SMPDL3A and hepatocellular carcinoma: Further application of CRISPR/Cas9 lentivirus vectors was used to knockout SMPDL3A in HepG2 and Huh7 cell lines to observe any changes in the biological function in HCC after knocking out SMPDL3A. Our results showed that the proliferation and tumorigenesis of HepG2 and Huh7 cells were significantly reduced after knocking out SMPDL3A. To further explore the reason for the decline in the cell proliferation through studying the cell cycle, we showed that knocking out SMPDL3A significantly prolonged early DNA synthesis and reduced late DNA synthesis in HCC cells.