Polymorphisms of glutathione S-transferases (GST) and thymidylate synthase (TS)--novel predictors for response and survival in gastric cancer patients

Clinical pharmacology and pharmacogenetics in a genomics era: the DMET platform

While no genome-wide pharmacogenetics study has yet been published, the field of pharmacogenetics is moving towards exploratory, large-scale analyses of the interaction between genetic variation and drug treatment. The Drug Metabolizing Enzymes and Transporters (DMET) platform offers a standardized set of 1936 variants in 225 genes related to drug absorption, distribution, metabolism and elimination that is useful to scan the genome for previously unknown associations between variation in absorption, distribution, metabolism and elimination genes and pharmacokinetic and pharmacodynamic outcomes of drug treatment. The purpose of this review is to put the DMET platform into context within the current study designs that have been used in pharmacogenetics, and to explore the role that DMET has played - and will play - in future pharmacogenetics studies.

Influence of GSTP1 I105V polymorphism on cumulative neuropathy and outcome of FOLFOX-4 treatment in Asian patients with colorectal carcinoma

Glutathione S-transferase P1 (GSTP1) participates in detoxification of potentially genotoxic compounds that may alter the efficacy and toxicity of platinum-based chemotherapy. We analyzed the influence of I105V polymorphism of GSTP1 on clinico-pathological features and outcomes in 166 Chinese patients with metastatic colorectal carcinoma who had been treated with first-line FOLFOX-4. Combined analysis of GSTP1 I105V, ERCC1-118, and XPD-751 polymorphisms was also conducted. The results showed that, in comparison with Caucasian populations, a remarkably lower prevalence of Val105 allele variants was noted (24.7%). Patients with Val105 allele variants had a higher response to FOLFOX-4 (56.1%vs 37.6%, P = 0.04), and a longer progression-free (P < 0.01) as well as overall (P < 0.01) survival. By adjusted analysis, this polymorphism was identified as an independent prognostic factor (P = 0.01). In combined analysis, patients without any risk genotype, including GSTP1-105 Ile/Ile, ERCC1-118 C/T or T/T, and XPD-751 Lys/Gln, had significantly longer progression-free and overall survivals (P < 0.01). In addition, patients with Val105 allele variants had a higher incidence of grade 3/4 cumulative neuropathy after different cycles of treatment. These data suggest that Asian populations have a lower prevalence of I105V polymorphism in GSTP1. I105V polymorphism in GSTP1, by reducing its enzymatic activity and consequential detoxification to oxaliplatin, could be a key determinant for a better outcome, but more neurotoxicity, to FOLFOX-4 treatment.

Pharmacogenomics in chemotherapy for GI tract cancer

The study of pharmacogenomics (PGx) has recently been intensively applied to gastrointestinal tract cancer. It has become clear that there are genetic differences in the activities of enzymes that influence the kinetics of chemotherapeutic agents. Moreover, genetic differences related to cellular sensitivity to anti-cancer agents have also been elucidated. In GI-tract cancer chemotherapy, 5-FU, gemcitabine, taxanes (docetaxel and paclitaxel), platinum (cisplatin and oxaliplatin) and irinotecan are often used, and molecular targeting therapy has also been developed. The respective PGx markers to such agents have been reported. Of the candidate PGx markers, K-ras mutation and UGT1A1 polymorphisms have sufficient evidence to justify routine clinical assessment for the selection of anti-cancer regimens. Progress in this field would facilitate the further development of PGx-guided individualized therapy, which could be expected to increase therapeutic efficacy and decrease the risk of adverse events.

Prognostic Significance and Clinicopathological Associations of COX-2 SNP in Patients with Nonsmall Cell Lung Cancer

Background. To further improve the screening, diagnosis, and therapy of patients with nonsmall cell lung cancer (NSCLC) additional diagnostic tools are urgently needed. Gene expression of Cyclooxygenase-2 (COX-2) has been linked to prognosis in patients with NSCLC. The role of the COX-2 926G>C Single Nucleotide Polymorphism (SNP) in patients with NSCLC remains unclear. The aim of this study was to investigate the potential of the COX-2 926G>C SNP as a molecular marker in this disease. Methods. COX-2 926G>C SNP was analyzed in surgically resected tumor tissue of 85 patients with NSCLC using a PCR-based RFLP technique. Results. The COX-2 926G>C SNP genotypes were detected with the following frequencies: GG n = 62 (73%), GC n = 20 (23%), CC n = 3 (4%). There were no associations between COX-2 SNP genotype and histology, grading or gender detectable. COX-2 SNP was significantly associated with tumor stage (P = .032) and lymph node status (P = .016, Chi-square test). With a median followup of 85.9 months, the median survival was 59.7 months. There were no associations seen between the COX-2 SNP genotype and patients prognosis. Conclusions. The COX-2 926G>C SNP is detectable at a high frequency in patients with NSCLC. The COX-2 926G>C SNP genotype is not a prognostic molecular marker in this disease. However, patients with the GC or CC genotype seem more susceptible to lymph node metastases and higher tumor stage than patients with the GG genotype. The results suggest COX-2 926G>C SNP as a molecular marker for lymph node involvement in this disease.

Polymorphism in cytochrome P450 2A6 and glutathione S-transferase P1 modifies head and neck cancer risk and treatment outcome

A case control study was carried out to investigate the association of functionally important polymorphism in cytochrome P450 2A6 (CYP2A6) and glutathione S-transferase P1 (GSTP1) genes with head and neck squamous cell carcinoma (HNSCC) and treatment response in cases receiving a combination of chemo-radiotherapy. The study group consisted of 350 males suffering from HNSCC and an equal number of male controls. Multivariate logistic regression analysis revealed statistically significant decrease in risk to HNSCC in cases with variant genotypes (CYP2A6*1B and CYP2A6*4C) of CYP2A6 (OR: 0.78; 95% CI: 0.43-1.22; P=0.04) or GSTP1 (OR: 0.71; 95% CI: 0.51-1.00; P=0.05). The risk associated with these variant genotypes was found to be further decreased in cases carrying a combination of variant genotypes of CYP2A6 and GSTP1 (OR: 0.40; 95% CI: 0.25-0.65; P=0.00). A similar decrease in risk was observed in cases with variant genotypes of CYP2A6 (OR: 0.59; 95% CI: 0.40-0.86; P=0.00) or GSTP1 (OR: 0.62; 95% CI: 0.42-0.91; P=0.01) and who were regular tobacco users (cigarette smokers or tobacco chewers). Interestingly, only 27% of the cases carrying the variant forms of CYP2A6 (*1A/*4C+*1B/*4C+*4C/*4C) responded to the treatment for HNSCC when compared to those with wild-type genotype (69%). However with GSTP1, cases with homozygous mutant genotype (Val/Val) showed a superior treatment response (75%) when compared to cases with wild-type genotype (25%). Further, cases carrying a combination of variant genotype of CYP2A6 and wild-type genotype of GSTP1 exhibited a very poor treatment response demonstrating that polymorphisms in CYP2A6 and GSTP1 not only modified the risk to HNSCC but also played a major role in determining the chemotherapeutic response.

Expression of thymidylate synthase and glutathione-s-transferase π in patients with esophageal squamous cell carcinoma

AIM: To investigate the expression of thymidylate synthase (TS) and glutathione-s-transferase π (GST-π) in esophageal squamous cell carcinoma and their association with the clinicopathologic characteristics.

METHODS: Immunohistochemical methods were used to detect the expression of TS and GST-π in surgically resected formalin-fixed, paraffin-embedded esophageal squamous cell carcinoma (ESCC) tissue sections from 102 patients (median age, 58 years) and in 28 normal esophageal mucosa (NEM) samples. The relationship between TS and GST-π expression and clinicopathologic factors was examined.

RESULTS: The expression of TS and GST-π was not statistically significantly associated with age of the patients, tumor size, lymph node metastasis, depth of invasion or tumor stage. TS staining was positive in 17.86% of normal esophageal mucosa and in 42.16% of ESCC samples (P < 0.05). The expression level of TS was not only significantly lower in well-differentiated (21.88%) than in poorly-differentiated carcinomas (51.43%, P < 0.05), but was also significantly higher in samples from male patients (46.51%) than from female patients (18.75%, P < 0.05). GST-π was positively stained in 78.57% of normal esophageal mucosa and in 53.92% of ESCC samples (P < 0.05). The expression level of GST-π was also significantly higher in well-differentiated carcinomas (65.63%) than in poorly-differentiated carcinomas (35.00%, P < 0.05).

CONCLUSION: The expression of TS and of GST-π may be used as molecular markers for the characterization of ESCC. Poorly-differentiated cells showed increased expression of TS and reduced expression of GST-π.

Glutathione S-transferase polymorphisms and survival in African-American and white colorectal cancer patients

BACKGROUND

Glutathione S-transferase (GST) enzymes are involved in electrophile detoxification. The authors investigated the association between GST genotype and survival in a racially diverse, population-based cohort of colorectal cancer (CRC) patients followed for a median of 9.6 years.

METHODS

Interviews were conducted with 315 African-American and White CRC patients in Connecticut, 1987-1991. Tumor tissue (n=197) was later retrieved from hospital of diagnosis and assayed using multiplex PCR (GSTM1 and GSTT1) and PCR and RFLP analysis (GSTP1). Cox proportional hazards models provided adjusted hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

Individuals with Ile/Val or Val/Val GSTP1 genotypes had a decreased risk of death (multivariate adjusted HR=0.72, 95% CI: 0.48, 1.09) relative to those with wild type (Ile/Ile). Among those who received chemotherapy, this benefit was more pronounced (HR=0.35, 95% CI: 0.16, 0.79); the interaction of reduced function GSTP1 genotype and chemotherapy was significant (P=0.05). GSTM1 and GSTT1 genotype were not associated with survival. GSTM1, GSTT1, and GSTP1 genotype did not vary by race and did not contribute significantly to the survival disadvantage observed in African-Americans.

CONCLUSIONS

In summary, GSTP1 genotype may play a role in CRC survival in African-Americans and Whites, particularly among those who receive chemotherapy.

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.

Pharmacogenetics of fluoropyrimidine and cisplatin. A future application to gastric cancer treatment

Chemotherapy plays an important role in the treatment of gastric cancer both in adjuvant or advanced settings. Recent randomized trials in Japan have proved that S-1, a novel fluoropyrimidine derivative, and cisplatin are the most promising agents. However, both the efficacy and toxicity of a given regimen vary widely among patients due to the inherited variability of genes that involve drug anabolism and catabolism. A narrow therapeutic index of antitumor agents, i.e. a given regimen being too toxic and/or less effective to some segment of patients, prevents the overall improvement of treatment outcomes. Pharmacogenetics, a research field elucidating genetic polymorphism in drug metabolizing enzymes, may contribute to identifying patients who benefit from chemotherapy or who will experience life-threatening toxicity. There are several crucial enzymes identified involving anabolism and the catabolism of fluoropyrimidine and cisplatin, including dihydropyrimidine dehydrogenase, thymidylate synthase, orotate phosphoribosyl transferase, glutathione S transferase, and excision repair cross complementary group. Various polymorphisms and ethnic variabilities of these genes have been elucidated. This review highlights variations within biological functions, detection systems, and possible clinical applications of these enzymatic polymorphisms. This knowledge provides a tool to determine an optimum regimen according to the patient's drug metabolizing characteristics. This stance will contribute to establishing individualized therapies for gastric cancer, which offers superior efficacy with a minimal chance of severe toxicity.

Pharmacokinetics and pharmacogenomics in esophageal cancer chemoradiotherapy

Esophageal cancer is one of the most lethal malignancies. Surgical resection of the tumor from the primary site has been the standard treatment, especially for localized squamous cell carcinoma, but considerable clinical efforts during the last decade have resulted in novel courses of treatment. These options include chemoradiotherapy, consisting of a continuous infusion of 5-fluorouracil (5-FU), cisplatin (CDDP), and concurrent radiation. Given the substantial inter- and/or intra-individual variation in clinical outcome, future improvements will likely require the incorporation of a novel anticancer drug, pharmacokinetically guided administration of CDDP or 5-FU, and identification of potential responders by patient genetic profiling prior to treatment. In this review, the latest information on incidence, risk factors, biomarkers, therapeutic strategies, and the pharmacokinetically guided or genotype-guided administration of CDDP and 5-FU is summarized for future individualization of esophageal cancer treatment.

Toward molecularly selected chemotherapy for advanced gastric cancer: state of the art and future perspectives

In the last few years therapeutic options for gastric cancer patients have slowly, but constantly expanded following the introduction of both new chemotherapy agents and innovative indications for treatment. Along with the medical therapy also our knowledge of the molecular mechanisms underlying this disease has progressively improved. However although the available treatment options have undoubtedly increased no clear definitive indications can be made for a standard chemotherapy regimen and we are still unable to accurately select the appropriate treatment for the appropriate patient. Many molecular determinants of response/toxicity to chemotherapy agents have been identified, but only few of them seem to possess the necessary potential for a subsequent application in the clinical practice. Some of these factors have also been indicated as a therapeutic target for a novel class of anti-cancer compounds. This systematic review will analyse available data about these factors with the aim to constitute a starting point for future research.

Pharmacogenetic analyses of a phase III trial in metastatic gastroesophageal adenocarcinoma with fluorouracil and leucovorin plus either oxaliplatin or cisplatin: a study of the arbeitsgemeinschaft internistische onkologie

PURPOSE

To evaluate the association of germ-line polymorphisms of genes that may impact treatment outcome of platinum and fluorouracil combination chemotherapy in advanced gastric cancer (AGC).

PATIENTS AND METHODS

Blood samples of 156 patients enrolled onto a phase III study comparing fluorouracil, leucovorin, and oxaliplatin with fluorouracil, leucovorin, and cisplatin were collected. Polymorphisms within genes of TS, MTHFR, MTR, OPRT, XPD, ERCC1, XRCC1, XPA, GSTP1, GSTT1, and GSTM1 were genotyped using polymerase chain reaction-based techniques.

RESULTS

Median overall survival (OS) was 11.8 months (95% CI, 9.75 to 13.79 months) and median progression-free survival (PFS) was 5.8 months (95% CI, 4.99 to 6.61 months). The TS-3R/+6 haplotype (P = .004), the GSTT1 deletion polymorphism (P = .015), and genotypes of OPRT-Gly213Ala (P = .003) and XRCC1-Arg399Gln (P = .023) could be identified as independent predictors of OS. For PFS analyses, the TS-3R/+6 haplotye (P = .003) and MTR-A2756G (P = .01) were identified as independent positive predictors. The association between the GSTT1 deletion polymorphism and PFS showed only borderline significance (P = .053). Treatment related hematotoxicity in terms of grade 3/4 leukopenia was lowest among TS-3R/+6 haplotype carriers (P = .037). Grade 3/4 neutropenia was directly associated with the MTR-2756G/G genotype (P = .011), GSTP1-105Ile/Ile genotype (P = .02), and with the ERCC1-118T/8092C-haplotype (P = .042). In addition, significant associations between GSTP1-105Ile/Ile genotype and neurotoxicity and between the XPD-Asn312/751Gln haplotype and nephrotoxicity could be identified (P = .028 and P = .005, respectively).

CONCLUSION

These findings underline the hypothesis that germ-line polymorphisms may play an important role in individualizing chemotherapy in AGC and deserve further prospective evaluation in AGC patients.

Polymorphisms in p53, GSTP1 and XRCC1 predict relapse and survival of gastric cancer patients treated with oxaliplatin-based adjuvant chemotherapy

PURPOSE

The aim of this study was to assess whether genetic polymorphisms in p53, glutathione S-transferase P1 (GSTP1), GSTM1, excision repair cross complementing group 1 (ERCC1) and X-ray repair cross-complementing group 1 (XRCC1) genes are associated with clinical outcome of gastric cancer patients treated with oxaliplatin-based adjuvant chemotherapy.

METHODS

The genetic polymorphisms in p53, GSTP1, GSTM1 (null), ERCC1 and XRCC1 were determined in 102 gastric cancer patients treated with oxaliplatin-based adjuvant chemotherapy using polymerase chain reaction-ligation detection reaction method.

RESULTS

Among the five studied polymorphisms, p53 codon 72 Pro/Pro, GSTP1 codon 105 Ile/Ile, and XRCC1 codon 399 Gln/Gln + Arg/Gln were associated with poor relapse-free survival and overall survival (P < 0.05); and the prognostic effect was retained in the Cox multivariate analysis. Combination analysis with the three polymorphisms using the Kaplan-Meier method and Cox multivariate analysis revealed that the relapse-free and overall survivals significantly increase with the number of favorable genotypes (P < 0.05). No significant association was found between the GSTM1 (null) or the ERCC1 codon 118 genotypes and the clinical outcome (P > 0.05).

CONCLUSION

Testing for p53 Arg72Pro, GSTP1 Ile105Val, and XRCC1 Arg399Gln polymorphisms may allow identification of gastric cancer patients who will benefit from oxaliplatin-based adjuvant chemotherapy. Selecting specific adjuvant treatments according to the individual genetic background may represent an innovative strategy that warrants prospective studies.

Pharmacogenetic analyses of hematotoxicity in advanced gastric cancer patients receiving biweekly fluorouracil, leucovorin, oxaliplatin and docetaxel (FLOT): a translational study of the Arbeitsgemeinschaft Internistische Onkologie (AIO)

BACKGROUND

Docetaxel-based chemotherapy regimens have demonstrated activity in advanced gastric cancer (AGC). However, a high rate of grade 3/4 hematotoxicity was reported with these regimens. Our purpose was to identify pharmacogenetic markers with potential to detect patients with increased risk to encounter severe hematotoxicity following treatment with 5-fluorouracil, leucovorin, oxaliplatin and docetaxel (FLOT).

PATIENTS AND METHODS

Polymorphisms of genes involved in DNA repair, drug transport and metabolism were determined in 50 AGC patients receiving FLOT within a phase II trial. DNA was extracted from peripheral blood. Genotyping was carried out using PCR-based techniques.

RESULTS

Patients possessing TS-group A genotypes (2R/2R, 2R/3RC, 3RC/3RC) were at increased risk for grade 3/4 hematotoxicity compared with patients harboring a TS-group B genotype (2R/3RG, 3RC/3RG, 3RG/3RG). In all, 59% (20 of 34) of patients with TS-group A genotypes developed grade 3/4 hematotoxicity compared with 25% (4 of 16) of those having TS-group B genotypes (P=0.035). Grade 3/4 neutropenia occurred in 53% (18 of 34) of TS-group A patients compared with 19% (3 of 16) in TS-group B patients (P=0.032). Multivariate analyses identified TS-group A genotypes as significant predictors of grade 3/4 overall hematotoxicity {odds ratio (OR) 4.62 [95% confidence interval (CI) 1.22; 17.44], P=0.024} and neutropenia [OR 5.74 (95% CI 1.03; 32.08), P=0.047].

CONCLUSION

TS-promoter polymorphisms may be associated with hematotoxicity in AGC patients receiving FLOT.

Glutathione-S-transferase pi (GSTP1) codon 105 polymorphism is not associated with oxaliplatin efficacy or toxicity in advanced colorectal cancer patients

PURPOSE

Oxaliplatin is detoxified by conjugation to glutathione via the enzyme Glutathione-S-transferase pi (GSTP1). The aim of this study is to investigate the association of GSTP1 Ile105Val genetic polymorphism with oxaliplatin efficacy and toxicity in advanced colorectal cancer (ACC) patients.

EXPERIMENTAL DESIGN

A total of 91 ACC patients received capecitabine and oxaliplatin (CAPOX) as a part of a multicentre phase-III study of the Dutch Colorectal Cancer Group. Tumour response was evaluated according to RECIST, toxicity was graded using CTC, and GSTP1 Ile105Val was determined by pyrosequencing.

RESULTS

Overall survival after CAPOX was similar for patients with the Ile/Ile (11.5 mo), Ile/Val (11.6 mo) and Val/Val (12.6 mo) genotypes (p=0.602). Likewise, there were no statistically significant differences in progression-free survival (p=0.252). Overall grades 3-4 toxicity was not related to genotype (p=0.313). There were no differences in any grade or grades 3-4 neurotoxicity amongst the patients who received > or =500 mg/m(2) of oxaliplatin (p-values of 0.376 and 0.772, respectively).

CONCLUSIONS

The results of this study indicate that the GSTP1 genotype is not predictive for progression-free survival or overall survival in ACC patients treated with CAPOX. Moreover, overall neurotoxicity and neurotoxicity in patients receiving 500 mg/m(2) of oxaliplatin was not associated with GSTP1 genotype.

Glutathione S-transferase M1 and T1 polymorphisms may predict adverse effects after therapy in children with medulloblastoma

Glutathione S-transferases (GSTs) are polymorphic enzymes that catalyze the glutathione conjugation of alkylating agents, platinum compounds, and free radicals formed by radiation used to treat medulloblastoma. We hypothesized that GST polymorphisms may be responsible, in part, for individual differences in toxicity and responses in pediatric medulloblastoma. We investigated the relationship between GSTM1 and GSTT1 polymorphisms and survival and toxicity in 42 children with medulloblastoma diagnosed and treated at the Texas Children's Cancer Center. We conducted Kaplan-Meier analyses to determine if the GST polymorphisms were related to progression-free survival (PFS) and performed logistic regression to explore associations between GST polymorphisms and occurrence of grade 3 or greater (> or =Gr 3) myelosuppression, ototoxicity, nephrotoxicity, neurotoxicity, and intellectual impairment. Patients with at least one null genotype had a 4.3 (95% confidence interval, 1.1-16.8), 3.7 (1-13.6), and 6.4 (1.2-34) times increased risk for any > or =Gr 3 toxicity, any > or =Gr 3 toxicity excluding peripheral neuropathy, and any > or =Gr 3 toxicity requiring omission or cessation of chemotherapy, respectively. Compared with all others, patients with at least one null genotype had, on average, 27.2 (p x= 0.0002), 29 (p = 0.0004), and 21.7 (p = 0.002) lower full-scale, performance, and verbal intelligence quotient (IQ) scores, respectively. GSTM1 and GSTT1 polymorphisms may predict adverse events, including cognitive impairment after therapy, in patients with medulloblastoma. A larger study to validate these findings is under way.

Long-term platinum retention after treatment with cisplatin and oxaliplatin

Background

The aim of this study was to evaluate long-term platinum retention in patients treated with cisplatin and oxaliplatin.

Methods

45 patients, treated 8–75 months before participating in this study, were included. Platinum levels in plasma and plasma ultrafiltrate (pUF) were determined. In addition, the reactivity of platinum species in pUF was evaluated. Relationships between platinum retention and possible determinants were evaluated.

Results

Platinum plasma concentrations ranged between 142–2.99 × 10³ ng/L. Up to 24% of plasma platinum was recovered in pUF. No platinum-DNA adducts in peripheral blood mononuclear cells (PBMCs) could be detected. Ex vivo incubation of DNA with pUF of patients revealed that up to 10% of the reactivity of platinum species was retained. Protein binding proceeded during sample storage. Sodium thiosulfate (STS) appeared to release platinum from the plasma proteins. Platinum levels were related to time, dose, STS co-administration, and glomerular filtration rates (GFR).

Conclusion

Our data suggest that plasma platinum levels are related to time, age, dose, GFR, and STS use. Platinum in plasma, probably, represent platinum eliminated from regenerating tissue. Platinum species in pUF were partly present in a reactive form. The effects of the reactivity on long-term consequences of Pt-containing chemotherapy, however, remains to be established.

GSTP1 Ile105Val polymorphism correlates with progression-free survival in MCRC patients treated with or without irinotecan: a study of the Dutch Colorectal Cancer Group

A Valine residue at position 105 of the GSTP1 protein results in decreased enzyme activity. As nuclear GSTP1 activity decreases irinotecan cytotoxicity, Val-allele carriers may benefit more from irinotecan chemotherapy. Our aim was to investigate the association of GSTP1 genotype with treatment outcome of irinotecan. Progression-free survival (PFS) and toxicity were determined in 267 metastatic colorectal cancer (MCRC) patients who were treated with first-line capecitabine (CAP) plus irinotecan (CAPIRI), or CAP single agent in a prospective randomised phase III trial (CAIRO). GSTP1 genotype was determined by Pyrosequencing. Patients receiving CAP showed a PFS of 6.6 (Ile/Ile), 6.0 (Ile/Val) and 6.5 months (Val/Val); compared to 7.0 (Ile/Ile), 8.8 (Ile/Val) and 9.2 months (Val/Val) with CAPIRI. Median PFS was 2.7 months longer in Val-allele carriers treated with CAPIRI compared to CAP (P=0.005). Patients with the Ile/Ile genotype showed similar PFS with CAPIRI and CAP (7.0 compared to 6.6 months, P=0.972). Toxicity did not differ significantly among genotypes. GSTP1 codon 105 polymorphism may be predictive for the response to irinotecan-based chemotherapy in patients with MCRC, with the Val-allele being associated with a better outcome. Ile/Ile genotype patients do not appear to benefit from the addition of irinotecan to CAP.

Thymidylate synthase genotypes and tumour regression in stage II/III rectal cancer patients after neoadjuvant fluorouracil-based chemoradiation

PURPOSE

According to the CAO-/ARO-/AIO-94 trial of the German Rectal Cancer Study Group, pre-operative 5-fluorouracil (5-FU)-based long-term chemoradiotherapy (CT/RT) is recommended for patients with rectal cancer UICC stage II/III. However, despite the local benefit of neoadjuvant treatment, the overall prognostic value remains uncertain in comparison to adjuvant CT/RT. We assessed the impact of standardized pre-operative CT/RT and intratumoural mRNA levels and polymorphisms of the TS gene on histopathological tumour regression.

PATIENTS AND METHODS

40 patients with rectal cancer UICC stage II/III, receiving pre-operative 5-FU-based CT/RT followed by standardized surgery, including total mesorectal excision, were investigated. TS gene expression and TS polymorphisms of surgical specimens were correlated with the grade of histopathological tumour regression (0-4). Patients achieved regression grades 2-4 were determined as responders.

RESULTS

TS polymorphisms (5'-28bp repeat+G/C SNP and TS1494del6) could be determined in 39/40 (97.5%) and in 38/40 (95%) patients, respectively. Quantification of TS mRNA expression was successful in 36/40 (90%) patients. There was a highly significant linkage disequilibrium between 5'- and 3'-TS polymorphisms (p=0.0013). Interestingly, the majority of patients (82.1%) with 5'-TS genotypes known to be associated with low mRNA expression (2R/2R, 2R/3RC, 3RC/3RC) also possessed the TS1494del6 +6bp/+6bp genotype correlating with high TS mRNA expression. TS1494del6 polymorphism was significantly associated with TS mRNA expression. Patients with TS1494del6 -6bp/-6bp or -6bp/+6bp genotypes showed significantly lower mean TS mRNA expression with 0.55 (range:0.33;0.84) as compared to +6bp homozygotes with a mean expression of 0.90 (range:0.20;1.91) (p=0.025). Furthermore, all patients with TS 3'-UTR -6bp/-6bp or -6bp/+6bp genotype (11/11) were responders as compared to only 20/26 (77%) of patients with TS 3'-UTR +6bp/+6bp genotype (p=0.082). TS 5'-polymorphisms were not associated with neither tumour regression nor gene expression.

CONCLUSION

Our data suggest that the TS1494del6 polymorphism may be an important predictor for histopathological tumour regression in UICC II/III rectal cancer patients receiving neoadjuvant 5-FU-based CT/RT.

The polymorphisms of TS and MTHFR predict survival of gastric cancer patients treated with fluorouracil-based adjuvant chemotherapy in Chinese population

PURPOSE

The aim of this study was to investigate the association of the thymidylate synthase (TS) and methylenetetrahydrofolate reductase (MTHFR) polymorphisms with the clinical outcomes of gastric cancer patients treated with 5-FU-based adjuvant chemotherapy.

METHODS

One-hundred and sixteen patients with gastric cancer were treated with 5-FU-based adjuvant chemotherapy. The TS (a 28-bp tandem repeat polymorphism in the TS enhancer region (TSER) and a 6 bp deletion/insertion polymorphism in the 3'-untranslated region) and MTHFR C677T polymorphisms were determined in blood samples from those patients using PCR and PCR-LDR (ligation detection reaction) method, respectively.

RESULTS

The overall survival (OS) in patients with the TS ins6/ins6 genotype was significantly shorter than those in patients with the del6/del6 (P = 0.017) and ins6/del6 (P = 0.022) genotype. The relapse-free survival (RFS) and OS in patients with the MTHFR C/C genotype were significantly worse than those in patients with the T/T or C/T genotype (P = 0.043 and 0.040, respectively). Cox multivariate analysis also showed that patients with the TS ins6/ins6 genotype have worse OS than patients with the T/T or C/T genotype (HR = 2.437, P = 0.041), and the MTHFR C/C genotype was associated with shorter RFS (HR = 1.723, P = 0.031) and OS (HR = 1.681, P = 0.056). No significant association was found between the TSER polymorphism and the clinical outcomes (P > 0.05).

CONCLUSION

The polymorphisms of TS 3'-UTR ins6/del6 and MTHFR C677T appear to be potential prognostic factors in gastric cancer patients treated with 5-FU-based adjuvant chemotherapy, which may allow identification of gastric cancer patients who will benefit from 5-FU chemotherapy.

Glutathione-S-transferase P1, T1 and M1 genetic polymorphisms in neoadjuvant-treated locally advanced gastric cancer: GSTM1-present genotype is associated with better prognosis in completely resected patients

OBJECTIVE

Neoadjuvant chemotherapy in gastric cancer is now standard in the Western world; however, only 30-40% of the patients respond to induction therapy. Pretherapeutic predictors of response and prognosis would be of utmost interest to individualize treatment. Glutathione-S-transferase enzymes detoxify therapeutic drugs such as platin derivates and may influence outcome of the treated patients. Therefore, glutathione-S-transferase (GST) polymorphisms were assessed as predictive markers in cisplatinum-based neoadjuvant-treated gastric cancer.

MATERIALS AND METHODS

DNA was isolated from 139 patients with locally advanced gastric cancer (cT3/4 anyN cM0) before chemotherapy. Multiplex polymerase chain reaction was used for GSTT1 and GSTM1 genes, and allelic discrimination assay with the TaqMan system for the GSTP1 gene.

RESULTS

One hundred ten patients could be analyzed for GSTT1 (T-:23; T+87), 112 for GSTM1 (M-:52; M+:60) and 132 for GSTP1 (Ile/Ile: 55; Ile/Val: 59; Val/Val: 18). There was no significant correlation between any of the GSTT1, GSTM1, or GSTP1 genotypes and patients' characteristics or histopathological data; only the GSTM1+ genotype was associated with the non-intestinal subtype of the Lauren classification (p=0.045). GSTT1, GSTM1, and GSTP1 genotypes were not correlated with response to chemotherapy (p=0.57, p=0.38, p=0.33). In R0 resected patients, we found an improved survival for patients with the GSTM1-present genotype compared to patients with the GSTM1-null genotype (p=0.017). Moreover, the GSTM1-present genotype showed a significantly better tumor-related (p=0.017) and disease-free survival (p=0.029).

CONCLUSION

None of the common GST polymorphisms predicts response in our study, but the GSTM1+ genotype was associated with a better prognosis in completely resected patients. Further investigations on chemotherapy-associated gene polymorphisms are warranted.

Effects of Genetic Polymorphisms of Glutathione S-transferase P1 on Helicobacter pylori-associated Gastric Cancer

BACKGROUND/AIMS

Glutathione S-transferase P1 (GSTP1) scavenges radicals via its peroxidase activity. The purpose of this study was to determine the association of GSTP1 genetic polymorphisms with the expression of H. pylori-associated gastroduodenal disease.

METHODS

This study involved 1,911 subjects, comprising patients with four diseases (gastric cancer, dysplasia, benign gastric ulcer, and duodenal ulcer disease) and controls. Biallelic polymorphisms were genotyped by restriction fragment length polymorphism techniques.

RESULTS

The frequency of the genetic polymorphism at nucleotide 313 of GSTP1 did not differ among the five study groups. However, when the gastric cancer group was subdivided into advanced gastric cancer (AGC) and early gastric cancer, the frequency of the G/G genotype was significantly higher in the AGC group than in all the control subgroups (OR: 1.2, 95% CI: 1.1-4.9). The frequency of this genotype differed significantly in the H. pylori-positive AGC group (OR: 2.7, 95% CI: 1.1-6.3) but not in the H. pylori-negative group. Furthermore, the difference was greater in the intestinal type, and was not found in diffuse types of disease.

CONCLUSIONS

This study found that genetic polymorphisms of GSTP1 were associated with H. pylori-associated gastric cancer only during the advanced stage of gastric cancer, with intestinal-type histology evident in H. pylori-positive subjects.

Modified FOLFOX-6 chemotherapy in advanced gastric cancer: Results of phase II study and comprehensive analysis of polymorphisms as a predictive and prognostic marker

Background

The objective of this study was to evaluate the efficacy and toxicity of infusional 5-fluorouracil (5-FU), folinic acid and oxaliplatin (modified FOLFOX-6) in patients with advanced gastric cancer (AGC), as first-line palliative combination chemotherapy. We also analyzed the predictive or prognostic value of germline polymorphisms of candidate genes associated with 5-FU and oxaliplatin.

Methods

Seventy-three patients were administered a 2 hour infusion of oxaliplatin (100 mg/m²) and folinic acid (100 mg/m²) followed by a 46 hour continuous infusion of 5-FU (2,400 mg/m²). Genomic DNA from the patients' peripheral blood mononuclear cells was extracted. Ten polymorphisms within five genes were investigated including TS, GSTP, ERCC, XPD and XRCC.

Results

The overall response rate (RR) was 43.8%. Median time to progression (TTP) and overall survival (OS) were 6.0 months and 12.6 months, respectively. Toxicities were generally tolerable and manageable. The RR was significantly higher in patients with a 6-bp deletion homozygote (-6 bp/-6 bp) in TS-3'UTR (55.0% vs. 30.3% in +6 bp/+6 bp or +6 bp/-6 bp, p = 0.034), and C/A or A/A in XPD156 (52.0% vs. 26.1% in C/C, p = 0.038). The -6 bp/-6 bp in TS-3'UTR was significantly associated with a prolonged TTP and OS. In a multivariate analysis, the 6-bp deletion in TS-3'UTR was identified as an independent prognostic marker of TTP (hazard ratio = 0.561, p = 0.032).

Conclusion

Modified FOLFOX-6 chemotherapy appears to be active and well tolerated as first line chemotherapy in AGC patients. The 6-bp deletion in TS-3'UTR might be a candidate to select patients who are likely to benefit from 5-FU based modified FOLFOX-6 in future large scale trial.

The genetics of cancer survivorship

Constitutional (hereditary) genetic variation and somatic genetic alterations acquired during transformation to the neoplastic phenotype are both critical determinants of cancer outcome, and can ultimately have a significant effect on cancer survivorship. This article discusses the role of constitutional and somatic genetics in determining outcome and survivorship following a diagnosis of cancer using illustrative examples primarily from the hematologic malignancies.

Prognostic role of p53 codon 72 polymorphism in gastric cancer patients treated with fluorouracil-based adjuvant chemotherapy

OBJECTIVE

The polymorphism of p53 codon 72 (Arg72Pro) has been suggested to play an important role in many cancers and may influence the response to chemotherapy. Our aim was to investigate the association of p53 Arg72Pro polymorphism with the clinical outcome of gastric cancer patients treated with 5-FU-based adjuvant chemotherapy.

METHODS

The p53 codon 72 genotype was determined in blood samples from 110 Chinese patients with gastric cancer treated with 5-fluorouracil (5-FU)-based adjuvant chemotherapy, using polymerase chain reaction-ligation detection reaction (PCR-LDR) method.

RESULTS

Kaplan-Meier survival analysis showed that gastric cancer patients with Pro/Pro genotype had shorter relapse-free survival (chi(2) = 10.632, P = 0.005) and overall survival (chi(2) = 7.104, P = 0.029) than patients with other genotypes. Cox multivariate analysis showed that Pro/Pro genotype was associated with statistically significant reduced relapse-free survival (adjusted OR = 3.049, 95% CI: 1.363-6.819, P = 0.007) and overall survival (adjusted OR = 2.581, 95% CI: 1.052-6.330, P = 0.038).

CONCLUSION

These results suggested that p53 codon 72 polymorphism appears to be an independent prognostic factor in gastric cancer patients treated with 5-FU-based adjuvant chemotherapy.

Pharmacogenetics and stomach cancer: an update

Although new drugs and association regimens have been used in recent years, the chemotherapeutic outcome for gastric cancer is still poor and improvement in patient survival is not satisfactory. Pharmacogenetics could represent a useful approach to optimize chemotherapeutic treatments in order to identify individuals that are true candidates for clinical benefits from therapy, avoiding the development of severe side effects. The most recent update regarding gastric cancer pharmacogenetics highlights a prominent role of genetic polymorphisms of thymidylate synthase and glutathione S-transferase in the pharmacological treatment with commonly used drugs, such as 5-fluorouracil and platinum derivatives. In order to validate the genetic markers, further larger scale and controlled studies are required. A future challenge is represented by the introduction of targeted therapy in gastric cancer treatment, with the potential emerging tool of pharmacogenetic impact on this field.

Polymorphisms in genes encoding drug metabolizing enzymes and their influence on the outcome of children with neuroblastoma

BACKGROUND

Although several studies have shown that drug metabolizing enzyme gene polymorphisms may influence the impact of therapy in childhood leukemia, no comprehensive investigations have been carried out in children with neuroblastoma. The aim of this study was to identify polymorphisms in the genes encoding phase I and II drug metabolizing enzymes associated with the risk of relapse or death in a cohort of 209 children with neuroblastoma.

METHODS

Real-time PCR allelic discrimination was used to characterize the presence of polymorphisms in DNA from children with neuroblastoma. Three broad gene categories were examined: cytochrome P450, glutathione-S-transferase and N-acetyltransferase. Cumulative event-free survival was computed by the Kaplan-Meier method. The influence of selected factors on event-free survival was tested using the Cox proportional hazards model.

RESULTS

As previously reported, amplification of MYCN (hazards ratio=4.25, 95% confidence interval=2.76-6.56, P<0.001), unfavorable stage (hazard ratio=4.14, 95% confidence interval=2.3-7.47, P<0.001) or age more than 1 year at diagnosis (hazard ratio=1.86, 95% confidence interval=1.19-2.92, P=0.007) were all associated with an increased risk of relapse or death. Carriers of a NAT1*11 allele variant were significantly less likely to relapse or die compared with those with NAT1*10 or other NAT1 allele variants (P<0.001). In multivariate analysis, children who were GSTM1 null were more likely to relapse or die during follow-up after adjusting for MYCN amplification, stage and age at diagnosis (hazard ratio=1.6, 95% confidence interval=1.02-2.9, P=0.04).

CONCLUSIONS

These observations suggest that the NAT1*11 variant and the GSTM1 wild-type genotype contribute to a more favorable outcome in patients treated for neuroblastoma and are the first to demonstrate a relationship between NAT1 and GSTM1 genotypes in childhood neuroblastoma.

Polymorphisms in manganese superoxide dismutase, myeloperoxidase and glutathione-S-transferase and survival after treatment for metastatic breast cancer

Treatments for metastatic breast cancer (MBC) are primarily palliative with variable efficacy and outcomes may be influenced by individual differences in drug metabolism. In this study, we examined the association of single nucleotide polymorphisms (SNPs) in genes involved in drug metabolism with progression free survival (PFS) and breast cancer specific survival (BCSS) in 95 patients with MBC that received high dose chemotherapy (HDC) with autologous stem cell transplantation (ASCT). SNPs in the SOD2 (SOD2-01, Val16Ala), MPO (MPO-02, -463 promoter variant) and GSTP1 [GSTP1-01 (Ile105Val), GSTP1-02 (Ala114Val)] genes were examined in DNA isolated from cryopreserved blood products using genotyping assays. Survival was analysed using Cox proportional hazard models and Kaplan-Meier estimates. Patients with the SOD2-01 (TT) genotype had increased risk of disease progression [hazard ratio (HR): 2.52; 95% confidence interval (CI), 1.31-4.85] and breast cancer specific death (HR: 1.92; 95% CI: 1.03-3.57). Risks were increased for patients with both SOD2-01 (TT) and GSTP1-01 (GG or AG) genotypes (HR for disease progression: 2.57, 95% CI: 1.32-5.00 and HR for breast cancer specific death: 2.27; 95% CI: 1.18-4.34). In multivariable analysis, the combined genotype group of SOD2-01 and GSTP1-01 was an independent predictor of PFS and BCSS. HRs progressively increased with increasing number of genotypes associated with worse survival, with p(trend) of 0.005 and 0.006 for PFS and BCSS, respectively. These results suggest that SNPs in genes involved in drug metabolism may influence survival outcome for patients with MBC receiving HDC and ASCT.

Implication de la pharmacogénétique dans les traitements des cancers colorectaux

SCOPE

Clinical implications associated with polymorphisms in drug-metabolizing genes involved in the chemotherapy of colorectal cancers (5-flurorouracil, oxaliplatin and irinotecan) are reviewed.

CURRENT SITUATION AND SALIENT POINTS

Treatments of colorectal cancers have been greatly improved last years but patients respond differently to identical medication. Genetic polymorphisms are one of the major causes of these individual responses to drugs associated with sometimes severe adverse effects. Pharmacogenetics is based on all polymorphisms that determine genetic human diversity associated with variable response to anticancer drugs.

PERSPECTIVES

Morbidity and mortality related to toxicity or inefficacy of these drugs could be reduced by analyzing the pharmacogenetic profile of patients before treatment. Results should be integrated in protocols for monitoring and assessment the dosage of drugs.

Genetic polymorphism and function of glutathione S-transferases in tumor drug resistance

The human glutathione S-transferase, GSTs, possess both enzymatic and non-enzymatic functions and are involved in many important cellular processes, such as, phase II metabolism, stress response, cell proliferation, apoptosis, oncogenesis, tumor progression and drug resistance. The non-enzymatic functions of GSTs involve their interactions with cellular proteins, such as, JNK, TRAF, ASK, PKC, and TGM2, during which, either the interacting protein partner undergoes functional alteration or the GST protein itself is post-translationally modified and/or functionally altered. The majority of GST genes harbor polymorphisms that influence their transcription and/or function of their encoded proteins. This overview focuses on recent insights into the biology and pharmacogenetics of GSTs as a determinant of cancer drug resistance and response of cancer patients to therapy.

Favorable genetic polymorphisms predictive of clinical outcome of chemoradiotherapy for stage II/III esophageal squamous cell carcinoma in Japanese

OBJECTIVES

This study was performed to find the genetic factors predictive of clinical outcome to a 5-fluorouracil (5-FU)/cisplatin (CDDP)-based chemoradiotherapy (CRT) in Japanese patients with locally advanced esophageal squamous cell carcinoma (ESCC).

MATERIALS AND METHODS

Thirty-one patients with stage I-IVa ESCC (I/II/III/IVa = 7/7/14/3) were enrolled in this study. One course of treatment consisted of protracted venous infusions (PVIs) of 5-FU (400 mg/m2/24 hours for days 1-5 and 8-12), CDDP (40 mg/m2/3 hours on days 1 and 8) and radiation (2 Gy/d on days 1-5, 8-12, and 15-19), and a 2nd course was successively repeated after a 2-week interval. A total of 8 measurements of the plasma concentration of 5-FU were made using high performance liquid chromatography. Genetic polymorphisms examined herein included those in the genes coding thymidylate synthase (TS), glutathione S-transferase P1 (GSTP1), multidrug resistant transporter MDR1/P-glycoprotein, and intercellular adhesion molecule-1, and in a circadian rhythm-relating gene, CLOCK.

RESULTS

The CR rate depended on stage (P = 0.001), but the analysis was not sufficiently powered to reach a level of statistical significance for the 2-year survival rate (P = 0.061). For stage II/III patients, to have 2 or 3 polymorphisms of 3R/3R of 5'-TSER, a 6 bp of 3'-TSUTR, and GSTP1-Ile105Val resulted in an extensively longer survival (P = 0.020), although no difference was found between 2 groups, with respect to the plasma concentrations of 5-FU and clinicopathologic characteristics.

CONCLUSIONS

The prognostic index may allow predictions of the clinical outcome of a 5-FU/CDDP-based CRT in stage II/III ESCC patients.

Polymorphism of XRCC1 predicts overall survival of gastric cancer patients receiving oxaliplatin-based chemotherapy in Chinese population

Pharmacogenetic advances in cancer chemotherapy have the potential to predict clinical benefit to particular regimens. Platinum agents have shown to be effective in the treatment of gastric cancer. We assessed whether single nucleotide polymorphisms (SNPs) in xeroderma pigmentosum group D (XPD), X-ray repair cross complementing group 1 (XRCC1) and glutathione S-transferase P1 (GSTP1) predicted overall survival in gastric cancer patients receiving oxaliplatin-based chemotherapy in Chinese population. SNPs of XPD-751, XRCC1-399 and GSTP1-105 in 62 gastric cancer patients were evaluated using the TaqMan 5' nuclease assay. Genotypes were correlated to survival. The median overall survival time was 322 days (range: 56-2058 days). The median survival times for patients with Arg/Arg or Arg/Gln genotypes of XRCC1 gene were significantly longer than others (P=0.03). For 58 patients with ECOG PS (Eastern Cooperative Oncology Group performance status)<or=2, more obvious significance was demonstrated (P=0.002). Patients with XRCC1-399 Gln/Gln genotype demonstrated a significant worse survival. No significant association was found between SNPs of XPD-751, GSTP1-105 and survival (P=0.125, 0.475, respectively). XRCC1 genotyping might make tailor chemotherapy possible for gastric cancer patients treated with oxaliplatin-based chemotherapy.

Relationship of glutathione S-transferase genotypes with side-effects of pulsed cyclophosphamide therapy in patients with systemic lupus erythematosus

AIMS

Cyclophosphamide (CTX) is an established treatment of severe systemic lupus erythematosus (SLE). Cytotoxic CTX metabolites are mainly detoxified by multiple glutathione S-transferases (GSTs). However, data are lacking on the relationship between the short-term side-effects of CTX therapy and GST genotypes. In the present study, the effects of common GSTM1, GSTT1, and GSTP1 genetic mutations on the severity of myelosuppression, gastrointestinal (GI) toxicity, and infection incidences induced by pulsed CTX therapy were evaluated in patients SLE.

METHODS

DNA was extracted from peripheral leucocytes in patients with confirmed SLE diagnosis (n = 102). GSTM1 and GSTT1 null mutations were analyzed by a polymerase chain reaction (PCR)-multiplex procedure, whereas the GSTP1 codon 105 polymorphism (Ile-->Val) was analyzed by a PCR-restriction fragment length polymorphism (RFLP) assay.

RESULTS

Our study demonstrated that SLE patients carrying the genotypes with GSTP1 codon 105 mutation [GSTP1*-105I/V (heterozygote) and GSTP1*-105 V/V (homozygote)] had an increased risk of myelotoxicity when treated with pulsed high-dose CTX therapy (Odds ratio (OR) 5.00, 95% confidence interval (CI) 1.96, 12.76); especially in patients younger than 30 years (OR 7.50, 95% CI 2.14, 26.24), or in patients treated with a total CTX dose greater than 1.0 g (OR 12.88, 95% CI 3.16, 52.57). Similarly, patients with these genotypes (GSTP1*I/V and GSTP1*V/V) also had an increased risk of GI toxicity when treated with an initial pulsed high-dose CTX regimen (OR 3.33, 95% CI 1.03, 10.79). However, GSTM1 and GSTT1 null mutations did not significantly alter the risks of these short-term side-effects of pulsed high-dose CTX therapy in SLE patients.

CONCLUSIONS

The GSTP1 codon 105 polymorphism, but not GSTM1 or GSTT1 null mutations, significantly increased the risks of short-term side-effects of pulsed high-dose CTX therapy in SLE patients. Because of the lack of selective substrates for a GST enzyme phenotyping study, timely detection of this mutation on codon 105 may assist in optimizing pulsed high-dose CTX therapy in SLE patients.

Prediction of clinical outcome of fluoropyrimidine-based chemotherapy for gastric cancer patients, in terms of the 5-fluorouracil metabolic pathway

Fluoropyrimidines are widely used in chemotherapy regimens for metastatic gastric cancer. Interindividual variation in the enzyme activity of the 5-fluorouracil (FU) metabolic pathway can affect the extent of 5-FU metabolism and affect the efficacy of 5-FU based chemotherapy. In this review, the role of the genetic factors affecting the therapeutic efficacy of fluoropyrimidines is discussed, with a special emphasis on enzymes involved in the 5-FU metabolic pathway. The gene expressions of thymidylate synthase, dihydropyrimidine dehydrogenase, thymidine phosphorylase, and orotate phosphoribosyltransferase are discussed in relation to the efficacy of fluoropyrimidine treatment for metastatic gastric cancer. These candidate genes, along with others yet to be identified, could allow accurate prediction of the clinical outcome in patients receiving fluoropyrimidine-based chemotherapy in the future. Well-designed and large prospective studies, which include relevant pharmacogenetic parameters, are needed to confirm the values required to predict clinical outcome.

Molecular-based choice of cancer therapy: realities and expectations

Current choice of cancer therapy is usually empirical and relies mainly on the statistical prediction of the treatment success. Molecular research provides some opportunities to personalize antitumor treatment. For example, life-threatening toxic reactions can be avoided by the identification of subjects, who carry susceptible genotypes of drug-metabolizing genes (e.g. TPMT, UGT1A1, MTHFR, DPYD). Tumor sensitivity can be predicted by molecular portraying of targets and other molecules associated with drug response. Tailoring of antiestrogen and trastuzumab therapy based on hormone and HER2 receptor status has already become a classical example of customized medicine. Other predictive markers have been identified both for cytotoxic and for targeted therapies, and include, for example, expression of TS, TP, DPD, OPRT, ERCC1, MGMT, TOP2A, class III beta-tubulin molecules as well as genomic alterations of EGFR, KIT, ABL oncogenes.

XRCC1 R399Q polymorphism is associated with response to platinum-based neoadjuvant chemotherapy in bulky cervical cancer

OBJECTIVES

The aim of the study was to assess whether the genetic polymorphisms were associated with the tumor response in patients treated with platinum-based neoadjuvant chemotherapy (NAC) for bulky cervical cancer.

METHODS

We retrospectively reviewed the clinical data and recruited paraffin-embedded, formalin-fixed tissues of 36 patients with bulky cervical carcinoma. All patients underwent two or three cycles of platinum-based NAC followed by radical hysterectomy. We determined the genotypes of each single nucleotide polymorphism (SNP) of ERCC1, ERCC2, GGH, GSTP1, MTHFR, SLC19A1 and XRCC1 using single base primer extension assay.

RESULTS

The response to platinum-based NAC was higher in patients with SNP of XRCC1 R399Q (P=0.015), and there was a significant increased chance of treatment response in women with the G/G genotype (OR 38.0; 95% CI 1.66-870.45; P=0.023). The probability of response was also higher in patients with SNP of SLC19A1 6318C/T (P=0.032). There were dose-dependent influence of the number of alleles on the response to platinum-based chemotherapy (chi2 test for linear-by-linear association; P=0.009 for XRCC1 R399Q and P=0.017 for SLC19A1 6318C/T, respectively). Moreover, the multifactor dimensionality reduction (MDR) analysis documented that the combinations of XRCC1 R399Q and GGH-401C/T genetic polymorphisms were significantly associated with response to chemotherapy (P<0.0001).

CONCLUSIONS

Genetic polymorphism of XRCC1 R399Q is associated with response to platinum-based NAC in bulky cervical cancer, and MDR analysis documented association between gene-gene interaction of XRCC1 R399Q and treatment response.

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.