Abstract: Background and purpose: miR-19b-3p is highly expressed in malignant tumors such as gastric cancer and prostate cancer, which may be used as a potential biomarker for early diagnosis of tumor and evaluation of prognosis of patients. The microtubule-associated tumor suppressor gene 1 (MTUS1) may be miR-19b-3p target gene screened by using TargetScan target gene prediction software, and the 3’-untranslated region (3’-UTR) of MTUS1 may be the binding site of miR-19b-3p. This study aimed to investigate whether miR-19b-3p regulating the expression of MTUS1 and its effect on apoptosis of medullary thyroid cancer (MTC) cells. Methods: MTC-TT cells were divided into anti-miR-19b-3p group, anti-miR-NC group, pcDNA-MTUS1 group, pcDNA group, anti-miR-19b-3p+si-MTUS1 group, anti-miR-19b-3p+si-NC group, miR-19b-3p group and miR-NC group. Expression of miR-19b-3p and MTUS1 were detected by real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR) and Western blot. Double luciferase reporter gene assay was performed to confirm whether MTUS1 was the target gene of miR-19b-3p. The expressions of Bcl-2, Bax and cleaved caspase-3 in cells were detected by Western blot. Results: Expression of miR-19b-3p was significantly increased in MTC tissues and cell lines, while the expression level of MTUS1 was significantly decreased. Transfection of anti-miR-19b-3p or pcDNA-MTUS1 significantly promoted the expression of Bax and cleaved caspase-3, while inhibiting Bcl-2 expression. The dual luciferase reporter assay confirmed that MTUS1 was target gene of miR-19b-3p. Inhibition of MTUS1 expression reversed the effect of inhibition of miR-19b-3p expression on apoptosis of MTC-TT cells. Conclusion: Silencing miR-19b-3p can induce apoptosis of MTC TT cells by up-regulating MTUS1 expression.

Key words: miR-19b-3p, Microtubule-associated tumor suppressor gene 1, Medullary thyroid cancer, Apoptosis