The Function And Mechanism Of UBE2S In Hepatocellular Carcinoma Cells Proliferation And Epithelial-Mesenchymal Transition

Primary liver cancer is one of the most common malignant tumor,and hepatocellular carcinoma(HCC)is the most prevalent primary liver cancer.There are about 800,0000 new cases of liver cancer and about half in China.The 5 year survival rate of HCC patients is very low.In addition,rapid proliferation and high metastasis are the significant characteristics of HCC.Therefore,study on the process of cell proliferation and metastasis of HCC is very important for early diagnosis and improving prognosis of HCC patients.Ubiquitin-conjugating enzyme E2S(UBE2S),a family of E2 protein in the ubiquitin-proteasome system,can catalyze the binding of ubiquitin to protein and regulate various physiological and pathological processes through ubiquitination,such as cell cycle,signal transduction.In recent years,many studies had showed that in breast cancer,esophageal squamous cell carcinoma and other tumors,the expression of UBE2S in tumor was significantly higher than that in the non tumor tissue.In addition,UBE2S can directly affect cell cycle progression to promote cell proliferation.It can also plays an important role in regulating epithelial-mesenchymal transition(EMT)of tumor cells,which resulted in promoting tumor invasion and metastasis.However,in HCC,the role of UBE2S and its correlation with the prognosis of HCC patients have not been reported.According to the previous studies,this study focuses on the role and mechanism of UBE2S in HCC.In this study,we first analyzed the expression of UBE2S in HCC through TCGA and GEO databases.The results showed that the expression of UBE2S in HCC was higher than that in the non tumor tissue.In addition,the expression of UBE2S was associated with malignant behavior in HCC patient,and the overall survival of the HCC patients with high expression of UBE2S was significantly shorter than the patients with low UBE2S expression.Then we used Western blotting and Real-time PCR to analyze the expression of UBE2S in HCC.It was found that the expression of UBE2S in tumor was higher than that in the adjacent tissue,and it was associated with the prognosis of HCC patients.The HCC patients with high expression of UBE2S had shorter disease-free survival and overall survival.Meanwhile,we analyzed the mRNA and protein levels of UBE2S in different HCC cell lines.It was found that the expression of UBE2S in most HCC cell lines was higher than that in LO2.Next,the role of UBE2S in HCC cell lines was studied.We found that down-regulated the expression of UBE2S in HCC cell lines significantly inhibited the cell proliferation and migration.In addition,up-regulation of UBE2S increased HCC cells proliferation and migration,which suggested that UBE2S plays an important role in the occurrence and development of HCC.However,it is still unclear on how UBE2S regulates HCC cells proliferation and migration.Furthermore,the mechanism of UBE2S in regulation the process of HCC cell proliferation has been studied.We found that after down-regulated the expression of UBE2S in HCC cells,the cell-cycle was arrested in the G2/M phase.In addition,the results showed that UBE2S could regulate the expression of p21 to affect cell cycle.According to the previous studies,UBE2S can bind directly to VHL in tumor cells,such as renal cell carcinoma,and they could regulate tumor cell proliferation and migration through VHL/HIF-1? pathway.Based on these results,we detected the expression of VHL,after up-regulated and down-regulated the expression of UBE2S in HCC cells.We found that VHL protein was negatively related by UBE2S protein in HCC cells.In addition,there was a direct interaction between UBE2S and VHL.We aslo found that the UBE2S/VHL complex can regulate the activation of HIF-1? in HCC cells,which resulted in the activation of TGF-? pathway.Furthermore,the UBE2S/VHL complex could aslo regulate the activation of JAK2/STAT3 pathway,which eventually resulted in the rapid cell proliferation and metastasis of HCC.Based on these studies,we revealed the function and molecular mechanism of UBE2S in HCC.The results showed that in HCC,UBE2S can directly bind with VHL and regulate the activation of HIF-1? and JAK2/STAT3,which could promote the cell proliferation and EMT.In addition,UBE2S also affects the phosphorylation level of Smad2 and Smad3,which showed that UBE2S regulated the activition of TGF-?pathway.In conclusion,UBE2S is an important regulator in HCC.Inhibited the expression of UBE2S may open a new approach for HCC diagnosis and it can provide a new treatment option for HCC.