We observed an increase in several mRNAs for mesenchymal markers, including α-smooth muscle actin (α-SMA), vimentin, S100A4, snail and twist, when primary urothelial cells were treated with exosomes isolated from invasive bladder cancer cell lines, as compared with the phosphate-buffered saline (PBS)-treated cells or to cells treated with exosomes isolated from human embryonic kidney cells, a non-transformed normal cell line (Figure 1a). The gene discussed is TWIST1; the disease is urinary bladder cancer.