POLD1 and urinary bladder cancer: POLD1, one of the four subunits of DNA polymerase δ (POLD1, POLD2, POLD3, and POLD4) and which is upregulated in many tumors including bladder cancer, has been shown to directly bind to MB1 domain of MYC competitively with Fbw7, preventing Fbw7-mediated MYC ubiquitination and degradation [137].