MTOR and breast cancer: For example, the HER2 overexpression observed in about one-third of breast cancers is associated with activation of PI3-kinase/Akt/mTOR signalling (Bacus et al, 2002; Zhou et al, 2004), resistance to stress-induced apoptosis (Bacus et al, 2002), and tumour aggressiveness (Cobleigh et al, 1999; Zhou et al, 2004).