ABCB1 and colonic neoplasm: 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.