Involvement of ROS in the inhibitory effect of thermotherapy combined with chemotherapy on A549 human lung adenocarcinoma cell growth through the Akt pathway.

Mechanisms of synergistic effect of thermotherapy and chemotherapy on human lung adenocarcinoma cell growth are unclear. The purpose of this study was to investigate these effects and explore the function of ROS, Akt and caspase-3 in relation to these. A549 cells were subjected to different thermochemotherapy treatments: 43˚C heat+50 µg/l paclitaxel (thermochemotherapy group), 43˚C heat+50 µg/l paclitaxel+1 µmol/l wortmannin (wortmannin group), 43˚C heat+50 µg/l paclitaxel+30 µmol/l NAC (NAC group) and 50 µg/l paclitaxel (chemotherapy group). The cells without any treatment were regarded as controls. Cell proliferation rates were measured with MTT assay and intracellular ROS levels were detected with fluorescence labeling technologies. Phosphorylation of Akt and caspase-3 expression were determined by western blotting and the cell apoptosis rates were examined by flow cytometry. Tests in vivo were carried out at the same time. It was found that the cell proliferation rates of the thermochemotherapy group were significantly lower compared to those of the controls or the chemotherapy group (P<0.05). The intracellular ROS levels of the thermochemotherapy group were elevated significantly compared with those of other groups, and these changes could be reversed using the ROS inhibitor NAC but not a PI3K inhibitor (wortmannin). Phosphorylation of Akt was significantly decreased in the thermochemotherapy group (P<0.05), which could be blocked by wortmannin, but increased by NAC (P<0.05). The caspase-3 expression levels and cell apoptosis rates of the thermochemotherapy group were higher compared to those of the other groups (P<0.05). All results have been confirmed by in vivo tests. Thus, the combination of thermotherapy with chemotherapy showed a stronger inhibitory effect on A549 cell growth compared to chemotherapy alone, which may be able to cause additional cell apoptosis through inhibition of Akt phosphorylation and activation of caspases by increased intracellular ROS production.