DNA analyses of lung adenocarcinomas, a type of non-small cell lung cancer (NSCLC), found that some tumors contain a kind of mutation called a gene fusion in a gene called NTRK1. The mutation consists of NTRK1, which is involved in cell growth, merging with a different gene. As a result, the gene’s product, a protein called TRKA, is continuously 'switched on,' independent of the signals that normally activate it. Treating cell cultures of lung cancer cells containing the NTRK1 gene fusion with TRKA inhibitors suppressed their growth. Patients with gene fusions in another gene, ALK, experience tumor shrinkage in response to treatment with the ALK inhibitor crizotinib (Xalkori). Similarly, TRKA inhibitors may act as targeted therapies for lung adenocarcinoma patients with NTRK1 mutations.