A recent study examining PIK3CA-mutant breast cancers showed that heightened PI3K-mTOR signaling is a key driver of Mcl-1 overexpression in these tumor cells, and that PI3K/mTOR inhibition impaired Mcl-1 expression, increasing PIK3CA-mutant cell sensitivity to ABT-263 [17]. The gene discussed is MCL1; the disease is breast carcinoma.