Metformin’s antitumor effect is multifaceted: metformin has been found to significantly reduce the in vitro growth and invasion capacities of A549 and H1651 cells [21], inhibit ROS-TFE3-dependent autophagy [17], decrease the production of Mesothelin (MSLN), downregulate IL-6/STAT3 signaling activity, and induce apoptosis in ovarian cancer cells [22]. Here, STAT3 is linked to ovarian cancer.