THE ROLE OF P-GLYCOPROTEIN, GLUTATHIONE-S-TRANSFERASE-PI, THYMIDYLATESYNTHASE AND METALLOTHIONEIN IN THE EXPRESSION OF DIFFERENTIAL SENSITIVITIES TO ANTITUMOR AGENTS IN HUMAN TUMOR XENOGRAFTS

Expression of P-glycoprotein (P-gp), glutathione S-transferase-pi (GST -pi), thymidylate synthase (TS) and metallothionein (MT) was studied i n a series of different human tumors growing in nude mice and expressi ng a range of in vivo sensitivities to certain antitumor agents. Quant itative relationships between resistance parameters and sensitivities to seven clinically used antitumor drugs in vivo, as judged by specifi c growth delay, were determined by Wilcoxon test. A positive relations hip was identified between expression of GST-pi and TS and sensitiviti es to cyclophosphamide, doxorubicin, and 5-fluorouracil. No relationsh ip was noted between MT expression and P-gp expression and any of thes e drug sensitivities in this series of tumors.