Expression Of SETD8 And Its Effect On EMT-related Proteins In Colorectal Cancer

Background:SETD8 is a lysine methyltransferase,which is up-regulated in a variety of tumors and promotes tumor progression and migration.However,the role of SETD8 in colorectal cancer(CRC)cells is still unclear.Objective:To explore the expression of SETD8 in CRC and its effect on epithelial-mesenchymal transformation(EMT),so as to provide experimental basis for clinical diagnosis and treatment of colorectal cancer.Methods:Tissue microarray of human colorectal tissue(36 cases of normal mucosa,10 cases of adenoma and 102 cases of CRC)was selected with a median follow-up period of 112 months.The expression of SETD8 was observed by immunohistochemical staining,and the relationship between the expression of SETD8 and the clinicopathological features of CRC was analyzed.The relationship between the expression of SETD8 and the prognosis of CRC patients was analyzed by Kaplan-Meier survival curve method.Immunohistochemical staining was used to observe the expression of SETD8 and EMT-related proteins(E-Cadherin,Snail and Vimentin)in CRC tissues.Esi RNA transfection technique was used to silence the expression of SETD8 gene in HCT116 and SW620 cell lines.Western blotting and immunofluorescence were used to detect the expression of SETD8 and EMT-related proteins in HCT116 and SW620 cell lines and their correlation.Results:1.The positive expression rate of SETD8 in CRC(59.8%)was significantly higher than that in normal colorectal mucosa(2.8%)and colorectal adenoma(20%)(P<0.001).The expression of SETD8 was correlated with clinical stage(P=0.016),distant metastasis(P=0.005)and chemotherapy(P=0.041)of CRC.2.The 10-year overall survival rate(OS:P=0.001)and disease-free survival rate(DFS:P=0.002)of CRC patients with SETD8 positive expression were significantly lower than those with negative expression.3.The results of Cox univariate analysis showed that age and T stage were not correlated with OS and DFS in CRC patients,but the positive expression of SETD8(OS:P=0.001;DFS:P=0.001),lymph nodes(OS:P<0.001;DFS:P<0.001)and distant metastasis(OS:P<0.001;DFS:P<0.001)were all correlated with OS and DFS in CRC patients,which were statistically significant.4.The results of Cox multivariate analysis showed that the positive expression of SETD8(OS:P=0.025;DFS:P=0.045)and distant metastasis(OS:P<0.001;DFS:P<0.001)were statistically significant.5.The expression of SETD8 was not correlated with EMT-related protein E-Cadherin(P=0.483),but positively correlated with Snail(P=0.025)and Vimentin(P=0.005).6.The results of Western blotting showed that after knocking down SETD8,the expression of E-Cadherin was significantly higher than that of the control group,while the expression of Snail and Vimentin was significantly lower than that of the control group.The results of immunofluorescence analysis showed that after knocking down SETD8,the fluorescence of E-Cadherin increased and that of Vimentin decreased.Conclusion:1.The high expression of SETD8 can be used as an independent predictor of prognosis in patients with CRC.2.SETD8 may be related to EMT-related proteins in CRC.