Abstract 410: Tumor heterogeneity via AXL activation on primary resistance to EGFR tyrosine kinase inhibitors in EGFR mutated lung cancer

Abstract Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are the standard treatments for patients with advanced non-small cell lung cancer (NSCLC) harboring EGFR mutations. However, some patients show primary resistance to EGFR-TKIs at the first-line treatment setting. AXL, a member of the TAM family of receptor tyrosine kinase, was reported to be involved in primary resistance to EGFR-TKIs for EGFR mutated NSCLC patients. In the present study, we investigated spatial tumor heterogeneity using autopsy specimens from EGFR mutated NSCLC patients, showing primary resistance to erlotinib plus ramucirumab. qPCR analysis showed that the AXL mRNA expression levels differed in each metastatic site. In addition, the AXL expression levels were likely to negatively correlate with the efficacy of erlotinib plus ramucirumab therapy. The analysis of patient-derived cell lines, established from left pleural effusion before initiation of the treatment, showed that the combination of EGFR-TKIs and an AXL inhibitor remarkably inhibited cell viability compared with EGFR-TKI monotherapy or combination with ramucirumab. Our observations suggested that tumor AXL expression might play a critical role in progression of spatial tumor heterogeneity and primary resistance to EGFR-TKIs for EGFR mutated NSCLC patients. Citation Format: Tadaaki Yamada, Ryota Nakamura, Hiroyuki Fujii, Takeshi Yaoi, Kyoko Itoh, Shinsaku Tokuda, Koichi Takayama. Tumor heterogeneity via AXL activation on primary resistance to EGFR tyrosine kinase inhibitors in EGFR mutated lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 410.