Association Between Single Nucleotide Polymorphisms Of BRAF Gene And Susceptibility Of Papillary Thyroid Carcinoma

ObjectivesPapillary thyroid carcinoma, a polygenic disease, is the most common type in thyroid cancer, accounting for80%-85%of al malignant thyroid carcinoma, frequently harbors the oncogenic BRAF. Single nucleotide polymorphisms(SNP) is the most common individual genetic differences, the most widespread, and takes the most closely relationship with all kinds of susceptibility or phenotype.We hypothesized that there were associations between single nucleotide polymorphisms of BRAF gene and susceptibility of papillary thyroid carcinoma and intended to investigate enviroment risk factors of papillary thyroid carcinoma.MethodsA hospital-based case-control study was conducted in Tianjin Medical University Cancer Hospital and Institute from June2007to September2009. A total of368papillary thyroid carcinoma patients and564healthy controls enrolled in this study.(1) All information was collected by questionnaire in face-to-face interview, which included demographic data, disease history, family history of cancer, behavior pattern, clinical data and laboratory data.(2) We used the blood samples10ml collected from cases and controls. Genomic DNA was extracted using TKM method.(3) The selection of SNP:screening tag SNP point (tSNP)(rs11762469A/T, rs17161747G/C, rs3748093T/A) through Hapmap database, coding DNA SNP point rs1042179A/G was obtained by examine relevant literature.(4) Polymorphism of BRAF gene was assessed by TaqMan-MGB Probe fluorescence real-time quantitative PCR.(5) Two-sided chi square test was used to identify Hardy-Weinberg equivalence and frequency differences between groups. Odds ratios and their95%confidence intervals for papillary thyroid carcinoma were derived using univariate and multivariate unconditional logistic regression analysis.Results(1) Anlysis frequency of genotype and allele frequencies of BRAF gene SNPs(rs104 2179A/G、rs11762469A/T、rs17161747G/C、rs3748093T/A)in cases and controls, but no significant difference between groups was found.Results from univatiate logistic regression analysis showed that the selected polymorphism of BRAF gene SNPs was not significantly associated with the risk of papillary thyroid cancer.(2) When we do a stratified analysis about BRAF gene rs3748093, there is a significantly differ between papillary thyroid carcinoma patients and healthy controls of age<45years(χ2=8.255,P=0.016) and age≥45years(χ2=6.049, P=0.049). Results from multivariate univatiate logistic regression analysis showed that BRAF gene rs3748093genotype carries the AT genotype and combind genetype AT+AA with age<45years could increase the risk of papillary thyroid carcinoma (aOR=1.751,95%CI=1.139-2.692, aOR=1.676,95%CI=1.106-2.541).(3) There is a significantly differ about BRAF gene rs1716174genotypes between papillary thyroid carcinoma patients and healthy controls in these with family history of tumor (χ2=8.739,P=0.012).BRAF gene rs17161747carries the CG genotype and combind CG+CC genotype with family history of tumor could increase the risk of papillary thyroid carcinoma(aOR=4.738,95%CI=1.703-13.180, aOR=3.235,95%CI=1.289-8.121).(4) There is no significantly differ about BRAF gene SNPs between papillary thyroid carcinoma patients and healthy controls in these without alcohol use status.BRAF gene rs3748093carries the AA genotype with alcohol use could increase the risk of papillary thyroid carcinoma (aOR=2.119,95%CI=1.004-4.472).(5) There is a significantly differ about BRAF gene rs1042179AA genetype and combined genetype AG+GG between papillary thyroid carcinoma patients and healthy controls with smoking status (χ2=5.588, P=0.018).BRAF gene rs1042179carries the combined genetype AG+GG with smoking could increase risk of papillary thyroid carcinoma (aOR=2.514,95%CI=1.100-5.744).(6) In papillary thyroid carcinoma patients separately, anlysis frequency of genotype and allele frequencies of BRAF gene SNPs about the groups whether the cases with extrathyroidal extension, there is no significantly differ about BRAF gene SNPs between the two groups (P>0.005). Results from multivariate univatiate logistic regression analysis showed that the selected polymorphism of BRAF gene rs17161747carries the AA genotype could decrease the risk of extrathyroidal extension (aOR=0.189,95%CI=0.041-0.873).(7) In papillary thyroid carcinoma patients separately, anlysis frequency of genotype and allele frequencies of BRAF gene SNPs about the groups whether the cases with lymph node metastasis, there is a significantly differ about BRAF gene rs3748093genotypes between the two groups (x2=10.786, P=0.005). Results from multivariate univatiate logistic regression analysis showed that the selected polymorphism of BRAF gene rs3748093carries the AT genotype and combined genotype AT+AA could decrease the lymph node metastasis (aOR=0.478,95%CI=0.307-0.746,aOR=0.500,95%CI=0.327-0.765).(8) In papillary thyroid carcinoma patients separately, when we do a stratified analysis by age layered, there is a significantly differ about BRAF gene(rs3748093)genotypes between two groups(χ2=8.186,P=0.017). Results from multivariate univatiate logistic regression analysis showed that the selected polymorphism of BRAF gene SNPs(rs3748093)carries the AT genotype in papillary thyroid carcinoma in choosing preference for younger(<45years)(aOR=0.619,95%CI=0.398-0.962).Conclusions1. Anlysis frequency of genotype and allele frequencies of BRAF gene SNPs(rs1042179A/G、rs11762469A/T、rs17161747G/C、rs3748093T/A)in cases and controls, but no significant difference between groups was found. But when we do a stratified analysis we reach that:1) With age<45years, rs3748093carriers of the genotype AT and combind genotype AT+AA increase the risk of papillary thyroid carcinoma2) with family history of tumor, rs17161747carriers of the genotype CG and combind genotype CG+CC increase the risk of papillary thyroid carcinoma3) Without alcohol use, rs3748093carriers of the genotype AA increase the risk of papillary thyroid carcinoma4) With smoking, rs1042179carriers of the combind genotype AG+GG increase the risk of papillary thyroid carcinoma2. In patients of papillary thyroid carcinoma:1) BRAF gene rs17161747carries the CC genotype could decrease the risk of extrathyroidal extension2) BRAF gene rs3748093carries the AT genotype could decrease the risk of lymph node metastasis3) BRAF gene rs3748093carries the AT genotype in papillary thyroid carcinoma in choosing preference for younger(<45years).3. In our study smoking and alcohol use may reduce the risk of papillary thyroid carcinoma.