TP53 and urinary bladder carcinoma: To determine the relationship between APOBEC mutagenesis, APOBEC gene expression, and molecular subtype, we next investigated the association of APOBEC3 enzyme expression with total mutations in both the entire TCGA bladder cancer dataset and in the four molecular subtypes (luminal, p53-like, basal, and claudin-low; Supplementary Figure 1).