Anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitors (TKIs), including crizotinib, are effective treatments in preclinical models and in cancer patients with ALK-translocated cancers. However, their efficacy will ultimately be limited by the development of acquired drug resistance. Here we report two mechanisms of ALK TKI resistance identified from, a crizotinib treated non-small cell lung cancer (NSCLC) patient and in a cell line generated from the resistant tumor (DFCI076), and from studying a resistant version of the ALK TKI (TAE684) sensitive H3122 cell line. The crizotinib resistant DFCI076 cell line, harboured a unique L1152R ALK secondary mutation, and was also resistant to the structurally unrelated ALK TKI TAE684. Although the DFCI076 cell line was still partially dependent on ALK for survival, it also contained concurrent co-activation of epidermal growth factor receptor (EGFR) signalling. In contrast, the TAE684 resistant (TR3) H3122 cell line did not contain an ALK secondary mutation but instead harboured co-activation of EGFR signalling. Dual inhibition of both ALK and EGFR was the most effective therapeutic strategy for the DFCI076 and H3122 TR3 cell lines. We further identified a subset (3/50; 6%) of treatment naïve NSCLC patients with ALK rearrangements that also had concurrent EGFR activating mutations. Our studies identify resistance mechanisms to ALK TKIs mediated by both ALK and by a bypass signalling pathway mediated by EGFR. These mechanisms can occur independently, or in the same cancer, suggesting that the combination of both ALK and EGFR inhibitors may represent an effective therapy for these subsets of NSCLC patients.

Purpose BRAF mutations are found in a subset of non-small cell lung cancers (NSCLCs). We examined the clinical characteristics and treatment outcomes of patients with NSCLC harboring BRAF mutations. Experimental Design Using DNA sequencing, we successfully screened 883 NSCLC patients for BRAF mutations between 7/1/09 and 7/16/12. Baseline characteristics and treatment outcomes were compared between patients with and without BRAF mutations. Wild type controls consisted of NSCLC patients without a somatic alteration in BRAF, KRAS, EGFR, and ALK. In vitro studies assessed the biological properties of selected non-V600E BRAF mutations identified from NSCLC patients. Results Of 883 tumors screened, 36 (4%) harbored BRAF mutations (V600E: 18; non-V600E: 18) and 257 were wild type for BRAF, EGFR, KRAS, and ALK negative. Twenty-nine of the 36 BRAF mutant patients were smokers. There were no distinguishing clinical features between BRAF mutant and wild type patients. Advanced NSCLC patients with BRAF mutations and wild type tumors showed similar response rates and progression-free survival (PFS) to platinum-based combination chemotherapy and no difference in overall survival. Within the BRAF cohort, patients with V600E mutated tumors had a shorter PFS to platinum-based chemotherapy compared to those with non-V600E mutations, although this did not reach statistical significance (4.1 versus 8.9 months; P=0.297). We identified five BRAF mutations not previously reported in NSCLC; two of the five were associated with increased BRAF kinase activity. Conclusions BRAF mutations occur in 4% of NSCLCs and half are non-V600E. Prospective trials are ongoing to validate BRAF as a therapeutic target in NSCLC.