CSCs have been characterized as a unique sub-population that has the ability of self-renewable, metastasis, and drug resistance leading to relapse.102,128 During the last decades, CSCs have been observed in a variety of human cancers, including ovarian, pancreatic, breast, liver, and lung.129,130 Several groups have displayed the involvement of the Wnt/β-catenin, Hedgehog, STAT3, TGF-β, PI3K/AKT/mTOR signaling cascade in the CSCs. This evidence concerns the gene MTOR and cancer.