Abstract: Objective The Objective of this study was to investigate the inhibitory effect of ¹³¹I combined with angiogenesis inhibitor apatinib on refractory thyroid cancer cells and its mechanism.Methods The refractory thyroid cancer cells were divided into the control group,¹³¹I group,apatinib group,and ¹³¹I combined with apatinib group(combined group).After treatment for 24 and 48 h,the proliferation of thyroid cancer cells was determined by thiazolyl blue(MTT)assay.The expression of Caspase-3 and VEGF proteins was determined by immunofluorescence and Western blot.Results The proliferative rate of refractory thyroid cancer cells in the combined group was significantly lower than that in the other groups,and the difference was statistically significant(P＜0.01).The expression of Caspase-3 protein in the combined group was significantly higher than that in the other groups(P＜0.01),and the expression of VEGF protein in the combined group was significantly lower than that in the other groups(P＜0.01).Conclusion ¹³¹I combined with apatinib has synergistic effect on refractory thyroid cancer cells.This combination can up-regulate the pro-apoptotic protein Caspase-3 and down-regulate the expression of VEGF protein to inhibit the proliferation of refractory thyroid cancer cells.Thus,this will provide a better strategy for clinical treatment of refractory thyroid cancer.

Key words: ¹³¹I, Apatinib, Radioactive iodine-refractory differentiated thyroid cancer cells, Caspase-3, VEGF