The TNF/ADAM 17 system: implication of an ADAM 17 haplotype in the clinical response to infliximab in Crohn's disease

Genetic Polymorphisms on TNFA, TNFRSF1A, and TNFRSF1B Genes Predict the Effectiveness of Anti-TNF-α Treatment in Inflammatory Bowel Disease Patients

Background/Objectives: Tumor necrosis factor alpha (TNF-α) is the key inflammatory cytokine involved in the pathogenesis of inflammatory bowel diseases (IBDs). Anti-TNF-α therapy has been successfully used for IBD treatment, although the therapeutic response differs among patients due to the genetic background. The aim of this study was to investigate whether the presence of single nucleotide polymorphisms (SNPs) on TNFA, TNFRSF1A, and TNFRSF1B genes could affect anti-TNF-α treatment effectiveness in IBD patients. Methods: In this prospective cohort study, 83 European IBD patients treated with infliximab or adalimumab (with or without steroid bridge therapy) as first-line therapy were enrolled. Genomic DNA was extracted from peripheral blood, and TNF-α (rs1800629, rs361525, rs1799724), TNFRSF1A (rs767455), and TNFRSF1B (rs1061622, rs1061624, rs3397, rs976881) SNPs were assessed. Steroid-free remission (SFR) (clinical remission together with steroid interruption) and anti-TNF-α therapy persistence after 12 months of follow-up were evaluated. Patients who stopped anti-TNF-α therapy before the end of follow-up, due to side effects or treatment failure, were defined as discontinuers. Results: A higher frequency of the G/G genotype in rs1800629 and the A/A genotype in rs1061624 was observed in the SFR group compared to non-SFR (97.7% vs. 82.8%; p = 0.025 and 32.6% vs. 10.3%; p = 0.029, respectively). Moreover, carriers of the A/A genotype in rs361525 and the C/C genotype in rs767455 had a lower probability of achieving SFR than wild-type patients (OR = 0.14; 95% CI= 0.03-0.69; p = 0.016 and OR = 0.10; 95% CI = 0.02-0.60; p = 0.012, respectively). Furthermore, an increased frequency of rs1800629 A allele was observed in patients who discontinued treatment compared to completers (27.3% vs. 6.9%; p = 0.033), as well as a high risk of interrupting therapy (HR = 6.47; 95% CI = 1.15-36.38). Conclusions: These results suggest that the evaluation of SNPs in TNF-α, TNFR1A, and TNFR1B genes could improve the management of IBD, leading to more effective, individualized treatment plans and a reduction in healthcare costs associated with ineffective therapies and disease complications.

Pharmacogenetics in Response to Biological Agents in Inflammatory Bowel Disease: A Systematic Review

Inflammatory bowel diseases (IBDs) are chronic inflammatory disorders influenced by microbial, environmental, genetic, and immune factors. The introduction of biological agents has transformed IBD therapy, improving symptoms, reducing complications, and enhancing patients' quality of life. However, approximately 30% of patients exhibit primary non-response, and 50% experience a loss of response over time. Genetic and non-genetic factors contribute to variability in treatment outcomes. This systematic review aims to thoroughly analyze and assess existing studies exploring the relationships between genetic variations and individual responses to biologic drugs, in order to identify genetic markers that are predictive of treatment efficacy, risk of adverse effects, or drug toxicity, thereby informing clinical practice and guiding future research. PubMed and EMBASE papers were reviewed by three independent reviewers according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses [PRISMA] guidelines. Of the 883 records screened, 99 met the inclusion criteria. The findings of this review represent an initial step toward personalized medicine in IBD, with the potential to improve clinical outcomes in biological therapy.

The Association between Genetics and Response to Treatment with Biologics in Patients with Psoriasis, Psoriatic Arthritis, Rheumatoid Arthritis, and Inflammatory Bowel Diseases: A Systematic Review and Meta-Analysis

Genetic biomarkers could potentially lower the risk of treatment failure in chronic inflammatory diseases (CID) like psoriasis, psoriatic arthritis (PsA), rheumatoid arthritis (RA), and inflammatory bowel disease (IBD). We performed a systematic review and meta-analysis assessing the association between single nucleotide polymorphisms (SNPs) and response to biologics. Odds ratio (OR) with 95% confidence interval (CI) meta-analyses were performed. In total, 185 studies examining 62,774 individuals were included. For the diseases combined, the minor allele of MYD88 (rs7744) was associated with good response to TNFi (OR: 1.24 [1.02-1.51], 6 studies, 3158 patients with psoriasis or RA) and the minor alleles of NLRP3 (rs4612666) (OR: 0.71 [0.58-0.87], 5 studies, 3819 patients with RA or IBD), TNF-308 (rs1800629) (OR: 0.71 [0.55-0.92], 25 studies, 4341 patients with psoriasis, RA, or IBD), FCGR3A (rs396991) (OR: 0.77 [0.65-0.93], 18 studies, 2562 patients with psoriasis, PsA, RA, or IBD), and TNF-238 (rs361525) (OR: 0.57 [0.34-0.96]), 7 studies, 818 patients with psoriasis, RA, or IBD) were associated with poor response to TNFi together or infliximab alone. Genetic variants in TNFα, NLRP3, MYD88, and FcRγ genes are associated with response to TNFi across several inflammatory diseases. Most other genetic variants associated with response were observed in a few studies, and further validation is needed.

Single nucleotide polymorphisms in ADAM17, IL23R and SLCO1C1 genes protect against infliximab failure in adults with Crohn's disease

BACKGROUND

To predict primary failure of infliximab (IFX) therapy in Crohn's disease (CD) and to identify patients who maintain long-term effectiveness to IFX is currently not feasible. Some genetic variations are proposed as potential biomarkers.

AIM

We assessed a set of single nucleotide polymorphisms (SNPs) in genes related to the IFX mechanism of action and the presence of HLA-DQA1 * 05 allele on the primary response and long-term durability in CD patients.

METHODS

A multi-centre cross-sectional study of IFX-exposed adult patients with CD was undertaken. Treatment persistence and time to failure were co-primary endpoints. DNA from the 131 patients was genotyped. Association between SNPs and clinical variables with IFX persistence was assessed.

RESULTS

Failure to IFX was documented in 65 (49.6%) out of 131 patients. IFX persistence was associated either with carrying the TT genotype in ADAM17 rs10929587 (ORa=0.2; 95%CI=0.1-0.8; p = 0.021), or the CC genotype in SLCO1C1 rs3794271 (ORa=0.2; 95%CI=0.1-0.7; p = 0.008), according to multivariate logistic regression. In contrast, previous bowel resection increased the risk of IFX failure (ORa=2.8; 95%CI=1.1-7.3; p = 0.025). Cox regression analysis confirmed these findings and also identified IL23R rs10489629-TT (HRa 0.41; 95%CI=0.22-0.75; p = 0.004) and concomitant immunosuppressants (HRa 0.46; 95%CI=0.27-0.77; p = 0.003) as protection from IFX failure. However, no association between HLA-DQA1 * 05 allele and persistence of IFX therapy was found, with similar failure rates among carriers and non-carriers (52.8% vs. 47.4%, respectively; p = 0.544).

CONCLUSIONS

SNPs rs10929587-TT in ADAM17, rs10489629-TT in IL23R and rs3794271-CC in SLCO1C1, together with no previous bowel surgery and concomitant immunosuppression, were identified as protection from failure to IFX.

Pharmacogenetics of Biological Agents Used in Inflammatory Bowel Disease: A Systematic Review

Inflammatory Bowel Disease (IBD) comprises a group of disorders, in particular Crohn's disease (CD) and ulcerative colitis (UC), characterized by chronic inflammation affecting the gastrointestinal tract. The treatment of these conditions is primarily based on anti-inflammatory drugs, although the use of biological drugs with lower side effects quickly increased in the last decade. However, the presence of certain polymorphisms in the population may determine a different outcome in response to therapy, reflecting the heterogeneity of the efficacy in patients. Considering that several studies showed important correlations between genetic polymorphisms and response to biological treatments in IBD patients, this systematic review aims to summarize the pharmacogenetics of biologicals approved for IBD, thus highlighting a possible association between some polymorphisms and drug response. With this purpose, we reviewed PubMed papers published over the past 21 years (2000-2021), using as the search term "drug name and IBD or CD or UC and polymorphisms" to underline the role of pharmacogenetic tests in approaching the disease with a targeted therapy.

Pharmacogenetics of inflammatory bowel disease

Patients with inflammatory bowel disease (IBD) show large variability in disease course, and also treatment response. The variability in treatment response has led to many initiatives in search of genetic markers to optimize treatment and avoid severe side effects. This has been very successful for thiopurines, one of the drugs used to induce and maintain remission in IBD. However, for the newer treatment options for IBD, like biologicals, the search for genetic predictors has not yielded any candidate biomarkers with clinical utility. In this review, a summary of recent advances in pharmacogenetics focusing on thiopurines and anti-TNF agents is given.

Predictors of Primary Response to Biologic Treatment [Anti-TNF, Vedolizumab, and Ustekinumab] in Patients With Inflammatory Bowel Disease: From Basic Science to Clinical Practice

BACKGROUND

Inflammatory bowel diseases [IBD]-ulcerative colitis and Crohn's disease-are commonly treated with biologic drugs. However, only approximately two-thirds of patients have an initial response to these therapies. Personalised medicine has the potential to optimise efficacy, decrease the risk of adverse drug events, and reduce costs by establishing the most suitable therapy for a selected patient.

AIM

The present study reviews the potential predictors of short-term primary response to biologic treatment, including not only anti-tumour necrosis factor [TNF] agents [such as infliximab, adalimumab, certolizumab, and golimumab] but also vedolizumab and ustekinumab.

METHODS

We performed a systematic bibliographical search to identify studies investigating predictive factors of response to biologic therapy.

RESULTS

For anti-TNF agents, most of the evaluated factors have not demonstrated usefulness, and many others are still controversial. Thus, only a few factors may have a potential role in the prediction of the response, including disease behaviour/phenotype, disease severity, C-reactive protein, albumin, cytokine expression in serum, previous anti-TNF therapy, some proteomic markers, and some colorectal mucosa markers. For vedolizumab, the availability of useful predictive markers seems to be even lower, with only some factors showing a limited value, such as the expression of α4β7 integrin in blood, the faecal microbiota, some proteomic markers, and some colorectal mucosa markers. Finally, in the case of ustekinumab, no predictive factor has been reported yet to be helpful in clinical practice.

CONCLUSION

In summary, currently no single marker fulfils all criteria for being an appropriate prognostic indicator of response to any biologic treatment in IBD.

<p>ADAM17 Genetic Variants and the Response of TNF-α Inhibitor in Rheumatoid Arthritis Patients</p>

Purpose

TNF-α is a transmembrane protein which requires cleavage by ADAM17 in order to act systemically. The activation of ADAM17 to generate soluble TNF‑α results in an increased inflammatory activity. We hypothesized that variants spanning the ADAM17 gene contribute towards the observed variation in patient response defined by the number of changes in TNF‑α inhibitors.

Patients and Methods

Seven single-nucleotide polymorphisms (SNPs) of ADAM17 in 63 patients with rheumatoid arthritis who received TNF-α inhibitors were analyzed: rs57467365, rs62117540, rs117645314, rs6432013, rs532704607, rs117179141, and rs12692386. Univariate and multivariate regression analysis were employed to investigate the independent predictable factors for changes in TNF-α inhibitors.

Results

ADAM17 rs117645314 and rs117179141 showed significant association with the number of changes in TNF-α inhibitors. Patients with GA in rs117645314 and AT in rs117179141 had significantly higher chance of two or more changes of TNF-α inhibitors than those with wild homozygous alleles. Multivariate analysis showed that rs117179141 explained 5.7% of the 23.8% variability in TNF-α inhibitor response.

Conclusion

This study showed that the number of changes in TNF-α inhibitor is associated with ADAM17 SNPs.

Pre-Treatment Biomarkers of Anti-Tumour Necrosis Factor Therapy Response in Crohn's Disease-A Systematic Review and Gene Ontology Analysis

The most prominent treatment for the serious cases of Crohn’s disease (CD) are biological tumour necrosis factor (TNF) inhibitors. Unfortunately, therapy nonresponse is still a serious issue in ~1/3 of CD patients. Accurate prediction of responsiveness prior to therapy start would therefore be of great value. Clinical predictors have, however, proved insufficient. Here, we integrate genomic and expression data on potential pre-treatment biomarkers of anti-TNF nonresponse. We show that there is almost no overlap between genomic (annotated with tissue-specific expression quantitative trait loci data) and transcription (RNA and protein data) biomarkers. Furthermore, using interaction networks we demonstrate there is little direct interaction between the proposed biomarkers, though a majority do have common interactors connecting them into networks. Our gene ontology analysis shows that these networks have roles in apoptotic signalling, response to oxidative stress and inflammation pathways. We conclude that a more systematic approach with genome-wide search of genomic and expression biomarkers in the same patients is needed in future studies.

Pharmacogenetics of treatments for inflammatory bowel disease

Inflammatory bowel disease is a chronic inflammation of the gut whose pathogenesis is still unclear. Although no curative therapy is currently available, a number of drugs are used in induction and maintenance therapy; however, for most of these drugs, a high inter-individual variability in response is observed. Among the factors of this variability, genetics plays an important role. Areas covered: This review summarizes the results of pharmacogenetic studies, considering the most important drugs used and in particular aminosalycilates, glucocorticoids, thiopurines, monoclonal antibodies and thalidomide. Most studies used a candidate gene approach, even if significant breakthroughs have been obtained recently from applying genome-wide studies. When available, also investigations considering epigenetics and pharmacogenetic dosing guidelines have been included. Expert opinion: Only for thiopurines, genetic markers identified as predictors of efficacy or adverse events have allowed the development of dosing guidelines. For the other drugs, encouraging results are available and great expectations rely on the study of epigenetics and integration with pharmacokinetic information, especially useful for biologics. However, to improve therapy of IBD patients with these drugs, for implementation in the clinics of pharmacogenetics, informatic clinical decision support systems and training about pharmacogenetics of health providers are needed.

Long-range PCR libraries and next-generation sequencing for pharmacogenetic studies of patients treated with anti-TNF drugs

Biological therapy with anti-tumor necrosis factor-α (anti-TNF-α) monoclonal antibodies significantly increased the effectiveness of autoimmune disease treatment compared with conventional medicines. However, anti-TNF-α drugs are relatively expensive and a response to the therapy is reported in only 60-70% of patients. Moreover, in up to 5% of patients adverse drug reactions occur. The various effects of biological treatment may be a potential consequence of interindividual genetic variability. Only a few studies have been conducted in this field and which refer to single gene loci. Our aim was to design and optimize a methodology for a broader application of pharmacogenetic studies in patients undergoing anti-TNF-α treatment. Based on the current knowledge, we selected 16 candidate genes: TNFRSF1A, TNFRSF1B, ADAM17, CASP9, FCGR3A, LTA, TNF, FAS, IL1B, IL17A, IL6, MMP1, MMP3, S100A8, S100A9, and S100A12, which are potentially involved in the response to anti-TNF-α therapy. As a research model, three DNA samples from Crohn's disease (CD) patients were used. Targeted genomic regions were amplified in 23 long-range (LR) PCR reactions and after enzymatic fragmentation amplicon libraries were prepared and analyzed by next-generation sequencing (NGS). Our results indicated 592 sequence variations located in all fragments with coverage range of 5-1089. We demonstrate a highly sensitive, flexible, rapid, and economical approach to the pharmacogenetic investigation of anti-TNF-α therapy using amplicon libraries and NGS technology.

Pharmacogenetics of inflammatory bowel disease: a focus on Crohn's disease

Crohn's disease is an inflammatory bowel disease showing a high heterogeneity in phenotype and a strong genetic component. The treatment is complex, due to different severity of clinical parameters and to the fact that therapies only permit to control symptoms and to induce remission for short periods. Moreover, all categories of drugs present a great interindividual variability both in terms of efficacy and side effects appearance. For this reason, the identification of specific genomic biomarkers involved in drugs response will be of great clinical utility in order to foresee drug's efficacy and to prevent adverse reactions, permitting a more personalized therapeutic approach. In this review, we focus the attention on the pharmacogenetic studies regarding drugs commonly utilized in Crohn's disease treatment.

Systematic review: genetic biomarkers associated with anti-TNF treatment response in inflammatory bowel diseases

BACKGROUND

Personalised medicine, including biomarkers for treatment selection, may provide new algorithms for more effective treatment of patients. Genetic variation may impact drug response and genetic markers could help selecting the best treatment strategy for the individual patient.

AIM

To identify polymorphisms and candidate genes from the literature that are associated with anti-tumour necrosis factor (TNF) treatment response in patients with inflammatory bowel diseases (IBD), Crohn's disease (CD) and ulcerative colitis.

METHODS

We performed a PubMed literature search and retrieved studies reporting original data on association between polymorphisms and anti-TNF treatment response and conducted a meta-analysis.

RESULTS

A functional polymorphism in FCGR3A was significantly associated with anti-TNF treatment response among CD patients using biological response criterion (decrease in C-reactive protein, levels). Meta-analyses showed that polymorphisms in TLR2 (rs3804099, OR (95% CI) = 2.17 (1.35-3.47)], rs11938228 [OR = 0.64 (0.43-0.96)], TLR4 (rs5030728) [OR = 3.18 (1.63-6.21)], TLR9 (rs352139) [OR = 0.43 (0.21-0.88)], TNFRSF1A (rs4149570) [OR = 2.06 (1.02-4.17)], IFNG (rs2430561) [OR = 1.66 (1.05-2.63)], IL6 (rs10499563) [OR = 1.65 (1.04-2.63)] and IL1B (rs4848306) [OR = 1.88 (1.05-3.35)] were significantly associated with response among IBD patients using clinical response criteria. A positive predictive value of 0.96 was achieved by combining five genetic markers in an explorative analysis.

CONCLUSIONS

There are no genetic markers currently available which are adequately predictive of anti-TNF response for use in the clinic. Genetic markers bear the advantage that they do not change over time. Therefore, hypothesis-free approaches, testing a large number of polymorphisms in large, well-characterised cohorts, are required in order to identify genetic profiles with larger effect sizes, which could be employed as biomarkers for treatment selection in clinical settings.

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.

Current stage in inflammatory bowel disease: What is next?

In recent years, the incidence of inflammatory bowel disease (IBD) has been on the rise, extending to countries where it was infrequent in the past. As a result, the gap between high and low incidence countries is decreasing. The disease, therefore, has an important economic impact on the healthcare system. Advances in recent years in pharmacogenetics and clinical pharmacology have allowed for the development of treatment strategies adjusted to the patient profile. Concurrently, new drugs aimed at inflammatory targets have been developed that may expand future treatment options. This review examines advances in the optimization of existing drug treatments and the development of novel treatment options for IBD.

Role for therapeutic drug monitoring during induction therapy with TNF antagonists in IBD: evolution in the definition and management of primary nonresponse

: Primary nonresponse and primary nonremission are important limitations of tumor necrosis factor (TNF) antagonists, occurring in 10% to 40% and 50% to 80% of patients with inflammatory bowel disease, respectively. The magnitude of primary nonresponse differs between phase III clinical trials and cohort studies, indicating differences, e.g., in definition, patient population or blinding. The causes of nonresponse can be attributed to the drug (pharmacokinetics, immunogenicity), the patient (genetics, disease activity), the disease (type, location, severity), and/or the treatment strategy (dosing regimen, combination therapy). Primary nonresponse has been attributed to "non-TNF-driven disease" which is an overly simplified and potentially misleading approach to the problem. Many patients with primary nonresponse could successfully be treated with dose optimization during the induction phase or switching to another TNF antagonist. Therefore, primary nonresponse is frequently not a non-TNF-driven disease. Recent studies from rheumatoid arthritis and preliminary data from inflammatory bowel disease evaluating therapeutic drug monitoring have suggested that early measurement of drug and anti-drug antibody concentrations could help to define primary nonresponse and rationalize patient management of this problem. Moreover, a modeling approach including pharmacological parameters and patient-related covariants could potentially be predictive for response to the treatment. We describe an overview of this evolution in thinking, underpinned by previous findings, and assess the potential role of early measurement of drug and antidrug antibody concentrations in the definition and management of primary nonresponse.

Genetic polymorphism in ATG16L1 gene influences the response to adalimumab in Crohn's disease patients

AIM

To see if SNPs could help predict response to biological therapy using adalimumab (ADA) in Crohn's disease (CD).

MATERIALS & METHODS

IBDQ index and CRP levels were used to monitor therapy response. We genotyped 31 CD-associated genes in 102 Slovenian CD patients.

RESULTS

The strongest association for treatment response defined as decrease in CRP levels was found for ATG16L1 SNP rs10210302. Additional SNPs in 7 out of 31 tested CD-associated genes (PTGER4, CASP9, IL27, C11orf30, CCNY, IL13, NR1I2) showed suggestive association with ADA response.

CONCLUSION

Our results suggest ADA response in CD patients is genetically predisposed by SNPs in CD risk genes and suggest ATG16L1 as most promising candidate gene for drug response in ADA treatment. Original submitted 24 September 2014; Revision submitted 1 December 2014.

Strain-induced differentiation of fetal type II epithelial cells is mediated via the integrin α6β1-ADAM17/tumor necrosis factor-α-converting enzyme (TACE) signaling pathway

Mechanical forces are critical for normal fetal lung development. However, the mechanisms regulating this process are not well-characterized. We hypothesized that strain-induced release of HB-EGF and TGF-α is mediated via integrin-ADAM17/TACE interactions. Employing an in vitro system to simulate mechanical forces in fetal lung development, we showed that mechanical strain of fetal epithelial cells actives TACE, releases HB-EGF and TGF-α, and promotes differentiation. In contrast, in samples incubated with the TACE inhibitor IC-3 or in cells isolated from TACE knock-out mice, mechanical strain did not release ligands or promote cell differentiation, which were both rescued after transfection of ADAM17. Cell adhesion assay and co-immunoprecipitation experiments in wild-type and TACE knock-out cells using several TACE constructs demonstrated not only that integrins α6 and β1 bind to TACE via the disintegrin domain but also that mechanical strain enhances these interactions. Furthermore, force applied to these integrin receptors by magnetic beads activated TACE and shed HB-EGF and TGF-α. The contribution of integrins α6 and β1 to differentiation of fetal epithelial cells by strain was demonstrated by blocking their binding site with specific antibodies and by culturing the cells on membranes coated with anti-integrin α6 and β1 antibodies. In conclusion, mechanical strain releases HB-EGF and TGF-α and promotes fetal type II cell differentiation via α6β1 integrin-ADAM17/TACE signaling pathway. These investigations provide novel mechanistic information on how mechanical forces promote fetal lung development and specifically differentiation of epithelial cells. This information could be also relevant to other tissues exposed to mechanical forces.

Current relevance of pharmacogenetics in immunomodulation treatment for Crohn's disease

No drug therapy is completely risk free, and the costs associated with non-response and adverse effects can exceed the cost of the therapy. The ultimate goal of pharmacogenetic research is to find robust genetic predictors of drug response that enable the development of prospective genetic tests to reliably identify patients at risk of non-response or of developing an adverse effect prior to the drug being prescribed. Currently, thiopurine S-methyltransferase (TPMT) deficiency is the only pharmacogenetic factor that is prospectively assessed before azathioprine or 6-mercaptopurine immunomodulation is commenced in patients with Crohn's disease (CD). As yet no other inherited determinant of drug response has made the transition from bench to bedside for the management of this disease. In this review we summarize what is known about TPMT deficiency and explore whether there is evidence to support a role of other genetic polymorphisms in predicting the response of CD patients to thiopurine drugs, methotrexate, and anti-tumor necrosis factor α (TNFα) therapy.

Profiles of circulating cytokines in patients with Crohn's disease under maintenance therapy with infliximab

BACKGROUND AND AIMS

The effects of maintenance infliximab for Crohn's disease vary widely among patients. The aim of this study was to examine the cytokine profiles and to identify possible markers predictive of therapeutic effect of maintenance infliximab.

METHODS

Cytokine profiles of 35 Crohn's disease patients under maintenance infliximab therapy were analyzed prospectively. Blood samples were obtained prior to, and 2 and 6 weeks after infliximab infusion. Circulating cytokine values of interleukin (IL)-23, IL-17A, IL-12, IL-6, interferon gamma (IFN-γ), and tumor necrosis factor alpha (TNF-α) were compared according to the disease activity and therapeutic efficacy. Patients were classified into either the active or quiescent phase according to their disease activity at baseline. Patients were also divided into a sustained response group and non-sustained response group according to therapeutic efficacy of infliximab determined 2 and 6 weeks after infliximab infusion.

RESULTS

At baseline, serum levels of IL-23 (p<0.05), IL-17A (p<0.01), IFN-γ (p<0.05), and IL-6 (p<0.01) were significantly higher in active Crohn's disease than in quiescent disease. These cytokine levels remained unchanged during the follow-up period. When serum cytokine levels were compared between groups classified by therapeutic efficacy of infliximab, patients in the non-sustained response group had a significantly higher level of serum IL-17A than those in the sustained response group (p<0.05). There were also trends toward higher serum IL-23 and IL-12 in the former than in the latter.

CONCLUSION

Higher levels of IL-17A, IL-23, and IL-12 at baseline may be predictive markers for poor therapeutic response to maintenance infliximab therapy.

Interleukin-15 and its soluble receptor mediate the response to infliximab in patients with Crohn's disease

BACKGROUND & AIMS

Infliximab is a monoclonal antibody against tumor necrosis factor that is used to treat patients with inflammatory bowel disease. We investigated serum levels and cellular expression of interleukin (IL)-15 and its receptor (sIL-15Ralpha) in patients with Crohn's disease (CD) treated with infliximab; and the effect on sIL-15Ralpha secretion by epithelial cells.

METHODS

CD patients were given infliximab (n = 40; 3 infusions); 37 healthy controls were studied. Serum levels of IL-15, sIL-15Ralpha, and complex were determined by radioimmunoassay and cytokine levels by enzyme-linked immunosorbent assay. IL-15Ralpha and A Desintegrin and Metalloproteinase 17 levels were assessed by immunohistochemistry. Epithelial cell lines (HT-29 and Caco-2) were cultured with infliximab, adalimumab, or etanercept. Patients were classified as responders and nonresponders according to their Crohn's Disease Activity Index and clinical observations.

RESULTS

Before infliximab, IL-15 was higher in responders than in controls and nonresponders. After infliximab, IL-15 decreased in responders while remaining stable in nonresponders. sIL-15Ralpha and IL-15/sIL-15Ralpha complex levels were higher in CD than in controls and increased only in responders after infliximab. IL-15Ralpha and A Desintegrin and Metalloproteinase 17 colocalized in epithelial cells and were higher in CD patients. In vitro, infliximab but not adalimumab and etanercept induced sIL-15Ralpha secretion by epithelial cells.

CONCLUSIONS

Serum level of sIL-15Ralpha and the IL-15/sIL-15Ralpha complex increased in responder patients and the response was associated with a decrease of IL-15. Infliximab induced the release of the IL-15 receptor alpha, suggesting a specific modulation of IL-15 and its soluble receptor by reverse signaling through transmembrane tumor necrosis factor alpha.

Pharmacogenomics in the treatment of inflammatory bowel disease

In recent years, the benefits of early aggressive treatment paradigms for inflammatory bowel disease have emerged. Symptomatic improvement is no longer considered adequate; instead, the aim of treatment has become mucosal healing and altered natural history. Nonetheless, we still fail to achieve these end points in a large number of our patients. There are many reasons why patients fail to respond or develop toxicity when exposed to drugs used for inflammatory bowel disease, but genetic variation is likely to account for a significant proportion of this. Some examples, notably thiopurine methyltransferase polymorphism in thiopurine treatment, are already established in clinical practice. We present a review of the expanding literature in this field, highlighting many interesting developments in pharmacogenomics applied to inflammatory bowel disease and, where possible, providing guidance on the translation of these developments into clinical practice.

Regulation of mature ADAM17 by redox agents for L-selectin shedding

L-selectin is constitutively expressed by neutrophils and plays a key role in directing these cells to sites of inflammation. Upon neutrophil activation, L-selectin is rapidly and efficiently down-regulated from the cell surface by ectodomain shedding. We have directly shown that A disintegrin and metalloprotease 17 (ADAM17) is a primary and nonredundant sheddase of L-selection by activated neutrophils in vivo. Following cell activation, intracellular signals lead to the induction of ADAM17's enzymatic activity; however, the target of this inducer mechanism remains unclear. Our study provides evidence of an activation mechanism that involves the extracellular region of the mature form of cell surface ADAM17 and not its intracellular region. We demonstrate that the catalytic activity of purified ADAM17 lacking a prodomain and its intracellular region is diminished under mild reducing conditions by DTT and enhanced by H(2)O(2) oxidation. Moreover, H(2)O(2) reversed ADAM17 inhibition by DTT. The treatment of neutrophils with H(2)O(2) also induced L-selectin shedding in an ADAM17-dependent manner. These findings suggest that thiol-disulfide conversion occurring in the extracellular region of ADAM17 may be involved in its activation. An analysis of ADAM17 revealed that within its disintegrin/cysteine-rich region are two highly conserved, vicinal cysteine sulfhydryl motifs (cysteine-X-X-cysteine), which are well-characterized targets for thiol-disulfide exchange in various other proteins. Using a cell-based ADAM17 reconstitution assay, we demonstrate that the cysteine-X-X-cysteine motifs are critical for L-selectin cleavage. Taken together, our findings suggest that reduction-oxidation modifications of cysteinyl sulfhydryl groups in mature ADAM17 may serve as a mechanism for regulating the shedding of L-selectin following neutrophil stimulation.

Pharmacogenetics of Crohn’s disease

The considerable interindividual differences in efficacy and side effects of commonly used medications in Crohn’s disease are partly owing to genetic polymorphisms. Many genetic variants have been studied in genes possibly involved in the metabolism or mechanism of action of therapeutic agents such as glucocorticosteroids, azathioprine/6-mercaptopurine, methotrexate, calcineurin inhibitors or anti-TNF agents. However, the only test translated into clinical practice is thiopurine S-methyltransferase (TPMT) genotyping for hematological toxicity of thiopurine treatment. To date, there are no other meaningful applications for pharmacogenomics in clinical practice of Crohn’s disease. In the future, designed therapeutic trials should possibly permit the development of predictive models including genotypic markers, such as that proposed for the clinical outcome after infliximab therapy, which includes an apoptotic pharmacogenetic index. The recent identification of new susceptibility genes provides additional candidate markers that have possible effects on the outcomes of therapies, and prioritizes new therapeutic targets, such as the IL-23 pathway. Futher innovative approaches might be relevant for the pharmacogenetic investigation of gene variants implied in innate immune pattern recognition and autophagy.

Proteomics for prediction and characterization of response to infliximab in Crohn's disease: a pilot study

OBJECTIVES

Infliximab is the first anti-TNFalpha accepted by the Food and Drug Administration for use in inflammatory bowel disease treatment. Few clinical, biological and genetic factors tend to predict response in Crohn's disease (CD) patient subcategories, none widely predicting response to infliximab.

DESIGN AND METHODS

Twenty CD patients showing clinical response or non response to infliximab were used for serum proteomic profiling on Surface Enhanced Lazer Desorption Ionisation-Time of Flight-Mass Spectrometry (SELDI-TOF-MS), each before and after treatment. Univariate and multivariate data analysis were performed for prediction and characterization of response to infliximab.

RESULTS

We obtained a model of classification predicting response to treatment and selected relevant potential biomarkers, among which platelet aggregation factor 4 (PF4). We quantified PF4, sCD40L and IL-6 by ELISA for correlation studies.

CONCLUSIONS

This first proteomic pilot study on response to infliximab in CD suggests association between platelet metabolism and response to infliximab and requires validation studies on a larger cohort of patients.

Pharmacogenomics in gastrointestinal disorders

It is anticipated that unraveling the human genome will have a direct impact on the management of specific diseases. Variations or mutations in genes involved in drug metabolism or disease pathophysiology in gastroenterology and hepatology are expected to have effect on response to therapy. The spectrum of diseases is vast. Thus, we focus this review on clinical pharmacogenetics of inflammatory bowel disease, Helicobacter pylori infections, gastroesophageal reflux disease, irritable bowel syndrome, liver transplantation, and colon cancer. Although only a few genotyping tests are used regularly in clinical practice, we anticipate that in the future there will be more routine use of many of the tests described in this review.

The genetics of inflammatory bowel disease

Great progress in the understanding of the molecular genetics of inflammatory bowel disease (IBD) has been made over the last 10 years. Strong epidemiological evidence, based initially on concordance data in twin/family studies, led to the application of genome-wide linkage analysis involving multiply affected families and the identification of a number of susceptibility loci. Further characterization of the IBD1 locus on chromosome 16 led to the discovery of the NOD2/CARD15 gene as the first susceptibility gene in Crohn's disease for 2001. This landmark finding has led to a redirection of basic research in IBD with interest focused principally on regulation of the innate immune response and mucosal barrier function. Within the last year, the use of genome-wide association studies has provided new insights into primary pathogenetic mechanisms; several new genes such as the Interleukin-23 receptor (IL23R) and ATG16L1 (autophagy-related 16-like 1) genes are strongly implicated. Overall, these studies promise to change our fundamental understanding of IBD pathophysiology and to have implications for clinical practice.

Clinical pharmacokinetics and use of infliximab

Tumor necrosis factor-alpha (TNFalpha) is a key proinflammatory cytokine involved in chronic inflammatory diseases. Infliximab, a chimeric (human-murine) monoclonal IgG1 anti-TNFalpha antibody, is used in the treatment of Crohn's disease (including fistulising disease) and rheumatoid arthritis (in combination with methotrexate) if standard treatments have failed. The indications for infliximab have recently been expanded to include ankylosing spondylitis, psoriatic arthritis, psoriasis and ulcerative colitis. The biological agent infliximab is given by multiple intravenous infusions in a dosage of 3-5 mg/kg (initially at weeks 0, 2 and 6; subsequently in intervals of 4-8 weeks). In controlled trials, clinical response rates of 20-40% have been achieved with such regimens in Crohn's disease and rheumatoid arthritis. However, the therapeutic benefits must be balanced against the risks of a variety of severe adverse events (e.g. severe infections including tuberculosis, hepatotoxicity, infusion reactions, serum sickness-like disease and lymphoma). Following single and multiple infusions of infliximab, no relevant differences in median concentration-time profiles have been observed between patients with Crohn's disease, patients with rheumatoid arthritis and patients with psoriasis. The apparent volume of distribution of the high-molecular-weight infliximab (149.1 kDa) is low (3-6L) and represents the intravascular space. The long persistence in this compartment (elimination half-life 7-12 days, mean residence time 12-17 days) is due to the very low systemic clearance of about 11-15 mL/hour (0.18-0.25 mL/minute). Elimination of infliximab is most probably accomplished through degradation by unspecific proteases. During multiple infusions (every 4-8 weeks), no accumulation was observed, and serum concentrations and the area under the plasma concentration-time curve of infliximab increased in proportion to the infused dose, indicating linear pharmacokinetics. Co-medication with methotrexate delayed the decline in the serum concentrations of infliximab. When relating serum concentrations to the clinical response in patients with rheumatoid arthritis and patients with Crohn's disease, it can be assumed that trough concentrations above 1 microg/mL could be used as a kind of therapeutic target. In the future, identification of biomarkers for (non-)response and risk factors for adverse drug reactions would be very helpful. Furthermore, combined biological, pharmacokinetic, pharmacogenomic and clinical studies have not yet been performed and are needed to optimise the therapeutic potential of infliximab, which is currently established as a rescue treatment in refractory patients.