POLD1 and cancer: Mutations in the genes associated with MMR (MSH2, MSH6, PMS2, and MLH1) and those encoding for proof-reading polymerases epsilon (POLE) and delta (POLD1) show higher mutation rates in BRAF/PIK3CA double mutant colorectal cancers while cancers with BRAF mutations and PIK3CA wild type display similarly high mutation rates except for PMS2 and MLH1 which show significantly lower mutation rates (Figure 3A).