Upregulated STAG3 Restrains The Biological Behaviors Of Hepatocellular Carcinoma Via Regulating Cell Cycle Pathway

Background and Objective: Liver cancer is a malignant tumor with high morbidity and mortality.Although Hepatocellular carcinoma(HCC)has a variety of therapeutic methods,the prognosis is still poor.Therefore,to reveal the molecular mechanism of the occurrence and development of HCC is the crucial to explore effective treatment methods.Stromal antigen 3(STAG3),as a subunit of the complex encoding adhesin,can regulate the cohesion of sister chromatids during cell division.Accumulated studies have found that STAG3 mutations cause chromosomal instability,which may potentially accelerate tumor progression.Currently,there have been relevant literature reports on epithelial ovarian cancer,colorectal cancer and melanoma.However,no studies have reported the effects of STAG3 on liver cancer and the related molecular mechanisms.This study aims to research the effects of overexpression of STAG3 on the biological functions of HCC cells and explore the related molecular mechanisms.Methods: Firstly,bioinformatics was used to analyze the expression of STAG3 in HCC patients and the correlation between STAG3 expression and survival rate(OS)in HCC patients.Then,in this study,normal liver cells and 4 kinds of HCC cells were used as the research objects.The level of m RNA relative expression of STAG3 in cell lines was detected by qRT-PCR assay.After that,the STAG3 overexpression(STAG3-OE)vector was constructed to obtain HCC cells that could stably express the STAG3.Further cytological experiments were carried out to find the biological function effects of STAG3 on HCC cells,such as CCK-8 assay,colony formation assay,wound-healing assay,Transwell assay,flow cytometry,tumor formation assay,western blot assay,etc.Results: 1.Bioinformation analysis showed that the expression level of STAG3 in HCC tissues was lower than that in paracancerous tissues,and that the expression level of STAG3 was positively correlated with the OS.2.The m RNA expression of STAG3 in HCC cell lines was significantly lower than that in human normal liver cell line MIHA.3.STAG3 inhibited the growth of HCC cells,induced the arrest of the G1/S phase in the cell cycle process and promoted the cell apoptosis.4.Tumor formation assay in nude mice showed that STAG3 inhibited tumor growth and promoted apoptosis.5.Western blot results showed that the protein expression Smad3 in HCC cells by STAG3-OE was increased,while the expression levels of CDK4,CDK6,Cyclin D1,CXCR4 and RhoA were all decreased.Conclusion: As a tumor suppressor gene,STAG3 regulates the biological function of HCC cells through the Smad3-CDK4/6-Cyclin D1 and CXCR4/RhoA pathways.As a potential target molecule,STAG3 provides a new idea for the treatment of HCC.