Effect of hyperthermia on the apoptosis and proliferation of CaSki cells

Hyperthermia is a promising treatment for human cervical cancer. However, little is known about whether and under what conditions heat treatment exerts tumor inhibition effects on cervical cancer, and the molecular mechanisms behind these cellular responses have yet to be elucidated. We employed the human cervical cancer cell line CaSki as a cellular model and examined the effect of cell apoptosis and proliferation under gradient thermal conditions (43, 45 and 47˚C for 40 min). Heat treatment was found to induce CaSki cell apoptosis and necrosis. Cell cycle analysis showed that cells were arrested in S phase upon the application of hyperthermia, and MTT analysis revealed that cell viability was also reduced. Of the thermal conditions, 45˚C exhibited the best induction of apoptosis, while 47˚C induced direct fierce necrosis. This was further demonstrated by examining the expression level of several key apoptosis-related genes: caspase-3, Smac and Survivin. During apoptosis, caspase-3 and Smac levels were up-regulated, whereas anti-apoptotic Survivin was down-regulated, enhancing programmed cell death. Our results reveal that heating at ≥45˚C induced cell apoptosis and necrosis, and inhibited cell proliferation at both the cellular and molecular levels. These findings support the use of hyperthermia in a clinical setting for the treatment of human cervical cancer.