Combined action of anticancer drug with sodium selenite, selenomethionine, and D-pantethine showed a cytoprotective activity toward tumor cell lines that are sensitive to the action of doxorubicin and a reverse effect (enhancing of cytotoxic activity of the doxorubicin) toward drug-resistant tumor cells with various defects (overexpression of P-glycoprotein or p53 and Bax knockouts). The gene discussed is ABCB1; the disease is neoplasm.