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Despite initial benefit from tyrosine kinase inhibitors (TKIs), patients with advanced non-small cell lung cancer (NSCLC) harboring (ALK) and (ROS1) gene fusions ultimately progress. Here, we report on the potential resistance mechanisms in a series of patients with ALK and ROS1 NSCLC progressing on different types and/or lines of -targeted therapy. We used a combination of next-generation sequencing (NGS), multiplex mutation assay, direct DNA sequencing, RT-PCR, and FISH to identify fusion variants/partners and copy-number gain (CNG), kinase domain mutations (KDM), and copy-number variations (CNVs) in other cancer-related genes. We performed testing on 12 and 43 patients. One of 12 ROS1 (8%) and 15 of 43 (35%) ALK patients harbored KDM. In the ROS1 cohort, we identified and β-catenin mutations and HER2-mediated bypass signaling as non-ROS1-dominant resistance mechanisms. In the ALK cohort, we identified a novel gene fusion, a fusion, 2 , and 3 mutations, as well as mutations in , and In addition, we identified CNV in multiple proto-oncogenes genes including and others. We identified a putative TKI resistance mechanism in six of 12 (50%) ROS1 patients and 37 of 43 (86%) ALK patients. Our data suggest that a focus on KDMs will miss most resistance mechanisms; broader gene testing strategies and functional validation is warranted to devise new therapeutic strategies for drug resistance. .

Oncogenic kinase fusions of ALK, ROS1, RET and NTRK1 act as drivers in human lung and other cancers. Residual tumor burden following treatment of ALK or ROS1+ lung cancer patients with oncogene-targeted therapy ultimately enables the emergence of drug-resistant clones, limiting the long-term effectiveness of these therapies. To determine the signaling mechanisms underlying incomplete tumor cell killing in oncogene-addicted cancer cells, we investigated the role of EGFR signaling in drug-naive cancer cells harboring these oncogene fusions. We defined three distinct roles for EGFR in the response to oncogene-specific therapies. First, EGF-mediated activation of EGFR blunted fusion kinase inhibitor binding and restored fusion kinase signaling complexes. Second, fusion kinase inhibition shifted adaptor protein binding from the fusion oncoprotein to EGFR. Third, EGFR enabled bypass signaling to critical downstream pathways such as MAPK. While evidence of EGFR-mediated bypass signaling has been reported after ALK and ROS1 blockade, our results extended this effect to RET and NTRK1 blockade and uncovered the other additional mechanisms in gene fusion-positive lung cancer cells, mouse models and human clinical specimens before onset of acquired drug resistance. Collectively, our findings show how EGFR signaling can provide a critical adaptive survival mechanism that allows cancer cells to evade oncogene-specific inhibitors, providing a rationale to co-target EGFR to reduce risks of developing drug resistance.

IMPORTANCE Lung cancer is the leading cause of cancer death in the United States in all ethnic and racial groups. The overall death rate from lung cancer is higher in black patients than in white patients. OBJECTIVE To compare the prevalence and types of somatic alterations between lung cancers from black patients and white patients. Differences in mutational frequencies could illuminate differences in prognosis and lead to the reduction of outcome disparities by more precisely targeting patients’ treatment. DESIGN, SETTING, AND PARTICIPANTS Tumor specimens were collected from Baptist Cancer Center (Memphis, Tennessee) over the course of 9 years (January 2004-December 2012). Genomic analysis by massively parallel sequencing of 504 cancer genes was performed at Dana-Farber Cancer Institute (Boston, Massachusetts). Overall, 509 lung cancer tumors specimens (319 adenocarcinomas; 142 squamous cell carcinomas) were profiled from 245 black patients and 264 white patients. MAIN OUTCOMES AND MEASURES The frequencies of genomic alterations were compared between tumors from black and white populations. RESULTS Overall, 509 lung cancers were collected and analyzed (273 women [129 black patients; 144 white patients] and 236 men [116 black patients; 120 white patients]). Using 313 adenocarcinomas and 138 squamous cell carcinomas with genetically supported ancestry, overall mutational frequencies and copy number changes were not significantly different between black and white populations in either tumor type after correcting for multiple hypothesis testing. Furthermore, specific activating alterations in members of the receptor tyrosine kinase/Ras/Raf pathway including EGFR and KRAS were not significantly different between populations in lung adenocarcinoma. CONCLUSIONS AND RELEVANCE These results demonstrate that lung cancers from black patients are similar to cancers from white patients with respect to clinically actionable genomic alterations and suggest that clinical trials of targeted therapies could significantly benefit patients in both groups.