SCUBE3 Downregulation Modulates Hepatocellular Carcinoma By Inhibiting CCNE1 Via TGFβ/PI3K/AKT/GSK3β Pathway

Abstract Objectives: We aimed to verify the role of signal peptide-CUB-EGF-like domain-containing protein3 (SCUBE3) in the hepatocellular carcinoma (HCC) progression.Methods: The role·of SCUBE3 in HCC cell proliferation, apoptosis, and cell cycle in vitro were investigated using MTT assay, 5-ethynyl-2´-deoxyuridine assay (EDU), Celigo cell counting assay, Caspase3/7 activity assay, and flow cytometry. The effect of SCUBE3 on HCC cell proliferation in vivo was investigated by a xenograft tumor model in nude mice. The related mechanisms were further investigated.Results: SCUBE3 was upregulated in HCC tissues and cell lines. Knockdown of SCUBE3 inhibited proliferation, promoted apoptosis, and induced cell cycle arrest in HCC cell lines in vitro and vivo. Screening of cell cycle-related proteins revealed CCNL2, CDK6, CCNE1, and CCND1 exhibited a significantly different expression profile. We found that SCUBE3 may promote the proliferation of HCC cells by regulating CCNE1 expression. The pathway enrichment analysis showed that the TGFβ signaling pathway and the PI3K/AKT signaling pathway were significantly altered. Co-immunoprecipitation results showed that SCUBE3 binds to the TGFβRII receptor. SCUBE3 knockdown inhibited the PI3K/AKT signaling pathway and the phosphorylation of GSK3β to inhibit its kinase activity.Conclusions：SCUBE3 promotes HCC development by regulating CCNE1 via TGFβ/PI3K/AKT/GSK3βpathway. In addition, SCUBE3 may be a new molecular target for clinical diagnosis and treatment of HCC.