Brief Report: Rapid Acquisition of Alectinib Resistance in ALK-positive Lung Cancer with High Tumor Mutation Burden

Abstract Introduction The highly selective ALK inhibitor alectinib is standard therapy for ALK-positive lung cancers; however, some tumors quickly develop resistance. Here, we investigated the mechanism associated with rapid acquisition of resistance using clinical samples. Methods Autopsied samples were obtained from lung, liver, and renal tumors from a 51-year-old male patient with advanced ALK-positive lung cancer and who had acquired resistance to alectinib in only 3 months. We established an alectinib-resistant cell line (ABC-14) from pleural effusion and an alectinib/crizotinib-resistant cell line (ABC-17) and patient-derived xenograft (PDX) model from liver tumors. Additionally, we performed next-generation sequencing (NGS), direct DNA sequencing, and quantitative real-time reverse-transcription polymerase chain reaction. Results ABC-14 cells harbored no ALK mutations and were sensitive to crizotinib while also exhibiting MET geneamplification and amphiregulin overexpression. Additionally, combined treatment with crizotinib/erlotinib inhibited cell growth. ABC-17 and PDX tumors harbored ALK G1202R, and PDX tumors metastasized to multiple organs in vivo, whereas the third generation ALK-inhibitor, lorlatinib, diminished tumor growth in vitro and in vivo. NGS indicated high tumor mutation burden (TMB) and heterogeneous tumor evolution. The autopsied lung tumors harbored ALK G1202R (c. 3604 G>A) and the right renal metastasis harbored ALK G1202R (c. 3604 G>C); the mutation thus comprised different codon changes. Conclusions High TMB and heterogeneous tumor evolution might be responsible for rapid acquisition of alectinib resistance. Timely lorlatinib administration or combined therapy with an ALK inhibitor and other receptor tyrosine-kinase inhibitors might constitute a potent strategy.