Effect of cryptotanshinone on the viability of bladder cancer cells. (A) Chemical structure of CTT. (B, C) Bladder cancer cell lines (5637, T24) were treated with various concentrations of CTT (0, 10, 20, 40, 80 or 160 μM) for 24, 48 and 72 h. Cell viability was measured by a CCK-8 assay. (D) Anti-proliferation effect of CTT on 5637 and T24 cells by colony formation assay. (E) Histograms show the colony numbers of 5637 and T24 cells. The data shown are representative of at least three independent experiments. * P < 0.05, ** P < 0.01, *** P < 0.001, compared with the control group.