The relationship between colorectal cancer (CRC) and cholesterol has been confirmed for many years, but the mechanism was not very clear. miR-33a was important in cholesterol metabolism and was abnormally expressed in many tumors, thus our study hypothesized that cholesterol effect on CRC by regulating miR-33a and its target gene PIM3, and verify it by series of assay. From results of CCK8 and flow cytometry, we confirmed cholesterol can stimulate CRC cell proliferation, promote cell cycle progression and inhibit cell apoptosis. miR-33a and SREBP2 mRNA expression were inhibited by cholesterol, and when cells transfected with miR-33a mimics or inhibitor the effect of cholesterol appeared a significant difference than before. In addition, PIM3 showed up-regulation with cholesterol treatment, and it was proved to be the target gene of miR-33a by dual luciferase reporter assay, it modulated CRC cells proliferation and apoptosis by phosphorylating p27, p21 and Bad protein. Thus, it inferred that cholesterol can regulate CRC development by miR-33a-PIM3 pathway. (C) 2019 Elsevier Inc. All rights reserved.