CM082 Enhanced the Sensitivity of Chemotherapeutic Agents by Inhibiting the Function of ABCG2

Background: Overexpression of ATP-binding cassette (ABC) transporters was one of the important mechanisms of multidrug resistance (MDR). Some tyrosine kinase inhibitors (TKIs) such as CM082 might be the potential ABC-transporter inhibitors due to their similar ATP binding sites to tyrosine kinase, which could potentially reverse MDR. Methods: MTT assay and H460/MX20 cell xenograft model were established to evaluate the reversal MDR efficacy in vitro and in vivo. Drug efflux assay, intracellular drug accumulation and cellular localization assay were measured by flow cytometry. Competition of CM082 for photolabeling of ABCG2 with [125I]- IAAP was performed to ascertain the binding sites. Vanadate-sensitive ATPase activity of ABCG2 was measured to evaluate the effect of CM082 on ATP hydrolysis. Western blotting and RT-PCR were employed to study the effect of CM082 on protein and mRNA expression levels. Findings: CM082 could enhance the efficacy of chemotherapeutic substrate in ABCG2-overexpressing MDR cancer cells both in vitro and in vivo. CM082 significantly increased ABCG2 substrates intracellular accumulation by inhibiting the efflux of ABCG2, stimulated ABCG2 ATPase activity and competed with [125I]-IAAP photolabeling of ABCG2. CM082 did neither alter ABCG2 expression at protein and mRNA levels nor inhibit ErbB downstream signaling of AKT and ERK. Interpretation: This study indicates that CM082 could enhanced the sensitivity of chemotherapeutic agents in vitro and in vivo by inhibiting the activity of ABCG2, suggests CM082 might be potential ABC modulator to overcome MDR. Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Declaration of Interest: There are no conflicts of interest to disclose. Ethical Approval: The protocol obtained approval from the Institutional Animal Care and Use Committee of Sun Yat-Sen University Cancer Center.