ERCC1 and colorectal carcinoma: In our study, we have found that the protein expression of ERCC1 in DLD-1(KRASG13D mutation) cells is up-regulated after 5′-azacitidine (de-methylating agent) treatment for 96 hours (Figure 6A), which indicated that the downregulation of ERCC1 in KRAS-mutant CRC cells might be partly through ERCC1 hypermethylation.