The up-regulation of BCL2-associated X (BAX), cyclin dependent kinase inhibitor 1A (P21), Caspase 3 (CASP3), and Caspase 9 (CASP9), the down-regulation of BCL2 apoptosis regulator (BCL2), Annexin V-FITC/propidium iodide, and reactive oxygen species (ROS) generation results suggested that BC-CuONPs had a significant apoptotic impact when compared to the control. This evidence concerns the gene CASP9 and breast cancer.