BACKGROUND The main purpose of this study was to assess in vitro and in vivo the anticancer effect of withaferin-A in human breast carcinoma cells (MDA-MB-231), and to assess its effects on autophagy, cell apoptosis, ROS production, cell migration and invasion, and Nf-kappaB/m-TOR signalling pathway. MATERIAL AND METHODS Proliferation of MDA-MB-231 cells at various doses of the drug was studied by CCK8 cell viability assay. Effects on cell apoptosis were studied by fluorescence microscopy in combination with flow cytometry and Western blot analysis. Effects on autophagy were evaluated by transmission electron microscopy and Western blot. Effects on cellular migration were examined in vitro by wound healing assay. RESULTS The results indicated that withaferin-A led to significant reduction of MDA-MB-231 cell viability. The anticancer action of withaferin-A was shown to be due to the stimulation of autophagy, which was accompanied by enhancement of LC3 expression. Withaferin-A prompted mitochondrial apoptosis, which was also associated with increased level of Bax and decreased Bcl-2 in MDA-MB-231 cells. It was also observed that withaferin-A has decreases cellular migration and invasion of the tested human breast cancer cells. The effects of withaferin-A were also investigated in vivo, and it was found that this molecule could inhibit the growth of tumor xenografts in tested mice. Withaferin-A led to suppression of the Nf-kappaB/m-TOR signalling pathway. CONCLUSIONS In brief, the withaferin-A molecule has great potential as an anticancer agent against drug-resistant breast cancer, and as such needs to be further studied in detail.