Micro-ribonucleic acid 29b inhibits cell proliferation and invasion and enhances cell apoptosis and chemotherapy effects of cisplatin via targeting of DNMT3b and AKT3 in prostate cancer

Background: Micro-ribonucleic acids (miRNAs) are crucial regulators in malignant tumors. miRNA-29b (miR-29b) has been identified as a tumor suppressor in prostate cancer (PCa). However, very few studies have investigated the effects of miR-29b in PCa, especially the mechanism and its association with chemotherapy. Our study aimed to explore the role and mechanism of miR-29b in PCa. Materials and methods: The expression levels of miR-29b were detected in ten clinical PCa specimens and four different PCa cell lines through quantitative real-time polymerase chain reaction. After miR-29b mimics and inhibitors were successfully transfected into LNCaP, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was then used to investigate cell proliferation and cisplatin sensitivity of PCa cells. Cell cycle, cell apoptosis, and cell invasion were detected via flow cytometry, annexin V-fluorescein isothiocyanate labeling, and transwell assay, respectively. Based on bioinformatic methods, Western blot analysis, and dual-luciferase reporter assay, novel target genes of miR-29b were identified. Results: miR-29b was downregulated in PCa tissues compared with matched adjacent nontumor tissues. In the androgen-independent PCa cell line (LNCaP-AI), the expression of miR-29b was much lower than the androgen-dependent PCa cell line (LNCaP). Subsequent studies showed that forced expression of miR-29b inhibited cell proliferation and cell invasion and induced cell apoptosis in PCa. Upregulation of miR-29b also enhanced the chemosensitivity of PCa cells to cisplatin. Moreover, we identified DNMT3b and AKT3 as novel target genes of miR-29b in PCa. Conclusion: Taken together, the results showed that miR-29b plays a tumor-suppressive role in PCa. It inhibits cell biological behavior and enhances the chemotherapy effects of cisplatin through its involvement in epigenetic regulation and PI3K/AKT pathway.