PO-345 Identification of AR-modulatory micrornas for prostate cancer progression and therapy

Introduction Prostate cancer (PCa) is the most common type of cancer affecting the male population. It is an androgen dependent malignancy that initially responds well to androgen ablation therapy. However, despite hormonal treatment, castrate resistant prostate cancer eventually emerges. MicroRNAs (miRs), a class of small non-coding RNAs, modulate gene silencing through inhibition of translation and mRNA degradation. MiRs and/or miR inhibitors that reduce AR activity represent a promising therapeutic strategy, therefore a high-throughput miR inhibitor screen was performed in PCa cell lines, expressing a luciferase-based AR reporter. We sought to validate and characterise AR-modulatory miRs and identify their targets in PCa cell lines. Material and methods Prostate cancer cell lines that stably expressed an AR reporter element were transfected with specific miR inhibitors and mimics. The effect of miR modulation on potential alteration of AR activity was investigated (through a luciferase assay), as well as the potential impact on cell growth by an SRB assay and on apoptosis, using a caspase 3/7 assay. Real-time qPCR and western blot assays were performed, to check the potential effect of miR manipulation on mRNA and protein levels of AR and miR specific target genes. Results and discussions MiR-1271–5 p inhibitor significantly reduced AR activity and increased apoptosis in a castrate resistant cell line and the opposite effect was seen with the use of the mimic. MiR-1271–5 p inhibitor significantly reduced growth of the AR dependent cell line and miR-1271–5 p mimic had the opposite effect. AR mRNA levels were altered, as well as levels of miR specific target genes, after manipulation of PCa cell lines with miR-1271–5 p inhibitor and mimic. Similar effects were noticed with the use of an antisense oligonucleotide for miR-27a-3p, which has been previously demonstrated to be an AR regulated oncomiR in PCa. Conclusion From a panel of different miRs, we have demonstrated the androgenic potential and oncogenic capacity of miR-1271–5 p in PCa. Also, the use of antisense oligonucleotides for inhibition of miR-27a-3p has therapeutic potential for castrate resistant disease. Predicted targets of both miR-27a-3p and miR-1271–5 p include genes with roles in growth arrest, apoptosis and DNA repair. Further studies are ongoing, to elucidate the molecular and biological role of these miRs in PCa, providing a better understanding of disease development, as well as a foundation for advances in diagnosis and in treatment.