RESUMEN
Objective To study the effect of thermo-radiotherapy on multidrug resistance (MDR) and levels of intracellular adriamycin (ADM) in tongue squamous cell carcinoma cell line Tca 8113 and its MDR cell line Tca 8113/CBDEA. Methods Samples of the two cell lines were treated with thermo-radiotherapy (42℃ for 0.5 h and 2 Gy of radiation). Four and 24 hours later, the expression of the MDR relative proteins P-glycoprotein (P-gp),multidrug resistance associate protein 1 (MRP1) and glutathione s-tranferase-π (GST-π) were detected using immu-nohistochemistry. Intracellular ADM concentrations were measured using an HTS 7000 Plus bioassay reader. Re-sults No change in the expression of P-gp was observed in the Tca 8113/CBDEA and Tca 8113 cell lines after 4 or 24 hours. Expression of MRP1 was not significantly altered in the Tca 8113/CBDEA cell line, but there was a signifi-cant drop in the Tca 8113 cell line 24 hours post-thermo-radiotherapy. Expression of GST-π was not altered in either the Tca 8113/CBDEA or the Tca 8113 cell line at 4 hours post-thermo-radiotherapy, but there was a significant de-crease at 24 hours. At both 4 and 24 hours, drug tolerance had decreased and intracellular drug concentration had in-creased significantly in both cell lines. Conclusions Thermo-radiotherapy can enhance the effects of chemotherapy and suppress the expression of MDR factors induced by radiation. The combination of hyperthermia and radiotherapy does not induce MDR.