T24 cells were treated with 19-BJB in concentration of 0, 2, 4 μM for 48 h or ATMI (10 μM) 3 h before treating with 19-BJB for 48 h. And total cell lysates were analyzed for the expression of p-H2A.X, p-Chk1 and p-Chk2 (A). Equal protein loading was confirmed by reprobing membrane with β-actin after stripping. The relative levels of all proteins are performed (B) as means ± SD from triplicate samples for each treatment. **p < 0.01, ****p < 0.0001.