In particular, we found that several other members of DNA polymerase δ, including POLD2, POLD3, and POLD4, were not significantly upregulated in BLCA (Supplementary Fig. 1c), which implies that POLD1 may act in BLCA in a manner that is independent of DNA polymerase. This evidence concerns the gene POLD1 and bladder transitional cell carcinoma.