Human renal UOK130 tumor cells: a drug resistant cell line with highly selective over-expression of glutathione S-transferase-pi isozyme.

Drug resistance remains one of the primary causes of suboptimal outcomes in cancer chemotherapy. This study reports the development of a drug resistant cell line with over-expression of glutathione S-transferase (GST). The resistant tumor cell model was established by continuous exposure of UOK130, a human renal tumor cell line, to escalating concentrations of cisplatin. By immunoblotting the cisplatin-resistant cells (UOK(CR)) were found to express an elevated level of GST-pi isozyme. Neither alpha nor mu isozyme was detected by the corresponding polyclonal antibodies. A significant increase in cellular glutathione (GSH) was also observed in UOK(CR) cells comparative to the parental cells. In addition, the continuous exposure to cisplatin resulted in decreased cell susceptibility not only to cisplatin (resistant factor: 5.7) but also to melphalan (resistant factor: 2.9) and chlorambucil (resistant factor: 2.3). A transgenic cell line was developed by transfecting of UOK130 cells with GST-pi cDNA. The transfection of the GST-pi virus into UOK130 cell apparently increased its intracellular GST-pi activity. The resistance of the transfectants to cisplatin was consistently increased, compared with that of mock transfectants. A haloenol lactone (HEL) derivative known as a selective inhibitor of GST-pi was applied to evaluate the suitableness of the cell model for GST-pi-mediated drug resistance studies. The inhibitor was found to potentiate the cytoxicity of cisplatin to both UOK130 and UOK(CR) cell lines and to reverse their resistance to cisplatin. In conclusion, we developed a multiple drug resistant tumor cell line with selective over-expression of GST-pi. The cell model provides a unique tool for mechanistic studies of drug resistance mediated by over-expression of GST-pi.