GSK2606414 Sensitizes ABCG2-Overexpressing Multidrug-Resistant Colorectal Cancer Cells to Chemotherapeutic Drugs

Abstract

Colorectal cancer is a common malignant tumor. A major factor in the high mortality rate of colorectal cancer is the emergence of multidrug resistance (MDR). Overexpression of the ABCG2 gene in cancer cells directly leads to MDR. Finding new inhibitors of ABCG2 may be an effective way to overcome drug resistance. We found that the compound GSK2606414 enhanced the sensitivity of the ABCG2 substrate to the chemotherapeutic drugs mitoxantrone and doxorubicin in ABCG2-overexpressing multidrug-resistant colorectal cancer cells by increasing their intracellular accumulation without affecting the protein expression of ABCG2. Molecular docking experiments predicted that GSK2606414 could stably bind in the drug-binding pocket of ABCG2. In conclusion, GSK2606414 can sensitize ABCG2-overexpressed multidrug-resistant colorectal cancer cells to chemotherapy drugs and can be used as a potential inhibitor of ABCG2.

Keywords: ABCG2; GSK2606414; colorectal cancer; multidrug resistance.

Figure 1

GSK2606414 sensitizes ABCG2-overexpressing colorectal cancer cells to ABCG2-substrate chemotherapeutic drugs. (A) The chemical structure of GSK2606414 is shown. Cells were treated with the indicated agents for 72 h and examined by MTT assay. The representative cell survival curves are shown (B–D).* p < 0.05, and ** p < 0.01 vs. the corresponding group.

Figure 2

GSK2606414 augmented the intracellular levels of ABCG2 substrates in ABCG2-overexpressing colorectal cancer cells. Cells were incubated with 10 μM mitoxantrone, doxorubicin, or rhodamine 123 for another 2 h after pre-incubation with GSK2606414 or KU55933 for 1 h at 37 °C, photographed by confocal microscope and quantified by flow cytometer (A–C). ** p < 0.01 were compared with the corresponding group.

Figure 3

GSK2606414 does not affect the protein expression of ABCG2 in colorectal cancer cells and the binding model of GSK2606414 with ABCG2. (A) The ABCG2 expression level in S1-M1-80 vector cells treated with GSK2606414 3 μM for 24, 48, and 72 h was measured by Western blot assay. The optimal docked pose of GSK2606414 (blue sticks) within the drug-binding pocket of human ABCG2 is based on the three-dimensional crystal structure available from PDB (ID: 6vxi). ABCG2 conformation is presented as a ribbon diagram and colored according to secondary structure: red: helix, yellow: sheet, green: loop. GSK2606414 is shown as stick mode within a slit-like cavity of ABCG2, and the binding surface is exhibited as magenta (B). (C) Zoomed-in, the highlighted area shows that GSK2606414 interacts with the residues Gln398, Val-401, Leu-405, Ph-439, Val-546, Thr-542, and Ile-543 of ABCG2.