ABSTRACT
Lung cancer is notorious for its ability to metastasize, but the pathways regulating lung cancer metastasis are largely unknown. An in vitro system designed to discover factors critical for lung cancer cell migration identified brain-derived neurotrophic factor, which stimulates cell migration through activation of tropomyosin-related kinase B (TrkB; also called NTRK2). Knockdown of TrkB in human lung cancer cell lines significantly decreased their migratory and metastatic ability in vitro and in vivo. In an autochthonous lung adenocarcinoma model driven by activated oncogenic Kras and p53 loss, TrkB deficiency significantly reduced metastasis. Hypoxia-inducible factor-1 directly regulated TrkB expression, and, in turn, TrkB activated Akt signaling in metastatic lung cancer cells. Finally, TrkB expression was correlated with metastasis in patient samples, and TrkB was detected more often in tumors that did not have Kras or epidermal growth factor receptor mutations. These studies demonstrate that TrkB is an important therapeutic target in metastatic lung adenocarcinoma.
Subject(s)
Adenocarcinoma/enzymology , Cell Movement , Gene Expression Regulation, Enzymologic , Gene Expression Regulation, Neoplastic , Lung Neoplasms/enzymology , Membrane Glycoproteins/biosynthesis , Protein-Tyrosine Kinases/biosynthesis , Receptor, trkB/biosynthesis , Adenocarcinoma/drug therapy , Adenocarcinoma/genetics , Adenocarcinoma/pathology , Animals , Cell Line, Tumor , Gene Knockdown Techniques , Humans , Hypoxia-Inducible Factor 1/genetics , Hypoxia-Inducible Factor 1/metabolism , Lung Neoplasms/drug therapy , Lung Neoplasms/genetics , Lung Neoplasms/pathology , Lung Neoplasms/secondary , Membrane Glycoproteins/genetics , Mice, Mutant Strains , Neoplasm Metastasis/genetics , Neoplasm Metastasis/pathology , Protein-Tyrosine Kinases/genetics , Proto-Oncogene Proteins c-akt/genetics , Proto-Oncogene Proteins c-akt/metabolism , Receptor, trkB/genetics , Signal Transduction/geneticsABSTRACT
Metastasis is the leading cause of morbidity for lung cancer patients. Here we demonstrate that murine tumor propagating cells (TPCs) with the markers Sca1 and CD24 are enriched for metastatic potential in orthotopic transplantation assays. CD24 knockdown decreased the metastatic potential of lung cancer cell lines resembling TPCs. In lung cancer patient data sets, metastatic spread and patient survival could be stratified with a murine lung TPC gene signature. The TPC signature was enriched for genes in the Hippo signaling pathway. Knockdown of the Hippo mediators Yap1 or Taz decreased in vitro cellular migration and transplantation of metastatic disease. Furthermore, constitutively active Yap was sufficient to drive lung tumor progression in vivo. These results demonstrate functional roles for two different pathways, CD24-dependent and Yap/Taz-dependent pathways, in lung tumor propagation and metastasis. This study demonstrates the utility of TPCs for identifying molecules contributing to metastatic lung cancer, potentially enabling the therapeutic targeting of this devastating disease.
