| Objective:In recent years,the incidence rate and mortality of colorectal cancer(CRC)have been increasing year by year in China.An effective way to reduce the morbidity and mortality CRC colorectal cancer is early detection and early treatment.Finding meaningful susceptibility biological markers associated with colorectal cancer susceptibility is important for its early prevention.The development of colorectal cancer is the result of the combination of genetic and environmental factors.CRC molecular etiology reveals that this malignancy is developed by accumulation of genetic damage.DNA damage,if not properly repaired,and then accumulated can lead to genomic instability,cell senescence or apoptosis,and may eventually predispose organisms to multiple diseases,including malignant tumors.double-strand break(double-strand breaks,DSBs)is one of the most serious types of DNA damage,and its effective repair is an important mechanism to maintain genomic stability.Bioinformatics technology was used to carry out this study.Rad51 and BRCA1 in DSBR(DNA double strand break repair)repair system such as HR(homologous recombination)repair and XRCC4 and XRCC5 in NHEJ(non homologous end link)repair were selected as target genes,and SNP in 3’UTR region of target gene was selected based on the number of CRC cases selected in this study and MAF value(minimum allele frequency).The relationship between selected SNP and CRC risk was verified by case-control study of colorectal cancer and the possible mechanism of influencing CRC occurrence of SNP locus was studied by bioinformatics.For early diagnosis and detection CRC this study can find clear biological markers of susceptibility and provide new theoretical basis for its later precise treatment.Methods: 1.Bioinformatics method was used to select key enzyme genes BRCA1,BRCA2,RAD51,XRCC4 and XRCC5 in the double-strand fracture repair system as candidate target genes in this study.2.The method of Taqman hydrolysis probe wasused to detect the candidate SNPs of 202 CRC cases and 202 healthy control targets,and analyze the relationship between SNP polymorphism and risk of CRC.3.Bioinformatics predicted that AA genotype at BRCA1rs12516 promoted mir-4278 binding.In addition,GTEx database showed that the expression of mir-4278 in colorectal tissues of AA genotype was higher than that of GG genotype,while the expression of lncRNA-linc00910 that could bind to AA genotype was contrary to that of GG genotype,and the differences were statistically significant.Real-time quantitative PCR results showed that the expression of linc00910 and BRCA1 in AA genotype CRC at BRCA1rs12516 SNP decreased compared with that of GG genotype.Combined with the above results,when the BRCA1rs12516 SNP site was AA genotype,the mir-4278 binding site was created to bind to BRCA1 and the expression of BRCA1 was decreased,while the low expression of linc00910 decreased the ability of competitive binding to mir-4278,which indirectly caused the increase of mir-4278 expression and further promoted the binding of mir-4278 to BRCA1.Results: 1.Key enzyme genes RAD51,BRCA1,BRCA2,XRCC4,XRCC5 of DSBR system were selected as candidate genes in this study by bioinformatics technology.2.The gene polymorphism at BRCA1 rs12516 site is related to CRC susceptibility.The risk of CRC is higher for AA genotype carriers than GG genotype carriers(OR = 2.716,95% CI: 1.091-6.171);Male carriers with AA genotype have higher risk of CRC than those with GG genotype(OR=3.089,95%CI:1.315～7.255).Among people older than50 years old,the risk of CRC was higher among BRCA1 rs12516 AA genotype carriers than GG genotype carriers(OR=3.318,95%CI:1.571～7.006).Real-time quantitative fluorescence PCR results showed that the expression levels of linc00910 and BRCA1 in the CRC of AA genotype at BRCA1 rs12516 SNP were decreased compared with GG genotype.However,GTEx database showed that mir-4278 expression in colorectal tissues of AA genotype was higher than that of GG genotype.Combined with the above results,the linc00910-mir-4278-BRCA1 network created the binding site of mir-4278 when the BRCA1 rs12516 SNP site was AA genotype,thereby resulting in the bindingsite of mir-4278 and the decreased expression of BRCA1,while the low expression level of linc00910 was able to competitively bind mir-4278,which indirectly resulted in the increased expression of mir-4278 and further the binding of mir-4278 and BRCA1.Conclusion: AA genotype at rs12516 site of BRCA1 is a risk factor,which can increase the risk of CRC.The mechanism of action may be to reduce BRCA1 mRNA expression by binding miR-4278.The linc00910-mir-4278-ceRNA ceRNA network was predicted to be a possible mechanism of SNP rs12516 as a biomarker of CRC. |
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