA methylation of the regions analysed may not be responsible for regulating miR-205 expression; thus, other regions within the promoter and locus region which have not been identified may be more important. Furthermore, histone modifications may have a role, in conjunction with DNA methylation, in regulating miR-205 expression. Ongoing and future work entails investigating the biological and prognostic value of miR-205 in PCa.

Citation Format: Seodhna M. Lynch, Karla M. O'Neill, Michael M. McKenna, Colum P. Walsh, William Watson, William M. Gallagher, Declan J. McKenna. Investigation of miR-205 expression and its methylation status in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4418.