Thymidylate synthase polymorphism in sporadic colorectal and gastric cancer in Tunisian population: a predictive role in 5-fluorouracil based chemotherapy treatment

Association between polymorphisms of thymidylate synthase gene 5'- and 3'-UTR and gastric cancer risk: meta-analysis

Gastric cancer is the most common cancer and the most frequent cause of cancer death worldwide. Several studies have identified the role of thymidylate synthase (TS) 5′- and 3′-UTR and gastric cancer susceptibility; however, the results still remain inconclusive. The purpose of this meta-analysis was to reinvestigate this correlation. In the present study, online databases were searched to retrieve relevant articles published between January 2000 and 2016. The odds ratio (OR) and 95% confidence interval (CI) were employed to calculate the strength of association. Overall, a total of 13 articles were screened out, including 2382 gastric cancer patients and 3171 healthy controls. We found that polymorphisms of TS 5′-UTR 2R (double repeats)/3R (triple repeats) of a 28-bp sequence (11 articles) and 3′-UTR del6/ins6 (seven articles) were not significantly associated with increased risk of gastric cancer. Subgroup analysis by ethnicity showed that 2R allele and 2R/2R genotype in TS 5′-UTR were associated with gastric cancer susceptibility in Caucasian and African populations; del6 allele, del6/del6 and del6/ins6 genotypes were correlated with gastric cancer in Caucasian population. In conclusion, our result suggested that TS polymorphisms might be the risk factors for gastric cancer risk in Caucasian population, although this association needs further study, and future large-scale researches are still required.

Thymidylate Synthase Polymorphisms and Risk of Lung Cancer among the Jordanian Population: a Case Control Study

BACKGROUND

Thymidylate synthase (TS) catalyzes the methylation of deoxyuridylate to deoxythymidylate and is involved in DNA methylation, synthesis and repair. Two common polymorphisms have been reported, tandem repeats in the promoter-enhancer region (TSER), and 6bp ins/del in the 5'UTR, that are implicated in a number of human diseases, including cancer. The association between the two polymorphisms in risk for lung cancer (LC) was here investigated in the Jordanian population.

MATERIALS AND METHODS

An age, gender, and smoking-matched case-control study involving 84 lung cancer cases and 71 controls was conducted. The polymerase chain reaction/restriction fragment length polymorphism (PCR-RFLP) technique was used to detect the polymorphism of interest.

RESULTS

Individuals bearing the ins/ins genotype were 2.5 times more likely to have lung cancer [(95%CI: 0.98-6.37), p=0.051]. Individuals who were less than or equal to 57 years and carrying ins/ins genotype were 4.6 times more susceptible to lung cancer [OR<57 vs >57years: 4.6 (95%CI: 0.93-22.5), p=0.059)]. Genotypes and alleles of TSER were distributed similarly between cases and controls. Weak linkage disequilibrium existed between the two loci of interest (Lewontin's coefficient [D']) (LC: D' =0.03, r2: 0. 001, p= 0.8;

CONTROLS

D' =0.29, r2: 0.08, p=0.02). Carriers of the "3 tandem repeats_insertion" haplotype (3R_ins) were 2 times more likely to have lung cancer [2 (95%CI: 1.13-3.48), p=0.061].

CONCLUSIONS

Genetic polymorphism of TS at 3` UTR and its haplotype analysis may modulate the risk of lung cancer in Jordanians. The 6bp ins/del polymorphism of TS at 3 `UTR is more informative than TSER polymorphism in predicting increased risk.