MicroRNA-17-5p Enhances Radiosensitivity in Prostatic Cancer by Targeting MeCP2

Background: Several studies have shown that microRNAs (miRNAs), such as miR-17-5p, play critical roles in tumor cell ra-diosensitivity. However, its mechanism in radiosensitivity regulation in prostate cancer (PCa) is still unclear.Methods: PC3 cell lines were irradiated to screen out radiation-resistant PC3-R (Radioresistant PC3) cells. After irradiation at different doses, the expression levels of miR-17-5p and methyl CpG-binding protein 2 (MeCP2) in PC3 and PC3-R cells were detected by quantitative RT-PCR and Western blot analyses. MiR-17-5p mimic and MeCP2 plasmids and their negative control plasmids were constructed, and introduced into cells by liposome transfection. The colony survival and apoptosis rates of PC3-R cells were determined clonogenic survival assay and DAPI (4,6-diamino-2-phenyl indole) staining. Annexin V-PI (annexin V and Propidium lodide) staining and Western blot analysis were used to detect PC3-R cell apoptosis and expression of the apoptosis-related proteins Bax, Bcl-2 (B-cell CLL/lymphoma 2) and cleaved caspase3. Wounding healing and Matrigel transwell assays were performed the metastasis and invasion and EMT (Epithelial-Mesenchymal Transition) bio-marker protein expression was evaluated by Western blot analysis.Results: First, we assessed the radiation-resistant in PC3-R (Radioresistant PC3) cells from PC3 cell lines at different radiation doses. It was observed that miR-17-5p level was reduced and Methyl-CpG-binding protein 2 (MeCP2) level was enhanced in PC3-R cells. Then, it was identified that miR-17-5p enhance radiation resistance of PCa by targeting the 3 ' UTR (3 '-Untranslated region) of MeCP2 and down-regulating MeCP2 level. Moreover, the clonogenic survival assay and DAPI (4,6-diamino-2-phenyl indole) staining suggested that over-expressed miR-17-5p impaired cell colony survival and promoted apoptosis of PC3-R cells. The annexin V-PI (annexin V and Propidium lodide) staining and Western blot assays verified that over-expressed miR-17-5p enhanced Bax, cleaved-caspase 3 level and restrained Bcl-2 (B-cell CLL/lymphoma 2) level. Over-expressed miR-17-5p reduced cell migration, invasion, and EMT (Epithelial-Mesenchymal Transition). Finally, MeCP2 counteracted the effects and functions of miR-17-5p overexpression.Conclusions: These findigns suggest that miR-17-5p has a regulatory effect on MeCP2, enhancing the radio-resistance of PCa cells by targeting MeCP2. Thus, miR-17-5p is implicated as a potential regulator of radiation resistance in PCa cells.