Modulation of several waves of gene expression during FGF-1 induced epithelial-mesenchymal transition of carcinoma cells

During epithelial-mesenchymal transition (EMT), epithelial cells are converted into isolated motile and invasive mesenchymal cells. In model systems, EMT is induced most often by the activation of tyrosine kinase receptors through signaling pathways involving translational and post-translational regulation. In this study, we have used the NBT-II bladder carcinoma cell system to investigate in vitro Fibroblast Growth Factor-1 (FGF-1)-induced EMT. Transcriptome analyses were performed on NBT-II cells stimulated for 2, 6, 24, and 48 h with FGF-1. As some phenotypic changes occurred around 6 h post-stimulation, a supervised analysis was designed to identify transcript variations across defined time-periods. Our results clearly indicate that immediately after FGF-1 stimulation a set of genes assigned to transcriptional regulation (e.g., jun-B and v-ets) and to EMT induction (e.g., Notch 1) is transiently up-regulated. A set of genes involved in proteolytic systems (e.g., MMP-13 and uPAR) is immediately up-regulated but subsequently maintained throughout FGF-1 stimulation. Then follows a second wave of gene expression that includes a strong but transient up-regulation of ephrin B1 and arginase I. Finally, a third group of genes is stably modulated over 48 h which consists primarily of down-regulated genes specifically associated with the EMT-based loss of the epithelial phenotype and maintenance of the mesenchymal and invasive phenotype of carcinoma cells. Using genome-wide oligoarray technology, we have identified novel expressions of immediate, immediate-early and later EMT biomarkers that are specifically activated downstream of the FGF/FGFR pathway and which might be significant prognostic factors for tumor progression of carcinoma.