ABSTRACT
Purpose:To evaluate the feasibility and study the mechanism of buthionine sulfoximine (B SO) as an effective sensitizer to overcome cisplatin resistance caused by overex pressing multidrug resistance associated protein(MRP).Methods:T he vector pcDNA3.1(-)-MRP, which included the complete cDNA of mrp, was transf ected into human lung cancer cell line SPC-A-1 and the positive clone(SPC-A- 1/MRP) was screened by G418,MRP expression comfirmed by Werstern blot and immuno histochemistry. The cell line SPC-A-1/MRP(-) was constructed by transfected p lasmid pcDNA3.1(-) as control. Comparing the sensitivities of SPC-A-1/MRP and control cells to anticancer drug- cisplatin(CDDP) with or without 1mg/mL BSO w as done by MTT assay. At the same time, the changes of glutathione detoxifcation system (glutathione,glutathione S-transferase , glutathione peroxidase) by RT -PCR and biochemistry methods under treated with CDDP and/or BSO were determine d.Results:SPC-A-1/MRP cells showed 2 fold resistance to CDDP as compared to the parent S PC-A-1/MRP(-) cell line and the cytotoxicity was markedly enhanced by 1mg/m B SO at low cisplatin concentration. When treated with CDDP , accompanied by a hig her transscript of MRP, it was found there was greater GSH content and lower tot al GSH-Px activity in the resistant SPC-A-1/MRP cells. Combined with BSO, the GSH content decreased greatly ,the MRP mRNA was reduced and the transscript of GST and GSH-Px were increased although the activities of both GST and GSH-Px were all decreased.Conclusions:Cisplatin resistance can be caused by over-expression MRP, glutation detoxifcat ion system played an important role in MRP-mediated resistance which can be ove rcomed by BSO.