DETECTION OF P-GLYCOPROTEIN IN SOLID TUMORS BY FLOW-CYTOMETRY

P-glycoprotein (P-gp) detection by FCM (flow cytometry) was correlated with P-gp defection by immunohistochemical staining or Western blotti ng in K562 cell lines variably resistant to doxorubicin (DOX). A stron g corrlation was noted between the flow cytometric data and the degree of resistance assessed by thymidine incorporation assay (TIA). Of the human carcinomas rested, 37.5% were P-gp positive by flow cytometry. The flow cytometry data correlated strongly with the immunohistochemic al staining (p<0.001). Thirteen of the 15 P-gp positive tumors were re sistant to DOX and vincristine (VCR) on TIA. Thus, P-gp detection by F CM correlates strongly with tumor sensitivity to DOX and VCR (p<0.001) .