CDA and urothelial carcinoma: The most common mutational signature in urothelial carcinoma (UC), the most common type of urinary bladder cancer is assumed to be caused by the misdirected activity of APOBEC3 (A3) cytidine deaminases, especially A3A or A3B, which are known to normally restrict the propagation of exogenous viruses and endogenous retroelements such as LINE-1 (L1).