Laurence J. Egan

IKKβ Links Inflammation and Tumorigenesis in a Mouse Model of Colitis-Associated Cancer

A link between inflammation and cancer has long been suspected, but its molecular nature remained ill defined. A key player in inflammation is transcription factor NF-kappaB whose activity is triggered in response to infectious agents and proinflammatory cytokines via the IkappaB kinase (IKK) complex. Using a colitis-associated cancer model, we show that although deletion of IKKbeta in intestinal epithelial cells does not decrease inflammation, it leads to a dramatic decrease in tumor incidence without affecting tumor size. This is linked to increased epithelial apoptosis during tumor promotion. Deleting IKKbeta in myeloid cells, however, results in a significant decrease in tumor size. This deletion diminishes expression of proinflammatory cytokines that may serve as tumor growth factors, without affecting apoptosis. Thus, specific inactivation of the IKK/NF-kappaB pathway in two different cell types can attenuate formation of inflammation-associated tumors. In addition to suppressing apoptosis in advanced tumors, IKKbeta may link inflammation to cancer.

Risk Factors for Opportunistic Infections in Patients With Inflammatory Bowel Disease

BACKGROUND & AIMS We sought to identify and quantify the clinical factors that were associated with opportunistic infections in inflammatory bowel disease patients. METHODS We identified 100 consecutive IBD patients with opportunistic infections. For each case, 2 matched IBD patients who did not have a history of opportunistic infection were selected as controls. Conditional logistic regression was used to assess associations between putative risk factors and opportunistic infections, presented as odds ratios (OR) and 95% confidence intervals (CIs). RESULTS In univariate analysis, use of corticosteroids (OR, 3.4; 95% CI, 1.8-6.2), azathioprine/6-mercaptopurine (OR, 3.1; 95% CI, 1.7-5.5), and infliximab (OR, 4.4; 95% CI, 1.2-17.1) were associated individually with significantly increased odds for opportunistic infection. Multivariate analysis indicated that use of any one of these drugs yielded an OR of 2.9 (95% CI, 1.5-5.3), whereas use of 2 or 3 of these drugs yielded an OR of 14.5 (95% CI, 4.9-43) for opportunistic infection. The relative risk of opportunistic infection was greatest in IBD patients seen at older than 50 years of age (OR, 3.0; 95% CI, 1.2-7.2, relative to those 24 years or younger). No patient died from opportunistic infection. CONCLUSIONS Immunosuppressive medications, especially when used in combination, and older age are associated with increased risk of opportunistic infections. The absolute risk of opportunistic infection in IBD patients remains to be determined, as does any potential benefit of any preventive strategy.

Small-bowel imaging in Crohn's disease: a prospective, blinded, 4-way comparison trial

BACKGROUND With the introduction of new techniques to image the small bowel, there remains uncertainty about their role for diagnosing Crohns disease. OBJECTIVE To assess the sensitivity and specificity of capsule endoscopy (CE), CT enterography (CTE), ileocolonoscopy, and small-bowel follow-through (SBFT) in the diagnosis of small bowel Crohns disease. METHODS Prospective, blinded trial. SETTING Inflammatory bowel disease clinic at an academic medical center. PATIENTS Known or suspected Crohns disease. Exclusion criteria included known abdominal abscess and non-steroidal anti-inflammatory drug (NSAID) use. Partial small-bowel obstruction (PSBO) at CTE excluded patients from subsequent CE. INTERVENTIONS Patients underwent all 4 tests over a 4-day period. MAIN OUTCOME MEASUREMENTS Sensitivity, specificity, and accuracy of each test to detect active small-bowel Crohns disease. The criterion standard was a consensus diagnosis based upon clinical presentation and all 4 studies. RESULTS Forty-one CTE examinations were performed. Seven patients (17%) had an asymptomatic PSBO. Forty patients underwent colonoscopy, 38 had SBFT studies, and 28 had CE examinations. Small-bowel Crohns disease was active in 51%, absent in 42%, inactive in 5%, and suspicious in 2% of patients. The sensitivity of CE for detecting active small-bowel Crohns disease was 83%, not significantly higher than CTE (83%), ileocolonoscopy (74%), or SBFT (65%). However, the specificity of CE (53%) was significantly lower than the other tests (P < .05). One patient developed a transient PSBO due to CE, but no patients had retained capsules. LIMITATION Use of a consensus clinical diagnosis as the criterion standard-but this is how Crohns disease is diagnosed in practice. CONCLUSIONS The sensitivity of CE for active small-bowel Crohns disease was not significantly different from CTE, ileocolonoscopy, or SBFT. However, lower specificity and the need for preceding small-bowel radiography (due to the high frequency of asymptomatic PSBO) may limit the utility of CE as a first-line test for Crohns disease.

Inhibition of Interleukin-1-stimulated NF-κB RelA/p65 Phosphorylation by Mesalamine Is Accompanied by Decreased Transcriptional Activity

Nuclear factor κB (NF-κB) is an inducible transcription factor that regulates genes important in immunity and inflammation. The activity of NF-κB is highly regulated: transcriptionally active NF-κB proteins are sequestered in the cytoplasm by inhibitory proteins, IκB. A variety of extracellular signals, including interleukin-1 (IL-1), activate NF-κB by inducing phosphorylation and degradation of IκB, allowing nuclear translocation and DNA binding of NF-κB. Many of the stimuli that activate NF-κB by inducing IκB degradation also cause phosphorylation of the NF-κB RelA (p65) polypeptide. The transactivating capacity of RelA is positively regulated by phosphorylation, suggesting that in addition to cytosolic sequestration by IκB, phosphorylation represents another mechanism for control of NF-κB activity. In this report, we demonstrate that mesalamine, an anti-inflammatory aminosalicylate, dose-dependently inhibits IL-1-stimulated NF-κB-dependent transcription without preventing IκB degradation or nuclear translocation and DNA binding of the transcriptionally active NF-κB proteins, RelA, c-Rel, or RelB. Mesalamine was found to inhibit IL-1-stimulated RelA phosphorylation. These data suggest that pharmacologic modulation of the phosphorylation status of RelA regulates the transcriptional activity of NF-κB, independent of nuclear translocation and DNA binding. These findings highlight the importance of inducible phosphorylation of RelA in the control of NF-κB activity.

Celiac-associated lymphoma. A single institution experience of 30 cases in the combination chemotherapy era.

Celiac sprue (CS) is frequently complicated by malignancy, most commonly small intestinal lymphoma. Our study was performed in an area with a high prevalence of CS to define the clinical features, response to treatment, and outcome of this tumor. Of a total of 31 lymphomas complicating CS identified, 30 case records and 24 tumor specimens were reviewed. Overall 1-year survival was 9 of 29 (31%) and 5-year survival 3 of 27 (11%). Seven previously diagnosed celiac patients developed lymphoma; length on gluten-free diet ranged from 12 to 252 months (median 44 months). In this group, presentation was nonspecific, diagnosis difficult, and survival poor (lymphoma diagnosed in life in four of seven, mean survival 2.25 months). Twenty-three patients had CS and lymphoma diagnosed during the same illness. In this group, 14 of 23 presented with a surgical emergency and were treated with tumor resection and chemotherapy. Nine are disease-free and alive or died of another cause after 10-196 months (mean 74 follow-up). Celiac-associated lymphoma is a frequent, difficult to diagnose, and commonly fatal complication of CS. An aggressive diagnostic approach, including laparoscopy, is recommended. Long-term survival can be expected in a significant number of these patients and in our series was almost exclusively confined to those treated with chemotherapy.

Selective Inhibition of Inflammatory Gene Expression in Activated T Lymphocytes: A Mechanism of Immune Suppression by Thiopurines

Azathioprine and 6-mercaptopurine are antimetabolite thiopurine drugs that play important roles in the treatment of leukemia and in the management of conditions requiring immunosuppression, such as inflammatory bowel disease. The biochemical pharmacology of these drugs suggests that inhibition of purine nucleotide formation through the 6-thioguanine nucleotide metabolites is their key molecular mechanism. However, it is unclear how these metabolites suppress immunity. We hypothesized that azathioprine produces a selective inhibitory effect on activated but not quiescent T lymphocytes. We first established a model system of T lymphocyte culture with azathioprine that produced pharmacologically relevant concentrations of 6-thioguanine nucleotides. Using genome-wide expression profiling, we identified a group of azathioprine-regulated genes in quiescent and activated T lymphocytes. Several genes involved in immunity and inflammation were selectively down-regulated by azathioprine in stimulated but not quiescent cells. Quantitative reverse transcription-polymerase chain reaction for three of these genes, tumor necrosis factor-related apoptosis-inducing ligand, tumor necrosis factor receptor superfamily member 7, and α4-integrin, confirmed down-regulated expression of transcript levels. Tumor necrosis factor-related apoptosis-inducing ligand protein expression was further studied and found to be inhibited by azathioprine, 6-mercaptopurine, and 6-thioguanine, implying that the inhibitory effects of azathioprine on expression are mediated by 6-thioguanine nucleotides. These results therefore provide a previously unrecognized molecular mechanism for the immunosuppressive properties of thiopurine antimetabolite drugs.

Inflammation, DNA methylation and colitis-associated cancer.

Inflammation can result from a range of sources including microbial infections, exposure to allergens and toxic chemicals, autoimmune disease and obesity. A well-balanced immune response can be anti-tumorigenic; however, a sustained or chronic inflammatory response is generally harmful as the immune response becomes distorted. A causal link between chronic inflammation and cancer is now well accepted and many chronically inflamed organs of the gastrointestinal tract show this association. For example, patients with inflammatory bowel disease (IBD), including both ulcerative colitis and Crohns disease, have a 2- to 3-fold greater lifetime risk of developing colorectal cancer compared with the general population. The development of colitis-associated cancer (CAC) is thought to be multifaceted and is probably due to a combination of genetic factors, epigenetic factors and the duration, extent and severity of disease. Recently, epigenetic alterations, in particular alterations in DNA methylation, have been observed during inflammation and inflammation-associated carcinogenesis. The mediators of this, the significance of these changes in DNA methylation and the effect this has on gene expression and the malignant transformation of the epithelial cells during IBD and CAC are discussed in this review. The recent advances in technologies to study genome-wide DNA methylation and the therapeutic potential of understanding these molecular mechanisms are also highlighted.

Nitric oxide promotes endothelial cell survival signaling through S-nitrosylation and activation of dynamin-2

Endothelial cell-based angiogenesis requires activation of survival signals that generate resistance to external apoptotic stimuli, such as tumor necrosis factor-alpha (TNF-α), during pathobiologic settings. Mechanisms by which this is achieved are not fully defined. Here, we use a model in which the multifunctional cytokine nitric oxide counterbalances TNF-α-induced apoptosis, to define a role for membrane trafficking in the process of endothelial cell survival signaling. By perturbing dynamin GTPase function, we identify a key role of dynamin for ensuing downstream endothelial cell survival signals and vascular tube formation. Furthermore, nitric oxide is directly demonstrated to promote dynamin function through specific cysteine residue nitrosylation, which promotes endocytosis and endothelial cell survival signaling. Thus, these studies identify a novel role for dynamin as a survival factor in endothelial cells, through a mechanism by which dynamin S-nitrosylation regulates the counterbalances of TNF-α-induced apoptosis and nitric oxide-dependent survival signals, with implications highly relevant to angiogenesis.

Upregulation of DNA Methyltransferase–Mediated Gene Silencing, Anchorage-Independent Growth, and Migration of Colon Cancer Cells by Interleukin-6

Inflammatory bowel disease is characterized by chronic inflammation which predisposes to colorectal cancer. The mechanisms by which inflammation promotes tumorigenesis are not fully known. We aimed to investigate the links between colonic inflammation and tumorigenesis via epigenetic gene silencing. Colon cancer specimens were assessed for the expression of DNA methyltransferase-1 (DNMT-1) using immunohistochemistry. Colorectal carcinoma cell lines were assessed for DNMT1 expression, methylcytosine content, promoter methylation, gene expression, and tumorigenesis in response to interleukin (IL)-6. DNMT1 was expressed at higher levels in both the peritumoral stroma and tumor in inflammatory bowel disease–associated cancers compared with sporadic colon cancers. IL-6 treatment of colon cancer cells resulted in an increase in DNMT1 expression, independent of de novo gene expression. IL-6 increased the methylation of promoter regions of genes associated with tumor suppression, adhesion, and apoptosis resistance. Expression of a subset of these genes was downregulated by IL-6, an effect that was prevented by preincubation with 5-azadeoxycytidine, a DNMT1 inhibitor. Anchorage-independent growth and migration of colon cancer cells was also increased by IL-6 in a 5-azadeoxycytidine–sensitive manner. Our results indicate that DNMT-mediated gene silencing may play a role in inflammation-associated colon tumorigenesis. Mol Cancer Res; 8(4); 471–81. ©2010 AACR.

European Evidence-based Consensus: Inflammatory Bowel Disease and Malignancies

The global prevalence of cancer is increasing, largely as more patients are living into old age. Therefore, gastroenterologists caring for patients with inflammatory bowel disease [IBD] increasingly are managing patients with cancer, or a previous history of cancer. This often requires joint management with the patient’s oncologist, enabling case-by-case decision-making based on the characteristics and expected evolution of the index cancer. Previously, no European guidelines existed describing the impact of IBD on malignancy. For this reason, the European Crohn’s and Colitis Organisation [ECCO] Guidelines Committee [GuiCom] decided to elaborate a set of Consensus Statements on optimal risk/benefit strategies for treating IBD patients with cancer or a history of cancer. The development of clinical practice guidelines is expensive and time consuming, and it is the Committee’s hope that these statements will facilitate and accelerate future efforts to elaborate formal guidelines, providing useful information on areas for which evidence is lacking and where controlled studies are needed. The strategy used to produce the Consensus Statements involved five steps: 1. Two members of Guicom [VA and RE] identified four main topics that needed to be addressed: a] IBD and solid tumours; b] IBD and skin and haematological malignancies; c] malignancy related to therapy: risk and prevention; and d] management of IBD patients with a history of malignancy. During 2014, calls for participation in the drafting of consensus statements were issued to ECCO members, and selected oncologists known for their expertise and active research in the field were invited to join the Consensus. Participants were selected by the Committee, and four working groups were created, each composed of a chairperson [LE, RE, LB, and VA], two ECCO members including young members [Y-ECCO], and one or two experienced oncologists. The chairmen and their groups elaborated relevant questions on topics dealing with current practice and/or areas …