Genome-wide association study of asthma exacerbations despite inhaled corticosteroid use.

RATIONALE: Substantial variability in response to asthma treatment with inhaled corticosteroids (ICS) has been described among individuals and populations, suggesting the contribution of genetic factors. Nonetheless, only a few genes have been identified to date. We aimed to identify genetic variants associated with asthma exacerbations despite ICS use in European children and young adults and to validate the findings in non-Europeans. Moreover, we explored whether a gene-set enrichment analysis could suggest potential novel asthma therapies. METHODS: A genome-wide association study (GWAS) of asthma exacerbations was tested in 2681 children of European descent treated with ICS from eight studies. Suggestive association signals were followed up for replication in 538 European asthma patients. Further evaluation was performed in 1773 non-Europeans. Variants revealed by published GWAS were assessed for replication. Additionally, gene-set enrichment analysis focused on drugs was performed. RESULTS: 10 independent variants were associated with asthma exacerbations despite ICS treatment in the discovery phase (p≤5×10-6). Of those, one variant at the CACNA2D3-WNT5A locus was nominally replicated in Europeans (rs67026078; p=0.010), but this was not validated in non-European populations. Five other genes associated with ICS response in previous studies were replicated. Additionally, an enrichment of associations in genes regulated by trichostatin A treatment was found. CONCLUSIONS: The intergenic region of CACNA2D3 and WNT5A was revealed as a novel locus for asthma exacerbations despite ICS treatment in European populations. Genes associated were related to trichostatin A, suggesting that this drug could regulate the molecular mechanisms involved in treatment response.

Pharmacogenomic associations of adverse drug reactions in asthma: systematic review and research prioritisation.

A systematic review of pharmacogenomic studies capturing adverse drug reactions (ADRs) related to asthma medications was undertaken, and a survey of Pharmacogenomics in Childhood Asthma (PiCA) consortia members was conducted. Studies were eligible if genetic polymorphisms were compared with suspected ADR(s) in a patient with asthma, as either a primary or secondary outcome. Five studies met the inclusion criteria. The ADRs and polymorphisms identified were change in lung function tests (rs1042713), adrenal suppression (rs591118), and decreased bone mineral density (rs6461639) and accretion (rs9896933, rs2074439). Two of these polymorphisms were replicated within the paper, but none had external replication. Priorities from PiCA consortia members (representing 15 institution in eight countries) for future studies were tachycardia (SABA/LABA), adrenal suppression/crisis and growth suppression (corticosteroids), sleep/behaviour disturbances (leukotriene receptor antagonists), and nausea and vomiting (theophylline). Future pharmacogenomic studies in asthma should collect relevant ADR data as well as markers of efficacy.

Correction: Pharmacogenomic associations of adverse drug reactions in asthma: systematic review and research prioritization.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Genome-wide association study of inhaled corticosteroid response in admixed children with asthma.

BACKGROUND: Inhaled corticosteroids (ICS) are the most widely prescribed and effective medication to control asthma symptoms and exacerbations. However, many children still have asthma exacerbations despite treatment, particularly in admixed populations, such as Puerto Ricans and African Americans. A few genome-wide association studies (GWAS) have been performed in European and Asian populations, and they have demonstrated the importance of the genetic component in ICS response. OBJECTIVE: We aimed to identify genetic variants associated with asthma exacerbations in admixed children treated with ICS and to validate previous GWAS findings. METHODS: A meta-analysis of two GWAS of asthma exacerbations was performed in 1347 admixed children treated with ICS (Hispanics/Latinos and African Americans), analysing 8.7 million genetic variants. Those with P ≤ 5 × 10-6 were followed up for replication in 1697 asthmatic patients from six European studies. Associations of ICS response described in published GWAS were followed up for replication in the admixed populations. RESULTS: A total of 15 independent variants were suggestively associated with asthma exacerbations in admixed populations (P ≤ 5 × 10-6 ). One of them, located in the intergenic region of APOBEC3B and APOBEC3C, showed evidence of replication in Europeans (rs5995653, P = 7.52 × 10-3 ) and was also associated with change in lung function after treatment with ICS (P = 4.91 × 10-3 ). Additionally, the reported association of the L3MBTL4-ARHGAP28 genomic region was confirmed in admixed populations, although a different variant was identified. CONCLUSIONS AND CLINICAL RELEVANCE: This study revealed the novel association of APOBEC3B and APOBEC3C with asthma exacerbations in children treated with ICS and replicated previously identified genomic regions. This contributes to the current knowledge about the multiple genetic markers determining responsiveness to ICS which could lead in the future the clinical identification of those asthma patients who are not able to respond to such treatment.

Downregulation of ABCB1 gene in patients with total hip or knee arthroplasty influences pharmacokinetics of rivaroxaban: a population pharmacokinetic-pharmacodynamic study.

PURPOSE: Rivaroxaban is a substrate for ABCB1 transporter and is commonly used in patients undergoing hip or knee replacement surgery for thromboprophylaxis. The objective of this study was to develop a population pharmacokinetic-pharmacodynamic (PK-PD) model to investigate the influence of ABCB1 gene expression and polymorphism on rivaroxaban exposure and anticoagulation effects. METHODS: Five blood samples per patient were collected during 5 days after the surgery for the determination of rivaroxaban concentration in plasma and for determination of prothrombin time and partial thromboplastin time. Non-linear mixed effects model was used for a population PK-PD analysis and for testing covariate effects. RESULTS: A one-compartment PK model with first-order absorption adequately described the pharmacokinetic data. The typical oral clearance (CL/F) was 6.12 L/h (relative standard error, 15.8%) and was associated with ABCB1 expression. Compared to base line before the surgery, a significant ABCB1 downregulation was observed 5 days after the surgery (p < 0.001). Prothrombin time and partial thromboplastin time were both linearly associated to the logarithm of the rivaroxaban plasma concentration. CONCLUSIONS: We confirmed that variable rivaroxaban CL/F is associated with ABCB1 expression, which is in accordance with previous studies on P-glycoprotein involvement in rivaroxaban PK. Furthermore, we observed the downregulation of ABCB1 expression after the surgery. The cause remains unclear and further research is needed to explain the underlying mechanisms.

Could polymorphisms of some hormonal receptor genes, involved in folliculogenesis help in predicting patient response to controlled ovarian stimulation?

PURPOSE: The aim of this study was to investigate whether single nucleotide polymorphisms (SNPs) in selected genes, responsible for hormonal regulation of folliculogenesis, are associated with response to controlled ovarian hyperstimulation (COH) and clinical characteristics of women enrolled in in vitro fertilization (IVF) programs. METHODS: In a cross-sectional study, 60 (IVF) patients underwent COH by using gonadotropin-releasing hormone (GnRH) antagonist and recombinant follicle-stimulating hormone (rFSH) protocol. Patients were classified into three groups: poor-responders (according to Bologna criteria), normo-responders (≤ 15 oocytes), and hyper-responders (> 15 oocytes). Genotyping of SNPs AMH rs10407022, AMHR rs3741664, FSHR rs1394205 and rs6166, and ESR1 rs2234693 was performed using high-resolution melting analysis (HRMA). Basal FSH (bFSH), estradiol (E2), and anti-Müllerian hormone (AMH) were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: Patients with GG genotype of FSHR rs1394205 had significantly lower AMH level (P = 0.016) and required higher rFSH dose per oocyte compared to women with AA or AG genotype (P = 0.036). We also found higher frequency of GG genotype of FSHR rs1394205 in poor- (76.5%) than in hyper-responders (37.5%, P = 0.002). Patients with AA genotype of FSHR rs6166 had higher level of measured bFSH compared to those with AG or GG genotypes (P = 0.043). Women with GG genotype of AMHR rs3741664 required higher rFSH dose in comparison with patients carrying genotypes AA or AG (P = 0.028). CONCLUSIONS: The GG genotype at position rs1394205 is associated with poor ovarian response to COH. Patients with this genotype may require higher doses of rFSH for ovulation induction.

Genetic prediction profile for adalimumab response in Slovenian Crohn's disease patients.

INTRODUCTION: Response to anti-TNF therapy is crucial for life expectancy and life quality in patients with severe Crohn's disease. We investigated if a previously reported gene expression profile predictive for infliximab response could be also applied to adalimumab response in an independent cohort. METHODS: Forty-seven Slovene Crohn's disease patients indicated for adalimumab therapy were enrolled in the study. Inflamed and non-inflamed colon biopsy samples were obtained during routine colonoscopy prior to adalimumab treatment. Response to adalimumab was measured with IBDQ. Gene expression in inflamed and non-inflamed colon biopsy samples was measured with RT-qPCR. Genotypes were extracted from previously available genotype data. Statistical analysis was performed with SPSS software. The R package e1071 was used to train bootstrap aggregated support vector machines (SVM). RESULTS: SVM prediction model analysis was used to analyze pooled, non-inflamed, and inflamed colon tissue datasets using IBDQ response after 4, 12, 20 and 30 weeks of adalimumab treatment. The bagging approach was used in an endeavor to obtain 100 % accuracy using 10 × 100 or 100 × 100 iterations. Average adalimumab response prediction accuracy is 75.5 % for pooled samples, 90.5 % for inflamed samples, and 100 % for non-inflamed samples. Moreover, models trained on selected SNPs from analyzed genes had an average accuracy of 92.8 %, confirming the involvement of genetic regions mapping the reported genes. Finally, using combined gene expression and SNP data we observed 100 % adalimumab response prediction accuracy for pooled, inflamed, and non-inflamed datasets. DISCUSSION: Our study supports the reported genetic anti-TNF response profile and extends it for adalimumab prediction.

Single Nucleotide Polymorphisms in Genes MACC1, RAD18, MMP7 and SDF-1a As Prognostic Factors in Resectable Colorectal Cancer.

BACKGROUND: Colorectal cancer (CRC) represents one of the most common malignancies worldwide. Research has indicated that functional gene changes such as single nucleotide polymorphism (SNP) influence carcinogenesis and metastasis and might have an influence on disease relapse. The aim of our study was to evaluate the role of SNPs in selected genes as prognostic markers in resectable CRC. PATIENTS AND METHODS: In total, 163 consecutive patients treated surgically for CRC of stages I, II and III at the University Medical Centre in Maribor in 2007 and 2008 were investigated. DNA was isolated from formalin-fixed paraffin-embedded CRC tissue from the Department of Pathology and SNPs in genes SDF-1a, MMP7, RAD18 and MACC1 were genotyped using polymerase chain reaction followed by high resolution melting curve analysis or restriction fragment length polymorphism. RESULTS: We found worse disease-free survival (DFS) for patients with TT genotype of SNP rs1990172 in gene MACC1 (p = 0.029). Next, we found worse DFS for patients with GG genotype for SNP rs373572 in gene RAD18 (p = 0.020). Higher frequency of genotype GG of MMP7 SNP rs11568818 was found in patients with T3/T4 stage (p = 0.014), N1/N2 stage (p = 0.041) and with lymphovascular invasion (p = 0.018). For MACC1 rs1990172 SNP we found higher frequency of genotype TT in patients with T3/T4 staging (p = 0.024). Higher frequency of genotype GG of RAD18 rs373572 was also found in patients with T1/T2 stage with disease relapse (p = 0.041). CONCLUSIONS: Our results indicate the role of SNPs as prognostic factors in resectable CRC.

Transferrin Level Before Treatment and Genetic Polymorphism in HFE Gene as Predictive Markers for Response to Adalimumab in Crohn's Disease Patients.

Tumor necrosis factor α inhibitors (anti-TNF) have improved treatment of several complex diseases, including Crohn's disease (CD). However, the effect varies and approximately one-third of the patients do not respond. Since blood parameters as well as genetic factors have shown a great potential to predict response during treatment, the aim of the study was to evaluate response to anti-TNF treatment with adalimumab (ADA) between genes HFE and TF and haematological parameters in Slovenian refractory CD patients. Single nucleotide polymorphisms (SNPs) rs1799852 in gene TF and rs2071303 in gene HFE were genotyped in 68 refractory CD patients for which response has been measured using inflammatory bowel disease questionnaire (IBDQ) index. Haematological parameters and IBDQ index were determined before therapy and after 4, 12, 20 and 30 weeks. We found novel strong association between SNP rs2071303 in gene HFE and response to ADA treatment, particularly patients with G allele comparing to A allele had better response after 20 weeks (p = 0.008). Further, we found strong association between transferrin level at baseline and treatment response after 12, 20 and 30 weeks, where average transferrin level before therapy was lower in responders (2.38 g/L) compared to non-responders (2.89 g/L, p = 0.005). Association was found between transferrin level in week 30 and SNP rs1799852 (p = 0.023), and between MCHC level before treatment and SNP rs2071303 (p = 0.007). Our results suggest that SNP in gene HFE as well as haematological markers serve as promising prognostic markers of response to anti-TNF treatment in CD patients.

Identification of ROBO2 as a Potential Locus Associated with Inhaled Corticosteroid Response in Childhood Asthma.

Inhaled corticosteroids (ICS) are the most common asthma controller medication. An important contribution of genetic factors in ICS response has been evidenced. Here, we aimed to identify novel genetic markers involved in ICS response in asthma. A genome-wide association study (GWAS) of the change in lung function after 6 weeks of ICS treatment was performed in 166 asthma patients from the SLOVENIA study. Patients with an improvement in lung function ≥8% were considered as ICS responders. Suggestively associated variants (p-value ≤ 5 × 10-6) were evaluated in an independent study (n = 175). Validation of the association with asthma exacerbations despite ICS use was attempted in European (n = 2681) and admixed (n = 1347) populations. Variants previously associated with ICS response were also assessed for replication. As a result, the SNP rs1166980 from the ROBO2 gene was suggestively associated with the change in lung function (OR for G allele: 7.01, 95% CI: 3.29-14.93, p = 4.61 × 10-7), although this was not validated in CAMP. ROBO2 showed gene-level evidence of replication with asthma exacerbations despite ICS use in Europeans (minimum p-value = 1.44 × 10-5), but not in admixed individuals. The association of PDE10A-T with ICS response described by a previous study was validated. This study suggests that ROBO2 could be a potential novel locus for ICS response in Europeans.

Determining the Molecular Background of Endometrial Receptivity in Adenomyosis.

BACKGROUND: Adenomyosis is a gynaecological condition with limited evidence of negative impact to endometrial receptivity. It is commonly associated with endometriosis, which has been shown to alter endometrial expression patterns. Therefore, the candidate genes identified in endometriosis could serve as a source to study endometrial function in adenomyosis. METHODS: Transcripts/proteins associated with endometrial receptivity in women with adenomyosis or endometriosis and healthy women were obtained from publications and their nomenclature was adopted according to the HUGO Gene Nomenclature Committee (HGNC). Retrieved genes were analysed for enriched pathways using Cytoscape/Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) and Reactome tools to prioritise candidates for endometrial receptivity. These were used for validation on women with (n = 9) and without (n = 13) adenomyosis. RESULTS: Functional enrichment analysis of 173, 42 and 151 genes associated with endometriosis, adenomyosis and healthy women, respectively, revealed signalling by interleukins and interleukin-4 and interleukin-13 signalling pathways, from which annotated LIF, JUNB, IL6, FOS, IL10 and SOCS3 were prioritised. Selected genes showed downregulated expression levels in adenomyosis compared to the control group, but without statistical significance. CONCLUSION: This is the first integrative study providing putative candidate genes and pathways characterising endometrial receptivity in women with adenomyosis in comparison to healthy women and women with endometriosis.

Carboxymethyl cellulose/diclofenac bioactive coatings on AISI 316LVM for controlled drug delivery, and improved osteogenic potential.

This work reports on the preparation and systematic testing of a novel multi-layered coating, comprised of the non-steroid anti-inflammatory drug diclofenac and biopolymer carboxymethyl cellulose. Drug release testing was performed on an Automated Transdermal Diffusion Cells Sampling System in combination with UV-VIS spectroscopy as the released drug concentration determination method. The results showed that most of the drug is released in the first six hours, whereas the overall released amount could be tailored through changes in the multi-layered coating composition. Biocompatibility tests performed on human osteoblast cells, showed cell viability improvement between 7% and 17% compared to the control sample. The expression of proteins playing important roles in extracellular matrix production and functioning was performed in order to obtain additional proof of the prepared materials' osteointegration boosting capacity. Finally, electrochemical measurements confirmed that the coatings do not influence the corrosion susceptibility of AISI 316LVM stainless steel.

Association of CCR5-delta32 mutation with reduced risk of nonatopic asthma in Slovenian children.

Asthma is one of the most common chronic diseases of childhood. Asthma results from the interaction of several genes and environmental influences. Viral infections are common triggers of asthma attacks, especially in nonatopic asthmatics. CCR5 is a chemokine receptor involved in the immune response against a number of viruses. A 32 base pair deletion (delta32) in the CCR5 receptor gene causes loss of gene function and is associated with several chronic diseases due to the resulting altered immunity. The results of the association studies exploring the role of the CCR5 receptor gene in asthma pathogenesis are contradictory. We studied 111 children aged between 5 and 18 years with mild or moderate persistent asthma; 75 of them were atopic and 36 had nonatopic asthma. We carried out allergy and spirometry tests, a bronchoprovocation test with methacholine and performed measurement of exhaled nitric oxide and genotyping for CCR5-delta32 mutation. Compared with 365 nonatopic, nonasthmatic controls we found significantly lower CCR5-delta32 allelic frequency in nonatopic asthmatics (p = 0.016, OR 0.139, 95% CI 0.02 to 0.984) but not in atopic asthmatics. CCR5-delta32 mutation protects against nonatopic asthma. This association offers new insights into the pathogenesis of an important asthma phenotype and could serve as useful information for the future research of new asthma management strategies.

Crohn's Disease Candidate Gene Alleles Predict Time to Progression from Inflammatory B1 to Stricturing B2, or Penetrating B3 Phenotype.

AIM: Crohn's disease (CD) patients are mostly diagnosed with the uncomplicated inflammatory form of disease; however, the majority will progress to complicated stricturing or penetrating disease over time. It is important to identify patients at risk for disease progression at an early stage. The aim of our study was to examine the role of 33 candidate CD genes as possible predictors of disease progression and their influence on time to progression from an inflammatory to a stricturing or penetrating phenotype. METHODS: Patients with an inflammatory phenotype at diagnosis were followed for 10 years and 33 CD-associated polymorphisms were genotyped. To test for association with CD, 449 healthy individuals were analyzed as the control group. RESULTS: Ten years after diagnosis, 39.1% of patients had not progressed beyond an inflammatory phenotype, but 60.9% had progressed to complicated disease, with average time to progression being 5.91 years. Association analyses of selected single nucleotide polymorphisms (SNPs) confirmed associations with CD for 12 SNPs. Furthermore, seven loci were associated with disease progression, out of which SNP rs4263839 in the gene TNFSF15 showed the strongest association with disease progression and the frameshift mutation rs2066847 in the gene NOD2 showed the strongest association with time to progression. CONCLUSIONS: The results of our study identified specific genetic biomarkers as useful predictors of both disease progression and speed of disease progression in patients with CD.

DNA polymorphisms predict time to progression from uncomplicated to complicated Crohn's disease.

OBJECTIVE: Most patients with Crohn's disease (CD) are diagnosed with the uncomplicated inflammatory form of the disease (Montreal stage B1). However, the majority of them will progress to complicated stricturing (B2) and penetrating (B3) CD during their lifetimes. The aim of our study was to identify the genetic factors associated with time to progression from uncomplicated to complicated CD. PATIENTS AND METHODS: Patients with an inflammatory phenotype at diagnosis were followed up for 10 years. Genotyping was carried out using Illumina ImmunoChip. After quality control, association analyses, Bonferroni's adjustments, linear and Cox's regression, and Kaplan-Meier analysis were carried out for 111 patients and Manhattan plots were constructed. RESULTS: Ten years after diagnosis, 39.1% of the patients still had the inflammatory form and 60.9% progressed to complicated disease, with an average time to progression of 5.91 years. Ileal and ileocolonic locations were associated with the complicated CD (P=1.08E-03). We found that patients with the AA genotype at single-nucleotide polymorphism rs16857259 near the gene CACNA1E progressed to the complicated form later (8.80 years) compared with patients with the AC (5.11 years) or CC (2.00 years) genotypes (P=3.82E-07). In addition, nine single-nucleotide polymorphisms (near the genes RASGRP1, SULF2, XPO1, ZBTB44, HLA DOA/BRD2, HLA DRB1/HLA DQA1, PPARA, PUDP, and KIAA1614) showed a suggestive association with disease progression (P<10). Multivariate Cox's regression analysis on the basis of clinical and genetic data confirmed the association of the selected model with disease progression (P=5.73E-16). CONCLUSION: Our study confirmed the association between the locus on chromosome 1 near the gene CACNA1E with time to progression from inflammatory to stricturing or penetrating CD. Predicting the time to progression is useful to the clinician in terms of individualizing patients' management.

Rationale and design of the multiethnic Pharmacogenomics in Childhood Asthma consortium.

AIM: International collaboration is needed to enable large-scale pharmacogenomics studies in childhood asthma. Here, we describe the design of the Pharmacogenomics in Childhood Asthma (PiCA) consortium. MATERIALS & METHODS: Investigators of each study participating in PiCA provided data on the study characteristics by answering an online questionnaire. RESULTS: A total of 21 studies, including 14,227 children/young persons (58% male), from 12 different countries are currently enrolled in the PiCA consortium. Fifty six percent of the patients are Caucasians. In total, 7619 were inhaled corticosteroid users. Among patients from 13 studies with available data on asthma exacerbations, a third reported exacerbations despite inhaled corticosteroid use. In the future pharmacogenomics studies within the consortium, the pharmacogenomics analyses will be performed separately in each center and the results will be meta-analyzed. CONCLUSION: PiCA is a valuable platform to perform pharmacogenetics studies within a multiethnic pediatric asthma population.

eQTL analysis links inflammatory bowel disease associated 1q21 locus to ECM1 gene.

Genome-wide association studies (GWAS) have been highly successful in inflammatory bowel disease (IBD) with 163 confirmed associations so far. We used expression quantitative trait loci (eQTL) mapping to analyze IBD associated regions for which causative gene from the region is still unknown. First, we performed an extensive literature search and in silico analysis of published GWAS in IBD and eQTL studies and extracted 402 IBD associated SNPs assigned to 208 candidate loci, and 9562 eQTL correlations. When crossing GWA and eQTL data we found that for 50 % of loci there is no eQTL gene, while for 31.2 % we can determine one gene, for 11.1 % two genes and for the remaining 7.7 % three or more genes. Based on that we selected loci with one, two, and three or more eQTL genes and analyzed them in peripheral blood lymphocytes and intestine tissue samples of 606 Slovene patients with IBD and in 449 controls. Association analysis of selected SNPs showed statistical significance for three (rs2631372 and rs1050152 on 5q locus and rs13294 on 1q locus) out of six selected SNPs with at least one phenotype. Furthermore, with eQTL analysis of selected chromosomal regions, we confirmed a link between SNP and gene for four (SLC22A5 on 5q, ECM1 on 1q, ORMDL3 on 17q, and PUS10 on 2p locus) out of five selected regions. For 1q21 loci, we confirmed gene ECM1 as the most plausible gene from this region to be involved in pathogenesis of IBD and thereby contributed new eQTL correlation from this genomic region.

A Prospective Pharmacogenomic Study of Crohn's Disease Patients during Routine Therapy with Anti-TNF-α Drug Adalimumab: Contribution of ATG5, NFKB1, and CRP Genes to Pharmacodynamic Variability.

Crohn's disease is often treated with the anti-tumor necrosis factor-α drug adalimumab. However, about 20%-40% of patients do not display adequate therapeutic response. We prospectively evaluated, during a routine therapy of Crohn's disease patients, the candidate autophagy-related genes ATG12 and ATG5 and the inflammation-related genes NFKB1, NFKBIA, and CRP as potential predictors of adalimumab treatment response (pharmacodynamics). The associations of haplotypes and SNPs in these genes with response to drug therapy, biochemical parameters, and body mass were determined at baseline and after 4, 12, 20, and 30 weeks of therapy. Association analysis showed that haplotypes defined with the SNPs rs9373839 and rs510432 in ATG5 gene were significantly associated with positive response to therapy (p < 0.002). In addition, allele C and genotypes CC and CT of the rs1130864 in the CRP gene were positively associated with therapeutic response (p < 0.002). To the best of our knowledge, this is the first report that supports the association of SNPs in ATG5 and CRP genes with response to adalimumab therapy in Crohn's disease. Further study of these biological pathways in larger and independent clinical samples is warranted as novel streams of research on precision medicine and diagnostics for Crohn's disease.

Single Nucleotide Polymorphisms as Prognostic and Predictive Factors of Adjuvant Chemotherapy in Colorectal Cancer of Stages I and II.

Colorectal cancer (CRC) is a highly heterogeneous disease regarding the stage at time of diagnosis and there is special attention regarding adjuvant chemotherapy in unselected patients with stage I and stage II. The clinicohistologically based TNM staging system with emphasis on histological evaluation of primary tumor and resected regional lymph nodes remains the standard of staging, but it has restricted sensitivity resulting in false downward stage migration. Molecular characteristics might predispose tumors to a worse prognosis and identification of those enables identifying patients with high risk of disease recurrence. Suitable predictive markers also enable choosing the most appropriate therapy. The current challenge facing adjuvant chemotherapy in stages I and II CRC is choosing patients with the highest risk of disease recurrence who are going to derive most benefit without facing unnecessary adverse effects. Single nucleotide polymorphisms (SNPs) are one of the potential molecular markers that might help us identify patients with unfavorable prognostic factors regarding disease initiation and recurrence and could determine selection of an appropriate chemotherapy regimen in the adjuvant and metastatic setting. In this paper, we discuss SNPs of genes involved in the multistep processes of cancerogenesis, metastasis, and the metabolism of chemotherapy that might prove clinically significant.