Abstract LB453: Distinct mechanism of CXCR7 activation in EGFR-mutated NSCLC by chemokines

Abstract

Abstract Erlotinib and gefitinib, EGFR TKIs, have markedly improved outcomes for NSCLC patients with EGFR mutations. However, resistance eventually develops, with the T790M mutation evident in over 50% of resistant tumors. Other resistance pathways include MET amplification, SCLC transformation, and EMT. Osimertinib, a third-generation EGFR TKI, targets the T790M mutation and is approved as a first-line treatment, reducing the incidence of T790M-related resistance. Nonetheless, non-T790M resistance mechanisms such as mesenchymal transformation are on the rise. The molecular targets or exact mechanisms of EGFR TKI resistance with mesenchymal phenotypes remain elusive. We have discovered that ERK reactivation, commonly found in EGFR TKI-resistant cells with a mesenchymal phenotype, is due to activation of an atypical GPCR, CXC chemokine receptor type 7 (CXCR7). CXCR7 is overexpressed in a cell line, an EGFR TKI-resistant tumor model, and in samples from patients that progressed on EGFR TKIs. Currently, there are no effective CXCR7 inhibitors to evaluate in NSCLC; the mechanisms and ligands for CXCR7 are not fully understood. To evaluate ligand-dependent activation of CXCR7, we generated HEK293 cells and EGFR-mutant NSCLC cells ectopically-expressing CXCR7 and stimulated the cells with CXCL12, a well-documented ligand for CXCR7. Exposures of HEK293 cells with CXCR7 to CXCL12 resulted in the internalization of CXCR7 followed by the activation of the MAPK pathway within 30 minutes of EGFR TKI treatment whereas MAPK activation in EGFR mutant NSCLC cells took 8 hours. MIF activation was also delayed in NSCLC compared to the HEK293 model, requiring the presence of an EGFR TKI. We discovered that CXCR7 co-immunoprecipitated with mutant EGFR in NSCLC cells while CXCR7 did not co-immunoprecipitate when EGFR was inhibited. Furthermore, we discovered additional chemokines including GDF15 that activate the CXCR7-MAPK axis and promote cell migration, a key characteristic of the mesenchymal phenotype in EGFR mutant cells. Taken together, we elucidated a unique mechanism of ligand-induced activation of CXCR7 and downstream MAPK pathway by canonical and putative ligands. This complex mechanism of CXCR7 activation in EGFR mutant NSCLC suggests that preventing the receptor-ligand binding may not be feasible in the context of overcoming EGFR TKI resistance. Citation Format: Laura C. Gunder, Ines Pulido, Jeffrey H. Becker, Malek G. Massad, Takeshi Shimamura. Distinct mechanism of CXCR7 activation in EGFR-mutated NSCLC by chemokines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB453.