ABSTRACT
Normal fibroblasts surrounding tumor cells play a crucial role in cancer progression through formation of the tumor microenvironment. Because factors secreted from normal fibroblasts can modulate the tumor microenvironment, it is necessary to identify key factors associated with regulation of secreted factors and to investigate the molecular mechanisms contributing to the tumor microenvironment formation process. In this study, we found that radiation induced the expression and K63-linkage poly-ubiquitination of TRAF4 in normal lung fibroblasts. The K63-linkage poly-ubiquitinated TRAF4 formed complexes with NOX2 or NOX4 by mediating phosphorylated p47-phox in normal lung fibroblasts. Moreover, we showed that TRAF4 stabilized NOX complexes by decreasing lysosomal degradation of NOX2 and NOX4 after irradiation. NOX complexes increased endosomal ROS levels that were permeable into cytoplasm, leading to NF-κB-mediated ICAM1 up-regulation. Soluble ICAM1 was subsequently secreted into conditioned media of radiation-activated normal lung fibroblasts. The conditioned media from irradiated normal fibroblasts enhanced proliferation and epithelial-mesenchymal transition of non-small cell lung cancer cells both in vitro and in vivo. These results demonstrate that TRAF4 in irradiated fibroblasts is positively associated with aggressiveness of adjacent cancer cells by altering the tumor microenvironment. Thus, we suggest that regulation of TRAF4 might be a promising strategy for cancer therapy.
Subject(s)
Fibroblasts/metabolism , Lung Neoplasms/genetics , Lung Neoplasms/pathology , TNF Receptor-Associated Factor 4/genetics , Tumor Microenvironment/genetics , Animals , Cell Line, Tumor , Disease Progression , Endosomes/metabolism , Fibroblasts/pathology , Fibroblasts/radiation effects , Gene Expression Regulation , Humans , Intercellular Adhesion Molecule-1/blood , Intercellular Adhesion Molecule-1/metabolism , Lung Neoplasms/metabolism , Lysosomes/metabolism , Male , Mice , Models, Biological , NADPH Oxidase 2/genetics , NADPH Oxidase 2/metabolism , NADPH Oxidase 4/genetics , NADPH Oxidase 4/metabolism , NF-kappa B/metabolism , Protein Binding , Radiation, Ionizing , Reactive Oxygen Species/metabolism , Signal Transduction , TNF Receptor-Associated Factor 4/metabolism , Ubiquitination , Xenograft Model Antitumor AssaysABSTRACT
TFAP2C (transcription factor-activating enhancer-binding protein 2C) expression has been positively correlated with poor prognosis in patients with certain types of cancer, but the mechanisms underlying TFAP2C-mediated tumorigenesis in non-small-cell lung cancer (NSCLC) are still unknown. We previously performed a microarray analysis to identify TFAP2C regulation genes, and TGFBR1 (transforming growth factor-ß receptor type 1) was found to be upregulated by TFAP2C. We observed that TFAP2C or TGFBR1 overexpression led to oncogenic properties, such as cell viability, proliferation and cell cycle progression. TGFBR1 upregulation induced by TFAP2C also promoted cell motility and migration, leading to malignant development. We also found that PAK1 (p21 protein (Cdc42/Rac)-activated kinase 1) signaling was involved in TFAP2C/TGFBR1-induced tumorigenesis. These results were confirmed by an in vivo xenograft model and patient tissue samples. This study shows that TFAP2C promoted tumor progression by upregulation of TGFBR1 and consequent activation of PAK1 signaling.
