ABCB1 and colorectal adenocarcinoma: Its cytotoxicity, ability to change doxorubicin (Dox) accumulation and resistance to this drug, as well as ABCB1 inhibition potency were studied in drug-sensitive and resistant human colorectal adenocarcinoma cells (HT29), and in the variant of MDCK cells expressing human ABCB1 protein.