MTOR and cancer: The phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, a complicated intracellular signaling cascade involved in multiple cellular processes, such as survival, growth, proliferation, autophagy, apoptosis, angiogenesis, and metabolism, is aberrantly hyper-activated in many cancer types, including oral cancer [142].