H2AX and malignant colon neoplasm: HCT116 wt, and HCT116 5-FU Res colon cancer cell lines were treated with 1 μg/ml 5-FU and 1 μM thiostrepton alone or in combination for 24 hours and immunostained for ɣH2AX, a known marker to detect the presence of DNA damage induced by the treatments.