PIK3CA and breast cancer: Specifically, in an orthoptopic model of advanced endocrine therapy resistant, PIK3CA mutant breast cancer, we observed that combined, low-dose treatment with the mTORC1/2 inhibitor MLN-0128 and the SMAC mimetic BV6 blocked tumor growth and extended survival without evidence of substantial toxicity (Fig. 6e, Supplementary Fig. 6e, f).