MTOR and neoplasm: Importantly, mTOR is the main negative regulator of tumor cell autophagy, which can be activated by Ras-Raf-1-MEK1/2-ERK1/2 and PI3KCI-Akt signaling pathways, while inhibited by kinase B1 (LKB1)-AMP-activated protein kinase (AMPK) pathway (Wang et al., 2011).