LncRNA GAS5 sponges miR-362-5p to promote sensitivity of thyroid cancer cells to 131 I by upregulating SMG1.

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This study aims to investigate the role of lncRNA growth arrest-specific transcript 5 (GAS5)/miR-362-5p/suppressor of morphogenesis in the genitalia 1 (SMG1) axis in 131 I-resistance in thyroid cancer (TC). GAS5, miR-362-5p, and SMG1 expression in TC tissues was assessed and the 131 I-resistant TC cells were established, which were treated with altered GAS5, miR-362-5p, and SMG1. The proliferation and apoptosis of 131 I-resistant TC cells were detected, and the expression of Akt/mTOR signaling pathway-related proteins was assessed. Binding relations between GAS5 and miR-362-5p, and miR-362-5p and SMG1 were confirmed. The role of GAS5 in 131 I-resistant TC cell growth in vivo was observed. GAS5 was downregulated and miR-362-5p was upregulated in TC tissues and 131 I-resistant cells. The 131 I-resistant TC cells had enhanced proliferation and repressed apoptosis, and the Akt/mTOR signaling pathway was activated. Overexpressed GAS5 strengthened 131 I sensitivity and suppressed TC cell growth, while upregulated miR-362-5p had an opposite effect. MiR-362-5p upregulation reversed the effect of GAS5, and SMG1 overexpression eliminated the impact of miR-362-5p upregulation on 131 I-resistant TC cells. GAS5 competitively binds to miR-362-5p and SMG1 is targeted by miR-362-5p. GAS5 sponges miR-362-5p to promote sensitivity of TC cells to 131 I by upregulating SMG1 and inactivating Akt/mTOR signaling pathway.