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Many studies reported that antioxidants and dietary supplements increase tumour progress and reduce survival. Hyperthermia is an adjuvant treatment to sensitise cancer cells for radio-or chemotherapy. The current study was carried out to determine the effects of berberine chloride and hyperthermia on bone cancer cells. MG-63 osteosarcoma cells were treated with hyperthermia (39, 43 and 45°C, respectively) for 1 h. Then, the cells were treated with a low toxic dose of berberine chloride (80 µg/mL). After that, all treated groups were recovered at 37°C for 24 h. Finally, all groups were treated with hyperthermia (39, 43 and 45°C) for the second time (1 h) and were recovered for 3 h at 37°C. Cells exposed to hyperthermia without treatment of berberine chloride were used as hyperthermia control. Cells treated with 80 µg/mL of berberine at 37°C served as berberine control and cells incubated at 37°C were used as an untreated control. All treated groups showed significant apoptosis compared to the control group (p<0.05) except 39°C. On the other hand, mild hyperthermia treatment (39°C) resulted in a reduction of berberine-induced apoptosis (p<0.001). Severe and moderate hyperthermia did not show a significant increase in the rate of apoptosis compared to berberine treated cells. Mild hyperthermia treatment can effectively reduce berberine cytotoxicity and implying negative effects on cancer therapy.

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BACKGROUND: Hyperthermia is used as an adjuvant treatment to sensitize cancer cells to subsequent radiotheraphy or chemotherapy. The aim of this study was to study the effect of severe hyperthermia on osteosarcoma cells and its underlying causes.METHODS: Short-term (1 h) severe hyperthermia (45°C) was applied to osteoblast-like osteosarcoma cells (MG-63) and the heat shock response and cell death mechanisms were investigated after recovery at 37°C for 72 h.RESULTS: Cell viability was significantly reduced (p<0.05) and apoptosis was significantly induced by severe hyperthermia in MG-63 cells (p<0.001). Caspase 3/7, 4 and 12 activities were significantly increased after 72 h of recovery at 37°C, indicating that severe hyperthermia induced endoplasmic reticulum (ER) stress and apoptosis (p<0.05). Heat shock protein 90 alpha (Hsp90α) was significantly down regulated at the protein level after recovery, in association with apoptosis induction (p<0.01). Additionally, caspase 8 and 9 were activated, possibly as a result of ER stress or other stimuli while, B-cell leukemia 2 family protein (BCL-2) mRNA was down regulated (p<0.01).CONCLUSION: Severe hyperthermia could cause prolonged cell cytotoxicity by inducing apoptosis in association with inhibition of Hsp90α. This indicates the therapeutic potential of severe hyperthermia for the treatment of osteosarcoma.KEYWORDS: hyperthermia, apoptosis, endoplasmic reticulum, stress, heat shock proteins, osteosarcoma