Expression of ABC Transporters in Multidrug Resistant Cancer Cell Lines

Abstract

ATP‐binding cassette (ABC) transporters are transmembrane proteins that act as drug efflux pumps and are associated with multi‐drug resistance (MDR) in cancers. Two specific proteins that belong to this protein superfamily are P‐glycoprotein (P‐gp) and breast cancer resistant protein (BCRP). These two proteins are known to pump chemotherapeutics out of cells, rendering treatments of some cancers less efficient. Certain cancer cell lines overexpress these proteins, leading to MDR. If a compound can be identified that inhibits these efflux pumps, then sensitivity to chemotherapeutics can be restored. The levels of expression of P‐gp and BCRP were quantitatively measured in four cancer cell lines that are used by us to screen for inhibitors of P‐gp or BCRP. The expression of P‐gp, BCRP, and MRP1 (multidrug resistance‐associated protein 1) was measured using quantitative One‐Step qPCR in a prostate cancer cell line, DU145, and compared to an MDR derivative line that overexpresses P‐gp, DU145 TXR. We found that DU145 TXR expresses P‐gp, BCRP, and MRP1 by about 14,000‐fold, 4‐fold, and 0.75‐fold, respectively, when compared to the parental cell line, DU145. A breast cancer cell line, MCF‐7, and its mitoxantrone‐resistant derivative, MCF‐7 M100, were also analyzed. The MCF‐7 M100 cell line was found to express BCRP, P‐gp, and MRP1 by about 600‐fold, 0.3‐fold, and 1.6‐fold, respectively, compared to the parental cell line, MCF‐7. The results were qualitatively confirmed at the protein level using Western Blot analyses. In other experiments, we demonstrated that P‐gp and BCRP inhibitors identified by us that reversed multidrug resistances in the MDR prostate and breast cancer cell lines, DU145 TXR and MCF‐7 M100, did not down‐regulate expression levels of P‐gp or BCRP, suggesting that reversal of MDR was accomplished by inhibiting transport processes and not transporter expression levels.Support or Funding InformationThis work is supported by NIH NIGMS [R15GM09477102] to John G. Wise, SMU University Research Council, the SMU Center for Drug Discovery, Design and Delivery, the Communities Foundation of Texas, and a private gift from Ms. Suzy Ruff of Dallas, Texas, as well as the Hamilton Undergraduate Research Scholars Program and the SMU Summer Research Assistantship and Undergraduate Research Assistantship Programs.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.