MTOR and neoplasm: Primarily metformin can directly or indirectly activate 5' adenosine monophosphate-activated protein kinase (AMPK), which leads to downregulation of mammalian Target Of Rapamycin complex 1 (mTORC1) and resultant inhibition of tumour progression or induction of apoptosis (a review of the mTOR pathway (Guertin and Sabatini, 2007); Figure 4).