Association And Functional Study Between Genetic Variation Of SSBP1 Gene And Gastric Cancer Prognosis

Object:In the present study,we set out to investigate the predictive role of single nucleotide polymorphisms(SNPs)in SSBP1 gene in gastric cancer(GC)patients'prognosis and explore the mechanisms underlying SSBP1 functional SNP and its gene expression.Methods:1.Correlation analysis between SSBP1 SNPs and GC patients'prognosis:We genotyped two functional SNPs(rs6976500 and rs12670074)in SSBP1 gene and evaluated their associations with clinicopathological parameters and prognosis of 1030surgical GC patients.The genotypes were determined using the Sequenom iPLEX system.Then we analyzed the associations between these two SNPs and GC patients'prognosis and chemotherapy by using Cox regression,Kaplan-Meier survival curve and log-rank test.2.Mechanisms investigation of the SNP rs6976500 on SSBP1 expression:We examined SSBP1 expression in GC cancerous tissues using immunochemistry to analyze the effect of rs6976500 genotypes on SSBP1 expression.Immunohistochemical(IHC)method was used to examined gastric cancer specimens,precancerous lesion and gastritis specimens SSBP1 expressions.Results:1.Correlation analysis between SSBP1 SNPs and GC patients'prognosis:(1)We found that SNP rs6976500 in SSBP1 gene was significantly associated with the overall survival(OS)and recurrence-free survival(RFS)of GC.The variant genotypes(CG+GG)of SNP rs6976500 significantly increased the risk of death(HR=1.41,95%CI=1.19-1.67,P<0.001)and recurrence(HR=1.50,95%CI=1.29-1.75,P<0.001)of GC patients when compared with the wild genotype(CC).Kaplan-Meier survival curves analysis showed that patients carrying variant genotypes(CG+GG)of SNP rs6976500 had a poorer OS and RFS than did those carrying wild(CC)genotype(all log-rank P<0.001).(2)SNP rs6976500 was an independent prognostic marker of GC.Receiver Operating Characteristic Curve(ROC)analysis demonstrated that SNP rs6976500 genotypes can improve the prognostic prediction of current TNM staging system in GC OS and RFS,the area under ROC(AUC)rose from 0.618 or 0.655 to 0.655 or 0.702,respectively(all P<0.05).Multivariate Cox analysis was further performed and found that patients carrying rs6976500 CG/GG genotypes at stage III and IV exhibited the highest risk of death(HR=3.10,95%CI=1.89-5.11;P<0.001)and recurrence(HR=2.39,95%CI=1.98-3.74;P<0.001)when using patients carrying rs6976500 CC genotype at stage I and II as reference.(3)We conducted stratified and interaction analyses of adjuvant chemotherapy(ACT)with rs6976500 and found that only patients carrying rs6976500 CG/GG genotypes could benefit from FOLFOX-based ACT.The risk of death and recurrence of patients received FOLFOX-based ACT were significantly reduced than those without FOLFOX-based ACT(OS:HR=0.51,95%CI=0.38-0.69,P<0.001;RFS:HR=0.44,95%CI=0.33-0.59,P<0.001),but not in those carrying CC genotype.2.Mechanisms investigation of the SNP rs6976500 on SSBP1 expression:(1)Compared to the variant genotypes(CG/GG)of rs6976500,the SSBP1 expression level in GCs with wild(CC)genotype of rs6976500 was significantly elevated in comparison to those with the variant genotypes(CG/GG)(4.68±0.58 vs.3.03±0.53,P=0.042).The expression of SSBP1 was significantly associated with malignant progression of gastric cancer(X~2=11.606,P=0.003).Kaplan-Meier curve analysis showed that GC patients with SSBP1 deletion had significantly shorter OS than those without SSBP1 deletion(Log-rank P=0.004).Conclusion:1.Our findings demonstrated that SSBP1 rs6976500 was an independent prognostic marker and can improve the prognostic prediction of current TNM staging system in GC.Additionally,SNP rs6976500 might serve as a potential marker to guide treatment decisions of GC patients.2.SNP rs6976500 can affect the expression of SSBP1 gene through an unknown mechanism,and then affect the biological function of many biological pathways,and ultimately affect the malignant progression and survival prognosis of gastric cancer.