Epigenetic Alteration And Functions Of ZNF331 In Colorectal Cancer

Background:Colorectal cancer(CRC)is the third most commonly diagnosed cancer in males and the second in females worldwide.The incidence has sharply increased in the past two decades in developing countries with changing environmental factors,such as lifestyle and diet.Accumulation of aberrant genetic and epigenetic changes plays an important role in CRC initiation and progression.All these factors may cause colorectal cell epigenetic changes and further induces tumorigenesis.Thus,identification of new epigenetic biomarkers for diagnosis,prognosis,prediction and targeting therapy for CRC is necessary.Zinc-finger protein 331(ZNF331)was first identified from thyroid tumors.The ZNF331 gene is located at Chromosome 19q13.42,a region in which loss of heterozygosity(LOH)was detected in prostate cancer.In our previous study,we found that the ZNF331 gene is frequently methylated in human esophageal squamous cell cancer(ESCC)and it serves as a tumor suppressor in ESCC.The function of ZNF331 in human CRC remains unclear.Aim:To study ZNF331 gene expression and methylation in CRC cells,to study the functions and mechanism of ZNF331 in CRC,and to analyze the correlation between ZNF331 methylation and clinical characteristics and prognosis of colorectal cancer.Materials&Methods:Six colorectal cancer cell lines(DLD1,SW48,HCT116,SW480,SW620,DKO)and 146 cases of primary colorectal cancer samples were analyzed in this study.MSP,RT-PCR,BSSQ technology were used to research gene methylation and its regulation mechanism.Gene transfection technique,MTT assay,plate colony formation assay,Western blot,flow cytometry and siRNA technology were employed to study the function of ZNF331 on colorectal cancer cell.Xenograft mice model were used to observe the function of ZNF331 in vivo.Clinical data was analysed to study the correlation between ZNF331 methylation and the occurrence and prognosis of colorectal cancer.Results:Loss/reduced expression of ZNF331 and methylation of the ZNF331 was found in CRC cells.Loss of/reduced expression of ZNF331 is correlated with promoter region methylation.ZNF331 was methylated in 67.1%(98/146)of human primary colorectal cancer samples.Methylation of ZNF331 was significantly associated with tumor size,overall survival(OS),and disease-free survival(DFS)(p<0.01,p<0.01,p<0.05).Methylation of ZNF331 was an independent poor prognostic marker for 5-year OS and 5-year DFS(both p<0.05).ZNF331 suppressed cell proliferation and colony formation in CRC cells and suppressed human CRC cells xenograft growth in mice.Conclusion:ZNF331 is frequently methylated in human colorectal cancer,and the expression of ZNF331 is regulated by promoter region methylation.Methylation of ZNF331 is an independent poor prognostic marker in human colorectal cancer.