Abstract 1106: Detection of MET alterations at the DNA, RNA and protein levels in NSCLC patients progressing on ALK and ROS1 targeted therapies
Authors: Jordana-Ariza Núria , Reischmann Nadine , Esparré Carlos , Román Ruth , Aguado-Esteban Cristina , García-Román Silvia , Stroh Christopher , Aguilar Andrés Aguilar , Rosell Rafael , Karachaliou Niki , Molina-Vila Miguel A. 
Published: June 2022

Abstract
Background: ALK and ROS1 fusion-positive NSCLC patients derive clinical benefit from tyrosine kinase inhibitors (TKIs) but ultimately relapse. Acquired resistance mechanisms include on-target secondary mutations or copy number gains and activation of bypass signaling. Although MET amplification has been described as a bypass resistance mechanism to ALK and ROS1 inhibitors, there are limited data on MET gene and protein overexpression. Aims: (i) detection of MET alterations at the DNA, mRNA and protein levels in ALK and ROS1 fusion-positive NSCLC patients progressing on TKIs, and (ii) establishment of primary cultures using samples from those patients.
Methods: MET alterations were studied in 12 patients after progression on TKIs, 10 ALK and 2 ROS1 fusion-positive. Informed consent was obtained from all patients. NGS and FISH were used to detect resistance mutations and amplifications. MET mRNA expression levels were determined by nCounter. Total and phospho-MET levels were assessed by IHC and Western blotting.
Results: A total of 21 samples were available from the 12 patients, including tumor biopsies (n=5), plasma (n=10), pleural effusions (n=3) and cerebrospinal fluids (n=3). MET alterations were detected in 4 patients, 3 ALK fusion-positive progressing on lorlatinib and one ROS1 fusion-positive patient progressing on crizotinib. The 3 ALK fusion-positive patients had MET amplification detected in liquid biopsy (n=2) or tumor tissue (n=1), collected after progression on lorlatinib. In the patient with tissue biopsy available, the increased MET copy number was in line with the presence of MET protein and RNA overexpression. MET amplification was not present on the pre-treatment biopsy available for one of the 3 patients. In primary cultures established from pleural effusion samples of 2 ALK fusion-positive patients, MET amplification was maintained, particularly if the cells were cultured in presence of an ALK TKI. Although the ROS1 fusion-positive patient had no MET amplification after progression on crizotinib, MET and phospho-MET upregulation were detected by IHC. These alterations were also present in primary culture that could be established from a pleural effusion sample of the patient.
Conclusions: We found MET alterations in 4 out of 12 (33%) fusion-positive patients after progression on TKIs. Three of them had MET amplification and one MET protein overexpression in the absence of MET copy number gain. Despite the small size of the cohort, our results suggest that testing not only at the DNA but also at the RNA and protein levels, discovers amplification-negative patients with MET alterations who may derive benefit from a MET targeted therapy. Finally, our findings highlight the potential of pleural effusion as a source of material for the establishment of primary cultures.
Citation Format: Núria Jordana-Ariza, Nadine Reischmann, Carlos Esparré, Ruth Román, Cristina Aguado-Esteban, Silvia García-Román, Christopher Stroh, Andrés Aguilar Aguilar, Rafael Rosell, Niki Karachaliou, Miguel A. Molina-Vila. Detection of MET alterations at the DNA, RNA and protein levels in NSCLC patients progressing on ALK and ROS1 targeted therapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1106.