Abstract 3003: MET mediates entrectinib resistance in ROS1 gene fusion positiveNSCLC

ROS1 gene fusions are predominantly found in non-small cell lung cancer (NSCLC), and ROS1 gene fusion-positive (ROS1+) tumors comprise 1-2% of all diagnosed lung adenocarcinomas. Currently, there are two ROS1 tyrosine kinase inhibitors (TKIs) which are US FDA approved, crizotinib and entrectinib, both of which generate tumor response rates in excess of 70% and demonstrate prolonged disease control. However, acquired resistance to TKIs is inevitable, and has been reported in ROS1+ NSCLC tumors or cancer cell models by our group and others and include ROS1 kinase domain mutations (e.g., L1951R, S1986Y/F, F2004V, L2026M, and G2032R), activation of bypass signaling pathways (e.g., EGFR, RAS, or KIT), or phenotypic transformation (such as epithelial to mesenchymal transition). In order to better understand mechanisms of acquired TKI resistance in ROS1 NSCLC, our lab utilized primary, patient-derived cancer cell models harboring these rare oncogenic kinase rearrangements. Herein, using a patient-derived NSCLC cancer cell line (CUTO28) harboring a TPM3-ROS1 fusion, we derived an entrectinib-resistant cell line (CUTO28-ER) through in vitro culture under drug selection. In these CUTO28-ER cells, we identified: (1) MET-mediated bypass signaling as an acquired resistance mechanism to entrectinib, (2) upregulation of MET signaling is accomplished via MET gene amplification, and (3) resistance could be overcome by the dual ROS1/MET inhibitor crizotinib. To our knowledge, this is the first reported case of MET-mediated acquired resistance in a ROS1+ cancer. This cell line model finding was supported by another primary, patient-derived cell line (CUTO38) harboring a CD74-ROS1 fusion; this cell line was derived from a NSCLC patient following disease progression on entrectenib in the clinic. CUTO38 is resistant to entrectinib in vitro and displays elevated MET expression, MET activation with increased phosphorylation, and dependence on MET for cell proliferation and survival. Notably, MET activation in CUTO38 was not generated by gene amplification, MET exon 14 splicing, MET gene fusion, or autocrine HGF expression, suggesting alternate means of MET activation. These findings suggest that interrogation of MET gene amplification or other MET biomarkers should be performed in ROS1+ NSCLC patients who experience disease progression on entrectinib or other ROS1 TKIs that do not inhibit MET, since there are clinically available MET inhibitors, some of which are dual ROS1/MET inhibitors, that may overcome drug resistance in these patients. Citation Format: Logan Tyler, Anh Le, Hala Nijmeh, Robert Doebele. MET mediates entrectinib resistance in ROS1 gene fusion positiveNSCLC [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3003.