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The discovery of oncogenic driver mutations and the subsequent developments in targeted therapies have led to improved outcomes for subsets of lung cancer patients. The identification of additional oncogenic and drug-sensitive alterations may similarly lead to new therapeutic approaches for lung cancer. We identify and characterize novel FGFR2 extracellular domain insertion mutations and demonstrate that they are both oncogenic and sensitive to inhibition by FGFR kinase inhibitors. We demonstrate that the mechanism of FGFR2 activation and subsequent transformation is mediated by ligand-independent dimerization and activation of FGFR2 kinase activity. Both FGFR2-mutant forms are predominantly located in the endoplasmic reticulum and Golgi but nevertheless can activate downstream signaling pathways through their interactions with fibroblast growth factor receptor substrate 2 (FRS2). Our findings provide a rationale for therapeutically targeting this unique subset of FGFR2-mutant cancers as well as insight into their oncogenic mechanisms. [ABSTRACT FROM AUTHOR]

Insertion mutations in EGFR and HER2 both occur at analogous positions in exon 20. Non-small cell lung cancer (NSCLC) patients with tumors harboring these mutations seldom achieve clinical responses to dacomitinib and afatinib, two covalent quinazoline-based inhibitors of EGFR or HER2, respectively. In this study, we investigated the effects of specific EGFR and HER2 exon 20 insertion mutations from NSCLC patients that had clinically achieved a partial response after dacomitinib treatment. We identified Gly770 as a common feature among the drug-sensitive mutations. Structural modeling suggested that this mutation may facilitate inhibitor binding to EGFR. Introduction of Gly770 into two dacomitinib-resistant EGFR exon 20 insertion mutants restored sensitivity to dacomitinib. Based on these findings, we used afatinib to treat an NSCLC patient whose tumor harbored the HER2 V777_G778insGSP mutation and achieved a durable partial response. We further identified secondary mutations in EGFR (T790M or C797S) and HER2 (C805S) that mediated acquired drug resistance in drug-sensitive EGFR or HER2 exon 20 insertion models. Overall, our findings identified a subset of EGFR and HER2 exon 20 insertion mutations that are sensitive to existing covalent quinazoline-based EGFR/HER2 inhibitors, with implications for current clinical treatment and next-generation small-molecule inhibitors. Cancer Res; 77(10); 2712-21. ©2017 AACR ., (©2017 American Association for Cancer Research.)

The discovery of oncogenic driver mutations and the subsequent developments in targeted therapies have led to improved outcomes for subsets of lung cancer patients. The identification of additional oncogenic and drug-sensitive alterations may similarly lead to new therapeutic approaches for lung cancer. We identify and characterize novel FGFR2 extracellular domain insertion mutations and demonstrate that they are both oncogenic and sensitive to inhibition by FGFR kinase inhibitors. We demonstrate that the mechanism of FGFR2 activation and subsequent transformation is mediated by ligand-independent dimerization and activation of FGFR2 kinase activity. Both FGFR2-mutant forms are predominantly located in the endoplasmic reticulum and Golgi but nevertheless can activate downstream signaling pathways through their interactions with fibroblast growth factor receptor substrate 2 (FRS2). Our findings provide a rationale for therapeutically targeting this unique subset of FGFR2-mutant cancers as well as insight into their oncogenic mechanisms., (©2015 American Association for Cancer Research.)