MTOR and gastric cancer: Several gene mutations, including PIK3CA, TP53, ARID1A, CDH1, Ras, Raf, and ERBB3 are encountered in GC pathogenesis, leading to phosphatidylinositol 3-kinase (PI3K) protein kinase B (AKT)/mammalian target of rapamycin (mTOR)—PI3K/AKT/mTOR—and mitogen-activated protein kinase (MAPK) signaling pathway activation and promoting tumoral activity.