Magnifying endoscopic observation of the gastric mucosa, particularly in patients with atrophic gastritis

A gene-nutrient interaction between vitamin B6 and serine hydroxymethyltransferase (SHMT) affects genome integrity in Drosophila

Pyridoxal 5'-phosphate (PLP), the catalytically active form of vitamin B6, participates as a cofactor to one carbon (1C) pathway that produces precursors for DNA metabolism. The concerted action of PLP-dependent serine hydroxymethyltransferase (SHMT) and thymidylate synthase (TS) leads to the biosynthesis of thymidylate (dTMP), which plays an essential function in DNA synthesis and repair. PLP deficiency causes chromosome aberrations (CABs) in Drosophila and human cells, rising the hypothesis that an altered 1C metabolism may be involved. To test this hypothesis, we used Drosophila as a model system and found, firstly, that in PLP deficient larvae SHMT activity is reduced by 40%. Second, we found that RNAi-induced SHMT depletion causes chromosome damage rescued by PLP supplementation and strongly exacerbated by PLP depletion. RNAi-induced TS depletion causes severe chromosome damage, but this is only slightly enhanced by PLP depletion. dTMP supplementation rescues CABs in both PLP-deficient and PLP-proficient SHMT^RNAi . Altogether these data suggest that a reduction of SHMT activity caused by PLP deficiency contributes to chromosome damage by reducing dTMP biosynthesis. In addition, our work brings to light a gene-nutrient interaction between SHMT decreased activity and PLP deficiency impacting on genome stability that may be translated to humans.

Analysis of the TSER and G>C variants in the TYMS gene: a high frequency of low expression genotypes predicted in the Mexican population

BACKGROUND

In the TYMS gene promoter, there is a repeat polymorphism (TSER) that affects the expression level of the thymidylate synthetase (TS) enzyme involved in the response to some anticancer drugs. The G>C transversion located in the TSER*3R allele decreases the expression level of the TS enzyme avoiding the upstream stimulatory factor (USF-1) binding site. Despite the biomedical impact of the SNP G>C, only TSER has been reported in most worldwide populations. Thus, we studied both TSER and SNP G>C variants in the Mexican population.

SUBJECTS AND METHODS

A population sample (n = 156) was genotyped for the TSER and G>C variants by PCR and PCR-RFLPs, respectively, followed by PAGE and silver staining.

RESULTS

For TSER, the most frequent allele was 2 R (52.56%), as well as the genotype 2 R/3R (42.3%). Comparison with Latin American, European, and American (USA) populations suggest a heterogeneous worldwide distribution (F_ST-value = 0.01564; p-value = 0.0000). When the G>C variant was included (2RG, 3RG, and 3RC), a high frequency of low expression genotypes was observed: 2RG/2RG, 2RG/3RC, and 3RC/3RC (84.6%).

CONCLUSION

The high frequency of genotypes associated with low TS enzyme expression justifies obtaining the TYMS gene variant profile in Mexican patient's candidates to pharmaceutical treatments like 5'-Fluoracil, methotrexate, and pemetrex.

Association between 5'-UTR and 3'-UTR Polymorphisms of the TYMS Gene and Breast Cancer in Kurdish Women of Iraq

Breast cancer is a common cancer found among women worldwide. Many polymorphisms can play a role in the development of this disease. The study was conducted to evaluate whether 2R/3R and 6bp insertion/deletion polymorphisms of the TYMS gene are associated with breast cancer risk in the Kurdish Iraqi population.

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.

Evaluation of effects of thymidylate synthase and excision repair cross-complementing 1 polymorphisms on chemotherapy outcome in patients with gastrointestinal tumors using peripheral venous blood

The aim of the present study was to evaluate the effects of thymidylate synthase (TYMS) and excision repair cross-complementing 1 (ERCC1) polymorphisms on chemotherapeutic efficacy in patients with gastrointestinal tumors using peripheral venous blood. Preoperative peripheral venous blood and tumor tissue samples of 43 patients with gastric cancer and the peripheral venous blood samples of 76 patients with cancer who underwent chemotherapy were studied. The 3R/3R and 2R/2R or 2R/3R genotypes of TYMS were identified in 72.09 and 27.91%, respectively (P<0.01), of untreated patients, and the C/C and T/T or C/T genotypes of ERCC1 were present in 81.39 and 18.61%, respectively (P<0.01), of patients. The 3R/3R and 2R/2R or 2R/3R genotypes of TYMS were identified in 65.79 and 34.21%, respectively, of chemotherapy-treated patients. The overall response rates (ORRs) for the two aforementioned genotypes were 18.00 and 57.69%, respectively (P<0.01), and those for the C/C and T/T or C/T genotypes of ERCC1 were 63.16 and 36.84%, respectively. The ORRs were 47.91 and 3.57%, respectively (P<0.01). In conclusion, peripheral blood samples may be used to replace tumor tissue for detecting TYMS and ERCC1 polymorphisms, and may be used to evaluate the efficacy of 5-fluorouracil and platinum drugs.

Technical reproducibility of single-nucleotide and size-based DNA biomarker assessment using DNA extracted from formalin-fixed, paraffin-embedded tissues

DNA extracted from formalin-fixed, paraffin-embedded (FFPE) tissues has been used in the past to analyze genetic polymorphisms. We evaluated the technical reproducibility of different types of assays for gene polymorphisms using DNA extracted from FFPE material. By using the MassARRAY iPLEX system, we investigated polymorphisms in DPYD (rs1801159 and rs3918290), UMPS (rs1801019), ERCC1 (rs11615), ERCC1 (rs3212986), and ERCC2 (rs13181) in 56 FFPE DNA samples. By using PCR, followed by size-based gel electrophoresis, we also examined TYMS 5' untranslated region 2R/3R repeats and GSTT1 deletions in 50 FFPE DNA samples and 34 DNAs extracted from fresh-frozen tissues and cell lines. Each polymorphism was analyzed by two independent runs. We found that iPLEX biomarker assays measuring single-nucleotide polymorphisms provided consistent concordant results. However, by using FFPE DNA, size-based PCR biomarkers (GSTT1 and TYMS 5' untranslated region) were discrepant in 32.7% (16/49, with exact 95% CI, 19.9%-47.5%; exact binomial confidence limit test) and 4.2% (2/48, with exact 95% CI, 0.5%-14.3%) of cases, respectively, whereas no discrepancies were observed using intact genomic DNA. Our findings suggest that DNA from FFPE material can be used to reliably test single-nucleotide polymorphisms. However, results based on size-based PCR biomarkers, and particularly GSTT1 deletions, using FFPE DNA need to be interpreted with caution. Independent repeated assays should be performed on all cases to assess potential discrepancies.

Germline oncopharmacogenetics, a promising field in cancer therapy

Pharmacogenetics (PGx) is the study of the relationship between inter-individual genetic variation and drug responses. Germline variants of genes involved in drug metabolism, drug transport, and drug targets can affect individual response to medications. Cancer therapies are characterized by an intrinsically high toxicity; therefore, the application of pharmacogenetics to cancer patients is a particularly promising method for avoiding the use of inefficacious drugs and preventing the associated adverse effects. However, despite continuing efforts in this field, very few labels include information about germline genetic variants associated with drug responses. DPYD, TPMT, UGT1A1, G6PD, CYP2D6, and HLA are the sole loci for which the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA) report specific information. This review highlights the germline PGx variants that have been approved to date for anticancer treatments, and also provides some insights about other germline variants with potential clinical applications. The continuous and rapid evolution of next-generation sequencing applications, together with the development of computational methods, should help to refine the implementation of personalized medicine. One day, clinicians may be able to prescribe the best treatment and the correct drug dosage based on each patient's genotype. This approach would improve treatment efficacy, reduce toxicity, and predict non-responders, thereby decreasing chemotherapy-associated morbidity and improving health benefits.

Folate-related polymorphisms in gastrointestinal stromal tumours: susceptibility and correlation with tumour characteristics and clinical outcome

The folate metabolism pathway has a crucial role in tumorigenesis as it supports numerous critical intracellular reactions, including DNA synthesis, repair, and methylation. Despite its importance, little is known about the influence of the folate pathway on gastrointestinal stromal tumour (GIST), a rare tumour with an incidence ranging between 6 and 19.6 cases per million worldwide. The importance of folate metabolism led us to investigate the influence of polymorphisms in the genes coding folate-metabolising enzymes on GIST susceptibility, tumour characteristics and clinical outcome. We investigated a panel of 13 polymorphisms in 8 genes in 60 cases and 153 controls. The TS 6-bp deletion allele (formerly rs34489327, delTInsTTAAAG) was associated with reduced risk of GIST (OR=0.20, 95% CI 0.05-0.67, P=0.0032). Selected polymorphisms in patients stratified by age, gender, and other main molecular and clinical characteristics showed that few genotypes may show a likely correlation. We also observed a significant association between the RFC AA/AG genotype and time to progression (HR=0.107, 95% CI 0.014-0.82; P=0.032). Furthermore, we observed a tendency towards an association between the SHMT1 variant allele (TT, rs1979277) and early death (HR=4.53, 95% CI 0.77-26.58, P=0.087). Aware of the strengths and limitations of the study, these results suggest that polymorphisms may modify the risk of GIST and clinical outcome, pointing to the necessity for further investigations with information on folate plasma levels and a larger study population.

Genetic polymorphisms in the microRNA binding-sites of the thymidylate synthase gene predict risk and survival in gastric cancer

Thymidylate synthase (TYMS) plays a crucial role in folate metabolism as well as DNA synthesis and repair. We hypothesized that functional polymorphisms in the 3' UTR of TYMS are associated with gastric cancer risk and survival. In the present study, we tested our hypothesis by genotyping three potentially functional (at miRNA binding sites) TYMS SNPs (rs16430 6bp del/ins, rs2790 A>G and rs1059394 C>T) in 379 gastric cancer patients and 431 cancer-free controls. Compared with the rs16430 6bp/6bp + 6bp/0bp genotypes, the 0bp/0bp genotype was associated with significantly increased gastric cancer risk (adjusted OR = 1.72, 95% CI = 1.15-2.58). Similarly, rs2790 GG and rs1059394 TT genotypes were also associated with significantly increased risk (adjusted OR = 2.52, 95% CI = 1.25-5.10 and adjusted OR = 1.57, 95% CI = 1.04-2.35, respectively), compared with AA + AG and CC + CT genotypes, respectively. In the haplotype analysis, the T-G-0bp haplotype was associated with significantly increased gastric cancer risk, compared with the C-A-6bp haplotype (adjusted OR = 1.34, 95% CI = 1.05-1.72). Survival analysis revealed that rs16430 0bp/0bp and rs1059394 TT genotypes were also associated with poor survival in gastric cancer patients who received chemotherapy treatment (adjusted HR = 1.61, 95% CI = 1.05-2.48 and adjusted HR = 1.59, 95% CI = 1.02-2.48, respectively). These results suggest that these three variants in the miRNA binding sites of TYMS may be associated with cancer risk and survival of gastric cancer patients. Larger population studies are warranted to verify these findings.

Single tube genotyping of TYMS 1494del6 polymorphism in the Chinese Han population by duplex scorpion primers

BACKGROUND

The development of pharmacogenomics has created an urgent need for robust molecular characterization. And it has become a challenge to develop suitable detecting methods for routine clinical use.

AIM

The aim of the current study is to develop a simple and reliable TYMS 1494del6 polymorphism genotyping assay by duplex scorpion primers in the Chinese Han population.

METHOD

We evaluated the performance of the duplex scorpion primer assay in the genotyping of TYMS 1494del6 polymorphism and screened 54 DNA samples of the Chinese Han population. The results were further validated by pyrosequencing.

RESULTS

The duplex scorpion primer assay showed high specificity and accuracy for genotyping TYMS 1494del6 polymorphism. Complete concordance was observed between the duplex scorpion primer assay and pyrosequencing. The frequency of the TYMS +6 bp allele was 34% and the -6 bp allele was 66% in 54 Chinese Han population DNA samples.

CONCLUSION

The duplex scorpion primer assay provides a rapid, reliable and high-throughput method to genotype TYMS 1494del6 polymorphism in the Chinese Han population.

Thymidylate synthase polymorphisms are associated to therapeutic outcome of advanced non-small cell lung cancer patients treated with platinum-based chemotherapy

Thymidylate synthase (TYMS) has three polymorphisms that may modulate thymidylate synthase (TS) expression levels: (1) 28 base pairs (bp) variable number tandem repeat (VNTR) (rs34743033); (2) single nucleotide polymorphism (SNP) C>G at the twelfth nucleotide of the second repeat of 3R allele (rs2853542); and (3) 6 bp sequence deletion (1494del6, rs34489327). This study was conducted to evaluate the influence of TYMS polymorphisms on the survival of Portuguese patients with advanced non-small cell lung cancer (NSCLC) undergoing platinum-based chemotherapy. Our results showed no statistically significant differences between VNTR genotypes; although, considering the SNP C>G, homozygotes 3RG presented a better prognostic at 36 months (p=0.004) and overall survival (p=0.003) when compared to 2R3RG patients. Patients with "median/high expression genotypes" demonstrated a better survival at 12 months (p=0.041) when compared to "low expression genotypes". Furthermore, 6 bp- carriers (p=0.006) showed a better survival at 12 months when compared to 6 bp+ homozygotes patients. When analyzing TYMS haplotypes, better survival at 12 months was observed for patients carrying haplotypes with the 6 bp- allele (2R6 bp-; p=0.026 and 3RG6 bp-; p=0.045). This is the first report that evaluates the three major TYMS polymorphisms in the therapeutic outcome of NSCLC in Portugal. According to our results, the TYMS polymorphisms may be useful tools to predict which advanced NSCLC patients could benefit more from platinum-based chemotherapy regimens.

Current approaches for TYMS polymorphisms and their importance in molecular epidemiology and pharmacogenetics

TS is critical for providing the requisite nucleotide precursors in order to maintain DNA synthesis and repair. Furthermore, it is an important target for several drugs such as 5-fluorouracil and methotrexate. However, several mechanisms of resistance to TS inhibitors have been explained as linked to TYMS overexpression. Some authors have described the relationship between genetic polymorphisms on TYMS, in particular rs34743033, rs2853542 and rs34489327, with the development of several diseases and with the clinical response to drug therapy and/or survival. Nevertheless, the obtained results described in the literature are controversial, which has lead to a search strategy to understand the impact of these polymorphisms on molecular epidemiology and pharmacogenetics. With the progress of these scientific areas, early identification of individuals at risk of disease along with improvement in the prediction of patients’ outcome will offer a powerful tool for the translation of TYMS polymorphisms into clinical practice and individualization of treatments.

TS gene polymorphisms in gastric cancer and colorectal cancer

Gastric cancer and colorectal cancer are the most common gastrointestinal tumors worldwide. The development, metastasis and recurrence of gastric cancer and colorectal cancer are complex and are affected and regulated by many factors. These factors have important significance in guiding treatment and predicting prognosis. Recent studies have shown that thymidylic acid synthase (TS) is closely related with the occurrence, chemotherapy and prognosis of gastric cancer and colorectal cancer; however, there is still some controversy over this view. This review discusses the relationship between TS gene polymorphisms and gastric cancer and colorectal cancer.

Polymorphisms of folate pathway enzymes (methylenetetrahydrofolate reductase and thymidylate synthase) and their relationship with thymidylate synthase expression in human astrocytic tumors

Two important polymorphisms of folate cycle enzymes, methylenetetrahydrofolate reductase (MTHFR) C677T and thymidylate synthase (TS) enhancer region (TSER) 28-bp tandem repeat, are related to risk of various types of cancer, including brain tumors, although there are few studies on this subject. A case-control study of these two polymorphisms in astrocytomas of different grades was carried out using polymerase chain reaction-restriction fragment length polymorphism, also determining the immunohistochemical expression of TS. The MTHFR 677 TT genotype was less associated with astrocytic tumors (odds ratio [OR]=0.00; p=0.0238), but the TSER polymorphism did not show any significant association. Combined genotype TT-double repeats/triple repeats (2R/3R) had a protective effect against astrocytomas (OR=0.00; p=0.0388). Expression of TS protein was observed in the majority of cases, with grade IV tumors being the exception. Moreover, the median H-score for the pilocytic astrocytomas was significantly higher when compared with that for diffuse tumors. There was an inverse correlation between the 2R/2R genotype and the highest TS-expressing tumors, and 3R/3R was relatively more frequent among the tumors grouped in the third and fourth quartiles. Our results provide support for the role of MTHFR and TS polymorphism in gliomagenesis, possibly because of the alteration of DNA methylation and repair status. Moreover, high levels of TS expression were detected in these tumors.

Influence of thymidylate synthase gene polymorphisms on total plasma homocysteine concentrations

BACKGROUND

Thymidylate synthase (TS) is a key enzyme that regulates the production of nucleotide synthesis by catalyzing the conversion of deoxyuridylate to thymidylate. Three functional polymorphisms in the TS gene have been identified including: (i) the thymidylate synthase enhancer region (TSER) tandem repeat polymorphism and (ii) the G to C single nucleotide polymorphism (G/C SNP) both of which occur in the 5'untranslated region (UTR) of the TS gene; and (iii) the 6 base pair deletion at base pair 1494 (TS1494del6) located in the 3'UTR.

PURPOSE

The purpose of this research was to investigate the relationship between TS polymorphisms and total plasma homocysteine (tHcy) levels.

METHODS

The study population consisted of 396 healthy male and female volunteers from Kingston, Ontario and Halifax, Nova Scotia, Canada between 2006 and 2008. The effect of each TS polymorphism on tHcy concentrations was investigated and further analyses were conducted on categorization of polymorphisms based on 5' or 3'UTR. The combined effect of TS polymorphisms on tHcy concentration was also investigated, in addition to interactions between polymorphisms in TS and MTHFR 677C>T and interactions between TS polymorphisms and serum folate and vitamin B(12) status.

RESULTS

An association between TS 5'polymorphisms and tHcy concentration was observed (p=0.05). The combined effect of the TS polymorphisms was also found to be associated with tHcy concentration (p=0.05). Additionally, an antagonistic interaction was observed between TS 5'polymorphism and MTHFR 677C>T on tHcy concentrations (p=0.04).

CONCLUSIONS

The findings of this research provide evidence of an association between TS polymorphisms and tHcy concentrations.

Polymorphisms of thymidylate synthase in the 5'- and 3'-untranslated regions and gastric cancer

Studies investigating the association of polymorphisms in the 5'-untranslated regions (5'UTR) and 3'-untranslated regions (3'UTR) of thymidylate synthase with gastric cancer susceptibility and sensitivity to fluoropyrimidine-based chemotherapy report conflicting results. The objective of this study was to quantitatively summarize the evidence for such a relationship. This meta-analysis included ten studies, which included 1,730 gastric cancer cases and 1,843 controls. The combined results based on all studies showed that there was no significant difference in genotype distribution of 5'UTR or 3'UTR between gastric cancer and noncancer patients. When stratifying for race, we found that: (1) among Asians, patients with gastric cancer had significantly higher frequency of 2R/2R of 5'UTR than did noncancer patients, and (2) among Caucasians, patients with gastric cancer had significantly lower frequency of ins6/ins6 and higher frequency of ins6/del6 of 3'UTR than did noncancer patients. No significantly different response rate or survival of gastric cancer with fluoropyrimidine-based chemotherapy were observed with genotype distribution of 5'UTR or 3'UTR among Caucasians or Asians. This meta-analysis suggests that polymorphisms in the 5'UTR and 3'UTR of thymidylate synthase may be associated with gastric cancer susceptibility, but are not correlated with sensitivity of gastric cancer to fluoropyrimidine-based chemotherapy.

Association of thymidylate synthase gene with endometrial cancer risk in a Chinese population

We comprehensively evaluated genetic variants in the thymidylate synthase (TYMS) gene in association with endometrial cancer risk in a population-based case-control study of 1,199 incident endometrial cancer cases and 1,212 age frequency-matched population controls. Exposure information was obtained via in-person interview, and DNA samples (blood or buccal cell) were collected. Genotyping of 11 haplotype-tagging single nucleotide polymorphisms (SNP) for the TYMS gene plus the 5-kb flanking regions was done for 1,028 cases and 1,003 controls by using the Affymetrix MegAllele Targeted Genotyping System. Of 11 haplotype-tagging SNPs identified, 7 that are located in flanking regions of the TYMS gene are also in the ENOSF1 (rTS) gene. The SNP rs3819102, located in the 3'-flanking region of the TYMS gene and in an intron of the ENOSF1 gene, was associated with risk of endometrial cancer. The odds ratio (95% confidence interval) for the CC genotype was 1.5 (1.0-2.2) compared with the TT genotype. Haplotype TTG in block 2 of the TYMS gene, which includes SNPs rs10502289, rs2298583, and rs2298581 (located in introns of the ENOSF1 gene), was associated with a marginally significant decrease in risk of endometrial cancer under the dominant model (odds ratio, 0.8; 95% confidence interval, 0.6-1.0). This study suggests that genetic polymorphisms in the TYMS or ENOSF1 genes may play a role in the development of endometrial cancer among Chinese women.

Screening of 214 single nucleotide polymorphisms in 44 candidate cancer susceptibility genes: a case-control study on gastric and colorectal cancers in the Japanese population

OBJECTIVES

Single nucleotide polymorphisms (SNPs) have potential as markers for identifying genes responsible for common diseases and for personalized medicine. To investigate the association between polymorphisms and gastrointestinal (gastric and colorectal) cancer, we performed a hospital-based case-control study in Japan.

METHODS

We screened a total of 214 SNPs in 44 candidate genes by using a mass spectrometry-based technique (MassARRAY; Sequenom, Inc., San Diego, CA). In this study, 153 patients and 302 controls for gastric cancer and 121 patients and 245 controls for colorectal cancer were matched with regard to age, sex, and residential area. Genes were selected based on their possible interactions with the environment and lifestyle, and the candidate genes constitute those encoding xenobiotic metabolism enzymes, DNA repair enzymes, and other stress-related proteins. Each polymorphism was tested in controls to ensure its fit with Hardy-Weinberg equilibrium. Odds ratios (OR) and 95% confidence intervals (CI) were calculated by conditional logistic regression analysis to estimate the association between genetic polymorphisms and the risk of gastric and colorectal cancers.

RESULTS

Twenty-one SNPs in nine genes were associated with the risk of gastric cancer (P < 0.05) and 15 SNPs in nine genes were associated with the risk of colorectal cancer (P < 0.05).

CONCLUSIONS

The findings of the present study will be the basis for future large-scale association studies of gene-environment factors using the candidate gene approach for the Japanese population.

Pharmacogenetically relevant polymorphisms in Portugal

OBJECTIVE

Most drugs are developed based on data from European-derived 'reference' populations; however, clinically relevant DNA polymorphisms often demonstrate population-specific patterns of allele frequencies. Given that the knowledge of the frequency distribution of functional polymorphisms in a population may guide national planning for selection of therapeutic options, in the present study we examined the allele frequencies of enzymes responsible for drug disposition in Portugal.

PATIENTS & METHODS

Using PCR- and Pyrosequencing-based methods, the current study assessed the frequencies of 15 key polymorphisms from genes encoding enzymes involved in Phases I, II and III of drug metabolism, DNA repair and intracellular metabolism in 135 healthy individuals from Portugal.

RESULTS

Allele frequencies were derived for cytochrome P450 (CYP)2C9*2 (13.2%), CYP2C9*3 (8%), CYP2C19*2 (14%), CYP3A4*1B (7%), CYP3A5*3C (87.5%), glutathione S-transferase (GST)M1*0 (77.9%), GSTP1 313A>G (33%), inosine triphosphatase 94C>A (7%), UDP-glucuronosyltransferase (UGT)1A1*28 (28%), UGT1A1 -3156G>A (23%), ATP-binding cassette (ABC)B1 1236C>T (46%), ABCB1 2677G>A/T (2 and 42%), ABCG2 421C>A (8%), excision repair cross-complementing rodent repair deficiency 2 2251A>C (3%) and thymidylate synthetase 1494del (31%).

CONCLUSION

Although, on the whole, the frequency distributions among the Portuguese fitted the patterns commonly found in other Europeans well, evidence for some degree of African influence was observed. This is the most comprehensive study on pharmacogenetically relevant variations in Portugal to date, and the baseline of pharmacogenetic data might be important for determining policy guidelines for cancer prevention and drug treatments in the Portuguese population.

Pharmacogenetic study of methylenetetrahydrofolate reductase and thymidylate synthase in Japanese and assessment of ethnic and gender differences

OBJECTIVES

We investigated the four polymorphisms of the 5,10-methylenetetrahydrofolate reductase (MTHFR) and thymidylate synthase (TYMS) genes that are related to the pharmacologically active sites of methotrexate for the treatment of rheumatoid arthritis in 102 healthy Japanese adults and assessed the possibility of ethnic and gender differences.

METHODS

Polymorphisms of MTHFR C677T, A1298C, the two or three 28-bp tandem repeats in the TYMS 5'-untranslated regions (UTR), and the 6-bp deletion/insertion in the TYMS 3'-UTR were measured using polymerase chain reaction with restriction fragment length polymorphism method. Published data on allelic frequencies by ethnic group and gender were collected from Medline.

RESULTS

Allelic frequencies in healthy Japanese adults were: MTHFR 677T allele 41%, MTHFR 1298C allele 22%, TYMS 5'-UTR 3R allele 84%, and TYMS 3'-UTR-6-bp allele 59%. Significant differences were found in the distribution of MTHFR C677T between black and Japanese populations, of TYMS 5'-UTR alleles between Caucasian or black and Japanese populations, and of TYMS 3'-UTR alleles between Caucasian and Japanese populations (p < 0.001). Moreover, a gender difference was found in TYMS 3'-UTR allelic frequency in Japanese (p = 0.015).

CONCLUSION

Ethnic and gender variations in the distribution of these allelic frequencies may associate with the difference in the effects of methotrexate in rheumatoid arthritis patients.

Polymorphisms of MTHFD, plasma homocysteine levels, and risk of gastric cancer in a high-risk Chinese population

PURPOSE

Accumulative evidence suggests that folate has a protective effect on gastric cancer. The methylenetetrahydrofolate dehydrogenase (MTHFD) plays an important role in folate and homocysteine metabolisms, and polymorphisms of MTHFD may result in disturbance of the folate-mediated homocysteine pathway. The aim of this study is to test the hypothesis that genetic variants of MTHFD and plasma homocysteine levels are associated with risk of gastric cancer and modulated by genotypes of methylenetetrahydrofolate reductase (MTHFR).

EXPERIMENTAL DESIGN

We genotyped G1958A and T401C in MTHFD and C677T in MTHFR and detected total plasma homocysteine (tHcy) levels in a case-control study of 589 gastric cancer cases and 635 cancer-free controls in a high-risk Chinese population.

RESULTS

The variant genotypes of MTHFD 1958AA and 401CC were associated with a significantly increased risk of gastric cancer [adjusted odds ratio (OR), 2.05; 95% confidence interval (95% CI), 1.34-3.13 for 1958AA; adjusted OR, 1.43; 95% CI, 1.14-1.80 for 401CC] compared with 1958GG/GA and 401TT/TC genotypes, respectively. Both of the effects were more evident in the subjects carrying MTHFR 677CT/TT genotypes. The average tHcy level was significantly higher in gastric cancer cases than in controls (P < 0.01), and the upper quartile of tHcy (>13.6 micromol/L) was associated with an 82% significantly increased risk of gastric cancer, compared with the lowest quartile of tHcy (<or=8.0 micromol/L; adjusted OR, 1.82; 95% CI, 1.20-2.75).

CONCLUSIONS

The strong associations between MTHFD variants and the plasma tHcy levels and gastric cancer risk suggest, for the first time, a possible gene-environment interaction between genetic variants of folate-metabolizing genes and high tHcy levels in gastric carcinogenesis.

Polymorphisms involved in the folate metabolizing pathway and risk of multiple myeloma

Folate and methionine metabolism plays an essential role in both DNA synthesis and methylation. Polymorphisms in the genes of the folate-dependent enzymes have been shown to affect disease susceptibility. We conducted a Korean population-based case-control study to evaluate whether genetic variation in folate metabolism may have a role in the risk of multiple myeloma (MM). The study subjects were 173 patients with MM and 1,700 population-based controls. The polymorphisms studied include methylenetetrahydrofolate reductase (MTHFR) 677 C > T and 1298 A > C, methionine synthase (MS) 2756 A > G, methionine synthase reductase (MTRR) 66A > G, thymidylate synthase (TS) 28-bp repeat (2R-->3R) and 6-bp deletion/insertion. MS 2756 AG genotypes were associated with a 1.5-fold lower risk of MM (OR = 0.66, 95%CI; 0.43-0.99, P = 0.047). There was no association between MTHFR C677T, A1298C, MTRR A66G, TS 2R-->3R and 6-bp deletion/insertion polymorphisms and MM. These results suggest that MTHFR C677T, A1298C, MTRR A66G, TS 2R-->3R, and 6-bp deletion/insertion do not significantly factor into the pathogenesis of MM in the Korean population, but that MS A2756G polymorphism may play an important role.

Involvement of gene polymorphisms of thymidylate synthase in gene expression, protein activity and anticancer drug cytotoxicity using the NCI-60 panel

A significant association has been established, in clinical studies, between the expression or activity of thymidylate synthase (TYMS) and the efficiency of fluorouracil. TYMS expression is partly under the dependence of gene polymorphisms in the 5' and 3' untranslated regions (UTR), but conflicting results have been obtained about their roles on fluorouracil efficiency. In this study, we wanted to use the National Cancer Institute (NCI) panel of 60 human tumour cell lines to clarify this problem. Three relevant polymorphisms of the TYMS gene were studied: (i) the 5'UTR tandem repeat of 28-bp (2R/3R polymorphism); (ii) the single nucleotide polymorphism (SNP) within the second repeat (3C/3G polymorphism); (iii) the 3'UTR 6-bp deletion (+6/-6 polymorphism). Allele frequencies were close to those expected in a Caucasian population (2R/3C/3G: 53/29/18%; +6/-6: 68/32%), but the proportion of heterozygous genotypes was lower than expected from allele frequencies. The 2R and 3G alleles were significantly associated with the +6 and the -6 alleles, respectively. There was a significant association between the presence of the 3G allele and TYMS mRNA expression and catalytic activity, particularly in p53-mutated cell lines. However, no significant correlation existed between fluorouracil cytotoxicity, as extracted from the NCI databases, and TYMS expression, activity or polymorphisms.

Polymorphisms in the thymidylate synthase promoter and the DNA repair genes XRCC1 and XPD in a Brazilian population

Polymorphisms in genes responsible for maintaining genomic integrity are potential modifiers of disease risk. Since considerable interindividual and interethnic variation in DNA repair capacity has been associated with polymorphic alleles, we evaluated the frequency of the 2R/3R variants in the TS promoter, Arg194Trp and Arg399Gln in the XRCC1 gene, and Asp312Asn and Lys751Gln in the XPD gene in 364 healthy individuals from a Brazilian population separated by ethnicity (European ancestry and African ancestry). The genotypes were determined by PCR (TS) or by PCR-RFLP (XRCC1 and XPD). The frequency of the TS 3R allele was 0.56 for whites and 0.51 for nonwhites. In the case of the XRCC1 MspI polymorphism, the allele frequencies were 0.09 for 194Trp in both nonwhites and whites and 0.27 and 0.28 for 399Gln in nonwhites and whites, respectively. For the XPD 312Asn allele, we found a frequency of 0.25 in white individuals, which was significantly different (P = 0.025) from that seen in nonwhites (0.15). Similarly, the 751Gln polymorphic allele of the XPD gene was significantly more frequent (P < 0.002) in whites (0.30) than in nonwhites (0.20). The genotype frequencies were within Hardy-Weinberg equilibrium. We concluded that the genotype and allele frequencies of XPD gene polymorphism differed between white and nonwhite Brazilians, and that the frequencies of the XPD 312Asn and XRCC1 399Gln alleles in this Brazilian population showed ethnic variability when compared with those observed in other populations.

A novel G/C single-nucleotide polymorphism in the double 28-bp repeat thymidylate synthase allele

Thymidylate synthase (TYMS) is the main molecular target for fluoropyrimidine anticancer drugs, and its expression has been correlated with the number of repeats of a 28-bp sequence in the 5'-untranslated region of the TYMS gene and with the presence of a G --> C single-nucleotide polymorphism in the second repeat of 3R alleles. Based on this double polymorphism, three main TYMS alleles have so far been identified: TYMS 2R, TYMS 3RC and TYMS 3RG. During genetic analysis of TYMS polymorphisms in 100 colorectal cancer patients, three patients revealed an unexpected 113-bp band after electrophoresis of the restriction fragment length polymorphism analysis. Subsequent sequencing revealed two 28-bp repeats in the 5'-untranslated region and the presence in both repeats of cytosine instead of guanine at the 12th nucleotide. This allele variant (TYMS 2RC) has not been previously described in man. All three patients were heterozygotes for TYMS 2RC and experienced grade 2-3 chemotherapy-related toxicity.

A systematic analysis of disease-associated variants in the 3' regulatory regions of human protein-coding genes II: the importance of mRNA secondary structure in assessing the functionality of 3' UTR variants

In an attempt both to catalogue 3' regulatory region (3' RR)-mediated disease and to improve our understanding of the structure and function of the 3' RR, we have performed a systematic analysis of disease-associated variants in the 3' RRs of human protein-coding genes. We have previously analysed the variants that have occurred in two specific domains/motifs of the 3' untranslated region (3' UTR) as well as in the 3' flanking region. Here we have focused upon 83 known variants within the upstream sequence (USS; between the translational termination codon and the upstream core polyadenylation signal sequence) of the 3' UTR. To place these variants in their proper context, we first performed a comprehensive survey of known cis-regulatory elements within the USS and the mechanisms by which they effect post-transcriptional gene regulation. Although this survey supports the view that RNA regulatory elements function within the context of specific secondary structures, there are no general rules governing how secondary structure might exert its influence. We have therefore addressed this question by systematically evaluating both functional and non-functional (based upon in vitro reporter gene and/or electrophoretic mobility shift assay data) USS variant-containing sequences against known cis-regulatory motifs within the context of predicted RNA secondary structures. This has allowed us not only to establish a reliable and objective means to perform secondary structure prediction but also to identify consistent patterns of secondary structural change that could potentiate the discrimination of functional USS variants from their non-functional counterparts. The resulting rules were then used to infer potential functionality in the case of some of the remaining functionally uncharacterized USS variants, from their predicted secondary structures. This not only led us to identify further patterns of secondary structural change but also several potential novel cis-regulatory motifs within the 3' UTRs studied.

Genetic variants in the enhancer region of the thymidylate synthase gene in the Chilean population

AIMS

Thymidylate synthase (TYMS) is an important target enzyme for the fluoropyrimidines. The TYMS gene enhancer region possesses tandemly repeated (TSER) sequences that are polymorphic in humans and different among ethnic groups. The aims of this study were to estimate the frequencies of the TSER variants in two hospital samples located in the northern (HSJ) and eastern (CLC) parts of Santiago, Chile, and compare them with the frequencies in other populations of different ethnic origin.

METHODS

Genotyping of TSER variants in 368 Chilean subjects (HSJ = 178 and CLC = 190) by polymerase chain reaction; products of amplification were electrophoresed, obtaining fragments of 250 bp for allele TSER*3 and 220 bp for allele TSER*2.

RESULTS

The two hospital samples had different degrees of Amerindian admixture (HSJ 34.5%; CLC 15.9%), which was not reflected in the observed frequencies of the CLC TSER*3: 56.8% and HSJ TSER*3: 53.4%.

CONCLUSIONS

Our results are unexpected, considering that genetic markers in the Chilean population generally show allele frequencies between those observed in European Caucasians and Amerindians and that the percentage of Amerindian admixture in CLC is lower than in HSJ. Both hospitals should have had greater frequencies of TSER*3 than were found and the frequency should have been greater in HSJ than in CLC; the only logical explanation of our results is that the frequency of this allele in aboriginal Chilean people is much lower than the 80% estimated for Mongoloid populations.

Polymorphisms in thymidylate synthase gene and susceptibility to breast cancer in a Chinese population: a case-control analysis

Background

Accumulative evidence suggests that low folate intake is associated with increased risk of breast cancer. Polymorphisms in genes involved in folate metabolism may influence DNA methylation, nucleotide synthesis, and thus individual susceptibility to cancer. Thymidylate synthase (TYMS) is a key enzyme that participates in folate metabolism and catalyzes the conversion of dUMP to dTMP in the process of DNA synthesis. Two potentially functional polymorphisms [a 28-bp tandem repeat in the TYMS 5'-untranslated enhanced region (TSER) and a 6-bp deletion/insertion in the TYMS 3'-untranslated region (TS 3'-UTR)] were suggested to be correlated with alteration of thymidylate synthase expression and associated with cancer risk.

Methods

To test the hypothesis that polymorphisms of the TYMS gene are associated with risk of breast cancer, we genotyped these two polymorphisms in a case-control study of 432 incident cases with invasive breast cancer and 473 cancer-free controls in a Chinese population.

Results

We found that the distribution of TS3'-UTR (1494del6) genotype frequencies were significantly different between the cases and controls (P = 0.026). Compared with the TS3'-UTR del6/del6 wild-type genotype, a significantly reduced risk was associated with the ins6/ins6 homozygous variant genotype (adjusted OR = 0.58, 95% CI = 0.35–0.97) but not the del6/ins6 genotype (OR = 1.09, 95% CI = 0.82–1.46). Furthermore, breast cancer risks associated with the TS3'-UTR del6/del6 genotype were more evident in older women, postmenopausal subjects, individuals with a younger age at first-live birth and individuals with an older age at menarche. However, there was no evidence for an association between the TSER polymorphism and breast cancer risks.

Conclusion

These findings suggest that the TS3'-UTR del6 polymorphism may play a role in the etiology of breast cancer. Further larger population-based studies as well as functional evaluation of the variants are warranted to confirm our findings.

Pharmacogenetic profiling and clinical outcome of patients with advanced gastric cancer treated with palliative chemotherapy

PURPOSE

To investigate whether polymorphisms with putative influence on fluorouracil/cisplatin activity are associated with clinical outcomes of patients with advanced gastric cancer (AGC).

PATIENTS AND METHODS

Peripheral blood samples from 175 prospectively enrolled AGC patients treated with fluorouracil/cisplatin palliative chemotherapy were used for genotyping 13 polymorphisms in nine genes (TS, MTHFR, XPD, ERCC1, XRCC1, XRCC3, GSTPI, GSTTI, GSTMI). Genotypes were correlated to response and survival.

RESULTS

The overall response rate was 41%, the median progression-free survival (PFS) was 24 weeks (range, 4 to 50 weeks), and the median overall survival (OS) was 39 weeks (range, 8 to 72+ weeks). Chemoresistance and poor survival were significantly associated with TS 5'-UTR 3G-genotype (2R/3G, 3C/3G, 3G/3G) and GSTP1 105 A/A homozygous genotype. Sixty-one patients (35%) did not show any of these risk genotypes (group 0), 57 patients (32.5%) showed one of the two risk genotypes (group 1), and 57 patients (32.5%) showed both risk genotypes (group 2). Median PFS and OS in group 0 patients were 32 weeks (range, 8 to 50 weeks) and 49 weeks (range, 18 to 72+ weeks), respectively. Group 1 and group 2 patients showed significantly worse PFS (median, 26 weeks [range, 6 to 44 weeks] and 14 weeks [range, 4 to 38 weeks], respectively) and worse OS (median, 39 weeks [range, 10 to 58 weeks] and 28 weeks [range, 8 to 56 weeks]), respectively, than group 0 patients. This adverse effect was retained in multivariate analysis.

CONCLUSION

Specific polymorphisms may influence clinical outcomes of AGC patients. Selecting palliative chemotherapy on the basis of pretreatment genotyping may represent an innovative strategy that warrants prospective studies.

Tumor thymidylate synthase 1494del6 genotype as a prognostic factor in colorectal cancer patients receiving fluorouracil-based adjuvant treatment

PURPOSE

The purpose of this study was to analyze the value of germline and tumor thymidylate synthase (TS) genotyping as a prognostic marker in a series of colorectal cancer patients receiving adjuvant fluorouracil (FU) -based treatment.

PATIENTS AND METHODS

One hundred twenty-nine colorectal cancer patients homogeneously treated with FU plus levamisole or leucovorin in the adjuvant setting were included. TS enhancer region, 3R G > C single nucleotide polymorphism (SNP), and TS 1494del6 polymorphisms were assessed in both fresh-frozen normal mucosa and tumor. Mutational analyses of TS and allelic imbalances were studied in all primary tumors and in 18 additional metachronic metastases. TS protein immunostaining was assessed in an expanded series of 214 tumors. Multivariate Cox models were adjusted for stage, differentiation, and location.

RESULTS

Tumor genotyping (frequency of allelic loss, 26%) showed that the 3R/3R genotype was associated with a better outcome (hazard ratio [HR] = 0.38; 95% CI, 0.16 to 0.93; P = .020 for the recessive model). 3R G > C SNP genotyping did not add prognostic information. Tumor TS 1494del6 allele (frequency of allelic loss, 36%) was protective (for each allele with the deletion, based on an additive model, HR = 0.42; 95% CI, 0.22 to 0.82; P = .0034). Both polymorphisms were in strong linkage disequilibrium (D' = 0.71, P < .001), and the 3R/-6 base pair (bp) haplotype showed a significant overall survival benefit compared with the most prevalent haplotype 2R/+6bp (HR = 0.42; 95% CI, 0.20 to 0.85; P = .017). No TS point mutation was detected in primary tumors or metastases. TS protein immunostaining was not associated with survival or any of the genotypes analyzed.

CONCLUSION

Tumor TS 1494del6 genotype may be a prognostic factor in FU-based adjuvant treatment of colorectal cancer patients.

Thethymidylate synthase tandem repeat promoter polymorphism: A predictor for tumor-related survival in neoadjuvant treated locally advanced gastric cancer

We evaluated DNA polymorphisms in the thymidylate synthase (TS) and 5,10-methylene-tetrahydrofolate reductase (MTHFR) genes for an association with response and survival in locally advanced gastric cancer treated with 5-FU based preoperative chemotherapy (CTx). DNA of 238 patients (CTx-group: total n = 135, completely resected (R0) n = 102; without CTx: R0 n = 103) was isolated from blood or from nontumorous tissues. In the CTx-group, genotyping of the tandem repeat and the G/C polymorphism in the triple repeat in the promoter region of the TS gene and of the C677T polymorphism of the MTHFR gene was performed. None of the TS or MTHFR genotypes were associated with histopathological response and only the TS tandem repeat polymorphism was significantly related to survival (all patients n = 135, p = 0.002; R0 resected patients n = 102, p = 0.007; log-rank test). Multivariate analysis revealed ypN (p < 0.001) and the TS tandem repeat polymorphism as independent prognostic factors in the CTx-R0-group (p = 0.003). Analyzing the prognostic significance of the TS polymorphisms in the R0-group without CTx, TS genotypes were not significantly associated with survival. Comparing survival between R0 patients with and without CTx in the respective TS genotype groups of the tandem repeat polymorphism, a significant survival benefit for the patients with CTx was found for the 2rpt/2rpt (n = 49; p = 0.002) and 2rpt/3rpt genotypes (n = 99; p = 0.004), but not for the 3rpt/3rpt genotype (n = 57; p = 0.93). Patients' survival after CTx was associated with the TS tandem repeat polymorphism. CTx did not improve survival of patients with the 3rpt/3rpt genotype. Thus, a different therapy might be more appropriate for these patients.

Fourteen Novel Genetic Variations and Haplotype Structures of the TYMS Gene Encoding Human Thymidylate Synthase (TS)

Forty genetic variations including 14 novel ones were found in the human TYMS gene, which encodes thymidylate synthase, in 263 Japanese cancer patients who received 5-fluorouracil (FU)-based chemotherapy. Three novel variations were located within the 28-bp tandem repeat sequence in the 5'-untranslated region (UTR) and were designated 5Rc, 3Rc-ins and 4Rc. Allele frequencies were 0.021 for 5Rc, 0.006 for 3Rc-ins and 0.002 for 4Rc. Other novel variations included -133G>C and -125G>C in the 5'-UTR; IVS1-278G>A, IVS2-68C>T, IVS2-23T>C, IVS4+122_+123insATTG, IVS4-141G>A, IVS5-100A>T and IVS6-111G>A in the introns; and 1244(*302)A>G and 1264(*322)G>A in the 3'-UTR. The allele frequencies were 0.34 for IVS4+122_+123insATTG, 0.042 for -133G>C, 0.011 for IVS4-141G>A, 0.006 for -125G>C, 0.004 for IVS1-278G>A, IVS2-68C>T, 1244(*302)A>G and 1264(*322)G>A, and 0.002 for IVS2-23T>C, IVS5-100A>T and IVS6-111G>A. Using the detected polymorphisms, linkage disequilibrium (LD) analysis was performed, which divided the TYMS gene into three LD blocks. The 28-bp tandem repeat sequence in the 5'-UTR was assigned as Block 2 with a total of 7 alleles. In Blocks 1 and 3, 7 and 19 haplotypes were determined/inferred, respectively. Our findings provide fundamental and useful information for genotyping TYMS in the Japanese and probably other Asian populations.

Polymorphism at the 3'-UTR of the thymidylate synthase gene: a potential predictor for outcomes in Caucasian patients with esophageal adenocarcinoma treated with preoperative chemoradiation

PURPOSE

To test the hypothesis that TS3'UTR polymorphisms predict outcomes in 146 Caucasian patients with esophageal adenocarcinoma treated with preoperative 5-fluorouracil-based chemoradiation.

METHODS AND MATERIALS

DNA was extracted from hematoxylin-and-eosin stained histologic slides of normal esophageal or gastric mucosa sections from paraffin blocks of esophagectomy specimens. Genotypes of the TS3'UTR polymorphism were determined by polymerase chain reaction for a 6-bp insertion. The genotype groups (0bp/0bp, 6bp/0bp, and 6bp/6bp) were compared for clinical features and overall survival, recurrence-free-survival, locoregional control (LRC), and distant metastasis control. Multivariable Cox regression analyses were performed to find independent predictors for the stated outcomes.

RESULTS

There was a trend of association between 6bp/6bp genotype and a decreased risk of local regional recurrence (hazards ratio = 0.211, 95% confidence interval = 0.041-1.095, p = 0.06) compared with other genotypes. There was a trend that patients with 6bp/6bp genotype had a higher 3-year probability of LRC compared with patients with the other two genotypes combined (p = 0.07); however, the difference was not statistically significant.

CONCLUSIONS

The null hypotheses were not rejected in this study, probably owing to small sample size or the single gene examined. Prospective studies with adequate statistical power analyzing a family of genes involved in the 5-fluorouracil metabolism are needed to assess genetic determinants of treatment-related outcomes in esophageal adenocarcinoma.

Polymorphisms of thymidylate synthase in the 5′- and 3′-untranslated regions associated with risk of gastric cancer in South China: a case–control analysis

Fruits and certain vegetables have a protective effect on gastric cancer (GC) and folate is one of the nutrients in fruits and vegetables. We hypothesized that the polymorphisms of thymidylate synthase (TYMS) gene involved in folate metabolism are associated with GC risk. In a population-based case-control study of 337 GC cases and 326 controls, frequency-matched by age, sex and residential areas in a southern Chinese population, we genotyped the 28 bp tandem repeat in the TYMS 5'-untranslated enhanced region (TSER) and the 6 bp deletion/insertion at bp 1494 in the TYMS 3'-untranslated region (TS3'UTR). We found that although the TSER polymorphism had no main effect on GC risk, the TS3'UTR 6 bp/6 bp genotype was associated with a significantly increased risk of GC [adjusted odds ratio (OR) = 1.96, 95% confidence interval (CI) = 1.18-3.25], especially the non-cardiac gastric cancer (2.16, 1.22-3.82), compared with the 0 bp/0 bp genotype. However, when we evaluated these two polymorphisms together and used the combined genotype with zero variant allele (TSER 2R and TS3'UTR 6 bp variant alleles) as the reference, we found that the combined genotype with three or four variant alleles was associated with a significantly increased risk of GC (2.06, 1.12-3.79), especially the non-cardiac gastric cancer (2.33, 1.19-4.59), and this significant association was more pronounced among older women (>60 years old), non-smokers, and never tea drinkers. In conclusion, the TYMS polymorphisms, especially the TS3'UTR polymorphism, are associated with GC risk, especially the non-cardiac gastric cancer, and the TSER 2R and TS3'UTR 6 bp alleles may jointly play a role in the etiology of GC in the southern Chinese population. Larger studies are warranted to verify these findings.

Prognostic Role of Thymidylate Synthase Polymorphisms in Gastric Cancer Patients Treated with Surgery and Adjuvant Chemotherapy

PURPOSE

To investigate the prognostic role of thymidylate synthase (TS) polymorphisms in gastric cancer patients treated with radical surgery and fluorouracil-based adjuvant chemotherapy.

EXPERIMENTAL DESIGN

Ninety gastric cancer cases were identified among 187 patients previously enrolled in prospective case-control studies for disease susceptibility. Patients were genotyped for a G/C nucleotide change within a triple 28 bp variable number of tandem repeat sequence in the TS 5'-untranslated region (5'-UTR) and a 6 bp deletion in the TS 3'-untranslated region (3'-UTR). According to available functional data, patients with 5'-UTR 2R/2R, 2R/3C, 3C/3C genotypes were classified as low TS producers (5'-UTRlow) and patients with 5'-UTR 3G/3G, 3G/3C, 2R/3G genotypes as high TS producers (5'UTRhigh). Patients with 3'-UTR del6/del6 and del6/ins6 genotypes were classified as low TS producers (3'-UTRlow) and patients with 3'-UTR ins6/ins6 genotype as high TS producers (3'-UTRhigh). The prognostic analysis was based on 5'-UTR/3'-UTR combined genotypes.

RESULTS

Ten patients (11%) were 5'-UTRhigh/3'-UTRhigh, 36 patients were 5'-UTRhigh/3'-UTRlow, 19 patients were 5'-UTRlow/3'-UTRhigh, and 25 patients were 5'-UTRlow/3'-UTRlow. 5'-UTRlow/3'-UTRlow patients showed the best outcome and the threshold of statistical significance was achieved in the comparison of disease-free survival and overall survival with 5'-UTRhigh/3'-UTRlow patients and 5'-UTRhigh/3'-UTRhigh patients. The presence of at least one high TS expression genotype showed independent adverse prognostic role in multivariate analysis.

CONCLUSIONS

The prognostic role of TS polymorphisms in gastric cancer deserves further investigation because the adverse effect of high TS expression genotypes may be a relevant information to improve adjuvant chemotherapeutic strategies.