GSTP1 and MTHFR polymorphisms are related with toxicity in breast cancer adjuvant anthracycline-based treatment

GSTP1 c.313A > G mutation is an independent risk factor for neutropenia hematotoxicity induced by anthracycline-/paclitaxel-based chemotherapy in breast cancer patients

Background

The link between glutathione S-transferase P1 (GSTP1) c.313A > G polymorphism and chemotherapy-related adverse events remains controversial. The goal of this study was to assess how this variant affected the toxicity of anthracycline-/paclitaxel-based chemotherapy in patients with breast cancer.

Methods

This study retrospectively investigated pharmacogenetic associations of GSTP1 c.313A > G with chemotherapy-related adverse events in 142 breast cancer patients who received anthracycline and/or paclitaxel chemotherapy.

Results

There were 61 (43.0%), 81 (57.0%), 43 (30.3%), and 99 (69.7%) patients in the T0-T2, T3-T4, N0-N1, and N2-N3 stages, respectively. There were 108 (76.1%) patients in clinical stages I–III and 34 (23.9%) patients in clinical stage IV. The numbers of patients with luminal A, luminal B, HER2 + , and triple-negative breast cancer (TNBC) were 10 (7.0%), 77 (54.2%), 33 (23.2%), and 22 (15.5%), respectively. The numbers of patients who carried GSTP1 c.313A > G A/A, A/G, and G/G genotypes were 94 (66.2%), 45 (31.7%), and 3 (2.1%), respectively. There were no statistically significant differences in the proportion of certain toxicities in patients with A/G, G/G, and A/G + G/G genotypes, except for neutropenia, in which the proportion of patients with A/G + G/G (χ² = 6.586, P = 0.035) genotypes was significantly higher than that with the AA genotype. The logistic regression analysis indicated that GSTP1 c.313A > G mutation (A/G + G/G vs. A/A genotype) (adjusted OR 4.273, 95% CI 1.141–16.000, P = 0.031) was an independent variable associated with neutropenia.

Conclusions

The findings of this study indicate that the GSTP1 c.313A > G mutation is an independent risk factor for neutropenia hematotoxicity in breast cancer patients induced by anthracycline-/paclitaxel-based chemotherapy.

GSTP1 polymorphism predicts treatment outcome and toxicities for breast cancer

This study aimed to investigate the association of the GSTP1 gene polymorphism with the outcomes and toxicities of treatments in breast cancer. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated for the association of GSTP1 polymorphism with tumour response and toxicities, and the hazard ratios (HRs) and 95% CIs were calculated for the association between GSTP1 polymorphism and overall survival (OS). The statistical analysis showed that the GSTP1 polymorphism was not associated with tumour response or OS. A significant increase in the incidence of toxicities was observed (GA vs. AA OR = 1.45, 95% CI = 1.04–2.01, P = 0.028; GG vs. AA OR = 1.47, 95% CI = 1.03–2.10, P = 0.036; recessive model OR = 1.54, 95% CI = 1.13–2.09, P = 0.006; and allele model OR = 1.35, 95% CI = 1.07–1.71, P = 0.011), especially in the chemotherapy ± surgery group (GA vs. AA OR = 1.64, 95% CI = 1.05–2.56, P = 0.030; recessive model OR = 1.72, 95% CI = 1.17–2.54, P = 0.006; and allele model OR = 1.57, 95% CI = 1.11–2.21, P = 0.010). Our results indicate that the GSTP1 polymorphism may be associated with increased toxicity, especially in patients treated with chemotherapy ± surgery.

Relationship of MTHFR and NQO1 Pharmacogenetics and Chemotherapy Clinical Outcomes in Breast Cancer Patients

The study aimed at evaluating the influence of MTHFR 677C>T and NQO1 609C>T polymorphisms in toxicity and response to chemotherapy in breast cancer patients. These two genes are involved in the folate homeostasis and bioactivation of chemotherapeutic drugs, respectively. In this study, 243 patients treated with FEC/FAC/methotrexate chemotherapy regimen were recruited and followed up for toxicity (NCI-CTCAE ver. 3). While out of 243 patients, 115 patients who received neo-adjuvant chemotherapy (NACT) were followed for treatment response. Genetic analysis of MTHFR 677C>T and NQO1 609C>T was done by PCR-restriction fragment length polymorphism. We found significant association of variant genotype (TT) of NQO1 609C>T with grade 2-4 toxicity [OR 0.33 (0.13-0.88), P = 0.027] and with grade 2-4 anemia [OR 0.34 (0.12-0.95), P = 0.041]. However, no association of MTHFR 677C>T was seen with either response to NACT or drug-induced toxicity. The study provides useful information for prediction of clinical outcomes in breast cancer patients in terms of NQO1 609C>T by evaluating its association with chemotherapy-induced toxicity.

Functional polymorphisms in xenobiotic metabolizing enzymes and their impact on the therapy of breast cancer

Breast cancer is the top cancer among women, and its incidence is increasing worldwide. Although the mortality tends to decrease due to early detection and treatment, there is great variability in the rates of clinical response and survival, which makes breast cancer one of the most appealing targets for pharmacogenomic studies. The recognition that functional CYP2D6 polymorphisms affect tamoxifen pharmacokinetics has motivated the attempts of using CYP2D6 genotyping for predicting breast cancer outcomes. In addition to tamoxifen, the chemotherapy of breast cancer includes combinations of cytotoxic drugs, which are substrates for various xenobiotic metabolizing enzymes. Because of these drugs’ narrow therapeutic window, it has been postulated that impaired biotransformation could lead to increased toxicity. In the present review, we performed a systematic search of all published data exploring associations between polymorphisms in xenobiotic metabolizing enzymes and clinical outcomes of breast cancer. We retrieved 43 original articles involving either tamoxifen or other chemotherapeutic protocols, and compiled all information regarding response or toxicity. The data indicate that, although CYP2D6 polymorphisms can indeed modify tamoxifen pharmacokinetics, CYP2D6 genotyping alone is not enough for predicting breast cancer outcomes. The studies involving other chemotherapeutic protocols explored a great diversity of pharmacogenetic targets, but the number of studies for each functional polymorphism is still very limited, with usually no confirmation of positive associations. In conclusion, the application of pharmacogenetics to predict breast cancer outcomes and to select one individual’s chemotherapeutic protocol is still far from clinical routine. Although some very interesting results have been produced, no clear practical recommendations are recognized yet.

The effect of folate-related SNPs on clinicopathological features, response to neoadjuvant treatment and survival in pre- and postmenopausal breast cancer patients

This study aimed to investigate the relationship of ten single nucleotide polymorphisms (SNPs) in the MTHFR, MTR, MTRR, DHFR, MTHFD1, TS, RFC1 and DNMT3b genes with cancer survival, therapeutic response to neoadjuvant chemotherapy and clinicopathological characteristics in 300 pre- and postmenopausal breast cancer patients of a Russian Western Siberian population. We found that the MTHFR 677CT genotype as well as combination of MTHFR 677CT and 677TT genotype was related to tumor size and estrogen-positive status in postmenopausal group. The RFC1 80А allele was associated with an increased risk of lymph node metastases among postmenopausal women. The MTHFR 677TT genotype was significantly correlated with a better progression-free survival in premenopausal patients. In contrast, a worse outcome was observed in this group patient with MTHFD1 1958AA genotype. In the multivariate analysis, the MTHFD1 1958AA genotype was identified as an independent prognostic factor for premenopausal breast cancer survival. Our findings provide evidence for associations of breast cancer survival with folate-related SNPs in a population of Western Siberian region of Russia and the MTHFD1 (1958G>A) may have additional prognostic value especially among premenopausal patients.

Gene polymorphisms in cyclophosphamide metabolism pathway,treatment-related toxicity, and disease-free survival in SWOG 8897 clinical trial for breast cancer

PURPOSE

There are no established genetic markers for prediction of outcomes after cyclophosphamide (CP)-containing adjuvant therapy for breast cancer. In an ancillary study to a SWOG (Southwest Oncology Group) trial (S8897), we investigated functional polymorphisms in 4 genes in CP pharmacokinetic pathways in relation to hematologic toxicity and disease-free survival (DFS).

EXPERIMENTAL DESIGN

Germline DNA was available from 458 women who were at high risk of relapse and was randomized to CAF (CP, intravenous doxorubicin, and 5-fluorouracil) versus CMF (CP, intravenous methotrexate, and 5-fluorouracil) ± tamoxifen, and from 874 women who had a presumed favorable prognosis and did not receive adjuvant therapy. Odds ratios for grade 3 and 4 hematologic toxicity in the treated group and hazard ratios for DFS associated with selected functional polymorphisms in CYP2B6CYP3A4GSTA1 and GSTP1 were estimated by logistic regression and Cox proportional hazard regression.

RESULTS

Compared with women with AA genotypes, those with at least 1 GSTP1 variant G allele had reduced risk of grade 3 and 4 neutropenia [odds ratios (OR) = 0.63, 95% CI = 0.41-0.97] and leucopenia (OR = 0.59, 95% CI = 0.39-0.89). No other associations between single nucleotide polymorphisms and toxicity or survival were found in the treated or untreated group.

CONCLUSION

Known genetic variants in genes involved in CP pharmacokinetics may not have major effects on DFS in breast cancer patients. The lower risk of developing high-grade hematologic toxicity among women with variant GSTP1 alleles suggests that genetic markers in combination with clinical factors may be useful in defining a subgroup of women who are less susceptible to adverse hematologic toxicities with CP-containing therapies.

Breast cancer in the personal genomics era

Breast cancer is a heterogeneous disease with a complex etiology that develops from different cellular lineages, progresses along multiple molecular pathways, and demonstrates wide variability in response to treatment. The "standard of care" approach to breast cancer treatment in which all patients receive similar interventions is rapidly being replaced by personalized medicine, based on molecular characteristics of individual patients. Both inherited and somatic genomic variation is providing useful information for customizing treatment regimens for breast cancer to maximize efficacy and minimize adverse side effects. In this article, we review (1) hereditary breast cancer and current use of inherited susceptibility genes in patient management; (2) the potential of newly-identified breast cancer-susceptibility variants for improving risk assessment; (3) advantages and disadvantages of direct-to-consumer testing; (4) molecular characterization of sporadic breast cancer through immunohistochemistry and gene expression profiling and opportunities for personalized prognostics; and (5) pharmacogenomic influences on the effectiveness of current breast cancer treatments. Molecular genomics has the potential to revolutionize clinical practice and improve the lives of women with breast cancer.

Oxaliplatin, irinotecan and capecitabine as first-line therapy in metastatic colorectal cancer (mCRC): a dose-finding study and pharmacogenomic analysis

Background:

A dose-finding study was performed to evaluate the dose-limiting toxicity (DLT), maximum-tolerated dose (MTD) and the recommended dose (RD) of escalating the doses of capecitabine and fixed doses of irinotecan and oxaliplatin on a biweekly schedule for metastatic colorectal cancer patients (mCRC). A pharmacogenomic analysis was performed to investigate the association between SNPs and treatment outcome.

Methods:

Eighty-seven chemotherapy-naïve mCRC patients were recruited through a two-step study design; 27 were included in the dose-finding study and 60 in the pharmacogenomic analysis. Oxaliplatin (85 mg m^-2) and CPT-11 (150 mg m^-2), both on day 1, and capecitabine doses ranging from 850 to 1500 mg m^-2 bid on days 1–7 were explored. Peripheral blood samples were used to genotype 13 SNPs in 10 genes related to drug metabolism or efficacy. Univariate and multivariate Cox analysis was performed to examine associations between SNPs, ORR and PFS.

Results:

The capecitabine RD was 1000 mg m⁻² bid. Diarrhoea and neutropenia were the DLTs. After a median follow-up of 52.5 months, the median PFS and OS were 12 (95% CI; 10.6–13.4) and 27 months (95% CI; 17.2–36.8), respectively.

The GSTP1-G genotype, the Köhne low-risk category and use of a consolidation approach strongly correlated with decreased risk of progression. Patients with all favourable variables showed a median PFS of 42 months vs 3.4 months in the group with all adverse factors. A superior clinical response was obtained in patients with one GSTP1-G allele as compared with GSTP1-AA carriers (P=0.004).

Conclusion:

First-line therapy with oxaliplatin, irinotecan and capecitabine is efficient and well-tolerated. The GSTP1 polymorphism A>G status was significantly associated with ORR and PFS in mCRC treated with this triplet therapy.

Easy detection of 5,10-methylenetetrahydrofolate reductase 1298A/C genotype by mutagenically separated PCR assay

BACKGROUND

5,10-Methylenetetrahydrofolate reductase (MTHFR) plays a central role in folate metabolism. Previous studies have suggested an association between the MTHFR 1298A/C polymorphism and several diseases, such as cardiovascular and psychiatric diseases, neural tube defects, diabetes, and cancer. Currently, either PCR-restriction fragment length polymorphism (RFLP) technique or real-time PCR using Taqman assay are used to determine the MTHFR 1298 genotype.

METHODS

We developed a simple and efficient approach that employs mutagenically separated PCR to genotype MTHFR 1298A/C polymorphism. Two forward mutagenic allele-specific primers of different lengths for MTHFR 1298A/C were paired with the same reverse primer in a one-tube assay to genotype 20 genomic DNA samples.

RESULTS

Electrophoresis on 2.5% agarose gel showed two allele-specific fragments, a 113-bp A allele-specific and a 93-bp C allele-specific PCR product. The results were confirmed by the conventional PCR-RFLP method.

CONCLUSIONS

We conclude that mutagenically separated PCR could be used as an alternative simple, reliable, and cost-effective method for the genotyping of MTHFR 1298A/C polymorphism.