Differential expression of multidrug resistance‑related proteins in adriamycin‑resistant (pumc‑91/ADM) and parental (pumc‑91) human bladder cancer cell lines.

Abstract

Multidrug resistance (MDR) is the major obstacle to bladder cancer chemotherapy. Several mechanisms have been implicated in the development of MDR, including extrusion of the drug by cell membrane pumps, associated with P‑glycoprotein (P‑gp) and multidrug resistance‑associated protein (MRP); increased DNA damage repair, associated with topoisomeraseII (TopoII); suppression of drug‑induced apoptosis, associated with p53; and regulation of cancer cell growth, associated with vascular endothelial growth factor (VEGF). In the present study, the expression levels of these five markers were detected in an adriamycin (ADM)‑resistant human bladder cancer cell line (pumc‑91/ADM) and its parental cell line (pumc‑91), in order to determine which marker is more important, or whether all of them participate in drug resistance. The expression levels of P‑gp, MRP, TopoII, VEGF and p53 were measured in the two cell lines by reverse transcription‑quantitative polymerase chain reaction, western blotting and immunohistochemistry. A significant increase in P‑gp, MRP and VEGF, and a decrease in TopoII mRNA expression were detected in the pumc‑91/ADM drug‑resistant cell line compared with the pumc‑91 cell line; however, no difference in p53 mRNA expression was detected between the cells. In pumc‑91/ADM cells, the protein expression levels of P‑gp and MRP were upregulated, whereas TopoII was significantly decreased. However, no marked differences in p53 or VEGF expression were detected between the two cell lines at the protein level. The cytoplasmic and cell membrane localization of P‑gp and MRP, the cytoplasmic localization of VEGF, and the nuclear localization of p53 and TopoII were confirmed in the two cell lines. The present study detected increased P‑gp and MRP, and reduced TopoII expression in pumc‑91/ADM cells compared with pumc‑91 cells; however, no difference was detected in p53 and VEGF expression between the cell lines. In conclusion, a significant upregulation of MRP and downregulation of TopoII were detected in the ADM‑resistant human bladder cancer cell line (pumc‑91/ADM) compared with in the parental cell line (pumc‑91).