MTHFR gene polymorphisms and response to chemotherapy in colorectal cancer: a meta-analysis

Predicting drug response and toxicity in metastatic colorectal cancer: the role of germline markers

INTRODUCTION

Despite the introduction of targeted agents leading to therapeutic advances, clinical management of patients with metastatic colorectal cancer (mCRC) is still challenged by significant interindividual variability in treatment outcomes, both in terms of toxicity and therapy efficacy. The study of germline genetic variants could help to personalize and optimize therapeutic approaches in mCRC.

AREAS COVERED

A systematic review of pharmacogenetic studies in mCRC patients published on PubMed between 2011 and 2021, evaluating the role of germline variants as predictive markers of toxicity and efficacy of drugs currently approved for treatment of mCRC, was perfomed.

EXPERT OPINION

Despite the large amount of pharmacogenetic data published to date, only a few genetic markers (i.e., DPYD and UGT1A1 variants) reached the clinical practice, mainly to prevent the toxic effects of chemotherapy. The large heterogeneity of available studies represents the major limitation in comparing results and identifying potential markers for clinical use, the role of which remains exploratory in most cases. However, the available published findings are an important starting point for future investigations. They highlighted new promising pharmacogenetic markers within the network of inflammatory and immune response signaling. In addition, the emerging role of previously overlooked rare variants has been pointed out.

TYMS 3'-UTR Polymorphism: A Novel Association with FOLFIRINOX-Induced Neurotoxicity in Pancreatic Cancer Patients

Pancreatic ductal adenocarcinoma (PDAC) is a highly fatal malignancy that has the worst 5-year survival rate of all of the common malignant tumors. Surgery, chemotherapy, and/or chemoradiation remain the main tactics for PDAC treatment. The efficacy of chemotherapy is often compromised because of the substantial risk of severe toxicities. In our study, we focused on identification of polymorphisms in the genes involved in drug metabolism, DNA repair and replication that are associated with inter-individual differences in drug-induced toxicities. Using the microarray, we genotyped 12 polymorphisms in the DPYD, XPC, GSTP1, MTHFR, ERCC1, UGT1A1, and TYMS genes in 78 PDAC patients treated with FOLFIRINOX. It was found that the TYMS rs11280056 polymorphism (6 bp-deletion in TYMS 3'-UTR) predicted grade 1-2 neurotoxicity (p = 0.0072 and p = 0.0019, according to co-dominant (CDM) and recessive model (RM), respectively). It is the first report on the association between TYMS rs11280056 and peripheral neuropathy. We also found that PDAC patients carrying the GSTP1 rs1695 GG genotype had a decreased risk for grade 3-4 hematological toxicity as compared to those with the AA or AG genotypes (p = 0.032 and p = 0.014, CDM and RM, respectively). Due to relatively high p-values, we consider that the impact of GSTP1 rs1695 requires further investigation in a larger sample size.

MTHFR polymorphism as a predictive biomarker for gastrointestinal and hematological toxicity in North Indian adenocarcinoma patients

In the present study, we investigated the relationship between the methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms and overall survival, toxicity and treatment response for North Indian adenocarcinoma patients. The polymorphisms of MTHFR gene in north Indian adenocarcinoma patients were assessed by PCR-RFLP. Our data observed that patients with mutant genotype (C/C) for 1298 A>C) polymorphism showed higher trend of median survival time compared to patients bearing the wild type genotype (A/A) (MST= 13.93 vs. 7.97, p=0.12). Further, we observed patients with the heterozygous genotype for A1298C polymorphism had 12-fold risk of diarrhea (AOR =12.54, 95% CI = 1.54-101.86, p=0.018). The patients with heterozygous genotype (CT) of the C677T polymorphism had 5.34-fold increased risk of developing neutropenia (AOR=5.34, 95% CI=1.49-19.06, p=0.009). Our results suggest that MTHFR polymorphisms are associated with hematological toxicity. MTHFR polymorphism might impact the development of pemetrexed and platinum-related toxicities but not as a clinical predictor of efficiency.

Methylenetetrahydrofolate reductase polymorphisms and colorectal cancer prognosis: A meta-analysis

Background

The present study focused on understanding the prognostic value of the methylenetetrahydrofolate reductase (MTHFR) single nucleotide polymorphisms rs1801133 (C667T) and rs1801131 (A1298C) in patients with colorectal cancer (CRC).

Methods

A systematic literature search was conducted in March 2016. Databases, including Medline, EMBASE, Cochrane and Chinese databases (including CNKI, Wanfang and VIP), were searched to identify the relevant articles describing MTHFR polymorphisms in patients with CRC. Data regarding overall survival (OS), progression‐free survival (PFS) and disease‐free survival (DFS) were collected and analysed.

Results

Twenty‐four studies with 5423 patients with CRC were included. Significant differences in OS, PFS and DFS were not observed among the different comparisons of patients carrying different alleles of the MTHFR rs1801133 polymorphism (including TT versus CC, TT versus CT + CC, CT + TT versus CC and CT versus CC). Compared with patients with the rs1801131 CA + AA genotypes, patients with the CC genotype had a shorter OS (hazard ratio = 1.85; 95% confidence interval = 1.30–2.65) and DFS (hazard ratio = 2.16; 95% confidence interval= 1.19–3.93). Significant differences in OS, PFS and DFS were not observed among the other patient groups (including CC versus AA, CC + CA versus AA and CA versus AA). Subgroup analysis of rs1801133 and rs1801131 showed that patients with CRC from Asian regions and Western regions demonstrated similar results.

Conclusions

The MTHFR rs1801133 polymorphism was not associated with the prognosis of patients with CRC; however, rs1801131 may be associated with the prognosis of patients with CRC. Well‐designed prospective studies are necessary to obtain a better understanding of the prognostic value of rs1801133 and rs1801131.

Relevance of methylenetetrahydrofolate reductase gene variants C677T and A1298C with response to fluoropyrimidine-based chemotherapy in colorectal cancer: a systematic review and meta-analysis

Methylenetetrahydrofolate reductase (MTHFR) is a critical enzyme influencing the metabolism of fluoropyrimidines. The relevance of MTHFR polymorphisms with the clinical response to fluoropyrimidine-based chemotherapy has been explored, but the results remain controversial. Thus, a meta-analysis was performed to provide a comprehensive estimate in this account. Relevant studies were identified through PubMed, Embase and Web of Science databases from inception up to May 2017. Odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were applied to assess the strength of association. A total of 2118 colorectal cancer patients from 21 studies were included in the meta-analysis. Overall, there was no significant association between MTHFR C677T (rs1801133) or A1298C (rs1801131) polymorphisms and the clinical response to fluoropyrimidine-based chemotherapy under all of the three genetic models (allele model, dominant model, and recessive model) and stratification analysis, except for the retrospective study subgroup in the dominant model of MTHFR C677T and the “5-Fu + FA” treatment group in the allele contrast of MTHFR A1298C. No or moderate heterogeneity was observed in all genetic models. This meta-analysis suggested that MTHFR polymorphisms could not be considered as reliable factors for predicting the clinical response to fluoropyrimidine-based chemotherapy in colorectal cancer patients.

Relevance of MTHFR polymorphisms with response to fluoropyrimidine-based chemotherapy in oesophagogastric cancer: a meta-analysis

OBJECTIVE

To evaluate the association between methylenetetrahydrofolate reductase (MTHFR) polymorphisms and the response to fluoropyrimidine-based chemotherapy in oesophagogastric cancer.

DESIGN

Meta-analysis.

METHODS

We searched PubMed, Embase and Web of Science databases from inception up to October 2017 for relevant studies. The statistical analysis was performed using STATA V.12.0 software. The pooled ORs and 95% CIs were used to assess the strength of the association under the allele, dominant and recessive models. We also conducted subgroup analysis stratified by cancer type, ethnicity and study design. Additionally, the sensitivity analysis was performed by sequential omission of individual studies, and the publication bias was detected using both Begg's test and Egger's test.

RESULTS

A total of 2020 patients from 12 studies were included in this meta-analysis. The results showed that there was no significant association between MTHFR C677T (rs1801133) and A1298C (rs1801131) polymorphisms and the clinical response to fluoropyrimidine-based chemotherapy under all of the three genetic models (T vs C: OR 0.93, 95% CI 0.76 to 1.15; C vs A: OR 0.88, 95% CI 0.56 to 1.40. CT+TT vs CC: OR 0.94, 95% CI 0.72 to 1.23; AC+CC vs AA: OR 0.80, 95% CI 0.47 to 1.35. TT vs CC+CT: OR 1.02, 95% CI 0.74 to 1.39; CC vs AA+AC: OR 1.15, 95% CI 0.50 to 2.67). When stratified by cancer type, ethnicity or study design, the association was still not significant in all subgroups.

CONCLUSIONS

This meta-analysis suggested that MTHFR polymorphisms could not be considered as reliable factors for predicting the response to fluoropyrimidine-based chemotherapy in oesophagogastric cancer.

SNPs in predicting clinical efficacy and toxicity of chemotherapy: walking through the quicksand

In the "precision medicine" era, chemotherapy still remains the backbone for the treatment of many cancers, but no affordable predictors of response to the chemodrugs are available in clinical practice. Single nucleotide polymorphisms (SNPs) are gene sequence variations occurring in more than 1% of the full population, and account for approximately 80% of inter-individual genomic heterogeneity. A number of studies have investigated the predictive role of SNPs of genes enrolled in both pharmacodynamics and pharmacokinetics of chemotherapeutics, but the clinical implementation of related results has been modest so far. Among the examined germline polymorphic variants, several SNPs of dihydropyrimidine dehydrogenase (DPYD) and uridine diphosphate glucuronosyltransferases (UGT) have shown a robust role as predictors of toxicity following fluoropyrimidine- and/or irinotecan-based treatments respectively, and a few guidelines are mandatory in their detection before therapy initiation. Contrasting results, however, have been reported on the capability of variants of other genes as MTHFR, TYMS, ERCC1, XRCC1, GSTP1, CYP3A4/3A5 and ABCB1, in predicting either therapy efficacy or toxicity in patients undergoing treatment with pyrimidine antimetabolites, platinum derivatives, irinotecan and taxanes. While formal recommendations for routine testing of these SNPs cannot be drawn at this moment, therapeutic decisions may indeed benefit of germline genomic information, when available. Here, we summarize the clinical impact of germline genomic variants on the efficacy and toxicity of major chemodrugs, with the aim to facilitate the therapeutic expectance of clinicians in the odiern quicksand field of complex molecular biology concepts and controversial trial data interpretation.

Pattern recognition for predictive, preventive, and personalized medicine in cancer

Predictive, preventive, and personalized medicine (PPPM) is the hot spot and future direction in the field of cancer. Cancer is a complex, whole-body disease that involved multi-factors, multi-processes, and multi-consequences. A series of molecular alterations at different levels of genes (genome), RNAs (transcriptome), proteins (proteome), peptides (peptidome), metabolites (metabolome), and imaging characteristics (radiome) that resulted from exogenous and endogenous carcinogens are involved in tumorigenesis and mutually associate and function in a network system, thus determines the difficulty in the use of a single molecule as biomarker for personalized prediction, prevention, diagnosis, and treatment for cancer. A key molecule-panel is necessary for accurate PPPM practice. Pattern recognition is an effective methodology to discover key molecule-panel for cancer. The modern omics, computation biology, and systems biology technologies lead to the possibility in recognizing really reliable molecular pattern for PPPM practice in cancer. The present article reviewed the pathophysiological basis, methodology, and perspective usages of pattern recognition for PPPM in cancer so that our previous opinion on multi-parameter strategies for PPPM in cancer is translated into real research and development of PPPM or precision medicine (PM) in cancer.

Long Survival and Severe Toxicity Under 5-Fluorouracil-Based Therapy in a Patient With Colorectal Cancer Who Harbors a Germline Codon-Stop Mutation in TYMS

We report the first clinical description of a patient with cancer with a heterozygous germline codon-stop mutation in the TYMS gene. The mutation g.657795_657826del, c.53_84del (NM_001071.2), p.Gln18Argfs*42 causes loss of function of one of the TYMS alleles, resulting in a truncated protein. This gene codifies for the target enzyme of 5-fluorouracil (5-FU), the basic treatment in colorectal cancer. The patient, diagnosed with metastatic colorectal cancer, had diarrhea and neutropenia grade 4 and mucositis and neurological toxicity grade 3 under 5-FU-based therapy and exceeded by more than 50% the average survival after metastasectomy. On the basis of the patient's characteristics and the key role of TYMS in 5-FU activity, we hypothesize that this mutation may contribute to the drug response and toxicities suffered by the patient.

Homocysteine as a potential biomarker in bipolar disorders: a critical review and suggestions for improved studies

INTRODUCTION

Homocysteine levels have been associated with major depression, but associations with bipolar disorder remain less clear. Some data suggest homocysteine levels have potential as a biomarker of treatment response; however the literature is mixed.

AREAS COVERED

Oxidized forms of homocysteine can be potentially neurotoxic leading to glutamate toxicity, apoptotic transformation and neurodegenerative processes. High homocysteine may be a risk biomarker for bipolar disorders, but the empirical base remains too weak for firm conclusions. This review discusses the current literature for homocysteine levels as a biomarker.

EXPERT OPINION

It is premature to foreclose the utility of homocysteine levels as a biomarker for bipolar disorder due the methodological inadequacies in the existing literature. These methodological design issues include lack of control for the confounding variables of concurrent medication, phase of bipolar disorder, gender, age, nutritional status, thyroid, liver and renal function, smoking or lean body mass. Well-powered association studies with confounder control could help shed more light on the important clinical question of homocysteine's utility as a biomarker in bipolar disorder. Future experiments are needed to examine the outcome of interventions modulating homocysteine for treating bipolar disorder. Only prospective randomized control trials will provide definitive evidence of the utility of homocysteine as a biomarker or therapeutic target.

Germline oncopharmacogenetics, a promising field in cancer therapy

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

Pharmacogenetics research on chemotherapy resistance in colorectal cancer over the last 20 years

During the past two decades the first sequencing of the human genome was performed showing its high degree of inter-individual differentiation, as a result of large international research projects (Human Genome Project, the 1000 Genomes Project International HapMap Project, and Programs for Genomic Applications NHLBI-PGA). This period was also a time of intensive development of molecular biology techniques and enormous knowledge growth in the biology of cancer. For clinical use in the treatment of patients with colorectal cancer (CRC), in addition to fluoropyrimidines, another two new cytostatic drugs were allowed: irinotecan and oxaliplatin. Intensive research into new treatment regimens and a new generation of drugs used in targeted therapy has also been conducted. The last 20 years was a time of numerous in vitro and in vivo studies on the molecular basis of drug resistance. One of the most important factors limiting the effectiveness of chemotherapy is the primary and secondary resistance of cancer cells. Understanding the genetic factors and mechanisms that contribute to the lack of or low sensitivity of tumour tissue to cytostatics is a key element in the currently developing trend of personalized medicine. Scientists hope to increase the percentage of positive treatment response in CRC patients due to practical applications of pharmacogenetics/pharmacogenomics. Over the past 20 years the clinical usability of different predictive markers has been tested among which only a few have been confirmed to have high application potential. This review is a synthetic presentation of drug resistance in the context of CRC patient chemotherapy. The multifactorial nature and volume of the issues involved do not allow the author to present a comprehensive study on this subject in one review.

How folate metabolism affects colorectal cancer development and treatment; a story of heterogeneity and pleiotropy

Folate was identified as an essential micronutrient early in the twentieth century and anti-folate chemotherapy such as 5-fluorouracil (5-FU) has been central to the medical management of solid tumours including colorectal cancer for more than five decades. In the intervening years, evidence has been gathered which shows that folate deficiency leads to many human diseases throughout the life-course. However, we still do not know all of the mechanisms behind functional folate deficiency, or indeed its rescue through supplementation with natural and particularly synthetic folates. There is growing evidence that one adverse effect of folic acid fortification programmes is an increased risk of colorectal cancer within populations. The complexity of folate-dependent, one-carbon metabolism and the heterogeneity that exists between individuals with respect to the enzymes involved in the anabolic pathways, and the catabolism of 5-FU, are explored in this review. The enzyme products of some genes such as MTHFR exert multiple and perhaps unrelated effects on many phenotypes, including cancer development. We describe this pleiotropy and the common genetic variants that affect folate metabolism; and discuss some of the studies that have investigated their potential as predictive biomarkers.

One-carbon metabolism and bipolar disorder

OBJECTIVE

Folate is one of the most widely used nutraceuticals for the treatment of mood disorders. In this article, we review folate metabolism, its relationship with bipolar disorder, and its therapeutic potential.

METHODS

We searched PubMed and the Cochrane Library for relevant articles up to and including the year 2012. Background information, proposed mechanisms of action, and results from clinical trials were reviewed.

RESULTS

Folate is an essential cofactor involved in methylation reactions, which are critical for monoamine synthesis and homocysteine regulation. Folate level is thought to be associated with mood disorders and limited response to antidepressants. Functional deficiency, due to a common genetic variant of the methylenetetrahydrofolate reductase (NAD(P)H) (MTHFR) gene, could also affect the presentation of bipolar disorder. Sodium valproate and lamotrigine, commonly used mood stabilizers for the treatment of bipolar disorder, can potentially interfere with folate and homocysteine metabolism. Previous studies consistently support the efficacy of folate in the treatment of depression; one study showed efficacy in the treatment of mania. Biologically active forms of folate formulations, which do not require biochemical conversion, could be beneficial in the treatment of bipolar disorder.

CONCLUSIONS

Folate augmentation could be effective for the treatment of bipolar disorder. A common genetic variant of the MTHFR gene might impact the treatment effect of folate augmentation. The biologically active form of folate could potentially correct mood stabilizer-associated functional folate deficiency, help normalize monoamine synthesis, and improve outcomes.

MTHFR polymorphisms and capecitabine-induced toxicity in patients with metastatic colorectal cancer

OBJECTIVE

The availability of current chemotherapeutic options for metastatic colorectal cancer (mCRC) has increased survival, but it is also accompanied by considerable morbidity. Fluoropyrimidines are the mainstay of systemic therapy. Germline pharmacogenetic markers involved in 5-fluorouracil pharmacodynamics could provide individualized pretreatment tools for predicting toxicity. Research on methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and fluoropyrimidine treatment outcome has focused on intravenous 5-fluorouracil and has yielded inconclusive results. The literature on pharmacogenetics in capecitabine-based chemotherapy is scarce. Therefore, we analysed the association of MTHFR gene polymorphisms and the occurrence of serious toxicity of first-line capecitabine monotherapy and combination therapy.

METHODS

One hundred and twenty-seven patients treated with first-line monotherapy capecitabine and 141 patients on capecitabine-irinotecan combination therapy were recruited from the CAIRO trial, an open-label phase III randomized trial, comparing sequential versus combination chemotherapy with capecitabine, irinotecan and oxaliplatin in mCRC. All patients were genotyped for MTHFR 1298A>C and 677C>T polymorphisms and analysed in both cohorts separately for the association between the MTHFR genotype and incidence of grade 3-4 overall toxicity and specific adverse events, as well as efficacy parameters.

RESULTS

MTHFR 1298A>C and 677C>T genotypes were not associated with grade 3-4 overall toxicity, febrile neutropenia or hand-foot syndrome. MTHFR 1298CC homozygotes showed a borderline significantly higher incidence of grade 3-4 diarrhoea compared with MTHFR 1298AC or AA individuals (25 vs. 5%, P=0.041) in the monotherapy cohort. No significant association was found between the MTHFR genotypes and efficacy parameters in either treatment cohort.

CONCLUSION

MTHFR polymorphisms are not associated with toxicity or efficacy in mCRC patients treated with capecitabine-based chemotherapy.

Impact of the MTHFR C677T polymorphism on colorectal cancer in a population with low genetic variability

PURPOSES

Methylenetetrahydrofolate reductase (MTHFR) plays a key role in folate metabolism, and folate is implicated in carcinogenesis by its role in DNA methylation, repair, and synthesis. We analyzed the impact of MTHFR C677T polymorphism in colorectal cancer in a region of the Tenerife Island whose population has a history of genetic isolation and a low genetic variability. This allows analyzing the effects of the polymorphism that are not due to interactions with different genetic variants.

METHODS

Genomic DNA of 50 Spanish sporadic colorectal cancer (CRC) patients and 103 controls was analyzed by PCR/RFLP and sequencing.

RESULTS

The T allele is more frequent in controls than in patients (P < 0.01). The variant (T) carriers displayed significant odds ratio values for the CT heterozygotes (P = 0.026) and even when grouping heterozygote (CT) and homozygotes (TT) (P = 0.015). Patients carriers of the variant T (CT y TT) show a higher survival rate after chemotherapy than the CC homozygotes (log rank; P = 0.001).

CONCLUSIONS

The MTHRF C677T variant has a protective effect on CRC development in a population with low allelic variability and an optimal intake of folic acid. Moreover, patients carrying the variant (T) show a better prognosis after 5-fluorouracil/folinic acid-based chemotherapy.

Polymorphisms in thymidylate synthase and reduced folate carrier (SLC19A1) genes predict survival outcome in advanced non-small cell lung cancer patients treated with pemetrexed-based chemotherapy

The aim of this study was to evaluate the association between thymidylate synthase (TS), methylenetetrahydrofolate reductase (MTHFR) and reduced folate carrier (SLC19A1) gene polymorphisms and the treatment efficacy of pemetrexed-based chemotherapy in advanced non-small cell lung cancer (NSCLC). Advanced NSCLC patients received pemetrexed and cisplatin every three weeks. Polymorphisms in the TS, MTHFR and SLC19A1 genes were detected in peripheral blood samples using DNA sequencing and Taqman PCR. An analysis of gene polymorphisms was performed with respect to the progression-free survival (PFS), response rate (RR) and overall survival (OS) of patients treated with pemetrexed. The median PFS times for patients with the TS 2R/2R, 2R/3C or 3C/3C genotypes were significantly longer than those of patients with the 2R/3G, 3C/3G or 3G/3G genotypes (P=0.036). Patients with the SLC19A1 CC genotype had a significantly longer median OS compared with individuals with the homozygous and heterozygous genotypes (12.2 vs. 8.9 and 7.3 months, respectively; P=0.022). The PFS and OS did not differ for the three genotypes of MTHFR assessed. The RR was higher in patients with the TS 2R/2R, 2R/3C or 3C/3C genotypes than in the other groups (P=0.044). The polymorphisms of the 5'-UTR of the TS gene and exon 6 (2522) C/T of the SLC19A1 gene predict the survival of advanced NSCLC patients treated with pemetrexed. However, a large scale clinical trial is required to validate these findings.

Data-driven assessment of the association of polymorphisms in 5-Fluorouracil metabolism genes with outcome in adjuvant treatment of colorectal cancer

A major challenge in the assessment of medicines, treatment options, etc., is to establish a framework for the comparison of risks and benefits of many different types and magnitudes, a framework that at the same time allows a clear distinction between the roles played by the statistical analyses of data and by judgements based on personal experience and expertise. The purpose of this study was to demonstrate how clinical data can be weighted, scored and presented by the use of an eight-step data-driven benefit-risk assessment method, where two genetic profiles are compared. Our aim was to present a comprehensive approach that is simple to apply, allows direct comparison of different types of risks and benefits, quantifies the clinical relevance of data and is tailored for the comparison of different options. We analysed a cohort of 302 patients with colorectal cancer treated with 5-Fluorouracil (5-FU). Endpoints were cure rate, survival rate, time-to-death (TTD), time-to-relapse (TTR) and main adverse drug reactions. Multifactor dimensionality reduction (MDR) was used to identify genetic interaction profiles associated with outcome. We have been able to demonstrate that a specific MDR-derived combination (the MDR-1 group) of dihydropyrimidine dehydrogenase and thymidylate synthase polymorphisms is associated with increased and clinically significant difference for cure and survival rates, TTD and probably also for TTR, which are seen as the most important endpoints. An inferior profile was observed for severe myocardial ischaemia. A probably inferior profile was seen for severe arthralgia/myalgia and severe infections. A clear superior profile was seen for severe mucositis/stomatitis. The proposed approach offers comprehensive, data-driven assessment that can facilitate decision processes, for example, in a clinical setting. It employs descriptive statistical methods to highlight the clinically relevant differences between options.

Functional polymorphisms of folate metabolism and response to chemotherapy for colorectal cancer, a systematic review and meta-analysis

OBJECTIVES

Many primary studies have considered the association of polymorphisms of folate metabolism and response to 5-fluorouracil (5-FU) and capecitabine in patients with colorectal cancer. The conclusions from these studies have been conflicting and few have considered large cohorts of patients. Therefore, we have completed a systematic review and meta-analyses to summarize some of the findings to date. We conducted searches for any studies that had addressed the prognostic value of genotype analysis of thymidylate synthetase (TYMS), Methylenetetrahydrofolate reductase (MTHFR) and dihydrofolate reductase (DHFR).

METHODS

We collected data on the study designs, and completed meta-analyses to pool congruent data about treatment effect. A narrative summary is presented for 39 studies that describe three TYMS genotypes and two MTHFR genotypes associated with response to 5-FU-based chemotherapy.

RESULTS

Data were synthesized from up to 2402 patients for the most commonly studied markers TYMS 5' UTR repeat polymorphism (rs45445694) and MTHFR 677 C>T (rs1801133). We found that the TYMS genotype associated with the lowest protein expression (2R/2R) was significantly associated with improved clinical benefit; the pooled risk ratio was relative risk=1.36 [1.11, 1.65]; P=0.003. Moreover, the same trend was observed for adverse effects; the pooled risk ratio was 2.04 [1.42, 2.95]; P=0.0001.

CONCLUSION

There is a small but statistically significant association between treatment effect (both intended effects and adverse events) and a TYMS genotype associated with low protein expression; however, the effect size is small and therefore indicates limited clinical utility.

The association of polymorphisms in 5-fluorouracil metabolism genes with outcome in adjuvant treatment of colorectal cancer

AIM

The purpose of this study was to investigate whether specific combinations of polymorphisms in 5-fluorouracil (5-FU) metabolism-related genes were associated with outcome in 5-FU-based adjuvant treatment of colorectal cancer.

METHODS

We analyzed two cohorts of 302 and 290 patients, respectively, one cohort for exploratory analyses and another cohort for validating the exploratory analyses. A total of ten polymorphisms in genes involved in 5-FU pharmacodynamics and pharmacokinetics were studied. End points were disease-free survival (DFS) and overall survival. Multifactor dimensionality reduction was used to identify genetic interaction profiles associated with outcome.

RESULTS

Low-expression alleles in thymidylate synthase (TYMS) were associated with decreased DFS and overall survival (DFS:hazard ratio [HR] exploration 2.65 [1.40-4.65]; p = 0.004, HR validation 1.69 [1.03-2.66]; p = 0.03). A specific multifactor dimensionality reduction derived combination of dihydropyrimidine dehydrogenase and TYMS polymorphisms was associated with increased DFS (HR exploration 0.69 [0.49-0.98]; p = 0.04, HR validation 0.66 [0.45-0.95]; p = 0.03). Specific combinations of functional polymorphisms in DPYD and TYMS were demonstrated to be associated with DFS and overall survival in patients receiving adjuvant 5-FU-based treatment. Specifically high TYMS expression alleles seem to be associated with decreased DFS.

Lack of association between MDR1 C3435T polymorphism and chemotherapy response in advanced breast cancer patients: evidence from current studies

The transmembrane transport of anticancer drugs is mainly regulated by P-glycoprotein encoded by the human multidrug resistance gene 1 gene (MDR1). Since there were controversies regarding the association between MDR1 C3435T polymorphism and response to chemotherapy among patients with advanced breast cancer, a meta-analysis of the link was conducted. A total of 7 studies consist of 464 advanced breast cancer patients relating MDR1 C3435T polymorphism to the response of chemotherapy were included in this meta-analysis. The main analysis revealed a lack of association between the MDR1 C3435T and response to chemotherapy, with odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) of 1.37 (95% CI: 0.78-2.40), 1.17 (95% CI: 0.69-2.01), 1.18 (95% CI: 0.76-1.84) and 1.61 (95% CI: 0.70-3.68) for homozygous comparison, heterozygous comparison, dominant model and recessive model, respectively. The subgroup analysis by ethnicity did not change the pattern of results, with ORs of 0.99 (95% CI: 0.11-9.07), 0.68 (95% CI: 0.29-1.60), 0.81 (95% CI: 0.36-1.85) and 1.51 (95% CI: 0.77-2.96), in homozygous comparison, heterozygous comparison, dominant model and recessive model, respectively in Caucasian, and 1.50 (95% CI: 0.75-3.03), 1.72 (95% CI: 0.85-3.47), 1.59 (95% CI: 0.90-2.80) and 2.29 (95% CI: 0.51-10.35), respectively in Asian. The available evidence indicates that MDR1 C3435T polymorphism cannot be considered as a reliable predictor of response to chemotherapy in patients with advanced breast cancer.

Biomarker-based selection of therapy for colorectal cancer

Colorectal cancer (CRC) has been re-classified based on molecular analyses of various genes and proteins capable of separating morphologic types of tumors into molecular categories. The diagnosis and management of CRC has evolved with the discovery and validation of a wide variety of biomarkers designed to facilitate a personalized approach for the treatment of the disease. In addition, a number of new prognostic and predictive individual genes and proteins have been discovered that are designed to reflect the sensitivity and/or resistance of CRC to existing therapies. Multigene predictors have also been developed to predict the risk of relapse for intermediate-stage CRC after completion of surgical resection. Finally, a number of biomarkers have been proposed as specific predictors of chemotherapy and radiotherapy response and, in some instances, drug toxicity. In this article, a series of novel biomarkers are considered and compared with standard-of-care markers for their potential use as pharmacogenomic and pharmacogenetic predictors of disease outcome.

Part 4: pharmacogenetic variability in anticancer pharmacodynamic drug effects

Response to treatment with anticancer drugs is subject to wide interindividual variability. This variability is expressed not only as differences in severity and type of toxicity, but also as differences in effectiveness. Variability in the constitution of genes involved in the pharmacokinetic and pharmacodynamic pathways of anticancer drugs has been shown to possibly translate into differences in treatment outcome. The overall knowledge in the field of pharmacogenetics has tremendously increased over the last couple of years, and has thereby provided opportunities for patient-tailored anticancer therapy. In previous parts of this series, we described pharmacogenetic variability in anticancer phase I and phase II drug metabolism and drug transport. This fourth part of a four-part series of reviews is focused on pharmacodynamic variability and encompasses genetic variation in drug target genes such as those encoding thymidylate synthase, methylene tetrahydrofolate reductase, and ribonucleotide reductase. Furthermore, genetic variability in other pharmacodynamic candidate genes involved in response to anticancer drugs is discussed, including genes involved in DNA repair such as those encoding excision repair crosscomplementing group 1 and group 2, x-ray crosscomplementing group 1 and group 3, and breast cancer genes 1 and 2. Finally, somatic mutations in KRAS and the gene encoding epidermal growth factor receptor (EGFR) and implications for EGFR-targeted drugs are discussed. Potential implications and opportunities for patient and drug selection for genotype-driven anticancer therapy are outlined.

5-Fluorouracil pharmacogenomics: still rocking after all these years?

The 5-fluorouracil (5-FU) metabolic pathway is mainly dependent on the activity of several intracellular enzymes. Among them, four in particular; thymidylate synthase, methylenetetrahydrofolate reductase, dihydropyrimidine dehydrogenase and thymidine phosphorylase are considered the key points in determining sensitivity or resistance to this drug. These enzymes are needed to metabolize the drug in its active form (thymidylate phosphorylase) or to drop the concentration of the active drug in the cell (dihydropyrimidine dehydrogenase) or both (thymidylate synthase and methylenetetrahydrofolate reductase). Several different studies have tried to investigate the relationship between the presence of mutations in these enzymes and a reduced/improved activity of treatment based on 5-FU or its derivatives. In this article, we will focus on the often contradictory results of these studies.

Genetic-based biomarkers and next-generation sequencing: the future of personalized care in colorectal cancer

The past 5 years have witnessed extraordinary advances in the field of DNA sequencing technology. What once took years to accomplish with Sanger sequencing can now be accomplished in a matter of days with next-generation sequencing (NGS) technology. This has allowed researchers to sequence individual genomes and match combinations of mutations with specific diseases. As cancer is inherently a disease of the genome, it is not surprising to see NGS technology already being applied to cancer research with promises of greater understanding of carcinogenesis. While the task of deciphering the cancer genomic code remains ongoing, we are already beginning to see the application of genetic-based testing in the area of colorectal cancer. In this article we will provide an overview of current colorectal cancer genetic-based biomarkers, namely mutations and other genetic alterations in cancer genome DNA, discuss recent advances in NGS technology and speculate on future directions for the application of NGS technology to colorectal cancer diagnosis and treatment.

Biomarker-based prediction of response to therapy for colorectal cancer: current perspective

The diagnosis and management of colorectal cancer (CRC) has been impacted by the discovery and validation of a wide variety of biomarkers designed to facilitate a personalized approach for the treatment of the disease. Recently, CRC has been reclassified based on molecular analyses of various genes and proteins capable of separating morphologic types of tumors into molecular categories. At the same time, a number of new prognostic and predictive single genes and proteins have been discovered that are designed to reflect sensitivity and/or resistance to existing therapies. Multigene predictors have also been developed to predict the risk of relapse for intermediate-stage CRC after completion of surgical extirpation. More recently, a number of biomarkers tested by a variety of methods have been proposed as specific predictors of chemotherapy and radiotherapy response. Other markers have been successfully used to predict toxic effects of standard therapies. In this review, a series of novel biomarkers are considered and compared with standard-of-care markers for their potential use as pharmacogenomic and pharmacogenetic predictors of disease outcome.

MTHFR, MTR, and MTRR polymorphisms in relation to p16INK4A hypermethylation in mucosa of patients with colorectal cancer

We recently analyzed the hypermethylation status of the p16INK4a (p16) gene promoter in normal-appearing mucosa obtained from patients with colorectal cancer. Hypermethylation of p16 was associated with reduced survival of these patients. In the present study, germ line polymorphisms in the folate- and methyl-associated genes, methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR) and methionine synthase reductase (MTRR), were analyzed in the same patient cohort to find a possible link between these genetic variants and p16 hypermethylation. Genomic DNA was extracted from blood of patients (n = 181) and controls (n = 300). Genotype analyses were run on an ABI PRISM(®) 7900HT sequence-detection system (Applied Biosystems), using real-time polymerase chain reaction and TaqMan chemistry. The results showed that the genotype distributions of the patient and control groups were similar. No significant differences in cancer-specific or disease-free survival of stage I-III patients according to polymorphic variants were detected, nor were any differences in cancer-specific or disease-free survival detected when patients were subgrouped according to the MTHFR or MTR genotype groups and dichotomized by p16 hypermethylation status in mucosa. However, patients with the MTRR 66 AA/AG genotypes were found to have a significantly worse cancer-specific survival when the mucosa were positive, compared with negative, for p16 hypermethylation (hazard ratio 2.7; 95% confidence interval 1.2-6.4; P = 0.023). In contrast, there was no difference in survival among patients with the MTRR 66 GG genotype stratified by p16 hypermethylation status. These results indicate a relationship between genetic germ-line variants of the MTRR gene and p16 hypermethylation in mucosa, which may affect the clinical outcome of patients with colorectal cancer.

MTHFR, MTR, and MTRR polymorphisms in relation to p16INK4A hypermethylation in mucosa of patients with colorectal cancer

We recently analyzed the hypermethylation status of the p16INK4a (p16) gene promoter in normal-appearing mucosa obtained from patients with colorectal cancer. Hypermethylation of p16 was associated with reduced survival of these patients. In the present study, germ line polymorphisms in the folate- and methyl-associated genes, methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR) and methionine synthase reductase (MTRR), were analyzed in the same patient cohort to find a possible link between these genetic variants and p16 hypermethylation. Genomic DNA was extracted from blood of patients (n = 181) and controls (n = 300). Genotype analyses were run on an ABI PRISM(®) 7900HT sequence-detection system (Applied Biosystems), using real-time polymerase chain reaction and TaqMan chemistry. The results showed that the genotype distributions of the patient and control groups were similar. No significant differences in cancer-specific or disease-free survival of stage I-III patients according to polymorphic variants were detected, nor were any differences in cancer-specific or disease-free survival detected when patients were subgrouped according to the MTHFR or MTR genotype groups and dichotomized by p16 hypermethylation status in mucosa. However, patients with the MTRR 66 AA/AG genotypes were found to have a significantly worse cancer-specific survival when the mucosa were positive, compared with negative, for p16 hypermethylation (hazard ratio 2.7; 95% confidence interval 1.2-6.4; P = 0.023). In contrast, there was no difference in survival among patients with the MTRR 66 GG genotype stratified by p16 hypermethylation status. These results indicate a relationship between genetic germ-line variants of the MTRR gene and p16 hypermethylation in mucosa, which may affect the clinical outcome of patients with colorectal cancer.

Predictive diagnostics in colorectal cancer: impact of genetic polymorphisms on individual outcomes and treatment with fluoropyrimidine-based chemotherapy

The 5-fluorouracil (5-FU)-based chemotherapy is a standard treatment for patients with colorectal cancer. However, a relevant number of patients suffer from severe toxic side effects, such as haemotoxicity, while lacking clinical response to adjuvant therapy. The inter-individual variations of drug toxicity and efficacy of the pyrimidine antagonist observed in clinical practice are mainly determined by genetic polymorphisms. The screening of genotypes, such as thymidylate synthase, dihydropyrimidine dehydrogenase, methylene tetrahydrofolate reductase, orotate phosphoribosyltransferase or glutathione S-transferase, could help identifying those patients with colorectal carcinoma who can actually benefit from a 5-FU-based therapy. The current chapter elucidates the roles of the polymorphisms in the enzymes involved in the 5-FU metabolic pathway as prognostic and predictive markers. It reports on the relationship between various genotypes in patients with colorectal carcinoma and their responsiveness to a 5-FU-based chemotherapy, and concludes with an outlook on possible future directions in treatment of colorectal cancer.

Recent Publications on Medications and Pharmacy

Hospital Pharmacy presents this feature to keep pharmacists abreast of new publications in the medical/pharmacy literature. Articles of interest regarding a broad scope of topics are abstracted monthly.