SMAD2 and urinary bladder cancer: First, the TGFβ-Smad2/3-ZEB2-hENT1 axis is specifically involved in EMT-related GCB resistance in bladder cancer cells, including acquired GCB-resistant T24-GCB cells and de novo resistant J82 cells, although members of the β-catenin and Notch signaling pathways are also upregulated in GCB-resistant T24 cells.