RPS6KB1 and esophageal cancer: Metformin may inhibit esophageal cancer cell proliferation, both through an activation of 5′-adenosine monophosphate-activated protein kinase followed by the inhibition of mTOR/p70S6K/pS6 signaling, and through upregulation of USP7, a positive regulator of tumor suppressor p53 [31, 32].