In the present study we showed that treatment with AS Bcl-2 and AS Bcl-xL ODNs produced sequence-specific decreases in protein levels, thereby enhancing the chemosensitivity of BT-474, ZR-75-1, and MDA-MB-231 breast cancer cells to various anticancer drugs both in vitro and in vivo. This evidence concerns the gene BCL2 and breast carcinoma.