Previous studies have demonstrated that an increase in the expression of mesenchymal markers, such as vimentin, snail and twist, are associated with increased bladder cancer grade and stage.24, 30 Moreover, studies have shown that bladder cancer cell lines shed exosomes containing proteins important for tumor progression.9, 10, 11 Therefore, we wanted to determine whether exosomes shed from invasive bladder cancer cell lines could induce the expression of mesenchymal markers in primary urothelial cells. The gene discussed is SNAI1; the disease is urinary bladder cancer.