MTOR and obesity due to melanocortin 4 receptor deficiency: The phosphatidylinositol 3-kinase (PI3K)/V-Akt murine thymoma viral oncogene homolog (Akt) (PKB)/mechanistic target of rapamycin (mTOR) cascade is a key signaling pathway linking obesity and cancer and regulates cell proliferation, apoptosis, and metabolism20,21.