A 2016 study by Choi showed that an increase in Ref-1/APE1 expression at a cutoff of 0.376 ng/100μl was 82% sensitive and 80% specific for detecting bladder cancer in urine.273 A smaller study from 2015 showed higher sensitivity (90%) but lower specificity (59%) for utilizing Ref-1/APE1 in serum to detect bladder cancer.274 Quantitative, noninvasive measurement of Ref-1/APE1 expression in urine or serum may 1 day become a diagnostic biomarker for bladder cancer as well as other cancers with additional studies in this area. Here, APEX1 is linked to urinary bladder cancer.