This nanosystem shows the potential for treatment of doxorubicin-resistant MCF-7 breast cancer cells and MCF-7/Adr xenografts in nude mice due to caspase-dependent mechanisms involving the activation of Bax (Bcl-2-associated X protein) and Bid (Bax-like BH3 protein) and inhibition of Bcl-2 protein. This evidence concerns the gene BAX and breast cancer.