Methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and FOLFOX response in colorectal cancer patients

AIMS

To test prospectively the predictive value of germinal gene polymorphisms related to fluorouracil (FU) and oxaliplatin (Oxa) pharmacodynamics on toxicity and responsiveness of colorectal cancer (CRC) patients receiving FOLFOX therapy.

METHODS

Advanced CRC patients (n= 117) receiving FOLFOX 7 therapy were enrolled. Gene polymorphisms relevant for FU [thymidylate synthase (TYMS, 28 bp repeats including the G→C mutation + 6 bp deletion in 3''UTR), methylenetetrahydrofolate reductase (MTHFR, 677C→T, 1298A→C), dihydropyrimidine deshydrogenase (IVS14+1G→A) and Oxa: glutathione S-transferase (GST) π (105Ile→Val, 114Ala→Val), excision repair cross-complementing group 1 (ERCC1) (118AAT→AAC), ERCC2 (XPD, 751Lys→Gln) and XRCC1 (399Arg→Gln)] were determined (blood mononuclear cells).

RESULTS

None of the genotypes was predictive of toxicity. Response rate (54.7% complete response + partial response) was related to FU pharmacogenetics, with both 677C→T (P= 0.042) and 1298A→C (P= 0.004) MTHFR genotypes linked to clinical response. Importantly, the score of favourable MTHFR alleles (677T and 1298C) was positively linked to response, with response rates of 37.1, 53.3, 62.5 and 80.0% in patients bearing no, one, two or three favourable alleles, respectively (P= 0.040). Polymorphisms of genes related to Oxa pharmacodynamics showed an influence on progression-free survival, with a better outcome in patients bearing GSTπ 105 Val/Val genotype or XPD 751Lys-containing genotype (P= 0.054).

CONCLUSIONS

These results show that response to FOLFOX therapy in CRC patients may be driven by MTHFR germinal polymorphisms.     

Methylenetetrahydrofolate reductase gene polymorphisms and response to fluorouracil-based treatment in advanced colorectal cancer patients

Methylenetetrahydrofolate reductase (MTHFR) controls intracellular CH2FH4 concentrations (required for optimal fluoropyrimidine efficacy) by irreversibly converting CH2FH4 into 5-methyltetrahydrofolate. MTHFR 677C>T and 1298A>C polymorphisms are linked to altered enzyme activity. Thus, mutated MTHFR tumours should, in theory, be more sensitive to 5-fluorouracil (5FU) than wild-type tumours. MTHFR polymorphisms in position 677 and 1298 were analysed in 98 colorectal cancer patients with unresectable liver metastases (57 men, 41 women, mean age 64 years) receiving 5FU-folinic acid. 677C>T and 1298A>C genotypes were determined simultaneously by melting curve analyses on liver metastases. 677C>T genotype distribution was 46.9% wt/wt, 34.7% wt/mut and 18.4% mut/mut; that of 1298A>C was 52.0% wt/wt, 35.7% wt/mut and 12.3% mut/mut. The response rate was not related to 1298A>C genotype but was significantly linked to 677C>T genotype (response rate: 40%, 21% and 56% in wt/wt, wt/mut and mut/mut, respectively; P = 0.040), with an increased response rate in mut/mut tumours relative to wt/wt (odds ratio = 1.88). Thymidylate synthase activity measured in metastases was a significant predictor of 5FU responsiveness and the addition of the 677C>T genotype improved model prediction. MTHFR 1298A>C polymorphism was significantly linked to specific survival, with homozygous mutated patients having the worst prognosis (P = 0.009, relative risk = 2.48 in mut/mut versus wt/wt). MTHFR 1298A>C genotype remained a significant predictor in a multivariate analysis including metastasis characteristics. The results suggest that MTHFR genotypes are relevant and independent factors of patient outcome in 5FU-based treatment of advanced colorectal cancer.     

Methylenetetrahydrofolate reductase (MTHFR): a novel target for cancer therapy

Tumor cells have an enhanced requirement for glucose, amino acids and DNA precursors. Since folates are required for the synthesis of thymidine and purines, the metabolism of folate has been exploited as an anti-cancer target for over 6 decades, with emphasis on the inhibition of DNA synthesis. However, folate is also used to generate methionine, which is essential for proliferation by virtue of its role in protein synthesis, polyamine synthesis and transmethylation reactions. Tumor-derived cell lines and human tumor xenografts have been shown to be methionine dependent i.e., they are unable to survive without methionine and are unable to efficiently utilize homocysteine, the immediate metabolic precursor of methionine. Since non-transformed cells are methionine-independent, the targeting of methionine metabolism presents an opportunity to selectively disrupt the unique metabolic networks in cancer cells. This chapter provides an overview of the critical role of folate and methionine metabolism in tumor cells and summarizes the current anti-folate and anti-methionine strategies to inhibit growth of transformed lines and tumors. We also present our work on the development of a novel anti-cancer target, methylenetetrahydrofolate reductase (MTHFR), a key enzyme of both folate and methionine metabolism. Our data demonstrate that antisense-mediated inhibition of MTHFR is associated with increased cytotoxicity in vitro and with decreased growth of tumors in vivo. These findings warrant further investigation of this enzyme and the methionine biosynthetic pathway in exploring new strategies for cancer chemotherapy.     

甲基四氢叶酸还原酶基因多态性与阿尔茨海默病相关性探讨

目的探讨阿尔茨海默病(Alzheimerdisease,AD)患者中甲基四氢叶酸还原酶基因的多态性及其与AD的相关性。方法利用聚合酶链式反应-限制性片段长度多态性(PCR-RFLP)技术对48例AD患者及86例对照者的甲基四氢叶酸还原酶基因基因进行分型,从而进行AD与甲基四氢叶酸还原酶基因多态性的相关分析。结果(1)AD病人甲基四氢叶酸还原酶基因中,基因型C/T占56.06%,明显高于对照组的34.97%(P<0.01,RR=0.355),C/C占39.39%,明显低于对照组的62.94%(P<0.01,RR=2.567),T/T占4.25%,与对照组2.09%有显著性差异(P>0.05,RR=1.086)。AD病人中甲基四氢叶酸还原酶基因等位基因C的频率为67.43%、相对危险率(RR)为0.594,T的频率为32.57%、RR为1.683与对照组的C为80.42%、T为19.58无显著性差异(P>0.05)。结论AD病人中甲基四氢叶酸还原酶基因基因型T/T(MTHFR*T/T)频率明显高于正常人,与AD存在正关联;而MTHER*C/T频率则明显低于正常人,与AD存在负关联。     

Alternative spliced variants as biomarkers of colorectal cancer

Surgical resection and adjuvant therapy, which mainly involves 5-fluorouracil (5-FU), irinotecan (CPT-11), oxaliplatin (LOHP) chemotherapy and recently targeted therapy, are the most common treatments of colorectal cancer (CRC). As to improve the therapeutic efficacy and assist with therapeutic decisions, there is an urgent need for prognostic and predictive molecular biomarkers. Recent evidence demonstrates that aberrations in alternative splicing process of cancer will provide candidate biomarkers for cancers to meet this need. In this review, we outline the fundamental mechanism of alternative splicing that plays a major role in protein diversity, and summarize the relationship between imbalance alternative splicing with cancer. Moreover, several alternative spliced variants and cancer-specific splicing events at the mRNA level in CRC, which may serve as diagnostic, predictive, prognostic markers of CRC, are also discussed. These specific splice variants or the RNA splicing machinery will be new, potential targets for the treatment of CRC that offers a specific site of anti-cancer chemotherapy.     

亚甲基四氢叶酸还原酶基因多态性及同型半胱氨酸水平与冠心病的关系

目的观察高同型半胱氨酸(HCY)是否是冠心病的一个独立危险因素,并探讨亚甲基四氢叶酸还原酶(MTHFR)基因多态性与冠心病(CHD)的联系。方法选择CHD患者80例,对照组70例。应用荧光偏振免疫分析法测定血浆HCY,以聚合酶链反应-限制性内切酶片段长度多态性(PCR-RELP)分析MTHFR基因多态性。结果CHD患者血浆HCY浓度显著高于对照组[分别为(17±11)μmol/L与(12±7)μmol/L,P<0.01]。MTHFR有3种基因型,即纯合子突变(TT)、杂合子突变(TC)及野生纯合型(CC)。CHD组TT型、TC型、CC型基因频率分布及T、C等位基因频率与对照组比较差异无统计学意义(χ2=3.213,P>0.05;χ2=1.836,P>0.05)。CHD组和对照组的TT型的血浆HCY水平明显高于TC型和CC型(P<0.01)。Logistic回归分析显示高HCY血症是CHD发病的独立危险因素,其OR值为3.108,95%可信区间1.426～6.775。结论高HCY血症是CHD发病的独立危险因素。MTHFR基因的C677T突变是高同型半胱氨酸血症的原因,但MTHFRC677T基因多态性与冠心病的发生无显著相关。     

New treatments with curative intent for metastatic colorectal liver cancer

Although surgical resection is the mainstay of therapy in metastatic colorectal liver cancer, < 10 - 15% of patients are suitable for resection. In addition, recurrence rates after resection may reach 75% in the first 2 years, of which 50% involve local recurrences in the liver. This has provided an impetus for the development of neoadjuvant and adjuvant protocols in the treatment of this malignancy, techniques concentrating on improving the residual liver functional reserve, as well as local tumour ablative therapies using radiofrequency and cryotherapy. A multimodal interdisciplinary approach is a pre-requisite when treating secondary liver tumours from colorectal cancer and should be concentrated in centres of reference. The development of such innovative modalities as preoperative downstaging in the absence of extrahepatic tumour disease, local tumour control and new adjuvant therapies has expanded the patient population thus providing the opportunity to treat patients with large or advanced stage colorectal liver tumours. The following is a review of some of the approaches currently being evaluated in the treatment of colorectal liver metastases.     

Patient-tailored treatments with anti-EGFR monoclonal antibodies in advanced colorectal cancer: KRAS and beyond

Personalized medicine emphasizes the practice of considering individual patient characteristics as opposed to that centered on standards derived from epidemiological studies which, by definition, do not take into account the variability of individuals within a given population. When applied to oncology, personalized medicine is an even more complex concept because it extends the variability beyond the individual patient to the individual tumor. Indeed, the great genotypic and phenotypic variability (both in primary and metastatic sites of cancer) the development of targeted therapies, and the growing availability of biological assays complicate the scenario of personalized medicine in the oncological field. In this paper we review the results of anti-epidermal growth factor receptor (EGFR) monoclonal antibody (mAb) therapy in metastatic colorectal cancer (mCRC) in the context of tumor biology, delineating the future prospects of patient-tailored medicine in this area. In particular, we deal with EGFR inhibition by Cetuximab, a chimeric mouse human IgG1 mAb, and panitumumab, a fully human IgG2 mAb. We discuss the clinical impact of anti-EGFR mAbs on wild-type (WT) KRAS mCRC, also taking into account the feasibility of novel multi-marker approaches to treatment decision-making, aimed at increasing the predictive power of pre-therapy biomarkers. Experimental topics and fields of ongoing research, such as targeting microRNAs (miRNAs) with novel anticancer drugs and epigenetics in CRC are also addressed.     

Thioredoxin reductase and cancer cell growth inhibition by organogold(III) compounds

Thioredoxin (Trx) expression is increased in several human primary cancers associated with aggressive tumor growth and decreased patient survival, and the Trx/Trx reductase (TrxR) system therefore provides an attractive target for cancer drug development. Various gold(III) compounds with none, one, two or three carbon-gold bonds were evaluated for their capacity to inhibit TrxR and the growth of MCF-7 cancer cells in vitro. Compounds with up to two carbon-gold bonds were often potent inhibitors of TrxR with IC50 values as low as 2 nmol/l. In the presence of Trx and insulin the inhibiting capacity was much lower. However, the inhibitory concentrations of the compounds did not correlate with the ability to kill cells. Out of the organometallics tested, only compound 8 with two carbon-gold bonds was able to inhibit colony formation by MCF-7 breast cancer cells at low micromolar concentrations (IC50=1.6 micromol/l). Unfortunately, the compound did not show any anti-tumor activity against MCF-7 breast cancer and HT-29 colon cancer xenografts in scid mice.     

Methylenetetrahydrofolate reductase and reduced folate carrier-1 genotypes and methotrexate serum concentrations in patients with rheumatoid arthritis

We investigated the genotypes of methylenetetrahydrofolate reductase (MTHFR) and reduced folate carrier-1 (RFC-1), and the serum concentrations of methotrexate (MTX) in 100 outpatients with rheumatoid arthritis (RA). Frequencies of MTHFR C677T and A1298C were similar to those reported in Japanese RA patients, while frequencies of RFC-1 G80A genotypes differed from those reported in RA patients in the United States. No correlations were found between these genotypes and serum MTX levels.     

结直肠癌患者肿瘤组织与外周血中MTHFR C677T的多态性及相关性研究

目的 探索外周血代替肿瘤组织进行MTHFR C677T基因多态性检测的可行性.方法 选取首诊为结直肠癌且行根治性手术的患者26例,术前未接受任何化学治疗,应用聚合酶链反应-限制性内切片段长度多态性（PCR-RFLP）方法检测MTHFR C677T的基因多态性,比较外周血及肿瘤组织中相关基因型的一致性.结果 26例结直肠癌患者的肿瘤组织及外周血中MTHFR 677CT基因型、TT基因型、CC基因型一致的病例数分别为7、7、4例.肿瘤组织和外周血中MTHFR C677T的基因型一致率为69.2%.结论 外周血中MTHFR C677T的基因多态性可以反映肿瘤组织中相关基因型的突变.     

北京社区结直肠癌筛查的初步结果分析

目的探索城市居民中老年人群结直肠癌的发病情况,并通过积极干预降低社区结直肠癌的发病率。方法北京丰台区东高地居民区16个单位50～80岁共10740人接受大肠癌筛查,9843人(91.65%)接受连续3次的便隐血(免疫法)检查,阳性患者2709人(占受检者的27.52%),其中260人(占便隐血阳性者的9.60%)接受了电子肠镜检查。结果260例接受电子肠镜检查的患者中,检出大肠癌12例,男性8例,女姓4例,年龄66～77岁。其中息肉癌变2例,直肠类癌2例(均为早期),DukeⅡ期大肠癌4例,DukⅢA期大肠癌1例。检出结肠腺瘤127例。结直肠癌的检出率为121.9/105。结论城市居民中老年人群结直肠癌的发病率呈直线上升。通过便隐血检查后,阳性患者接受肠镜检查可以发现早期结直肠癌。建议此项工作应在城市居民中广泛开展以改善结直肠癌的预后。     

Critical aspects in rationale design of fluorouracil-based adjuvant therapies for the management of colon cancer

The strategic goal behind adjuvant therapy is to open novel avenues for colon cancer treatment by specifically inactivating pathways needed for the growth of tumor cells. 5-Fluorouracil (5-FU) therapy is a prominent conventional treatment for colon cancer that has been used for five decades. Among the rich diversity of chemotherapeutics, 5-FU has been extensively manipulated as an anticancer drug. The pharmacology of 5-FU has spawned myriad alternatives to achieve low-toxicity treatment for better colon cancer management. The existing highly toxic chemotherapeutic regimens, lack of new congeners with significant efficacy, and drug resistance to cancer cells have prompted scientists to manipulate conventional treatments. These factors make it imperative to rationalize the current 5-FU therapy in combination with synthetic or natural compounds by optimizing the dose with respect to pharmacokinetic and preclinical data. To attempt to tailor effective conventional 5-FU regimens, novel therapeutic perspectives associated with the 5-FU-based colon cancer chemotherapy currently available in clinical settings have been summarized. This review presents comprehensive summary of a dedicated literature search of databases (i.e., PUBMED, CAPLUS, and MEDLINE) for adjuvant approaches such as NSAIDs (COX-II inhibitors), natural compounds, viral vectors, novel agents/molecules, and various targeted therapies, in combination with 5-FU in developing treatment alternatives for colon cancer.     

Review article: The Lynch syndrome (hereditary nonpolyposis colorectal cancer)

Background The most common inherited colorectal cancer syndrome is the Lynch syndrome (HNPCC) which is characterized by the development of colorectal, endometrial, and other cancers and the presence of microsatellite instability (MSI) in tumours. The syndrome is due to a mutation in one of the mismatch repair (MMR) genes: MSH2, MLH1, MSH6 and PMS2. Aims To evaluate the clinical features of the Lynch syndrome and to assess the tools that are available for the identification of families with this syndrome. Methods A systematic literature search using PubMed and reference lists of retrieved articles was performed. Results The review provides an update of the clinical phenotype of the Lynch syndrome. Until recently, the Amsterdam criteria were the most important tool for the identification of Lynch syndrome. Nowadays, the Bethesda guidelines are more widely used. These guidelines describe all clinical conditions in which a search for MSI indicated. Both MSI‐analysis as well as immunohistochemical analysis of the MMR‐proteins are appropriate to identify patients with a high probability of carrying a MMR‐gene mutation. Conclusion All specialists that are involved in the treatment of cancer patients should know the Bethesda criteria in order to identify all families suspected of the Lynch syndrome.     

Nonlinear pharmacokinetic characteristics of 5-fluorouracil (5-FU) in colorectal cancer patients

Summary The nonlinear disposition kinetics of 5-fluorouracil (5-FU) were investigated in 6 patients with colorectal carcinoma. Each patient randomly received two single, intravenous doses of 5-FU (7.5 and 15 mg/kg) on separate days. Venous blood and urine samples were collected just prior to and for 5 h after drug administration. In addition to the kinetic studies, the in vitro whole blood/plasma concentration ratio and stability of 5-FU at 37°C were determined in whole blood from normal volunteers and from 5 patients with colorectal carcinoma.A disproportionate increase in area under the curve and corresponding decrease in total body clearance with increasing dose was observed suggesting dose-dependent behavior of 5-FU. Doubling the dose was accompanied by a 36% decrease in nonrenal clearance but no apparent change in renal clearance. Therefore, the mechanism for dose-dependent elimination appears to be primarily associated with nonrenal processes. The mean 5-FU half-life following the high dose was nearly twice as long as that observed for the low dose (12.3 versus 6.2 min). The log-linear decline in plasma concentrations and increase in half-life with dose suggest the potential role of product-inhibition as an explanation for the observed nonlinearity in 5-FU elimination.The present study demonstrates that 5-FU degrades when incubated in whole blood. This most likely reflects metabolism in red blood cells or other blood-formed elements since 5-FU was stable in plasma. Although degradation in whole blood occurs, the estimated whole blood clearance does not contribute significantly to the observed total body clearance value. These findings suggest the possibility of pulmonary clearance of 5-FU.     

Use of bevacizumab in metastatic colorectal cancer: report from the Mexican opinion and analysis forum on colorectal cancer treatment with bevacizumab (September 2009)

Colorectal cancer is one of the most common cancers worldwide, and although associated mortality rates in South American countries are generally among the lowest in the world, they are on the rise. The prognosis of patients diagnosed with metastatic colorectal cancer has improved markedly over the last 12 years, increasing from 5 months with best supportive care to almost 2 years with combination chemotherapy plus bevacizumab. New prognostic and predictive biomarkers have been identified to guide therapy. Prognostic markers indicate patient survival independent of therapy and include disease stage, mutational status, and carcinoembryonic antigen. More recently, predictive markers of treatment outcomes have been identified. The most studied are mutations of the KRAS and BRAF genes, which are associated with resistance to epidermal growth factor receptor-targeted therapy. Tumor blood vessels have a number of structural and functional abnormalities that result in increased tumor vascularity and growth driven by angiogenesis. The anti-vascular endothelial growth factor (VEGF) monoclonal antibody bevacizumab, which binds to and neutralizes VEGF-A, has become a central part of the treatment of metastatic colorectal cancer. The addition of bevacizumab to fluorouracil (5-FU)/leucovorin, irinotecan plus bolus 5-FU/leucovorin, or irinotecan plus infusional 5-FU/leucovorin significantly improves the overall survival of patients with previously untreated metastatic colorectal cancer. In addition, a significant increase in overall survival is seen when bevacizumab is added to oxaliplatin plus infusional 5-FU/leucovorin (FOLFOX) in patients with metastatic colorectal cancer who progressed on a non-bevacizumab-containing regimen. Although the majority of studies were performed prior to the identification of KRAS and BRAF as predictive biomarkers, subsequent analysis has shown the benefits of bevacizumab occur independently of the mutational status of these genes. In patients who have progressed on a bevacizumab-containing regimen, continuation of bevacizumab is significantly associated with an improved survival based on observational cohort studies. Surgical resection is recommended in patients with metastatic colorectal cancer where complete removal of tumors can be achieved. Perioperative chemotherapy using FOLFOX for 3 months before and 3 months after surgery is associated with a 9% improvement in 3-year survival. The use of chemotherapy in patients initially deemed unresectable has produced resection rates approaching 40%, and the addition of bevacizumab to chemotherapy in this setting is feasible, safe, and effective. In a study of 219 patients, the addition of bevacizumab to FOLFOX was associated with a significant increase in major or complete pathologic response compared with FOLFOX alone. Improvements in patient survival have changed the treatment paradigm for metastatic colorectal cancer. Newer approaches view treatment not as distinct lines of therapy but as a continuum that includes personalized treatment plans offering maintenance therapy and even drug holidays between aggressive treatment periods. This approach achieves similar efficacy outcomes with reduced toxicity, and investigation of the role of bevacizumab as maintenance therapy is ongoing.