BAK1 and breast cancer: In addition, Cheng and co-workers found that Bak induced S-phase arrest in breast cancer cells through the inactivation of Cdc2 and that it induced cell apoptosis via the intrinsic mitochondrial pathway, which showed the potential of Bak as an anti-breast cancer drug, as well as its potential to be used in HRT for relieving menopausal symptoms [11].