Targeting the PI3K/Akt/mTOR pathway inhibits the cancer stem cell population of breast cancer cells. (A) AS-B145 cells or (B) AS-B244 cells were treated with small molecule inhibitors of phosphoinositide-3-kinase (PI3K)/mammalian target of rapamycin (mTOR) (PI-103), Akt (CB-124005 or FPA-124) or mTOR (rapamycin) for 48 hours and the aldehyde dehydrogenase (ALDH)+ cell population within 7-aminoactinomycin D (7-AAD)-negative cells was determined with Aldefluor assay and displayed as the relative percentage of dimethylsulfoxide (DMSO) control. *P <0.05; #P <0.01 when compared with the DMSO group. (C) pAktser473 or p-mTORSer2448 was determined with western blot after treatment with inhibitors for 18 hours. Data are presented as the fold of changes relative to the DMSO control. All experiments were repeated independently at least twice and results shown were collected from a representative experiment.