Characteristics of NSCLCs harboring NRAS mutations.

Abstract

7532 Background: We sought to determine the frequency and clinical characteristics of patients with non-small cell lung cancers (NSCLCs) harboring NRAS mutations. We used preclinical models to identify targeted therapies likely to be of benefit against NRAS mutant lung cancer cells. Methods: We reviewed data in the Catalogue of Somatic Mutations in Cancer (COSMIC) and clinical history from patients with NSCLC whose tumors underwent systematic screening for driver mutations including NRAS. Patient characteristics examined included age, gender, race, smoking history, disease stage, treatment history, and overall survival (OS). 6 NSCLC cell lines with NRAS mutations were screened for sensitivity against multiple targeted agents. Gene expression was profiled using Affymetrix U133A arrays in 5 NRAS mutant NSCLC cell lines, 8 with EGFR mutations and 17 with KRAS mutations. Results: Among 4524 patients with NSCLC tested, NRAS mutations were present in 29 (0.64%). The types of substitutions found were Q61H/K/L/R and G12A/C/D/R/S, with NRAS Q61L the most common (n=14; 48%). One tumor had a concurrent KRAS mutation. 83% had adenocarcinoma histology, with no significant differences in gender. While 90% of patients were former or current smokers, smoking-related G:C>T:A transversions were significantly less frequent in NRAS than in KRAS-mutant NSCLC (KRAS: 66%, NRAS: 13%, p<0.05). Systemic chemotherapy showed limited efficacy in 7 patients with metastatic disease (median OS 7 mos). 5 of 6 NRAS mutant lung cancer cell lines were sensitive to the MEK inhibitors, AZD6244 and GSK1120212, while other targeted agents (against EGFR, ALK, MET, IGF-1R, PIK3CA, BRAF) were minimally effective. Gene expression profiles of NRAS mutant cell lines were distinct from those with KRAS or EGFR mutations. Conclusions: NRAS mutations define a distinct subset of NSCLCs (~1%) with potential sensitivity to MEK inhibitors. While NRAS gene mutations are more common in current/former smokers, the types of mutations are not those classically associated with smoking.