Therefore, we purposely chose the MMR-deficient colon carcinoma cell lines HCT116 and its counterpart 5-FU resistant derivative clones (HCT116R), together with an isogenic clone of HCT116 cells bearing a restored hMLH1 gene through a chromosome 3 transfer (HCT116+ch3) and its corresponding isogenic 5-FU resistant derivative clones (HCT116+ch3R). The gene discussed is MLH1; the disease is colon carcinoma.