One of the most frequent problems in the chemotherapy of hormone dependent tumors is the development of resistance in tumor cells to cytostatics. The main role among possible mechanisms of such resistance plays overexpression of P-glycoprotein, MRP and BCRP — the ABC-transporters family proteins, and Bcl-2 — antiapoptotic protein. In this study new synthetic analog of progesterone — buterol — was investigated as a perspective sensibilizing compound, e.g. compound, which increases sensitivity to anticancer drugs. It was shown, that buterol strengthens cytostatic effect of doxorubicin and etoposid in breast cancer cells in vitro. Also it was demonstrated that buterol decreases BCRP, P-glycoprotein and MRP mRNA expression in common on the 10th day of incubation. Besides, buterol suppresses mRNA expression of Bcl-2. Thus mechanisms of sensitization in MCF-7 cells are associated with the decrease of transporter proteins expression and antiapoptotic Bcl-2 protein expression.