This is the Accepted Version of the following article: Anti-diabetic drug metformin inhibits cell proliferation and tumor growth in gallbladder cancer via G0/G1 cell cycle arrest; Anti-cancer drugs; Volume 31 Number 3 (2020) Pages: 231-240; doi: 10.1097/CAD.0000000000000870, which has been published in final form at https://doi.org/10.1097/CAD.0000000000000870.