Leptomeningeal carcinomatosis (LMC) occurs frequently in anaplastic lymphoma kinase (ALK)-rearranged non-small-cell lung cancer (NSCLC) and develops acquired resistance to ALK tyrosine kinase inhibitors (ALK-TKIs). This study aimed to clarify the resistance mechanism to alectinib, a second generation ALK-TKI, in LMC and test a novel therapeutic strategy.
We induced alectinib-resistance in an LMC mouse model with ALK-rearranged NSCLC cell line, A925LPE3, by continuous oral alectinib treatment, established A925L/AR cells. Resistance mechanisms were analyzed using several assays, including western blot and receptor tyrosine kinase array. We also measured amphiregulin concentrations in cerebrospinal fluid (CSF) from ALK-rearranged NSCLC patients with alectinib-refractory LMC by ELISA.
A925L/AR cells were moderately resistant to various ALK-TKIs, such as alectinib, crizotinib, ceritinib, and lorlatinib, compared with parental cells in vitro. A925L/AR cells acquired the resistance by epidermal growth factor receptor (EGFR) activation due to amphiregulin overexpression caused by decreased expression of microRNA-449a. EGFR-TKIs and anti-EGFR antibody re-sensitized A925L/AR cells to alectinib in vitro. In the LMC model with A925L/AR cells, combined treatment with alectinib and EGFR-TKIs, such as erlotinib and osimertinib, successfully controlled progression of LMC. Imaging mass spectrometry showed accumulation of the EGFR-TKIs in the tumor lesions. Moreover, notably higher amphiregulin levels were detected in CSF from alectinib-resistant ALK-rearranged NSCLC patients with LMC (N=4), compared with those in EGFR-mutated NSCLC patients with EGFR-TKI-resistant LMC (N=30) or patients without LMC (N=24).
These findings indicate the potential of novel therapies targeting both ALK and EGFR for the treatment of ALK-TKI-resistant LMC in ALK-rearranged NSCLC.

Copyright © 2020. Published by Elsevier Inc.