NTRK1 gene fusions as a novel oncogene target in lung cancer.

Abstract

8023 Background: The identification and therapeutic targeting of oncogenic drivers in lung adenocarcinoma has led to significant clinical improvements for patients with EGFR mutations or ALK fusions. However, many lung cancer patients do not yet have an identified oncogenic driver and the discovery of new actionable oncogenic drivers is thus an active area of investigation. Methods: Tumor samples from 36 ‘pan-negative’ (EGFR, KRAS, ALK, and ROS1) lung adenocarcinoma patients were analyzed using a next generation sequencing (NGS) test performed in a CLIA-certified lab (Foundation Medicine, Cambridge, MA). Fluorescence in situ hybridization (FISH) screening using a novel NTRK1 break-apart assay was performed on an additional 61 pan-negative samples. Cells expressing the novel NTRK1 fusions were assayed for transformation and pharmacologic inhibition. Results: Two tumor samples were identified with gene fusions containing the kinase domain of TrkA, encoded by NTRK1, including one each with an MPRIP-NTRK1 (M21;N14) and CD74-NTRK1 (C8;N12) fusion. RT-PCR confirmed mRNA expression and identity of the fusion partner and FISH analysis detected split 5’/3’ signals corresponding to the NTRK1 gene. A third sample was identified by FISH analysis. Cloning and expression of MPRIP- and CD74-NTRK1 into NIH3T3 and Ba/F3 cells show constitutive activation of the TrkA kinase domain and transformation. Treatment of cells expressing NTRK1 fusions with several candidate pan-Trk inhibitors (ARRY-772, -523, and -470) as well as CEP-701 and crizotinib demonstrate decreased phosphorylation of the fusion oncoprotein and inhibition of cell proliferation. Treatment of the index patient harboring the MPRIP-NTRK1fusion with crizotinib led to minor transient tumor shrinkage. Conclusions: We identified a novel class of oncogenes, NTRK1 fusions, in lung adenocarcinomas that can be detected by NGS or FISH. Additional studies to determine the frequency and characteristics of NTRK1 fusions in lung cancer are ongoing. Our findings suggest prospective clinical trials of Trk inhibitors in NTRK1 fusion positive patients may be warranted. Support: CO Bioscience Discovery and Evaluation Grant and CO Clinical and Translational Sciences Institute Grant.