Since the PI3K pathway is frequently hyperactivated in breast cancer typified by a high frequency of PIK3CA mutations, we analyzed the effect of USP10 depletion in the breast cancer cell lines MCF7 (PIK3CA-E545K) and T47D (PIK3CA-H1047R), which both harbor activating mutations in PIK3CA. The gene discussed is PIK3CA; the disease is breast cancer.