[Detection of P-glycoprotein and its clinical significance]

There is considerable variation in the assays used to evaluate the expression of mdr1 in various human malignancies. Current methodology includes reverse transcriptase polymerase chain reaction (RT-PCR) for assay of mdr1 mRNA, and immunohistochemistry or flow cytometry for detection of the multidrug transporter, P-glycoprotein(P-gp). Normal tissues, such as gastrointestinal mucosa, biliary tract and kidney, express high levels of P-gp, which suggests physiologic functions for this transporter. The some evidence suggests that mdr1 expression is a prognostic factor for response to chemotherapy, as well as for subsequent survival in various kind of tumors. We have developed a novel method using flow cytometry for detection of P-gp in gastric carcinomas. A strong correlation was noted between the flow cytometric data and the degree of drug resistance assessed by thymidine incorporation assay (TIA). We believe that this technique may have a significant potential to be utilized in prediction of P-gp related drug resistance in clinical cancer chemotherapy.