Icotinib antagonizes ABCG2-mediated multidrug resistance, but not the pemetrexed resistance mediated by thymidylate...

Area of Science:

• Oncology
• Pharmacology
• Molecular Biology

Background:

• Multidrug resistance (MDR) mediated by ABCG2 transporter is a significant challenge in Non-Small Cell Lung Cancer (NSCLC) treatment.
• Identifying agents that can overcome ABCG2-mediated resistance is crucial for improving patient outcomes.

Purpose of the Study:

• To investigate the interaction between Icotinib, an EGFR tyrosine kinase inhibitor, and the ABCG2 transporter in NSCLC.
• To evaluate the potential of Icotinib in reversing ABCG2-mediated MDR and its synergistic effects with other chemotherapeutics.

Main Methods:

• Assessed Icotinib's effect on ABCG2 ATPase activity and photolabeling to determine interaction at the drug-binding pocket.
• Utilized homology modeling to predict Icotinib's binding conformation within ABCG2.
• Evaluated the synergistic anticancer activity of Icotinib combined with topotecan and pemetrexed in NSCLC xenografts and cell lines.

Main Results:

• Icotinib antagonized ABCG2's drug efflux function, reversing ABCG2-mediated MDR in a concentration-dependent manner.
• Icotinib demonstrated interaction with the ABCG2 drug-binding pocket without altering AKT or ABCG2 expression levels.
• Combination of Icotinib and topotecan showed significant synergistic anticancer activity in NCI-H460/MX20 tumor xenografts.
• Icotinib's inhibition of ABCG2 was insufficient to overcome pemetrexed resistance due to co-upregulated thymidylate synthase (TS) and ABCG2.

Conclusions:

• Icotinib effectively reverses ABCG2-mediated MDR in NSCLC by directly interacting with the transporter.
• The study highlights the differential efficacy of Icotinib-based combinations, suggesting distinct strategies are needed to overcome resistance to topotecan versus pemetrexed.
• Co-upregulation of TS and ABCG2 contributes to pemetrexed resistance, presenting a novel therapeutic consideration in NSCLC.