miR-24 regulates CDKN1B/p27 expression in prostate cancer

BACKGROUND: MicroRNAs (miRNAs) are small, non-coding RNA molecules with an important role in cancer. In prostate cancer, several miRNAs are expressed abnormally suggesting they may be useful markers for diagnosis, prognosis, and potential therapeutic intervention in this disease. However, the contribution of individual miRNAs to the development and progression of this disease remains poorly understood. This study investigated the role of miR-24, which has not been extensively studied in relation to prostate cancer. METHODS: We used PCR to investigate the expression of miR-24 in a panel of prostate cancer cell-lines and in a series of clinical prostate biopsy specimens. The biological significance of miR-24 expression in prostate cancer cells was assessed by a series of in vitro bioassays and the effect on proposed targets p27 (CDKN1B) and p16 (CDK2NA) was investigated. RESULTS: We showed that miR-24 expression was significantly lower in prostate cancer cell lines compared to a normal prostate epithelial cell line. Decreased expression of miR-24 was also more frequently observed in both needle core and prostatectomy tumor tissue relative to matched normal tissue. Low miR-24 expression correlated with high PSA serum levels and other markers of increased prostate cancer progression. Importantly, over-expression of miR-24 inhibited cell cycle, proliferation, migration, and clonogenic potential of prostate cancer cells, as well as inducing apoptosis. p27 and p16 were confirmed as targets of miR-24 in prostate cancer cells and a significant inverse correlation between miR-24 and p27 was revealed in clinical prostatectomy specimens. CONCLUSIONS: These findings provide evidence that miR-24 has a tumor suppressor role in prostate cancer and also targets p27 and p16 in prostate cancer cells. We propose that it may be a useful progression biomarker or focus of therapeutic intervention for this disease.