Intrinsic overexpression of two different mechanisms of resistance to chemotherapy (P-glycoprotein and GST-pi) in human endometrial carcinoma.

Endometrial carcinoma is considered a tumor which does not respond well to chemotherapeutic treatment. Among the various mechanisms of resistance to chemotherapy which are under investigation, two of them (multidrug resistance, mediated by P-glycoprotein, and glutathione-S-transferase-pi [GST-pi] overexpression) are of great interest for gynecologic oncologists, because they involve several drugs commonly used in practice, among which Adriamycin and cisplatin are probably the most important ones. We have studied 23 human endometrial carcinomas of different histological varieties and 3 normal endometrial samples for the overexpression of both P-glycoprotein and GST-pi by means of immunohistochemistry. Both resistance markers were detectable in all tumor samples, and in normal endometrial tissue as well. The concomitant intrinsic overexpression of these two resistance mechanisms may in part explain why these tumors tend to be extremely resistant to chemotherapy.