Epithelial-to-Mesenchymal Transition Is a Mechanism of ALK Inhibitor Resistance in Lung Cancer Independent of ALK Mutation Status

Mutations in the gene are detectable in approximately 40% of -rearranged lung cancers resistant to ALK inhibitors. Although epithelial-to-mesenchymal transition (EMT) is a mechanism of resistance to various targeted drugs, its involvement in ALK inhibitor resistance is largely unknown. In this study, we report that both -mutant L1196M and EMT were concomitantly detected in a single crizotinib-resistant lesion in a patient with -rearranged lung cancer. Digital PCR analyses combined with microdissection after IHC staining for EMT markers revealed that L1196M was predominantly detected in epithelial-type tumor cells, indicating that mesenchymal phenotype and mutation can coexist as independent mechanisms underlying ALK inhibitor-resistant cancers. Preclinical experiments with crizotinib-resistant lung cancer cells showed that EMT associated with decreased expression of miR-200c and increased expression of ZEB1 caused cross-resistance to new-generation ALK inhibitors alectinib, ceritinib, and lorlatinib. Pretreatment with the histone deacetylase (HDAC) inhibitor quisinostat overcame this resistance by reverting EMT and . These findings indicate that HDAC inhibitor pretreatment followed by a new ALK inhibitor may be useful to circumvent resistance constituted by coexistence of resistance mutations and EMT in the heterogeneous tumor. SIGNIFICANCE: These findings show that dual inhibition of HDAC and ALK receptor tyrosine kinase activities provides a means to circumvent crizotinib resistance in lung cancer.