APEX1 and urinary bladder cancer: Thus, we conducted this case-control study to investigate the associations between nineteen polymorphisms from five genes (PARP1, OGG1, APEX1, MUTYH, and XRCC1) of BER and two genes (XRCC2 and XRCC3) of HRR, which were chosen based on the literature on other types of human cancer [16–18], and the risk of bladder cancer in Gansu Province of China.