Hyperthermia exposure induces apoptosis and inhibits proliferation in HCT116 cells by upregulating miR-34a and causing transcriptional activation of p53

Hyperthermia, as an anticancer therapeutic strategy, presents notable advantages in conjunction with irradiation and/or chemotherapy in the treatment of cancer by promoting apoptosis and inhibiting proliferation. A number of studies have documented that hyperthermia inhibits cancer progression through transcriptional activation of p53, which promotes cell cycle arrest and apoptosis. However, the underlying molecular mechanisms of hyperthermia-regulated apoptosis and proliferation dependent on p53 remain largely unknown. To investigate the effects and molecular mechanism of hyperthermia on the apoptosis and proliferation of colorectal carcinoma (CRC) HCT116 cells, the present study assessed cell apoptosis and proliferation following exposure to hyperthermia (42 degrees C for 2-4 h). The results indicated that, compared with the control group at 0 h, hyperthermia exposure for 2 and 4 h induced the apoptosis of HCT116 cells (P<0.05), inhibited cell proliferation by causing cell cycle arrest at G1/G0 phase (P<0.05), and significantly increased microRNA (miR) -34a expression (P<0.05), but not miR-34b, miR-34c, miR-215 and miR-504 expression. The transcriptional activity of p53 on its consensus sequence and downstream target genes, namely p21, B cell lymphoma 2-associated X protein, mouse double minute 2 homolog, p53 upregulated modulator of apoptosis and growth arrest and DNA-damage-inducible 45a, was subsequently detected. The data indicated significantly higher transcriptional activity of p53 following hyperthermia exposure for 2 and 4 h (P<0.05), and these observations were similar to the effects of transfection with miR-34a mimics in HCT116 cells. Furthermore, transfection with miR-34a antagomiR supressed hyperthermia-induced apoptosis and promoted cell cycle progression following hyperthermia exposure when compared with transfection controls (P<0.05). Collectively, these findings indicate that miR-34a may serve an important role in hyperthermia-regulated apoptosis and proliferation in HCT116 cells by influencing the transcriptional activity of p53.