LEP and lung cancer: Leptin activates PI3K, an important molecule in the mTOR pathway, thereby activating Akt and mTOR, which are the downstream targets of PI3K. The activation of this signaling pathway can regulate the expression of various tyrosine kinase receptors in lung cancer cells, promote the survival and proliferation of cancer cells, and play an important role in the invasion and metastasis of lung cancer (32).