We proposed a previously unreported oncogenic mechanism of POLD1, and we found that among the four subunits of DNA polymerase (POLD1, POLD2, POLD3, and POLD4), only POLD1 was significantly upregulated in BLCA, indicating that POLD1’s effect on BLCA may be independent of its enzyme activity and has some specificity when compared to other subunits. This evidence concerns the gene POLD3 and bladder transitional cell carcinoma.