miR-224 Controls Human Colorectal Cancer Cell Line HCT116 Proliferation by Targeting Smad4

Background: Better understanding the molecular mechanisms responsible for the genesis and progression of colorectal cancer would help advance the novel therapeutics. miR-224 has been identified to be elevated in colorectal cancer and promote human colorectal cancer cell line SW480 proliferation and invasion. However, the effect of miRNAs on cancer cell proliferation could be significantly changeable among different cell lines. HCT116 is a commonly used cell line for colorectal cancer study and the target gene responsible for the function of miR-224 in its proliferation is unclear. Methods: miR-224 expression was determined by quantitative reverse transcription polymerase chain reactions (PCRs) in human colorectal cancer tissues compared with their corresponding matched peritumoral tissues. HCT116 cell viability and cell proliferation were determined by CCK-8, EdU incorporation assays and flow cytometry for cell cycle. Target gene of miR-224 was confirmed by Western blots and siRNA for Smad4. Results: miR-224 was significantly increased by 29.49 fold in colorectal cancer tissues compared with their corresponding matched peritumoral tissues based on 12 colorectal cancer patients. miR-224 mimic significantly increased HCT116 cell viability, EdU positive cells rate, and decreased G1 phase cell population and increased S phase cell population. miR-224 inhibitor had opposite effects. Smad4 could be negatively regulated by miR-224 in HCT116 cells and was responsible for its effects in proliferation. Conclusion: miR-224 mediates HCT116 cell proliferation by targeting Smad4.