ABSTRACT
Expression of the immediate-early response gene IER2 has been associated with the progression of several types of cancer, but its functional role is poorly understood. We found that increased IER2 expression in human melanoma is associated with shorter overall survival, and subsequently investigated the mechanisms through which IER2 exerts this effect. In experimental melanoma models, sustained expression of IER2 induced senescence in a subset of melanoma cells in a p53/MAPK/AKT-dependent manner. The senescent cells produced a characteristic secretome that included high levels of the extracellular phosphoglycoprotein osteopontin. Nuclear localization of the IER2 protein was critical for both the induction of senescence and osteopontin secretion. Osteopontin secreted by IER2-expressing senescent cells strongly stimulated the migration and invasion of non-senescent melanoma cells. Consistently, we observed coordinate expression of IER2, p53/p21, and osteopontin in primary human melanomas and metastases, highlighting the pathophysiological relevance of IER2-mediated senescence in melanoma progression. Together, our study reveals that sustained IER2 expression drives melanoma invasion and progression through stimulating osteopontin secretion via the stochastic induction of senescence.
Subject(s)
Biomarkers, Tumor/metabolism , Cellular Senescence , Gene Expression Regulation, Neoplastic , Immediate-Early Proteins/metabolism , Melanoma/pathology , Osteopontin/metabolism , Trans-Activators/metabolism , Animals , Apoptosis , Biomarkers, Tumor/genetics , Cell Proliferation , Humans , Immediate-Early Proteins/genetics , Melanoma/genetics , Melanoma/metabolism , Mice , Neoplasm Invasiveness , Osteopontin/genetics , Prognosis , Trans-Activators/genetics , Tumor Cells, CulturedABSTRACT
Inducible gene expression is a powerful tool for basic research, gene therapy and biotechnology, whose utility depends in part on consistent levels of induction regardless of metabolic status or physiological context. Here we examined the inducibility of the ecdysone receptor-based RheoSwitch mammalian inducible expression system in proliferating cells and in cell cycle-arrested cells. We found that both contact inhibition and growth arrest subsequent to serum deprivation dramatically reduced the levels of induction of reporter genes that could be achieved in 3T3 fibroblasts but in not NMuMG mammary epithelial cells. These data have implications for the use of the RheoSwitch system in inducible gene expression applications.
Subject(s)
Cell Cycle/genetics , Promoter Regions, Genetic/genetics , Receptors, Steroid/metabolism , Transcription, Genetic , Animals , Contact Inhibition , Culture Media, Serum-Free , Gene Expression Regulation , Humans , Ligands , Mice , NIH 3T3 CellsABSTRACT
Proof of concept experiments have shown that tissue factor/factor VIIa inhibitors have antithrombotic activity without enhancing bleeding propensity. Starting from lead compounds generated by a biased combinatorial approach, phenylglycine amide tissue factor/factor VIIa inhibitors with low nanomolar affinity and good selectivity against other serine proteases of the coagulation cascade were designed, using the guidance of X-ray structural analysis and molecular modelling.
