MicroRNA-643 promotes proliferation and inhibits apoptosis of papillary thyroid carcinoma by down-regulating the cytochrome P450 family member 11B1

BACKGROUND: Thyroid cancer is the most common malignant tumor in endocrine system. Papillary thyroid carcinoma (PTC), accounting for 60–70% of all thyroid cancer cases, is the most common type of thyroid cancer. Nowadays, the treatments for PTC are limited and the prognosis is poor. Exploring the underlying mechanism of PTC development and finding evidence for molecular targeted therapy have always been urgent problems. The purpose of the current study is to investigate the clinical value of microRNA (miR)-643, and its related mechanism regulating PTC proliferation and apoptosis by regulating cytochrome P450 family member 11b1 (CYP11B1). METHODS: Forty-two confirmed human PTC tissue specimens, corresponding adjacent normal thyroid tissue specimens, and serum samples were collected from September 2018 to April 2019. The transfected cell lines were divided into four groups: control group, empty group, si-miR-643 group, and si-miR-643 + si-CYP11B1 group. Real-time quantitative PCR (qRT-PCR) was used to detect the relative expression of miR-643 and CYP11B1 mRNA. The expression of CYP11B1 protein was detected by Western blot (WB). Cell proliferation was detected by cell counting kit-8 (CCK-8) and colony formation assay. Cell apoptosis was detected by flow cytometry. The dual-luciferase reporter gene assay was used to verify the targeting relationship between miR-643 and CYP11B1. RESULTS: Compared to adjacent non-tumor tissues, miR-643 expression in PTC tissues was significantly up-regulated (P=0.019). Pearson correlation analysis showed that miR-643 level in serum was significantly correlated with that in PTC tissue (r(Pearson) =0.546, P<0.001). MiR-643 expressions in both PTC tissue and serum were significantly associated with tumor size and histological grading (P<0.05). Patients with larger diameter tumors or moderate-poorly differentiated tumors were more likely to have higher miR-643 expression levels in both PTC tissue and serum. CYP11B1 was indicated to be an important downstream molecule of miR-643 by the results of online bioinformatics prediction software Targetscan and the luciferase reporter gene assay. Compared with the control group and empty group, the apoptotic ability of cells in si-miR-643 group increased significantly (P<0.05), while cell proliferation in si-miR-643 group was inhibited significantly (P<0.05). Further research showed that small interference RNA (siRNA)-mediated miR-643 silencing induced a notable reduction of antigen KI67 (ki-67) expression and a dramatic elevation of CYP11B1, BCL2-associated X protein (Bax) and caspase-3 expressions in TPC-1 cells in comparison with that in the control group and empty group, while CYP11B1 knockdown markedly reversed the above phenomenon. CONCLUSIONS: MiR-643 can promote the proliferation of TPC-1 cells and inhibit its apoptosis through regulating CYP11B1.