Thermotherapy enhances oxaliplatin-induced cytotoxicity in human colon carcinoma cells

Abstract

To observe the synergistic effects of hyperthermia in oxaliplatin-induced cytotoxicity in human colon adenocarcinoma Lovo cells. The human colon adenocarcinoma cell line Lovo was obtained from Sun Yat-Sen University. Cells were sealed with parafilm and placed in a circulating water bath, and was maintained within 0.01 °C of the desired temperature (37 °C, 39 °C, 41 °C, 43 °C and 45 °C). Thermal therapy was given alone to the negative control group while oxaliplatin was administered to the treatment group at doses of 12.5 μg/mL and 50 μg/mL. Identification of morphological changes, 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, flow cytometry and Western blotting were used to investigate the effect of thermochemotherapy on human colon adenocarcinoma Lovo cells, including changes in the signal pathway related to apoptosis. A temperature-dependent inhibition of cell growth was observed after oxaliplatin exposure, while a synergistic interaction was detected preferentially with sequential combination. Thermochemotherapy changed the morphology of Lovo cells, increased the inhibition rate of the Lovo cells (P < 0.05) and enhanced cellular population in the G₀/G₁ phase (16.7% ± 4.8 % in phase S plus 3.7% ± 2.4 % in phase G₂/M, P < 0.05). Thermochemotherapy increased apoptosis through upregulating p53, Bax and downregulating Bcl-2. Protein levels were elevated in p53, Bax/Bcl-2 in thermochemotherapy group as compared with the control group (P < 0.05). Thermochemotherapy may play an important role in apoptosis via the activation of p53, Bax and the repression of Bcl-2 in Lovo cells.