Correlation of expression levels of P-glycoprotein with resistance to adriamycin in a renal adenocarcinoma cell line.

We have demonstrated that low-level expression of P-glycoprotein (PGP), detectable by reverse transcriptase polymerase chain reaction (RT-PCR) assay and flow cytometric assay, is an important factor in multidrug resistance (MDR) in ACHN cancer cells. In this study, we established a subline highly resistant to adriamycin (ACHN/ADM) from ACHN cells, and determined the correlation between PGP levels and MDR levels using ACHN/ADM cells and their parent ACHN cells. The ACHN/ADM cells showed overexpression of PGP, and sensitivity to antitumor agents was lower than that found in ACHN cells. Intracellular accumulation of ADM in ACHN/ADM cells was approximately half the amount of its accumulation in ACHN cells. Sensitivity to ADM in ACHN/ADM cells was enhanced by chemosensitizers with an increase in intracellular ADM accumulation. These results indicate that PGP levels correlate with MDR levels and suggest that chemotherapy using chemosensitizers might be effective in the treatment of renal cancers with overexpression of PGP.