Abstract: Objective To investigate the effects of miR-135b-3p on migration, invasion and radio sensitivity of thyroid cancer cells and its possible regulatory mechanisms. Methods Normal thyroid cells Nthy-ori 3-1, thyroid cancer cells K1 and TPC-1 were cultured. The expression of miR-135b-3p was detected by RT-qPCR. The expression of XAF1 protein was detected by Western blot. Anti-miR-135b-3p was transfected to TPC-1 cells to inhibit the expression of miR-135b-3p. Transwell, Western blot and cloning formation assay were used to detect the effect of inhibition of miR-135b-3p expression on migration and invasion of TPC-1 cells, and the expression of E-cadherin and MMP-2 protein and radio sensitivity, respectively. The dual luciferase reporter gene assay verified the targeted regulatory relationship between miR-135b-3p and XAF1. Results Compared with Nthy-ori 3-1 cells, the expression of miR-135b-3p was significantly increased in K1 and TPC-1 cells (P＜0.05), and the expression of XAF1 protein was significantly decreased (P＜0.05). Inhibition of miR-135b-3p expression could inhibit the migration and invasion of TPC-1 cells (P＜0.05), promote the expression of E-cadherin protein in TPC-1 cells (P＜0.05), inhibit the expression of MMP-2 protein (P＜0.05), and enhance the radio sensitivity of TPC-1 cells (P＜0.05). miR-135b-3p targeted negative regulation of XAF1 expression. Inhibition of XAF1 expression partially reduced the effect of inhibiting miR-135b-3p expression on TPC-1 cell migration and invasion as well as the enhanced radio sensitivity. Conclusions R-135b-3p promotes the migration and invasion of thyroid cancer cells by down-regulating the expression of XAF1, and reduces its radio sensitization. It is a potential therapeutic target for thyroid cancer.

Key words: thyroid cancer, miR-135b-3p, XAF1, migration, radio sensitization