KRAS and cancer: Three human CRC cell lines that represent distinct epigenotypes of human colon cancers were used: HCT116 (microsatellite unstable – MSI - cancer cell line due to germline mutation in the MLH1, mismatch repair gene), RKO (MSI cancer cell line associated with MLH1 promoter hypermethylation in the context of the CpG island promoter methylation phenotype or CIMP) and HT29 (microsatellite stable or MSS, cell line with mutant KRAS- and p53 genes) [40].