Characterizing non-small cell lung cancer driven by mutations in ARAF and CRAF family members.

Abstract

e15085 Background: Cancer genome screening is becoming standard clinical practice, but the number of actionable mutations detected is limited. To expand on our previous report of the possibility that ARAF S214C and CRAF S257L located in the conserved region 2 (CR2) were actionable driver mutations, we investigated responses to targeted therapies in mouse models and the prevalence of these alterations across many cancer types represented in a large real-world database of molecularly profiled patient tumors. Methods: Conditional transgenic mice that expressed human ARAF S214C or CRAF S257L in their lungs were established and treated with sorafenib or trametinib. Activation of the MAPK pathway following sorafenib or trametinib treatment was assessed in vitro by phospho-ERK IHC. DNA sequencing (592-gene or whole exome) was performed for patient samples submitted to Caris Life Sciences (Phoenix, AZ), and the prevalence of ARAF/CRAF variants was determined for each cancer type. Results: Both ARAF S214C and CRAF S257L dimerized to activate the MAPK pathway. Although a low concentration of sorafenib promoted ERK phosphorylation, a high concentration of sorafenib inhibited ERK phosphorylation. Transgenic mice rapidly developed lung adenocarcinoma when the mutant proteins were expressed. Sorafenib treatment induced tumor necrosis in both ARAF- and CRAF-mutated tumors, and 3 months of sorafenib treatment prolonged the survival of CRAF-mutant mice. Pan-tumor analysis of real-world patient samples revealed that ARAF and CRAF mutations in CR2 were found in 0.125% and 0.234% of tumors, respectively. ARAF mutations in CR2 were found in 0.415% of cholangiocarcinoma, 0.132% of colorectal cancer, and 0.173% of non-small cell lung cancer (NSCLC). CRAF mutations in CR2 were found in 0.509% of colorectal cancer, 0.502% of gastric cancer, 0.303% of NSCLC, and 0.978% of melanoma. The most prevalent CR2 mutations were ARAF S214F and CRAF S257L. Conclusions: Our in vitro results suggest ARAF S214C and CRAF S257L mutations are rare driver mutations that may be effectively treated with RAF inhibitors and warrant further investigation. [Table: see text]