MET Copy Number Gain Is Associated with Gefitinib Resistance in Leptomeningeal Carcinomatosis of EGFR-mutant Lung Cancer

This study aimed to clarify the mechanism of EGFR-TKI resistance in leptomeningeal carcinomatosis and seek for a novel therapeutic strategy. We examined EGFR mutations, including the T790M gatekeeper mutation, in 32 re-biopsy specimens from 12 leptomeningeal carcinomatosis and 20 extracranial lesions of EGFR-mutant lung cancer patients who became refractory to EGFR-TKI treatment. All the 32 specimens had the same baseline EGFR mutations, but the T790M mutation was less frequent in leptomeningeal carcinomatosis specimens than in extracranial specimens (8% vs. 55%, P < 0.01). To study molecular mechanisms of acquired EGFR-TKI resistance in leptomeningeal carcinomatosis, we utilized our previously developed mouse model of leptomeningeal carcinomatosis with the EGFR-mutant lung cancer cell line PC-9/ffluc cells, in which acquired resistance to gefitinib was induced by continuous oral treatment. Compared with subcutaneously inoculated gefitinib-resistant tumors, the T790M mutation was less frequent in leptomeningeal carcinomatosis that acquired resistance to gefitinib. PC-9/LMC-GR cells were established from the gefitinib-resistant leptomeningeal carcinomatosis model, and they were found to be intermediately resistant to gefitinib and osimertinib (third-generation EGFR-TKI). Although EGFR-T790M was negative, gefitinib resistance of PC-9/LMC-GR cells was related to MET copy number gain with MET activation. Moreover, combined use of EGFR-TKI and crizotinib, a MET inhibitor, drama...
Source: Molecular Cancer Therapeutics - Category: Cancer & Oncology Authors: Tags: Cancer Biology and Signal Transduction Source Type: research