In order to investigate the cytotoxicity of DOX, DOX-TNP and TNP on different human normal and cancer cell lines, MTT assays were performed using a human normal colon fibroblast cell line CCD-18Co, a human colon cancer cell line SW620, and its doxorubicin-selected ABCB1 overexpressing subline SW620/Ad300. This evidence concerns the gene ABCB1 and malignant colon neoplasm.