Heterozygote deficiency in thymidylate synthase enhancer region polymorphism genotype distribution in Hungarian colorectal cancer patients

The prevalence and clinical relevance of 2R/2R TYMS genotype in patients with gastrointestinal malignancies treated with fluoropyrimidine-based chemotherapy regimens

Introduction

The prevalence of 2R/2R TYMS genotype is variable but estimated to be around 20–30% in Caucasians. The clinical relevance of TYMS 2R/2R genotype in predicting severe fluoropyrimidine-related adverse events (FrAE) is controversial. Here, we explored the prevalence and clinical relevance of 2R/2R TYMS genotype.

Methods

Between 2011 and 2018, 126 patients were genotyped for TYMS. FrAEs were graded according to CTCAE version 5.0. Fisher’s exact test was used for statistical analysis.

Results

The prevalence of TYMS 2R/2R genotype was 24.6%. Among patients with TYMS genotypes (N = 71) that predict decreased TS expression, 2R/2R TYMS genotype was the most common TYMS genotype seen in female (57%) and African American (60%) patients. Among patients with genotypes that predict increased TS expression (N = 55), 12 patients had grade 3–4 FrAEs (22%), while among patients with genotypes that predict decreased TS expression (N = 71), 30 patients had grade 3–4 FrAEs (42%) (p = 0.0219). Compared to patients with genotypes predicting increased TS expression, 17 out of 31 patients (55%) with TYMS 2R/2R genotype had grade 3–4 FrAEs (p = 0.0039) and 15 out 40 patients (38%) with TYMS 2R/3RC and TYMS 3RC/3RC genotype had grade 3–4 FrAEs (p = 0.1108).

Conclusion

The prevalence of TYMS 2R/2R genotype was 24.6%, and it had a unique sex and ethnic distribution. Polymorphism in the promoter region of TYMS gene that predicts decreased TS expression due to 2R/2R variant was associated with grade 3–4 FrAEs. These data suggest that genotyping patients who are not DPD deficient for TYMS might identify patients at risk of severe FrAEs.

Correlation between polymorphism of TYMS gene and toxicity response to treatment with 5-fluoruracil and capecitabine

Tumorigenesis is a multiphasic process in which genetic alterations guide the progressive transformation in cancer cells1. In order to evaluate the possible correlation between some gene variants and the risk of the toxicity development onset, two of the polymorphisms of the thymidylate synthase (TYMS), rs34743033 (2R/3R) and rs16430 (DEL/INS) were investigated. We enrolled in our study 47 patients from the Hospital of Sicily. Our preliminary findings suggest that there could be a linkage between the genotypes discussed and the development of the toxicity following the chemotherapy treatment. These results need to be confirmed by further studies, however this short paper offers some initial insight into the relationships between genetic background and the better outcome for patients.

Influence of chemotherapeutic drug-related gene polymorphisms on toxicity and survival of early breast cancer patients receiving adjuvant chemotherapy

BACKGROUND

We investigated whether GSTT1 ("null" allele), GSTM1 ("null"allele), GSTP1 (A313G), RFC1 (G80A), MTHFR (C677T), TS (2R/3R) polymorphisms were associated with toxicity and survival in patients with early breast cancer (EBC) treated with adjuvant chemotherapy (CT).

METHODS

This prospective trial included patients with stage I-III BC subjected to CT with CMF or FEC regimens. PCR-RFLP was performed for MTHFR, RFC1 and GSTP1, while PCR for TS, GSTT1 and GSTM1 genes.

RESULTS

Among the 244 patients consecutively enrolled, 48.7% were treated with FEC and 51.3% with CMF. Patients with TS2R/3R genotype showed less frequently severe neutropenia (G3/G4) than those with TS2R/2R and 3R/3R genotype (p = 0.038). Patients with MTHFRCT genotype had a higher probability of developing severe neutropenia than those with MTHFR CC genotype (p = 0.043). Patients with RFC1GG or GSTT1-null genotype or their combination (GSTT1-null/RFC1GG) were significantly associated with a shorter disease free survival (DFS) (p = 0.009, p = 0.053, p = 0.003, respectively) and overall survival (OS) (p = 0.036, p = 0.015, p = 0.005, respectively). Multivariate analysis confirmed the association of RFC1GG genotype with a shorter DFS (p = 0.018) and of GSTT1-null genotype of a worse OS (p = 0.003), as well as for the combined genotypes GSTT1-null/RFC1GG, (DFS: p = 0.004 and OS: p = 0.003).

CONCLUSIONS

Our data suggest that TS2R/2R and 3R/3R or MTHFR CT genotypes have a potential role in identifying patients with greater risk of toxicity to CMF/FEC and that RFC1 GG and GSTT1-null genotypes alone or in combination could be important markers in predicting clinical outcome in EBC patients.

Simultaneous, But Not Consecutive, Combination With Folinate Salts Potentiates 5-Fluorouracil Antitumor Activity In Vitro and In Vivo

The combination of folinate salts to 5-fluoruracil (5-FU)-based schedules is an established clinical routine in the landscape of colorectal cancer treatment. The aim of this study was to investigate the pharmacological differences between the sequential administration of folinate salts (1 h before, as in clinical routine) followed by 5-FU and the simultaneous administration of both drugs. Proliferation and apoptotic assays were performed on human colon cancer cells exposed to 5-FU, calcium (CaLV), or disodium (NaLV) levofolinate or their simultaneous and sequential combination for 24 and 72 h. TYMS and SLC19A1 gene expression was performed with real-time PCR. In vivo experiments were performed in xenografted nude mice, which were treated with 5-FU escalating doses and CaLV or NaLV alone or in simultaneous and sequential combination. The simultaneous combination of folinate salts and 5-FU was synergistic (NaLV) or additive (CaLV) in a 24-h treatment in both cell lines. In contrast, the sequential combination of both folinate salts and 5-FU was antagonistic at 24 and 72 h. The simultaneous combination of 5-FU and NaLV or CaLV inhibited TYMS gene expression at 24 h, whereas the sequential combination reduced SLC19A1 gene expression. In vivo experiments confirmed the enhanced antitumor activity of the 5-FU + NaLV simultaneous combination with a good toxicity profile, whereas the sequential combination with CaLV failed to potentiate 5-FU activity. In conclusion, only the simultaneous, but not the consecutive, in vitro and in vivo combination of 5-FU and both folinate salt formulations potentiated the antiproliferative effects of the drugs.

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.

Thymidylate synthase genetic polymorphisms and colorectal cancer risk: a meta-analysis

AIM

The effects of thymidylate synthase (TS) polymorphisms on susceptibility to colorectal cancer (CRC) have been investigated in many studies, but the results remain conflicting rather than conclusive. To resolve these conflicts, we performed a quantitative synthesis of the evidence on the association between these two polymorphisms and CRC risk.

METHODS

All eligible case-control studies published up to September 2013 were identified by searching PubMed, Web of Science and CNKI. Effect sizes of odds ratio (OR) and 95% confidence interval (95% CI) were calculated by using a fixed- or random-effect model.

RESULTS

A total of 11 case-control studies were included, including 10 studies (3324 cases and 4622 controls) for TSER polymorphism and 9 studies (3223 cases and 3886 controls) for TS1494del6 polymorphism. Overall, no significant association between the TS polymorphisms and CRC risk was found. In the subgroup analysis by ethnicity, a significantly association were found among Caucasian populations for TSER polymorphism; but for TS1494del6 polymorphism, no significantly association was observed in both Asian and Caucasian populations. When stratifying by source of controls, we found there was a statistically significant association between TSER polymorphism and risk of CRC in the population-based population; however, we detected no association in both population-based and hospital-based populations for TS1494del6 polymorphism.

CONCLUSIONS

This meta-analysis suggests that the TSER polymorphism in TS gene but not TS1494del6 polymorphism might be a protective factor for CRC among Caucasian populations.

The association between two polymorphisms in the TS gene and risk of cancer: a systematic review and pooled analysis

Thymidylate synthase (TS) is an important enzyme involved in folate metabolism and catalyzes methylation of deoxyuridine monophosphate to deoxythymidine monophosphate, which is essential for DNA replication. Thymidylate synthase enhancer region (TSER) and TS1494del6, two functionally important and ethnically diverse polymorphisms mapping to its gene region, are the most extensively studied. Considering the potential influence of altering TS activity, it is plausible that TS polymorphisms might play a role in the development of cancer. Although the effects of TS polymorphisms on susceptibility to human cancer have been investigated in many studies, the results remain conflicting rather than conclusive. To resolve these conflicts, we performed a quantitative synthesis of the evidence on the association between these two polymorphisms and cancer risk, including 63 studies (19,707 cases and 27,398 controls) for TSER polymorphism and 39 studies (13,489 cases and 16,297 controls) for TS1494del6 polymorphism. Our meta-analysis suggested that these two polymorphisms are not associated with cancer risk when all studies were pooled together. In the stratified analyses, we found that individuals with 2R/2R genotype had a significantly higher cancer risks among Asians (2R/2R vs. 3R/3R: odds ratio [OR] = 1.24, 95% confidence interval (95% CI) = 1.05-1.45; recessive model: OR = 1.23, 95% CI = 1.05-1.44). Further analyses revealed that 2R/2R genotype was significantly associated with an increased risk of gastroesophageal cancer among Asians, whereas it might provide protecting effects against colorectal cancer risk in a dominant genetic model for Caucasians. Additionally, TS1494del6 polymorphism may contribute to genetic susceptibility of breast cancer among Asians.

Impact of EXO1 polymorphism in susceptibility to colorectal cancer

BACKGROUND AND AIM

One candidate gene for colorectal cancer (CRC) susceptibility is exonuclease 1 (EXO1). It is a member of RAD2 nuclease family, which plays a major role in mismatch repair, DNA replication, and recombination. Single-nucleotide polymorphisms are shown to be related with cancer incidence. The aim of the present study was to examine the association between the L757P polymorphism at exon 13 of the EXO1 gene and the risk of CRC in Iranian patients.

METHODS

In this case-control study, 90 cases and 98 healthy control samples were analyzed genetically. The EXO1 polymorphism, P757L, was analyzed by polymerase chain reaction-restriction fragment length polymorphism. The obtained polymorphisms were examined for the relationship with CRC risk and also clinicopathological characteristics.

RESULTS

Our findings showed that patients with the Leu/Leu genotype have a reduced risk of CRC (adjusted odds ratio [OR] = 0.192, 95% confidence interval [CI]: 0.040-0.921) when the Pro/Leu and Pro/Pro genotypes were blended and they were considered as the reference. The Leu/Leu genotype also showed a reduced risk (adjusted OR = 0.168, 95% CI: 0.034-0.816) when the Pro/Pro genotype was a reference; nevertheless, the Pro/Leu genotype did not reveal a significant association with CRC at the same status (adjusted OR = 0.686, 95% CI: 0.367-1.284).

CONCLUSIONS

Our results provide evidence diagnosing that the Leu/Leu genotype of EXO1 showed an inverse association with CRC. In addition, despite other investigations, we could define a significant association between the Leu allele and CRC (p = 0.001).

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.

Role of genetic and nongenetic factors for fluorouracil treatment-related severe toxicity: a prospective clinical trial by the German 5-FU Toxicity Study Group

PURPOSE

To assess the predictive value of polymorphisms in dihydropyrimidine dehydrogenase (DPYD ), thymidylate synthase (TYMS ), and methylene tetrahydrofolate reductase (MTHFR ) and of nongenetic factors for severe leukopenia, diarrhea, and mucositis related to fluorouracil (FU) treatment.

PATIENTS AND METHODS

A multicenter prospective clinical trial included 683 patients with cancer treated with FU monotherapy. Toxicity was documented according to World Health Organization grades. DPYD, TYMS, and MTHFR genotypes were determined, and DPYD was resequenced in patients with severe toxicity.

RESULTS

Grade 3 to 4 toxicity occurred in 16.1% of patients. The sensitivity of DPYD*2A genotyping for overall toxicity was 5.5% (95%CI, 0.02 to 0.11), with a positive predictive value of 0.46 (95% CI, 0.19 to 0.75; P = .01). Inclusion of additional DPYD variants improved prediction only marginally. Analysis according to toxicity type revealed significant association of DPYD with mucositis and leukopenia, whereas TYMS was associated with diarrhea. Genotype, female sex, mode of FU administration, and modulation by folinic acid were identified as independent risk factors by multivariable analysis. A previously unrecognized significant interaction was found between sex and DPYD, which resulted in an odds ratio for toxicity of 41.8 for male patients (95% CI, 9.2 to 190; P < .0001) but only 1.33 (95% CI, 0.34 to 5.2) in female patients. Homozygosity for the TYMS enhancer region double repeat allele increased risk for toxicity 1.6-fold (95% CI, 1.08 to 2.22; P = .02).

CONCLUSION

DPYD, TYMS, and MTHFR play a limited role for FU related toxicity but a pronounced DPYD gene/sex-interaction increases prediction rate for male patients. Toxicity risk assessment should include sex, mode of administration, and folinic acid as additional predictive factors.

Thymidylate synthase polymorphisms, folate and B-vitamin intake, and risk of colorectal adenoma

The effects of polymorphisms in genes coding for key folate metabolism enzymes such as thymidylate synthetase (TS) on colorectal neoplasia risk are likely to be influenced by gene–gene and gene–nutrient interactions. We investigated the combined effects of three polymorphisms in the TS gene region, TSER, TS 3R G>C, and TS 1494del6, dietary intakes of folate and other B vitamins, and genotype for other folate metabolism variants, in a colorectal adenoma (CRA) case–control study. Individuals homozygous for TS 1494del6 del/del were at significantly reduced CRA risk compared to those with either ins/del or ins/ins genotypes (odds ratio 0.52; 95% confidence interval: 0.31–0.85, P=0.009). We also observed evidence of interactions between TS 1494del6 genotype and intake of folate, and vitamins B₆ and B₁₂, and MTHFR C677T genotype, with the reduction in risk in del/del homozygotes being largely confined to individuals with high nutrient intakes and MTHFR 677CC genotype (P_interaction=0.01, 0.006, 0.03, and 0.07, respectively). TSER genotype, when considered either alone or in combination with TS 3R G>C genotype, did not significantly influence CRA risk. These findings support a role for TS in colorectal carcinogenesis, and provide further evidence that functional polymorphisms in folate metabolism genes act as low-risk alleles for colorectal neoplasia and participate in complex gene–gene and gene–nutrient interactions.

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.

Dietary intake of B-vitamins, polymorphisms in thymidylate synthase and serine hydroxymethyltransferase 1, and colorectal adenoma risk: A Dutch case-control study

Thymidylate synthase and serine hydroxymethyltransferase are involved in folate metabolism. In a case-control study, including 768 cases and 709 controls, we investigated the associations between colorectal adenomas and TS tandem repeat and SHMT1 C1420T polymorphisms, and the interplay with B-vitamins. The polymorphisms were not associated with adenomas, but there was a borderline significant interaction between TS genotype and vitamin B6: the association between vitamin B6 and adenomas seemed positive in TS 3R/3R individuals, but inverse in TS 2R/2R individuals. This study does not provide evidence for a role of SHMT1 genotype in adenoma occurrence. Future research has to indicate whether the TS-B6 interplay is a real effect or a chance finding.

Thymidylate Synthase (TYMS) and Dihydropyrimidine Dehydrogenase (DPYD) Polymorphisms in the Korean Population for Prediction of 5-Fluorouracil-Associated Toxicity

The important cellular proteins for 5-fluorouracil (5-FU) metabolism are the major target enzymes, thymidylate synthase, and the rate-limiting enzyme in the degradation pathway, dihydropyrimidine dehydrogenase. Adverse drug reactions to 5-FU-based chemotherapy have been reported to be in part the result of polymorphisms in the thymidylate synthase (TYMS) and dihydropyrimidine dehydrogenase (DPYD) genes. Therefore, we examined the type and frequency of polymorphisms in the TYMS and DPYD genes in 100 healthy Korean individuals and compared these findings with 21 patients with colorectal cancer who had a grade 3 or greater toxic response to 5-FU treatment. Genotyping analysis of the promotor enhancer region (TSER) and the 3'-untranslated region (3'-UTR) of the TYMS gene as well as haplotype analysis were conducted in all 121 study participants. For the TSER and the 3'-UTR of the TYMS gene, similar genotypes and allele frequencies were observed in control subjects and patients. For the haplotype analysis of the single nucleotide polymorphism G > C at the 12th nucleotide of the second repeat of the 3R allele of the TSER, different haplotype frequencies were noted in comparisons between the two groups; in addition, we found that the 3RC-del 6bp was significantly associated with severe toxicity with 5-FU treatment. Extensive polymorphisms in the DPYD gene were observed; in addition, four polymorphisms were related to the known DPYD allelic variants or to allelic variants that alter protein structure, among which the most common polymorphism was 1627A > G, observed in 20.5% of all alleles. The 496A > G allele and a novel 1774C > T allele were identified in two patients. The DPYD*2A allele, causing exon 14 skipping, was not identified in the study group. The findings, from Korean patients with colon cancer, suggest that polymorphisms of the DPYD gene are not associated with an increased risk for toxic response to 5-FU. These findings suggest that there may be an important relationship between the TYMS haplotypes examined and 5-FU toxicity. The novel variant in the DPYD gene, identified in this study, should be further investigated to confirm its functional significance. A large sample is required before DPYD or TYMS genotyping could be used as markers for individualized treatment of patients with colorectal cancer.

ASCO 2006 Update of Recommendations for the Use of Tumor Markers in Gastrointestinal Cancer

Purpose

To update the recommendations for the use of tumor marker tests in the prevention, screening, treatment, and surveillance of gastrointestinal cancers.

Methods

For the 2006 update, an update committee composed of members from the full Panel was formed to complete the review and analysis of data published since 1999. Computerized literature searches of Medline and the Cochrane Collaboration Library were performed. The Update Committee's literature review focused attention on available systematic reviews and meta-analyses of published tumor marker studies.

Recommendations and Conclusion

For colorectal cancer, it is recommended that carcinoembryonic antigen (CEA) be ordered preoperatively, if it would assist in staging and surgical planning. Postoperative CEA levels should be performed every 3 months for stage II and III disease for at least 3 years if the patient is a potential candidate for surgery or chemotherapy of metastatic disease. CEA is the marker of choice for monitoring the response of metastatic disease to systemic therapy. Data are insufficient to recommend the routine use of p53, ras, thymidine synthase, dihydropyrimidine dehydrogenase, thymidine phosphorylase, microsatellite instability, 18q loss of heterozygosity, or deleted in colon cancer (DCC) protein in the management of patients with colorectal cancer. For pancreatic cancer, CA 19-9 can be measured every 1 to 3 months for patients with locally advanced or metastatic disease receiving active therapy. Elevations in serial CA 19-9 determinations suggest progressive disease but confirmation with other studies should be sought. New markers and new evidence to support the use of the currently reviewed markers will be evaluated in future updates of these guidelines.

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.

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.

Influence of thymidylate synthase gene polymorphisms on the survival of colorectal cancer patients receiving adjuvant 5-fluorouracil

The present study aimed to prospectively investigate the influence of thymidylate synthase (TS) polymorphisms (5'-TSER, 3'-TSUTR) on the disease-free survival (DFS) and overall survival (OS) of patients with colorectal cancer (CRC) who were treated with adjuvant 5-fluorouracil (5-FU) therapy. Patients were followed up for 19+/-14 months (median+/-SD). TS genotypes were determined from the peripheral blood mononuclear cells of 166 patients by polymerase chain reaction-polyacrylamide gel electrophoresis and restriction fragment length polymorphism methods. 5'-TSER 3R homozygotes showed significantly longer DFS (P = 0.048) and OS (P = 0.009). The 5'-TSER and 3'-TSUTR genotype combination groups showed a significant difference for DFS (P = 0.039) and OS (P = 0.029). Significantly better DFS (P = 0.049) and OS (P = 0.043) were observed for 6 bp/6 bp genotypes in 5'-TSER heterozygotes (n = 80). Based on this, and on hazard ratios obtained by Cox regression analysis of the DFS of genotype-combinations, the patients were classified as belonging to prognostic groups A and B. The DFS and OS of these two groups showed a highly significant difference (P = 0.002 and 0.001). In the multivariate Cox regression model, beside tumour location, the prognostic classification (groups A and B) proved to be an independent prognostic factor. Our data suggest that those TS genotypes and their combinations (group A: 3R/3R with any 3'-TSUTR genotype and 2R/3R with 6 bp/6 bp), which have been reported earlier as having high TS expression, predict significantly longer DFS and OS. We found that a combination of germline TS polymorphisms is an independent prognostic marker in selecting CRC patients with worse prognosis, and it may be worthwhile to examine whether these patients would benefit from an alternative therapy.

TYMS and DPYD polymorphisms in a Turkish population

OBJECTIVE

The thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) enzymes affect the outcome of 5-fluorouracil (5-FU)-based chemotherapy. Genetic polymorphisms of the thymidylate synthase (TYMS) and dihydropyrimidine dehydrogenase (DPYD) genes that may affect chemotherapy are described. The aim of this study was to determine the frequencies of TYMS and DPYD polymorphisms in healthy Turkish individuals.

METHODS

Genotyping analyses of the promoter enhancer region of TYMS (TSER) and the exon 14-skipping mutation of the DPYD (DPYD*2A) genes were conducted in 250 unrelated, healthy volunteers from the central region of Turkey using a PCR-based assay.

RESULTS

The distribution of the TSER*2/*2, *2/*3 and *3/*3 genotypes were 17.6%, 48.8%, and 33.6%, respectively. The frequencies of the TSER*2 and *3 alleles in the Turkish population were 0.42 and 0.58, respectively. No individuals with the variant DPYD*2A allele were identified in the study group.

CONCLUSION

The frequency of the TSER*3 allele among members of the Turkish population was similar to frequencies observed in other Caucasian populations but was lower than those found in Japanese and Chinese populations.

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.

Thymidylate Synthase 5′- and 3′-Untranslated Region Polymorphisms Associated with Risk and Progression of Squamous Cell Carcinoma of the Head and Neck

PURPOSE

Folate deficiency and reduced DNA repair capacity are established risk factors for squamous cell carcinoma of the head and neck (SCCHN). We hypothesized that polymorphisms of the thymidylate synthase (TYMS) gene, which regulates a key enzyme in folate metabolism required for DNA synthesis and repair, are associated with SCCHN risk.

EXPERIMENTAL DESIGN

In a hospital-based case-control study of 704 SCCHN cases and 1,085 controls, frequency matched by age, sex, and ethnicity, we genotyped the TSER (thymidylate synthase in the 5'-untranslated enhanced region) and TS3'UTR (thymidylate synthase in the 3'-untranslated region) polymorphisms.

RESULTS

The TS3'UTR 0bp/0bp genotype was associated with a significantly decreased risk of SCCHN [adjusted odd ratio (OR) = 0.67, 95% confidence interval (CI) = 0.47-0.94] compared with the 6bp/6bp genotype, but the TSER polymorphism had no main effect on risk of SCCHN. When we evaluated the two polymorphisms together by the number of protective alleles (the TSER 3R and TS3'UTR 0bp alleles), we found that the combined genotypes with four protective alleles (the TSER 3R3R and TS3'UTR 0bp/0bp) was associated with significantly decreased SCCHN risk (OR = 0.60, 95% CI = 0.37-0.98). In addition, the TS3'UTR 0bp genotypes were associated in an allele dose-dependent manner with a decreased risk of overall stage IV oral cancer (OR = 0.84, 95% CI = 0.52-1.34 for the 6bp/0bp genotype and OR = 0.26, 95% CI = 0.08-0.87 for the 0bp/0bp genotype; P(trend) = 0.035).

CONCLUSION

The TSER and TS3'UTR polymorphisms are associated with SCCHN risk. The TSER 3R and TS3'UTR 0bp alleles seemed to jointly protect against SCCHN. In particular, the 0bp allele seemed to protect against oral cancer progression.

Evolution of the tandem repeats in thymidylate synthase enhancer region (TSER) in primates

The upstream regulatory region of the human thymidylate synthase gene (thymidylate synthase enhancer region, TSER) is length polymorphic, attributable to variable numbers of tandemly repeated copies of a 28-bp fragment. It has been found that TSER length polymorphism is correlated to malignancy risk. To further our understanding of the origin and evolution of TSER, this region was investigated among different primates, including hominoids, two subfamilies of the Old World monkeys (OWMs): colobines and cercopithecines, and two species of the New World monkeys (NWMs). In addition to humans, our results show that length polymorphism in TSER is also present in some primate populations, although it appears that this region is length monomorphic in many other primates. We identified three unique repeat motifs in TSER and defined them as R1, R2, and R3, respectively, starting from the 3' end. The same repeat motifs from different species are more similar to each other than different repeat motifs within same species are. Such a paraphyletic pattern suggests that divergence of the three repeat motifs predated divergence of the OWMs/hominoids and the NWMs. The most recent common ancestor (MRCA) of hominoids and the OWMs probably possessed triple repeats but now double and triple repeats are two dominant types in hominoids and the OWMs. In addition, our results show that each of the three repeat motifs may be lost independently. We have also found clues that recombination was involved in formation of tandem repeat polymorphism in TSER.

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

The gastric mucosal surface was observed using the magnifying fibergastroscope (FGS-ML), and the fine gastric mucosal patterns, which were even smaller than one unit of gastric area, were examined at a magnification of about 30. For simplicification, we classified these patterns by magnifying endoscopy in the following ways; FP, FIP, FSP, SP and MP, modifying Yoshii's classification under the dissecting microscope. The FIP, which was found to have round and long elliptical gastric pits, is a new addition to our endoscopic classification. The relationship between the FIP and the intermediate zone was evaluated by superficial and histological studies of surgical and biopsy specimens. The width of the band of FIP seems to be related to the severity of atrophic gastritis. Also, the transformation of FP to FIP was assessed by comparing specimens taken from the resected and residual parts of the stomach, respectively. Moreover, it appears that severe gastritis occurs in the gastric mucosa which shows a FIP. Therefore, we consider that the FIP indicates the position of the atrophic border.