[The mechanism of aspirin combined with metformin induced apoptosis of thyroid cancer TPC-1 cells].

To explore the effect of aspirin combined with metformin on the apoptosis of thyroid cancer TPC-1 cells and its mechanism. The proliferation and apoptosis of TPC-1 cells treated with different concentrations of aspirin and metformin were detected using cell count kit-8 (CCK-8) assay and flow cytometry, respectively. Western blot was used to detect the expressions of microtubule-associated protein light chain 3 (LC3), p62 and cysteinyl aspartate specific proteinase 3 (caspase-3) after treatment with aspirin, metformin and 3-Methyladenine (3-MA). The relative cell viability of TPC-1 cells treated with 0.5, 1.0, 2.0, 4.0 mmol/L aspirin for 24 and 48 hours were (85.6±9.1)%, (79.9±8.6)%, (57.0±5.3)%, (55.7±5.4)%; (76.7±2.8)%, (75.4±6.1)%, (46.1±4.1)%, (36.3±3.2)%, respectively. The value of half maximal inhibitory concentration (IC(50)) for 24 and 48 hours were 4.297 mmol/L, 2.133 mmol/L, respectively. The apoptotic rate in the 1 mmol/L aspirin treatment group and negative control group were (29.2±8.5)%, (4.2±2.9)%, respectively (<0.05). Moreover, treatment with metformin increased the protein expression of LC3Ⅱ/Ⅰ ratio, and decreased the expression of p62, while treatment with aspirin decreased the expression of LC3Ⅱ/Ⅰ ratio and increased the expression of p62. The relative cell viability of TPC-1 cells treated with metformin, 3-MA, an autophagy inhibitor, and 3-MA combined with metformin were (73.2±9.2)%, (95.8±3.3)%, (59.9±9.2)%, respectively. The apoptotic rates in these groups were (35.5±1.5)%, (12.3±1.4)%, (49.9±5.4)%, respectively. Compared with the metformin group, the relative cell viability in metformin combined with 3-MA group was significantly lower while the apoptotic rate was higher (<0.05), which indicated that treatment with 3-MA enhanced the metformin-induced apoptosis of TPC-1 cells. The relative cell viability of TPC-1 cells in metformin group, aspirin group, metformin combined with aspirin group were (87.3±11.8)%, (85.7±9.6)%, (72.4±8.8)%, respectively. The apoptotic rates in these groups were (29.7±4.0)%, (30.5±6.5)%, (52.5±4.6)%, respectively. Compared with the metformin or aspirin group, the relative cell viability in metformin combined with aspirin group was significantly lower, while the apoptotic rate was higher (<0.05), which indicated that aspirin enhanced the metformin-induced apoptosis of TPC-1 cells. Our findings indicate that metformin-mediated autophagy plays a protective role in metformin-induced apoptosis and proliferation inhibition. Aspirin enhances the metformin-induced apoptosis of thyroid cancer TPC-1 cells through inhibition of autophagy.