Involvement of Akt in synergistic effects of hermochemotherapy on human small cell lung cancer H446 cell apoptosis

Abstract

BACKGROUND AND OBJECTIVE: Akt pathway plays an important role in cell growth and apoptosis. This study was to characterize the role of Akt in the synergistic effects of thermo-chemotherapy on lung cancer cell growth and its underlying mechanisms. METHODS: H446 cells were subjected to different thermo-chemotherapy schemes: 43°C + paclitaxel (120 μg/L) (thermo-chemotherapy group), 43°C + paclitaxel (120 μg/L) + Wortmannin (1 μmol/L, PI3K/Akt pathway inhibitor) (Wortmannin group), 43°C + paclitaxel (120 μg/L) + N-acety-L-cysteine (NAC) (30 μmol/L, reactive oxygen species, ROS inhibitor) (NAC group), and paclitaxel (120 μg/L) group. The cells without any treatment were used as the control. MTT assay was conducted to measure the cell proliferation rate. Cell apoptosis was analyzed by flow cytometry (FCM). ROS was detected with fluorescence. Phosphorylation of Akt and the expressions of Caspase-3 were determined by Western blot. RESULTS: The cell proliferation rate was significantly lower in the thermo-chemotherapy group than in the control and the chemotherapy groups ((59.83 ± 3.36)% vs. (100.00 ± 0.00)% and (69.16 ± 2.95)%, P < 0.05). The rate of cell apoptosis was the highest in the thermo-chemotherapy group (27.59 ± 5.47)% (P < 0.05). The ROS expression level was higher in the cells of thermo-chemotherapy group (102.14 ± 18.34) than in the other groups (P < 0.05), which could be inhibited by NAC(28.01 ± 1.19), but not by the PI3K inhibitor Wortmannin (99.87 ± 8.35). Phosphorylation of Akt significantly decreased in the thermo-chemotherapy group (0.69±0.03) (P < 0.05), which could be blocked by Wortmannin (0.00 ± 0.00), but increased by NAC (1.05 ± 0.29) (P < 0.05). The expression level of Caspase-3 was higher in the thermo-chemotherapy group (1.07 ± 0.08) than in other groups (P < 0.05). CONCLUSION: Thermo-chemotherapy has a stronger inhibitory effect than chemotherapy alone in lung tumor cell growth, probably through induction of ROS production and subsequent inhibition of Akt pathway activation and Caspase pathway-induced cancer cell apoptosis.