In the present study, we investigated the cytotoxic effect of OXY, evaluating possible mechanisms of action on MCF-7 and MDA-MB-231 breast cancer cells, in addition to demonstrating the synergistic association of this phytochemical with the chemotherapeutic agents DOX and MEL for the first time, thus providing promising outcomes for the utilization of OXY, either isolated or associated with anticancer drugs, as a novel template for future in vivo and clinical studies of breast cancer therapeutics. This evidence concerns the gene GCG and breast cancer.