Mammalian target of rapamycin, in its role of regulating protein translation and controlling cell growth, has been implicated in cancer progression (Schmelzle and Hall, 2000; Ruggero and Pandolfi, 2003), and several analogues of rapamycin, a natural mTOR antagonist, are in clinical trials for various cancers, including advanced and oestrogen receptor (ER)-dependent breast cancer (Carraway and Hidalgo, 2004). Here, MTOR is linked to breast cancer.