| Objective:Radiotherapy is a common treatment for esophageal squamous-cell carcinoma (ESCC). However, the efficacy of radiotherapy differs significantly from individual to individual and the reason remains to be clarified. The ability to predict tumor response in routine clinical practice is difficult. Genetic variations of individual might affect clinical response to radiotherapy and overall survival in cancer patients. This study explored the associations between genetic variants in genes involved in TGF-β pathway and overall survival or risk of radiation-induced esophagitis in ESCC patients receiving radiotherapy only.Methods:Forty five haplotype-tagging single nucleotide polymorphisms (htSNPs) in 12 genes involved in TGF-β pathway were genotyped in 296 ESCC patients receiving unique treatment of radiotherapy. The associations between genotypes and risk of esophagitis were measured by odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for sex, age, tumor location, staging, radiotherapy technology and total radiation dose. Kaplan-Meier survival curve and log-rank test were applied to evaluate the differences of survival time among genotypes. The hazard ratios (HRs) were estimated using multivariate Cox proportional hazards regression model while the univariate Cox proportional hazards regression model was used to analyze the association between the clinical pathological parameters and prognosis. We also conducted biochemical assays to investigate the function of the SNP and gene associated with ESCC survival.Results:Among 296 patients,260 (87.8%) had died of ESCC until the last date of follow-up (30 June,2014). The median survival time (MST) of these patients was 14.0 months (2.0-148.0 months). We found that clinical stage (stage Ⅳ vs. stage Ⅱ) and total radiation dose (≥60 Gy vs.<60 Gy) had significantly impact on overall survival time, with the adjusted HRs of 1.97 (95% CI=1.34-2.89, P<0.001) and 0.64 (95% CI= 0.49-0.84, P=0.001). For the genetic factors, individuals with the CYR61 rs2297140 C allele had worse MST compared with the A allele, with the HR for death of ESCC being 1.39 (95% CI,1.15-1.69, P<0.001) calculated using multivariable-adjusted Cox additive model. The rest 44 SNPs were not associated with overall survival of ESCC patients treated with radiotherapy. Biochemical assays showed that rs2297140 C→A change displayed a lower promoter activity. The C allele had significantly increased luciferase expression and CYR61 mRNA levels in esophageal tissues compared with the A allele. Real-time quantitative PCR analysis showed that the expression levels of CYR61 mRNA were significantly higher in ESCC tissues than in their paired normal tissues (0.0521 ± 0.0055 vs.0.0269 ± 0.0035, P<0.001, n=83). Among 296 patients, 160 (54.1%) suffered from radiation-induced esophagitis. We found that four SNPs, including rs954353 in CYR61, rs17788084 in SDC2, rs1792678 in SMAD2 and rs8028147 in SMAD3, were associated with the risk of esophagitis, with the ORs being 1.52 (95% CI=1.06-2.20, P=0.024),0.51 (95% CI=0.30-0.89, P=0.017),0.63 (95% CI=0.47-0.85, P=0.002) and 0.68 (95% CI=0.49-0.95, P=0.025), respectively. We found that patients carrying more risk alleles tended to have higher risk of radiation-induced esophagitis. Compared with patients carrying≤3 risk alleles, OR for patients carrying 4-5 risk alleles or ≥6 risk alleles was 1.94 (95% CI=1.26-2.97, P= 0.003) or 2.66 (95% CI=1.34-5.28, P=0.005), with P=0.006 for trend test.Conclusions:Our results indicate that the genetic variation rs2297140 influences the expression of CYR61 and is a genetic factor determing ESCC prognosis in patients treated with radiotherapy. Other four SNPs (rs954353, rs17788084, rs1792678 and rs8028147) are associated with risk of radiation-induced esophagitis. Together, these findings suggest that genetic variations in the TGF-P pathway might serve as biomarkers for predicting esophagitis and the prognosis of radiotherapy in ESCC patients. |
