Detection of Low‐level Expression of P‐Glycoprotein in ACHN Renal Adenocarcinoma Cells

A highly sensitive reverse transcriptase‐polymerase chain reaction (RT‐PCR) assay and a flow cytometric assay were used to examine ACHN cells for the expression of P‐glycoprotein. The expression of P‐glycoprotein was detected at the RNA and protein levels in ACHN cells by RT‐PCR and flow cytometry, respectively. However, it was below the limit of detection by immunoblotting. The intracellular accumulation of adriamycin in ACHN cells was enhanced by verapamil, cyclosporin A and medroxyprogesterone acetate. Therefore, this study has demonstrated that low‐level expression of P‐glycoprotein detectable only by RT‐PCR and flow cytometry plays a significant role in reducing the intracellular concentration of antitumor agents and thus contributes to the multidrug‐resistant phenotype of ACHN cells.