Cells with ARID1A defects are sensitive to DNA damage, and when ARID1B is also defective, this effect is amplified. Developing inhibitors that increase the DNA damage effects on cancer cells may be a new target for IR therapy. Since ARID1A is highly mutated in bladder cancer, this approach may also be effective for treating bladder cancer. Here, ARID1B is linked to urinary bladder carcinoma.