Which gene is a dominant predictor of response during FOLFOX chemotherapy for the treatment of metastatic colorectal cancer, the MTHFR or XRCC1 gene?

The Role of Single-Nucleotide Polymorphisms in Cholangiocarcinoma: A Systematic Review

Single-nucleotide polymorphisms (SNPs) play an essential role in various malignancies, but their role in cholangiocarcinoma (CCA) remains to be elucidated. Therefore, the purpose of this systematic review was to evaluate the association between SNPs and CCA, focusing on tumorigenesis and prognosis. A systematic literature search was carried out using PubMed, Embase, Web of Science and the Cochrane database for the association between SNPs and CCA, including literature published between January 2000 and April 2022. This systematic review compiles 43 SNPs in 32 genes associated with CCA risk, metastatic progression and overall prognosis based on 34 studies. Susceptibility to CCA was associated with SNPs in genes related to inflammation (PTGS2/COX2, IL6, IFNG/IFN-γ, TNF/TNF-α), DNA repair (ERCC1, MTHFR, MUTYH, XRCC1, OGG1), detoxification (NAT1, NAT2 and ABCC2), enzymes (SERPINA1, GSTO1, APOBEC3A, APOBEC3B), RNA (HOTAIR) and membrane-based proteins (EGFR, GAB1, KLRK1/NKG2D). Overall oncological prognosis was also related to SNPs in eight genes (GNB3, NFE2L2/NRF2, GALNT14, EGFR, XRCC1, EZH2, GNAS, CXCR1). Our findings indicate that multiple SNPs play different roles at various stages of CCA and might serve as biomarkers guiding treatment and allowing oncological risk assessment. Considering the differences in SNP detection methods, patient ethnicity and corresponding environmental factors, more large-scale multicentric investigations are needed to fully determine the potential of SNP analysis for CCA susceptibility prediction and prognostication.

Genetic Variants in DNA Repair Pathways as Potential Biomarkers in Predicting Treatment Outcome of Intraperitoneal Chemotherapy in Patients With Colorectal Peritoneal Metastasis: A Systematic Review

Background

The introduction of cytoreductive surgery (CRS) followed by hyperthermic intraperitoneal chemotherapy (HIPEC) with either oxaliplatin or mitomycin C for patients with colorectal peritoneal metastasis (CPM) has resulted in a major increase in overall survival. Nonetheless, despite critical patient selection, the majority of patients will develop recurrent disease within one year following CRS + HIPEC. Therefore, improvement of patient and treatment selection is needed and may be achieved by the incorporation of genetic biomarkers. This systematic review aims to provide an overview of genetic biomarkers in the DNA repair pathway that are potentially predictive for treatment outcome of patients with colorectal peritoneal metastases treated with CRS + HIPEC with oxaliplatin or mitomycin C.

Methods

A systematic review was conducted according to the PRISMA guidelines. Given the limited number of genetic association studies of intraperitoneal mitomycin C and oxaliplatin in patients with CPM, we expanded the review and extrapolated the data from biomarker studies conducted in colorectal cancer patients treated with systemic mitomycin C– and oxaliplatin-based chemotherapy.

Results

In total, 43 papers were included in this review. No study reported potential pharmacogenomic biomarkers in patients with colorectal cancer undergoing mitomycin C–based chemotherapy. For oxaliplatin-based chemotherapy, a total of 26 genetic biomarkers within 14 genes were identified that were significantly associated with treatment outcome. The most promising genetic biomarkers were ERCC1 rs11615, XPC rs1043953, XPD rs13181, XPG rs17655, MNAT rs3783819/rs973063/rs4151330, MMR status, ATM protein expression, HIC1 tandem repeat D17S5, and PIN1 rs2233678.

Conclusion

Several genetic biomarkers have proven predictive value for the treatment outcome of systemically administered oxaliplatin. By extrapolation, these genetic biomarkers may also be predictive for the efficacy of intraperitoneal oxaliplatin. This should be the subject of further investigation.

Comprehensive biomarker analyses identifies HER2, EGFR, MET RNA expression and thymidylate synthase 5'UTR SNP as predictors of benefit from S-1 adjuvant chemotherapy in Japanese patients with stage II/III gastric cancer

Purpose: A comprehensive molecular analysis was conducted to identify prognostic and predictive markers for adjuvant S-1 chemotherapy in stage II/III Japanese gastric cancer (GC) patients and to evaluate their potential suitability for alternative cytotoxic or targeted drugs.

Experimental Design: We investigated genetic polymorphisms of enzymes potentially involved in 5-fluoruracil (5-FU) metabolism as well as platinum resistance, previously identified genomic subtypes potentially predicting 5-FU benefit, and mRNA expression levels of receptor tyrosine kinases and KRAS as potential treatment targets in a single institution cohort of 252 stage II/III GC patients treated with or without S-1 after D2 gastrectomy.

Results: 88% and 62% GC had a potentially 5-FU sensitive phenotype by SNP analyses of TS 3'UTR, and TS 5'UTR, respectively. 24%, 46%, 40%, 5%, and 44% GC had a potentially platinum sensitive phenotype by SNP analyses of GSTP1, ERCC1 rs11615, ERCC1 rs3212986, ERCC2, and XRCC1, respectively. High HER2, EGFR, FGFR2, or MET mRNA expression was observed in 49%, 66%, 72%, and 54% GC, respectively. High HER2 expression was the only significant prognosticator (HR=3.912, 95%CI: 1.706-8.973, p=0.0005). High HER2 (p=0.031), low EGFR (p=0.124), high MET (p=0.165) RNA expression, and TS 5'UTR subtype 2R/2R, 2R/3C, or 3C (p=0.058) were significant independent predictors for S-1 resistance.

Conclusions: The present study suggests that platinum-based or RTK targeted agents could be alternative treatment options for a substantial subgroup of Japanese GC patients currently treated with S-1. HER2, EGFR, MET, and TS 5'UTR SNP appear to be promising predictive markers for S-1 resistance warranting validation in an independent GC series.

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.

Methylene tetrahydrofolate reductase (MTHFR) gene rs1801133 C>T polymorphisms and response to 5-FU based chemotherapy in patients with colorectal cancer: a meta-analysis

Background: Methylene tetrahydrofolate reductase (MTHFR) catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a cosubstrate for homocysteine remethylation to methionine. Single nucleotide polymorphisms (SNP) of MTHF rs1801133 C>T can influence susceptibility to colorectal cancer. However, an association between MTHFR rs1801133 C>T polymorphisms and response to 5-Fluorouracil (5-FU) based chemotherapy in patients with colorectal cancer was not clear. Methods: Studies relevant to MTHFR rs1801133 C>T polymorphisms and response to 5-FU based chemotherapy in patients with colorectal cancer were systematic searched in the electronic databases of PubMed, Web of Science, Embase, and China National Knowledge Infrastructure (CNKI). The genotypes of CC, CT, and TT were extracted from each included publication. The genotypes CC, CT, and TT distribution in 5-FU based chemotherapy response and resistance groups were calculated and pooled through random or fixed effect model by the effect size of odds ratio (OR) and 95% confidence interval (95% CI). The publication bias was evaluated through Begg’s funnel plot and Egger’s line regression test. Results: After searching the electronic databases, 16 studies related to MTHFR gene rs1801133 C>T polymorphisms and a response to 5-FU based chemotherapy in patients with colorectal cancer were included in the present meta-analysis. The pooled data showed no statistical difference in tumor response rate between CT+TT and CC groups in the dominant genetic model CT+CC vs CC (OR=1.21, 95% CI: 0.93~1.59, p>0.05) and recessive model TT vs CT+CC (OR=1.37, 95% CI: 0.91~2.06, p>0.05). The grade 3-4 adverse reaction rate between CT+TT and CC groups also had no statistical difference in the dominant genetic model CT+CC vs CC (OR=0.90, 95% CI: 0.76~1.07, p>0.05) and recessive model TT vs CT+CC (OR=1.12, 95% CI: 0.84~1.50, p>0.05). The Begg’s funnel plot and Egger’s line regression test demonstrated no publication bias. Conclusion: The response and adverse reaction of 5-FU based chemotherapy in colorectal patients were not different in terms of MTHFR rs1801133 C>T polymorphisms.

Identification of the predictive genes for the response of colorectal cancer patients to FOLFOX therapy

Background

Colorectal cancer is a malignant tumor with high death rate. Chemotherapy, radiotherapy and surgery are the three common treatments of colorectal cancer. For early colorectal cancer patients, postoperative adjuvant chemotherapy can reduce the risk of recurrence. For advanced colorectal cancer patients, palliative chemotherapy can significantly improve the life quality of patients and prolong survival. FOLFOX is one of the mainstream chemotherapies in colorectal cancer, however, its response rate is only about 50%.

Methods

To systematically investigate why some of the colorectal cancer patients have response to FOLFOX therapy while others do not, we searched all publicly available database and combined three gene expression datasets of colorectal cancer patients with FOLFOX therapy. With advanced minimal redundancy maximal relevance and incremental feature selection method, we identified the biomarker genes.

Results

A Support Vector Machine-based classifier was constructed to predict the response of colorectal cancer patients to FOLFOX therapy. Its accuracy, sensitivity and specificity were 0.854, 0.845 and 0.863, respectively.

Conclusion

The biological analysis of representative biomarker genes suggested that apoptosis and inflammation signaling pathways were essential for the response of colorectal cancer patients to FOLFOX chemotherapy.

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.

Pathway analysis of genetic variants in folate-mediated one-carbon metabolism-related genes and survival in a prospectively followed cohort of colorectal cancer patients

Folate-mediated one-carbon metabolism (FOCM) is a key pathway essential for nucleotide synthesis, DNA methylation, and repair. This pathway is a critical target for 5-fluorouracil (5-FU), which is predominantly used for colorectal cancer (CRC) treatment. A comprehensive assessment of polymorphisms in FOCM-related genes and their association with prognosis has not yet been performed. Within 1,739 CRC cases aged ≥30 years diagnosed from 2003 to 2007 (DACHS study), we investigated 397 single nucleotide polymorphisms (SNPs) and 50 candidates in 48 FOCM-related genes for associations with overall- (OS) and disease-free survival (DFS) using multiple Cox regression (adjusted for age, sex, stage, grade, BMI, and alcohol). We investigated effect modification by 5-FU-based chemotherapy and assessed pathway-specific effects. Correction for multiple testing was performed using false discovery rates (FDR). After a median follow-up time of 5.0 years, 585 patients were deceased. For one candidate SNP in MTHFR and two in TYMS, we observed significant inverse associations with OS (MTHFR: rs1801133, C677T: HRhet  = 0.81, 95% CI: 0.67-0.97; TYMS: rs1001761: HRhet  = 0.82, 95% CI: 0.68-0.99 and rs2847149: HRhet  = 0.82, 95% CI: 0.68-0.99). After FDR correction, one polymorphism in paraoxonase 1 (PON1; rs3917538) was significantly associated with OS (HRhet  = 1.28, 95% CI: 1.07-1.53; HRhzv  = 2.02, 95% CI:1.46-2.80; HRlogAdd  = 1.31, pFDR  = 0.01). Adjusted pathway analyses showed significant associations for pyrimidine biosynthesis (P = 0.04) and fluorouracil drug metabolism (P < 0.01) with significant gene-chemotherapy interactions, including PON1 rs3917538. This study supports the concept that FOCM-related genes could be associated with CRC survival and may modify effects of 5-FU-based chemotherapy in genes in pyrimidine and fluorouracil metabolism, which are relevant targets for therapeutic response and prognosis in CRC. These results require confirmation in additional clinical studies.

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.

Role of depth of response and MTHFR genotype as predictors of fluorouracil rechallenge therapy for refractory metastatic colorectal cancer

There is limited data on the clinical and biological parameters that enable the prediction of the benefits derived from additional chemotherapy after disease progression compared with standard chemotherapy in patients with metastatic colorectal cancer (mCRC). The present study evaluated the role of tumor response as a clinical parameter and single nucleotide polymorphisms (SNPs) as a biomarker to predict the benefit of additional 5-fluorouracil (5-FU) rechallenge chemotherapy in patients with refractory mCRC. Tumor responses were retrospectively reviewed based on the Response Evaluation Criteria in Solid Tumors, early tumor shrinkage (ETS) and depth of response (DoR) following first-line chemotherapy in patients with stage IV CRC. Together with these parameters, SNPs known to be associated with the response to chemotherapy were analyzed with survival outcomes. In total, the tumor responses of 242 patients with mCRC were evaluated. Overall response and ETS were identified in 110 (45.4%) and 103 patients (42.6%), respectively, and the median DoR was 38.5±30.08%. ETS and DoR were significantly associated with survival outcomes, including progression-free survival, post-progression survival and overall survival. Among these patients, SNPs were analyzed in 171 patients. X-ray repair cross complementing 1 (XRCC1) (AG/AA) with a DoR >60%, good performance status and the absence of bone lesions were associated with improved overall survival. In patients receiving third-line chemotherapy with 5-FU rechallenge therapy, the methylenetretrahydrofolate reductase (MTHFR) (C677T) CC genotype and a DoR >60% were significantly associated with a good prognosis in multivariate analysis. XRCC1 (AG/AA) was also associated with a good prognosis in patients with mCRC. Patients with a DoR >60% following first-line chemotherapy and a MTHFR (C677T) CC genotype exhibited a survival benefit from 5-FU retreatment. Therefore, the DoR and MTHFR genotype are potential markers for selecting patients with refractory mCRC that would benefit from 5-FU rechallenge therapy.

Pharmacogenetic and ethnicity influence on oxaliplatin therapy for colorectal cancer: a meta-analysis

Aims: Oxaliplatin-based chemotherapy for colorectal cancer demonstrates interindividual variability in response, and polymorphisms of ERCC1, ERCC2, XRCC1, GSTP1 and GSTM1 genes may be contributing factors. Additionally, the effect of these genotypes may differ between ethnic groups. Material & Methods: A meta-analysis of the association between these genotypes and response, progression-free survival and overall survival (OS) for patients with colorectal cancer treated with oxaliplatin-based therapy is reported. Results: ERCC1 C118T (TT vs CC OS [hazard ratio (HR): 2.59; p = 0.001]), ERCC2 A2251C (CC or AC vs AA OS [HR: 1.53; p = 0.04]) and GSTP1 A313G (GG vs AA OS, [HR: 0.47; p < 0.001]) polymorphisms were associated with survival. The effect size may be larger for ERCC1 C118T and XRCC1 G1196A in Asian compared with Caucasian populations. No association was apparent for the GSTM1 genotype. Conclusion: ERCC1 C118T, ERCC2 A2251C and GSTP1 A313G polymorphisms were associated with clinical outcomes

Degradation Rate of 5-Fluorouracil in Metastatic Colorectal Cancer: A New Predictive Outcome Biomarker?

Background

5-FU based chemotherapy is the most common first line regimen used for metastatic colorectal cancer (mCRC). Identification of predictive markers of response to chemotherapy is a challenging approach for drug selection. The present study analyzes the predictive role of 5-FU degradation rate (5-FUDR) and genetic polymorphisms (MTHFR, TSER, DPYD) on survival.

Materials and Methods

Genetic polymorphisms of MTHFR, TSER and DPYD, and the 5-FUDR of homogenous patients with mCRC were retrospectively studied. Genetic markers and the 5-FUDR were correlated with clinical outcome.

Results

133 patients affected by mCRC, treated with fluoropyrimidine-based chemotherapy from 2009 to 2014, were evaluated. Patients were classified into three metabolic classes, according to normal distribution of 5-FUDR in more than 1000 patients, as previously published: poor-metabolizer (PM) with 5-FU-DR ≤ 0,85 ng/ml/10⁶ cells/min (8 pts); normal metabolizer with 0,85 < 5-FU-DR < 2,2 ng/ml/10⁶ cells/min (119 pts); ultra-rapid metabolizer (UM) with 5-FU-DR ≥ 2,2 ng/ml/10⁶ cells/min (6 pts). PM and UM groups showed a longer PFS respect to normal metabolizer group (14.5 and 11 months respectively vs 8 months; p = 0.029). A higher G3-4 toxicity rate was observed in PM and UM, respect to normal metabolizer (50% in both PM and UM vs 18%; p = 0.019). No significant associations between genes polymorphisms and outcomes or toxicities were observed.

Conclusion

5-FUDR seems to be significantly involved in predicting survival of patients who underwent 5-FU based CHT for mCRC. Although our findings require confirmation in large prospective studies, they reinforce the concept that individual genetic variation may allow personalized selection of chemotherapy to optimize clinical outcomes.

Polymorphisms in folate-metabolizing enzymes and response to 5-fluorouracil among patients with stage II or III rectal cancer (INT-0144; SWOG 9304)

BACKGROUND

Recurrence and toxicity occur commonly among patients with rectal cancer who are treated with 5-fluorouracil (5-FU). The authors hypothesized that genetic variation in folate-metabolizing genes could play a role in interindividual variability. The objective of the current study was to evaluate the associations between genetic variants in folate-metabolizing genes and clinical outcomes among patients with rectal cancer treated with 5-FU.

METHODS

The authors investigated 8 functionally significant polymorphisms in 6 genes (methylenetetrahydrofolate reductase [MTHFR] [C677T, A1298C], SLC19A1 [G80A], SHMT1 [C1420T], dihydrofolate reductase [DHFR] [Del19bp], TS 1494del,and TSER) involved in folate metabolism in 745 patients with TNM stage II or III rectal cancer enrolled in a phase 3 adjuvant clinical trial of 3 regimens of 5-FU and radiotherapy (INT-0144 and SWOG 9304).

RESULTS

There were no statistically significant associations noted between polymorphisms in any of the genes and overall survival, disease-free survival (DFS), and toxicity in the overall analyses. Nevertheless, there was a trend toward worse DFS among patients with the variant allele of MTHFR C677T compared with wild-type, particularly in treatment arm 2, in which patients with the MTHFR C677T TT genotype had worse overall survival (hazards ratio, 1.76; 95% confidence interval, 1.06-2.93 [P = .03]) and DFS (hazards ratio, 1.84; 95% confidence interval, 1.12-3.03 [P = .02]) compared with those with homozygous wild-type. In addition, there was a trend toward reduced hematological toxicity among patients with variants of SLC19A1 G80A in treatment arm 1 (P for trend, .06) and reduced esophagitis/stomatitis noted among patients with variants of TSER in treatment arm 3 (P for trend, .06).

CONCLUSIONS

Genetic variability in folate-metabolizing enzymes was found to be associated only to a limited degree with clinical outcomes among patients with rectal cancer treated with 5-FU.

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.

X-ray repair cross-complementing 1 polymorphism and prognosis of platinum-based chemotherapy in gastric and colorectal cancer: a meta-analysis

BACKGROUND AND AIM

The relationships between the X-ray repair cross-complementing 1 (XRCC1) Arg399Gln polymorphism (rs25487, G > A) and responses to platinum-based chemotherapy of gastric and colorectal cancer patients are controversial. Therefore, we performed a meta-analysis to assess the relationships.

METHODS

We retrieved the relevant articles from MEDLINE and EMBASE databases. Fourteen studies with 1618 gastric and colorectal cancer patients were included. Primary outcomes included response rate (RR), progression-free survival (PFS), and overall survival (OS). Odds ratio (OR) or hazard ratio with 95% confidence interval (CI) were estimated. All analyses were performed using the Stata software version 11.0 and Review Manager (v5.0).

RESULTS

In the dominant model, the A allele of XRCC1 Arg399Gln polymorphism was associated with reduced RR to platinum-based chemotherapy in all gastric and colorectal cancer patients (A/G + A/A vs G/G OR, 0.73; 95% CI, 0.55-0.96) and in Asians (OR, 0.62; 95% CI, 0.44-0.89) but not in Caucasians (OR, 0.92; 95% CI, 0.60-1.42). In addition, stratified analysis for different types of cancers indicated a marginally significant decrease of RR in colorectal cancer patients (OR, 0.68; 95% CI, 0.46-1.00) but not in gastric cancer patients (OR, 0.78; 95% CI, 0.53-1.15). However, we did not observe a significant association between XRCC1 Arg399Gln polymorphism and hazard for PFS and OS for gastric and colorectal cancer patients in all tested models.

CONCLUSIONS

XRCC1 Arg399Gln polymorphism may be a valuable genetic marker for platinum-based chemotherapy of gastric and colorectal cancer patients, and more well-designed studies with large samples are needed to confirm our findings.

Pretreatment selection of regimen according to genetic analysis improves the efficacy of chemotherapy in the first line treatment of metastatic colorectal cancer

BACKGROUND AND OBJECTIVES

Metastatic colon cancer patients are treated with the chemotherapy regimens, FOLFOX and FOLFIRI, in either order. So far, we cannot predict the response of chemotherapeutic agent, so it is necessary to find which regimen is adequate before starting chemotherapy.

METHODS

Enrolled patients are randomized into either conventional treatment or planned treatment preceded by pretreatment genetic analysis. Blood samples of patients in planned treatment group (N = 53) were analyzed for the genetic polymorphism before selection of chemotherapeutic agents. Target genes were XPD-751, GSTP-1-105, XRCC1-399 for oxaliplatin, UGT1A1 for irinotecan. The response was measured by computed tomographic scan after completion of three cycles of chemotherapy.

RESULTS

Overall response rate was significantly higher in planned group (67.9% vs. 46.3%, P = 0.020). In FOLFOX group, response rate was significantly improved in the planned patients(77.1% vs. 50%, P = 0.018). In FOLFIRI group, the difference didn't reach statistical significance (50% vs. 42.5%, P = 0.776).

CONCLUSIONS

We found significantly improved response rates in the chemotherapy of metastatic colon cancer by pretreatment genetic analysis, especially in FOLFOX group.

Concordance of genotype for polymorphisms in DNA isolated from peripheral blood and colorectal cancer tumor samples

Background & aim: Results from different pharmacogenetic association studies in colorectal cancer are often conflicting. Both peripheral blood and formalin-fixed, paraffin-embedded (FFPE) tissue are routinely used as DNA source. This could cause bias due to somatic alterations in tumor tissue, such as loss of heterozygosity. We therefore compared genotypes in DNA from peripheral blood and FFPE colorectal tumor samples for SNPs with putative influence on the cytotoxicity of chemotherapy. Materials & methods: Eleven SNPs in nine genes involved in anticancer drug metabolism or efficacy were determined in matched samples from blood and FFPE tissue of colorectal tumors by pyrosequencing and TaqMan® techniques. The κ-statistic was calculated to assess concordance. Results: A total of 149 paired FFPE tissue and EDTA blood DNA samples were available for comparison. Overall, 20 out of 1418 genotypes were discordant (1.4%); in ten cases, loss of heterozygosity could not be ruled out. Only GSTP1 showed significant discordance between FFPE tissue and blood genotype (κ = 0.947; 95% CI: 0.896–0.998). Conclusion: FFPE tissue-derived DNA can be used as a valid proxy for germline DNA for a selection of SNPs in (retrospective) pharmacogenetic association studies in colorectal cancer. However, for future studies, genotyping of blood-derived DNA is preferred.

Original submitted 29 May 2013; Revision submitted 23 August 2013

Identification of HOXB8 and KLK11 expression levels as potential biomarkers to predict the effects of FOLFOX4 chemotherapy

AIM

To measure global gene expression in primary advanced colorectal cancer patients who have undergone fluorouracil, leucovorin and oxaliplatin (FOLFOX4) chemotherapy and screen valuable biomarkers to predict the effects of chemotherapy.

MATERIALS & METHODS

Samples from primary advanced colorectal cancer patients were collected. The effects of chemotherapy were evaluated, and patients were divided into an experimental group and a control group. Cancerous tissue gene expression profiles were detected by chip technology. Valuable biomarkers were screened by bioinformatic analysis. Immunohistochemical analysis was performed to characterize the pattern of HOXB8 and KLK11 expression. HOXB8 and KLK11 signal probe values were analyzed using receiver operating characteristic analysis.

RESULTS

There were differentially expressed genes in the two groups. HOXB8 and KLK11 proteins were observed in the nucleus and on the outside of the cancer cells, respectively. Their prediction accuracies were 79.9 and 76.7%, respectively.

CONCLUSION

HOXB8 and KLK11 may be classified as valuable biomarkers, as they can predict the effects of FOLFOX4 chemotherapy in primary advanced colorectal cancer patients.

Personalizing colon cancer therapeutics: targeting old and new mechanisms of action

The use of pharmaceuticals for colon cancer treatment has been increasingly personalized, in part due to the development of new molecular tools. In this review, we discuss the old and new colon cancer chemotherapeutics, and the parameters that have been shown to be predictive of efficacy and safety of these chemotherapeutics. In addition, we discuss how alternate pharmaceuticals have been developed in light of a potential lack of response or resistance to a particular chemotherapeutic.

Predicting chemotherapeutic response and toxicity in colorectal cancer

SUMMARY While treatment for colorectal cancer has evolved significantly over the past 10 years with the introduction of active chemotherapeutic agents and targeted therapies, this has been at the cost of increased toxicity for patients; and significant financial burden for governments and patients. Predicting clinical outcomes, especially given the largely elderly patient population involved, is therefore paramount. This review seeks to summarize existing data regarding the prediction of response and toxicity to chemotherapy agents currently used in the treatment of colorectal cancer.

Genetic polymorphisms of ERCC1‑118, XRCC1‑399 and GSTP1‑105 are associated with the clinical outcome of gastric cancer patients receiving oxaliplatin‑based adjuvant chemotherapy

The aim of the present study was to determine whether specific molecular parameters may serve as predictors of treatment outcomes and toxicity of oxaliplatin (OXA)‑based chemotherapy, which is used as an adjuvant treatment in resected gastric cancer. All gastric cancer patients examined in the study received an OXA/5‑fluorouracil chemotherapeutic regimen. Genetic polymorphisms of certain platinum‑related genes were determined by the TaqMan 5' nuclease assay and direct sequencing. Relapse‑free survival (RFS), overall survival (OS) and toxicity were evaluated according to each genotype. Following adjustment for the most relevant clinical variables, excision repair cross‑complimentary group 1 (ERCC1)‑118 and X-ray repair cross-complementing protein 1 (XRCC1‑399) demonstrated significant predictive value for RFS and OS. We also demonstrated that carrying at least one variant XRCC1 Arg399Gln or glutathione S-transferase π 1 (GSTP1) Ile105Val allele significantly increased the risk of any grade 3 or 4 hematological toxicity. In particular, carrying at least one variant GSTP1 Ile105Val allele was also significantly correlated with an increased risk of grade 3 or 4 gastrointestinal toxicity and neurotoxicity. Our data suggested that gastric cancer patients harboring ERCC1‑118 C/C and XRCC1‑399 A/G or A/A genotypes may benefit from receiving OXA‑based adjuvant chemotherapy, and carrying at least one variant XRCC1 Arg399Gln or GSTP1 Ile105Val allele may contribute to the occurrence of adverse drug effects associated with OXA‑based chemotherapy.

Polymorphisms in XPD and ERCC1 Associated with Colorectal Cancer Outcome

Using the comprehensive approach to selecting polymorphisms to date, we sought to examine whether recurrence in colorectal cancer was associated with inherited variation in three genes involved in DNA repair and cell proliferation. Three polymorphisms, which are excision repair cross-complementation 1 (ERCC1), xeroderma pigmentosum group D (XPD) and epidermal growth factor receptor (EGFR), were assessed in 257 postoperative stage II/III CRC patients with 5-fluorouracial chemotherapy in Taiwan. In addition, the correlations between genetic polymorphisms and patients’ clinicopathological features were investigated. Genotypes of XPD codon751 A/A and ERCC1 codon118 T/T were associated with regional recurrence in a statistically significant way (p = 0.018). Patients who carried XPD AA and ERCC1 TT genotypes demonstrated a significantly greater regional recurrence risk (OR = 5.625, 95% CI, 1.557–20.32). Inherited variation in XPD and ERCC1 was associated with outcome in patients with colorectal cancer in Taiwan. As the significant association of single-nucleotide polymorphisms has not been studied previously in colorectal cancer, these findings suggest novel sites of variation, in part explaining the range of treatment responses seen in this disease.

Molecular biomarkers of colorectal cancer: prognostic and predictive tools for clinical practice

Colorectal cancer remains one of the most common types of cancer and leading causes of cancer death worldwide. Although we have made steady progress in chemotherapy and targeted therapy, evidence suggests that the majority of patients undergoing drug therapy experience severe, debilitating, and even lethal adverse drug events which considerably outweigh the benefits. The identification of suitable biomarkers will allow clinicians to deliver the most appropriate drugs to specific patients and spare them ineffective and expensive treatments. Prognostic and predictive biomarkers have been the subjects of many published papers, but few have been widely incorporated into clinical practice. Here, we want to review recent biomarker data related to colorectal cancer, which may have been ready for clinical use.

Association between polymorphisms of XRCC1 and ADPRT genes and ovarian cancer survival with platinum-based chemotherapy in Chinese population

The role of DNA repair gene polymorphisms in cancer development, progression, and response to treatment has received increased attention. We conducted a prospective study to determine whether associations exist between two polymorphisms in XRCC1 and ADPRT and the outcomes of Chinese ovarian cancer patients treated with platinum-based chemotherapy. A total of 335 new cases of ovarian cancer were consecutively collected between May 2005 and May 2007. Follow-up lasted for 4 years, and the outcome measure was survival time. Individuals carrying XRCC1 194Trp/Trp had a longer survival time than did those with the Arg/Arg genotype. Similarly, those carrying XRCC1 399 Gln/Gln genotypes had 0.44-fold the risk of death than those with the Arg/Arg genotype. The combination of XRCC1 194 Trp allele and 399 Gln allele could decrease the death risk of ovarian cancer. In summary, this study is the first to evaluate the associations between polymorphisms in DNA repair gene polymorphism and the risk of ovarian cancer in Chinese population. Our study found a significant association between XRCC1 Arg399Gln and XRCC1 Arg194Trp polymorphism and the clinical outcome of ovarian cancer. Furthermore, studies with larger sample sizes are still needed to confirm these associations in Chinese population.

Identification of Nkx2-3 and TGFB1I1 expression levels as potential biomarkers to predict the effects of FOLFOX4 chemotherapy

This study was designed to detect global gene expressions of primary advanced colorectal cancer (ACC) patients who have undergone FOLFOX4 chemotherapy and screen valuable biomarkers to predict the effects of chemotherapy. Samples from primary ACC patients who have undergone FOLFOX4 chemotherapy were collected. Their chemotherapy effects were evaluated and divided into chemotherapy sensitive group (experimental group) and non-sensitive group (control group). Cancerous tissue gene expression profiles were detected by chip technology. Two groups with differentially expressed genes were screened by cluster analysis and significance analysis of microarrays (SAM). Valuable biomarkers were screened by bioinformatics analysis. Immunohistochemical analysis was performed to characterize the pattern of Nkx2-3 and TGFB1I1 expression. Nkx2-3 and TGFB1I1 signal log ratio were used Receiver Operating Characteristic (ROC) analyses to calculate its own predicting accuracy. Thirty cases were divided into experimental group (13 cases) and control group (17 cases). There was evident difference in the tumor cell biology states of the two groups; that is, 25 ESTs (21 genes) were upregulated and 5 ESTs (5 genes) were downregulated. Nkx2-3 protein was observed on the nucleus of the cancer cells and TGFB1I1 protein was observed on the nucleus and cytoplasm of the cancer cells in experimental group. Their prediction accuracies were 85.3% and 76.7% respectively. Nkx2-3 and TGFB1I1 expressions in control group are very low, but highly expressed in the experimental group; Nkx2-3 and TGFB1I1 may be classified as valuable biomarkers, as these can predict the effects of primary ACC patients who will undergo FOLFOX4.

Pharmacogenomics and metastatic colorectal cancer: current knowledge and perspectives

The pharmacogenomics field is crucial for optimizing the selection of which chemotherapy regimen to use according to the patient's genomic profile. Indeed, the individual's inherited genome accounts for a large proportion of the variation in his or her response to chemotherapeutic agents both in terms of efficiency and toxicity. Patients with metastatic disease are more likely to receive different lines of chemotherapy with variable efficacy and experience some related complications. It is therefore critical to tailor the best therapeutic arsenal to improve the efficacy and avoid as much as possible related complications that are susceptible to interrupt the treatment. The pharmacogenomics approach investigates for each drug the implicated metabolic pathway and the potential personal variations in gene function. The aim of this review is to present a clear overview of the most accurate polymorphisms that have been identified as related to drug response in patients with mCRC.

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.

Pharmacogenetic study in rectal cancer patients treated with preoperative chemoradiotherapy: polymorphisms in thymidylate synthase, epidermal growth factor receptor, GSTP1, and DNA repair genes

PURPOSE

Several studies have been performed to evaluate the usefulness of neoadjuvant treatment using oxaliplatin and fluoropyrimidines for locally advanced rectal cancer. However, preoperative biomarkers of outcome are lacking. We studied the polymorphisms in thymidylate synthase, epidermal growth factor receptor, glutathione S-transferase pi 1 (GSTP1), and several DNA repair genes to evaluate their usefulness as pharmacogenetic markers in a cohort of 128 rectal cancer patients treated with preoperative chemoradiotherapy.

METHODS AND MATERIALS

Blood samples were obtained from 128 patients with Stage II-III rectal cancer. DNA was extracted from the peripheral blood nucleated cells, and the genotypes were analyzed by polymerase chain reaction amplification and automated sequencing techniques or using a 48.48 dynamic array on the BioMark system. The germline polymorphisms studied were thymidylate synthase, (VNTR/5'UTR, 2R G>C single nucleotide polymorphism [SNP], 3R G>C SNP), epidermal growth factor receptor (Arg497Lys), GSTP1 (Ile105val), excision repair cross-complementing 1 (Asn118Asn, 8092C>A, 19716G>C), X-ray repair cross-complementing group 1 (XRCC1) (Arg194Trp, Arg280His, Arg399Gln), and xeroderma pigmentosum group D (Lys751Gln). The pathologic response, pathologic regression, progression-free survival, and overall survival were evaluated according to each genotype.

RESULTS

The ∗3/∗3 thymidylate synthase genotype was associated with a greater response rate (pathologic complete remission and microfoci residual tumor, 59% in ∗3/∗3 vs. 35% in ∗2/∗2 and ∗2/∗3; p=.013). For the thymidylate synthase genotype, the median progression-free survival was 103 months for the ∗3/∗3 patients and 84 months for the ∗2/∗2 and ∗2/∗3 patients (p=.039). For XRCC1 Arg399Gln SNP, the median progression-free survival was 101 months for the G/G, 78 months for the G/A, and 31 months for the A/A patients (p=.048).

CONCLUSIONS

The thymidylate synthase genotype and XRCC1 Arg399Gln polymorphism might help to identify Stage II-III rectal cancer patients with a better outcome after preoperative concomitant chemoradiotherapy.

Methylenetetrahydrofolate reductase polymorphism (677 C>T) predicts long time to progression in metastatic colon cancer treated with 5-fluorouracil and folinic acid

BACKGROUND AND AIMS

Fluoropyrimidine-based chemotherapy is the most common treatment for unresectable metastatic colorectal cancer (m-CRC). Therapy with 5-FU/folinic acid (FA) continues to be a standard treatment in developing countries. Pharmacogenomics allows the tailoring of cancer therapy to the patient. The polymorphism 677C>T of the methylenetetrahydrofolate reductase (MTHFR) gene seems to influence the effectiveness of treatment with 5-FU. We undertook this study to evaluate the frequency of MTHFR 677C>T polymorphism and its relationship to the time to progression (TTP) and overall survival (OS) in m-CRC treated with 5-FU/FA.

METHODS

The MTHFR 677C>T polymorphism was determined using PCR and allele-specific digestion. The clinical variables, TTP and OS, were analyzed in each case and compared between wild-type and variant polymorphic groups.

RESULTS

Among 34 patients (12 males and 22 females), we detected eight wild-type homozygous patients (CC; 24%), nine variant homozygous (TT; 26%), and 17 heterozygous (CT; 50%) individuals. The median TTP in patients with the MTHFR 677 CC, CT, and TT genotypes was 3.43, 4.77, and 4.80 months, respectively (p = 0.047, log rank). A longer TTP was observed in patients with polymorphic variant (CT and TT) compared with the wild-type homozygous patients (4.80 vs. 3.43 months; p = 0.031, log rank).

CONCLUSIONS

In this study, the frequency of the MTHFR 677C>T polymorphism is 50% among m-CRC Mexican patients. The results of this study appear to show that the presence of the MTHFR 677C>T polymorphism is associated with longer TTP and OS in m-CRC treated with 5-FU/FA.

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.

Clinical, laboratory and molecular factors predicting chemotherapy efficacy and toxicity in colorectal cancer

Colorectal cancer (CRC) treatment has evolved significantly over the last ten years with the use of active chemotherapeutic agents including fluoropyrimidines, oxaliplatin and irinotecan plus targeted monoclonal antibodies bevacizumab, cetuximab and panitumumab. The addition of newer chemotherapeutic agents and targeted therapies has improved patient outcomes at the cost of increased toxicity with not all patients benefiting from these treatments. It is necessary for clinicians to more accurately predict clinical outcomes particularly in the predominantly elderly CRC patient population. This review aims to summarise existing data regarding the use of clinical and laboratory variables plus molecular markers in predicting response, survival and toxicity to chemotherapy agents and targeted monoclonal antibodies currently used in the treatment of CRC.

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

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

* Numerous clinical studies, including a few prospective ones, have reported conflicting results on the impact of gene polymorphisms related to fluorouracil (FU) and oxaliplatin pharmacodynamics.

WHAT THIS STUDY ADDS

* This prospective study is the first to report that clinical response to FOLFOX is significantly related to methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms (677C-->T and 1298A-->C), with a response rate of 37, 53, 63 and 80% in patients harbouring no, one, two or three favourable MTHFR alleles, respectively. * Only polymorphisms of genes related to oxaliplatin pharmacodynamics (GSTpi 105Ile-->Val and XPD 751Ly-->Gln) influenced progression-free survival. * These results corroborate the observation that response was related to the cumulative FU dose, whereas progression-free survival was related to the cumulative oxaliplatin dose.

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) pi (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 GSTpi 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.

Bevacizumab improves pathological response of colorectal cancer liver metastases treated with XELOX/FOLFOX

BACKGROUND

Histological response of colorectal cancer liver metastases to chemotherapy may be graded based on the extent of tumor regression. The knowledge about the effect of bevacizumab, if given in addition to fluoropyrimidines and oxaliplatin, on tumor regression and its consequences on clinical outcome is limited.

MATERIALS AND METHODS

Resected liver metastases from patients of 2 prospective nonrandomized trials (fluoropyrimidines and oxaliplatin +/- bevacizumab) were analyzed retrospectively. Histological response was analyzed according to an established tumor regression grading for colorectal cancer liver metastases. Tumor regression grades (TRGs) were correlated to progression-free and overall survival.

RESULTS

Bevacizumab improved tumor regression to chemotherapy significantly. Improvement in histological response was translated into a significant prolongation of progression-free and overall survival.

CONCLUSIONS

Classifying histological response based on tumor regression grades qualifies to predict the outcome of patients with colorectal cancer liver metastases. Tumor regression grading provides a standardized pathological response evaluation, against which radiologic response on chemotherapy including biologicals can be prospectively evaluated.

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

AIMS

Pharmacogenetic studies investigating the relationship between MTHFR gene polymorphisms and response to fluorouracil-based chemotherapy in patients with colorectal cancer have produced inconclusive results. In an attempt to interpret these results, a meta-analysis of all eligible studies published up until January 2009 was carried out.

MATERIALS & METHODS

A total of ten studies relating MTHFR C677T and six studies relating MTHFR A1298C to the response to chemotherapy in patients with colorectal cancer were included in the meta-analysis and random effects pooled odds ratios were estimated. The heterogeneity between studies, the sources of potential bias and the consistency of genetic effects across ethnicities were explored. Cumulative and recursive cumulative meta-analyses were also performed.

RESULTS

For both the C677T and A1298C polymorphisms, the main analysis revealed nonsignificant heterogeneity and a lack of association under the allele contrast, the recessive and dominant models. The subgroup analysis by ethnicity did not change this pattern of results. The lack of stability of the relative change of odds ratio in the recursive cumulative meta-analysis for both polymorphisms indicated the need for more evidence to support a definite lack of association. There was no differential magnitude of the effect in large versus small studies.

CONCLUSION

The available evidence indicates that MTHFR C677T and A1298C gene polymorphisms cannot be considered as reliable predictors of response to fluorouracil-based chemotherapy in patients with colorectal cancer.

Molecular markers of response and toxicity to FOLFOX chemotherapy in metastatic colorectal cancer

Background:

To investigate three genetic alterations (TP53 mutation, Kras mutation and microsatellite instability (MSI)) and three polymorphisms (methylene tetrahydrofolate reductase (MTHFR) C677T, excision repair cross complementing group 1 (ERCC1)-118 and X-ray repair cross complementing group 1 (XRCC1)-399) for their ability to predict response, survival and toxicity to FOLFOX first line chemotherapy in the treatment of metastatic colorectal cancer (mCRC).

Methods:

Tumour tissues from 118 mCRC patients who underwent FOLFOX treatment from three successive phase II trials were evaluated for mutations in TP53 (exons 5–8) and Kras (codons 12 and 13) and for MSI using PCR-based analysis. Genotyping for common single nucleotide polymorphisms in the MTHFR (codon 677), ERCC1 (codon 118) and XRCC1 (codon 399) genes was also carried out using PCR techniques. These genetic markers were correlated with clinical response, survival and toxicity to treatment.

Results:

Patients with the T allele of ERCC1-118 showed significantly worse progression-free survival in univariate analysis (HR=2.62; 95% CI=1.14–6.02; P=0.02). None of the genetic alterations or polymorphisms showed significant association with clinical response to FOLFOX. The MTHFR, ERCC1 and XRCC1 polymorphisms showed no associations with overall haematological, gastrointestinal or neurological toxicity to FOLFOX, although MTHFR 677 TT genotype patients showed a significantly higher incidence of grade 3 or 4 diarrhoea (26%) compared with CC or CT genotype patients (6%, P=0.02).

Conclusions:

The ERCC1-118 and MTHFR C677T polymorphisms were associated with progression and severe diarrhoea, respectively, after FOLFOX treatment in mCRC. Although our findings require confirmation in large prospective studies, they reinforce the concept that individual genetic variation may allow personalized selection of chemotherapy to optimize clinical outcomes.

The association of XRCC1 gene single nucleotide polymorphisms with response to neoadjuvant chemotherapy in locally advanced cervical carcinoma

BACKGROUND

Platinum-based neoadjuvant chemotherapy (NAC) is new therapeutic strategy for locally advanced cervical carcinoma, but the variables used to predict NAC response are still infrequently reported. The aim of our study was to investigate the association between XRCC1 gene single nucleotide polymorphisms (SNPs) and NAC response.

METHODS

Seventy patients with locally advanced cervical carcinoma who underwent NAC were collected. SNPs of XRCC1 (at codon 194 and 399) and XRCC1 protein expression were detected. The association of XRCC1 gene SNPs and protein expression with NAC response were analyzed.

RESULTS

Response to NAC was not statistically significant in three genotypes, Arg/Arg, Arg/Trp, Trp/Trp of XRCC1 at codon 194(X(2) = 1.243, P = 0.07), while responses were significantly different in genotypes Arg/Arg, Arg/Gln, Gln/Gln of XRCC1 at codon 399 (X(2) = 2.283, P = 0.020). The risk of failure to chemotherapy in the patients with a Gln allele(Arg/Gln+Gln/Gln) was significantly greater than that with Arg/Arg(OR = 3.254, 95%CI 1.708 approximately 14.951). The expression level of XRCC1 protein was significantly associated with response to NAC. Moreover, the genotype with the Gln allele(Arg/Gln+Gln/Gln) at codon 399, but not codon at 194, presented a significantly higher level of XRCC1 protein expression than that with Arg/Arg genotype (F = 2.699, p = 0.009).

CONCLUSION

SNP of XRCC1 gene at codon 399 influences the response of cervical carcinoma to platinum-based NAC. This is probably due to changes in expression of XRCC1 protein, affecting response to chemotherapy.

MTHFR polymorphisms and 5-FU-based adjuvant chemotherapy in colorectal cancer

BACKGROUND

Methylenetetrahydrofolate reductase is a pivotal enzyme in folate metabolism and 5-fluorouracil (5-FU) cytotoxicity. Two common single-nucleotide polymorphisms (SNPs), MTHFR 677C>T (rs1801133) and 1298A>C (rs1801131), reduce enzyme activity. Initially, these SNPs were claimed to predict clinical efficacy, but further studies have yielded contradictory results. We tested whether these two polymorphisms are determinants of clinical outcome in a large patient group with a long follow-up time.

PATIENTS AND METHODS

We included 331 patients who had been treated with adjuvant 5-FU/leucovorin chemotherapy after intended curative resection between 1997 and 2003. Clinical data, including relapse rates, overall survival, and tumor stage, were collected. DNA was extracted from formalin-fixed tumor tissue and analyzed for the MTHFR 677C>T and 1298A>C SNPs with real-time PCR.

RESULTS

The MTHFR 677C>T and 1298A>C polymorphisms were not associated with survival or relapse-free survival (P > 0.2). The 677 CC genotype was associated to toxicity (odds ratio = 1.83, P = 0.01).

CONCLUSIONS

The MTHFR 677C>T and 1298A>C polymorphisms probably do not predict efficacy of adjuvant 5-FU treatment in colorectal cancer after complete resection; however, the 677C>T polymorphism may be associated with lower toxicity in 5-FU treatment. Implementation of SNP analysis for these polymorphisms for individualized treatment is premature.

Shifting to first-line regimen after previous failure of irinotecan and oxaliplatin containing chemotherapies in unresectable metastatic colorectal cancer: a retrospective study of case analysis

PURPOSE

Conventional use of FOLFIRI-FOLFOX or the reverse sequence is the optional regimen in metastatic unresectable colorectal cancer (CRC). We present our experience in chemotherapy (C/T) shifting to first-line regimen after previous failure of irinotecan and oxaliplatin containing regimens.

MATERIALS AND METHODS

A total of 48 patients with metastatic unresectable CRC were examined retrospectively. All the patients had both failure of a first-line C/T and a second-line C/T. Of these patients, 13 patients received C/T shifting to first-line regimen. Data were collected retrospectively.

RESULTS

Rate of disease control of 38.4% was achieved (five in 13 patients). In the positive disease control group, metastatic sites were all extra-hepatic (five patients). In the negative disease control group, hepatic metastatic rate was 62.5% (five in eight patients, P=0.044).

CONCLUSIONS

Even after previous failure of irinotecan and oxaliplatin containing C/T, we observe positive disease control response and survival benefit in selected patients with C/T shifting to the first-line regimen especially in extra-hepatic metastasis. The preliminary results are proposed to gain insight into the need for further investigations and large-scale studies.

Pharmacogenetics in chemotherapy of colorectal cancer

Although in recent years, chemotherapeutic options for colorectal carcinoma have expanded, overall response rates are still too low, with high rates of toxicity. Pharmacogenetics aim at predicting both treatment response and adverse effects in individual patients. This review describes the current knowledge of pharmacogenetic markers in the systemic treatment of colorectal cancer. UGT1A1*28 leads to reduced conjugation of SN-38, the active metabolite of irinotecan, resulting in an increased rate of adverse effects, especially neutropenia. To a lesser extent, increased 5-FU toxicity is predicted by DPYD*2A. A variable number of tandem repeats polymorphism in the thymidylate synthase enhancer region, in combination with a single nucleotide polymorphism C>G, may predict poorer response to 5-FU. Efficacy of oxaliplatin is influenced by polymorphisms in components of DNA repair systems, such as ERCC1 and XRCC1. Polymorphic changes in the endothelial growth factor receptor probably predict cetuximab efficacy. Furthermore, the antibody-depended cell-mediated cytotoxic effect of cetuximab may be reduced by polymorphisms in the immunoglobin G fragment C receptors. Bevacizumab efficacy is suspected to be influenced by polymorphisms in the VEGF gene and the hypoxia inducible factor 1alpha gene. Although the interpretation of pharmacogenetic studies is complicated, results imply a promising way of pretreatment prediction of chemotherapy efficacy and toxicity.

Pharmacogenetics in colorectal cancer: a systematic review

Pharmacological treatment of colorectal cancer has improved survival rates in recent years. Individual genetic variation in genes associated with metabolism and targets of commonly used drugs can be responsible for variability in treatment outcome and toxicity. Diverse study designs have been used and heterogeneous end points evaluated by studies assessing the association of genetic markers with treatment outcome. We conducted this systematic review, including 51 studies, to present a comprehensive overview and draw further conclusions. To facilitate comparison of reported study results, risk estimates for observed genetic variants in 33 key genes are presented using defined reference categories and recalculated risk estimates based on data provided in original publications, where necessary. Overall, evidence indicates associations of the UGT1A1(*) 28 variant genotype with toxicity after irinotecan treatment, mutations in GSTP1-105 with improved treatment outcome and the XPD-751 variant genotype with poor treatment outcome after oxaliplatin treatment, and amplification of the EGFR gene with improved treatment outcome after therapy with monoclonal antibodies. Adequately powered prospective investigations designed specifically for pharmacogenetics are needed.

Irinotecan pharmacogenetics: influence of pharmacodynamic genes

PURPOSE

Irinotecan is an important drug for the treatment of solid tumors. Although genes involved in irinotecan pharmacokinetics have been shown to influence toxicity, there are no data on pharmacodynamic genes. CDC45L, NFKB1, PARP1, TDP1, and XRCC1 have been shown to influence the cytotoxic action of camptothecins, including irinotecan. Polymorphisms in the drug target of camptothecins, topoisomerase I (TOP1), and downstream effectors may influence patient outcomes to irinotecan therapy. We undertook a retrospective candidate gene haplotype association study to investigate this hypothesis.

EXPERIMENTAL DESIGN

Haplotype compositions of six candidate genes were constructed in European (n = 93), East Asian (n = 94), and West African (n = 95) populations. Haplotype-tagging single nucleotide polymorphisms (htSNP) were selected based on genealogic relationships between haplotypes. DNA samples from 107 European, advanced colorectal cancer patients treated with irinotecan-based regimens were genotyped for htSNPs as well as three coding region SNPs. Associations between genetic variants and toxicity (grade 3/4 diarrhea and neutropenia) or efficacy (objective response) were assessed.

RESULTS

TOP1 and TDP1 htSNPs were related to grade 3/4 neutropenia (P = 0.04) and response (P = 0.04), respectively. Patients homozygous for an XRCC1 haplotype (GGCC-G) were more likely to show an objective response to therapy than other patients (83% versus 30%; P = 0.02). This effect was also seen in a multivariate analysis (odds ratio, 11.9; P = 0.04). No genetic variants were associated with diarrhea.

CONCLUSIONS

This is the first comprehensive pharmacogenetic investigation of irinotecan pharmacodynamic factors, and our findings suggest that genetic variation in the pharmacodynamic genes may influence the efficacy of irinotecan-containing therapies in advanced colorectal cancer patients.

Targeted therapy of cancer: new roles for pathologists in colorectal cancer

Personalized/individualized/tailored therapy for each patient is an important goal for improving the outcome of patients with colorectal adenocarcinoma and includes the intention to maximize efficacy and minimize toxicity of chemotherapeutic agents. Numerous barriers must be overcome to reach this goal because outcome is affected by an unholy trinity of tumor characteristics that include somatic alterations at the DNA, RNA, and protein level; patient characteristics that include germline genetic differences such as polymorphisms in enzymes affecting the metabolism of chemotherapeutic agents; and environmental exposures and factors that include diet and physical activity. At present, evaluation of epidermal growth factor receptor (EGFR) expression by immunohistochemistry in colorectal adenocarcinoma is generally required for treatment with one of the monoclonal antibody therapies directed against that target, despite the absence of evidence for predictive value of the assay, whereas EGFR fluorescent in situ hybridization (FISH) may be predictive. In addition, the Food and Drug Administration of the United States now requires a 'black box' warning on the packaging of irinotecan for evaluation of germline polymorphism in UGT1A1, the gene mutated in Gilbert's syndrome, for potential reduction of drug dosage in patients with the UGT1A1*28 polymorphism. Numerous other potential markers have been identified but have not yet reached levels of evidence that support their routine usage. For example, KRAS gene mutation appears to preclude improved survival after therapy with monoclonal antibody therapy directed at EGFR, and extensive DNA methylation is associated with lack of efficacy of 5-fluorouracil (5-FU)-based chemotherapy. Additional markers will come into routine usage as reports of research studies continue to appear in the literature. Clinical trials driven by molecular targets and agents directed against them, and understanding of the conflicting data on utility of markers reported in the literature, are needed to advance the field.