Translation initiation factor eIF2Bε promotes Wnt-mediated clonogenicity and global translation in intestinal epithelial cells

Modulation of global mRNA translation, which is essential for intestinal stem cell function, is controlled by Wnt signaling. Loss of tumor supressor APC in stem cells drives adenoma formation through hyperactivion of Wnt signaling and dysregulated translational control. It is unclear whether factors that coordinate global translation in the intestinal epithelium are needed for APC-driven malignant transformation. Here we identified nucleotide exchange factor eIF2Bε as a translation initiation factor involved in Wnt-mediated intestinal epithelial stemness. Using eIF2Bε^Arg191His mice with a homozygous point mutation that leads to dysfunction in the enzymatic activity, we demonstrate that eIF2Bε is involved in small intestinal crypt formation, stemness marker expression, and secreted Paneth cell-derived granule formation. Wnt hyperactivation in ex vivo eIF2Bε^Arg191His organoids, using a GSK3β inhibitor to mimic Apc driven transformation, shows that eIF2Bε is essential for Wnt-mediated clonogenicity and associated increase of the global translational capacity. Finally, we observe high eIF2Bε expression in human colonic adenoma tissues, exposing eIF2Bε as a potential target of CRC stem cells with aberrant Wnt signaling.

Profoundly Expanded T-cell Clones in the Inflamed and Uninflamed Intestine of Patients With Crohn's Disease

BACKGROUND AND AIM

T cells are key players in the chronic intestinal inflammation that characterises Crohn's disease. Here we aim to map the intestinal T-cell receptor [TCR] repertoire in patients with Crohn's disease, using next-generation sequencing technology to examine the clonality of the T-cell compartment in relation to mucosal inflammation and response to therapy.

METHODS

Biopsies were taken from endoscopically inflamed and uninflamed ileum and colon of 19 patients with Crohn's disease. From this cohort, additional biopsies were taken after 8 weeks of remission induction therapy from eight responders and eight non-responders. Control biopsies from 11 patients without inflammatory bowel disease [IBD] were included. The TCRβ repertoire was analysed by next-generation sequencing of biopsy RNA.

RESULTS

Both in Crohn's disease patients and in non-IBD controls, a broad intestinal T-cell repertoire was found, with a considerable part consisting of expanded clones. Clones in Crohn's disease were more expanded [p = 0.008], with the largest clones representing up to as much as 58% of the total repertoire. There was a substantial overlap of the repertoire between inflamed and uninflamed tissue and between ileum and colon. Following therapy, responders showed larger changes in the T-cell repertoire than non-responders, although a considerable part of the repertoire remained unchanged in both groups.

CONCLUSIONS

The intestinal T-cell repertoire distribution in Crohn's disease is different from that in the normal gut, containing profoundly expanded T-cell clones that take up a large part of the repertoire. The T-cell repertoire is fairly stable regardless of endoscopic mucosal inflammation or response to therapy.

Suppression of anti-drug antibodies to infliximab or adalimumab with the addition of an immunomodulator in patients with inflammatory bowel disease

BACKGROUND

Loss of response to anti-tumour necrosis factor (TNF) therapy in patients with inflammatory bowel disease (IBD) is often caused by anti-drug antibody formation with neutralisation of drug effect. Addition of an immunomodulator has been suggested to reduce immunogenicity, leading to regained response.

AIM

To investigate whether addition of an immunomodulator to anti-TNF monotherapy could lead to anti-drug antibody suppression and regained clinical response in IBD patients.

METHODS

We retrospectively collected measurements of infliximab or adalimumab serum concentrations and anti-drug antibodies to identify anti-drug positive patients with loss response who were given an immunomodulator.

RESULTS

Anti-drug antibodies against infliximab and adalimumab were detected in 98/376 (26%) and in 61/226 (27%) patients, respectively. Immunomodulators were given to 17/159 patients. Clinical response was recaptured in 6/10 patients receiving a thiopurine and in all (7/7) patients receiving methotrexate. In 7/8 patients on infliximab, serum concentrations increased (median 2.84 μg/mL; IQR: 1.19-4.98) and in 6/9 patients on adalimumab (median 3.10 μg/mL; IQR: 1.45-4.45). This was accompanied by a decrease in anti-drug antibodies to undetectable levels (median 11 months for both anti-TNF agents). In 23 patients, no immunomodulator was added but anti-TNF interval was shortened (17/23) or dosage was increased (6/23), which resulted in a clinical response in 10/17 and 2/6 patients, respectively.

CONCLUSION

In 77% of IBD patients with loss of response due to immunogenicity, addition of immunomodulator resulted in undetectable anti-drug antibody levels, increased serum drug concentrations and regained clinical response. This strategy should be considered in this patient population before switching to other agents.

The ATG16L1 risk allele associated with Crohn's disease results in a Rac1-dependent defect in dendritic cell migration that is corrected by thiopurines

Thiopurines are commonly used drugs in the therapy of Crohn's disease, but unfortunately only show a 30% response rate. The biological basis for the thiopurine response is unclear, thus hampering patient selection prior to treatment. A genetic risk factor associated specifically with Crohn's disease is a variant in ATG16L1 that reduces autophagy. We have previously shown that autophagy is involved in dendritic cell (DC)-T-cell interactions and cytoskeletal regulation. Here we further investigated the role of autophagy in DC cytoskeletal modulation and cellular trafficking. Autophagy-deficient DC displayed loss of filopodia, altered podosome distribution, and increased membrane ruffling, all consistent with increased cellular adhesion. Consequently, autophagy-deficient DC showed reduced migration. The cytoskeletal aberrations were mediated through hyperactivation of Rac1, a known thiopurine target. Indeed thiopurines restored the migratory defects in autophagy-deficient DC. Clinically, the ATG16L1 risk variant associated with increased response to thiopurine treatment in patients with Crohn's disease but not ulcerative colitis. These results suggest that the association between ATG16L1 and Crohn's disease is mediated at least in part through Rac1 hyperactivation and subsequent defective DC migration. As this phenotype can be corrected using thiopurines, ATG16L1 genotyping may be useful in the identification of patients that will benefit most from thiopurine treatment.

Risk factors for proximal disease extension and colectomy in left-sided ulcerative colitis

OBJECTIVE

The primary objective of this study was to assess proximal disease extension of ulcerative colitis (UC) over time, with disease behaviour pattern and risk factors for proximal disease extension and colectomy as secondary aims.

METHODS

All cumulative incident cases diagnosed with UC at the Academic Medical Center between January 1990 and December 2009 were studied. The cumulative risk of colectomy was calculated by Kaplan-Meier analysis. The Cox proportional hazards regression was used to identify risk factors associated with proximal disease extension and colectomy.

RESULTS

In total, 506 UC patients were included with a median age of 33 years (IQR 23-41) at diagnosis. Ninety-five (18.8%) patients underwent colectomy during follow-up. Median follow-up was 10 years (IQR 5-15). Initial disease extent was evaluable in 416 patients, of whom 142 (34.1%) had proctitis, 155 (37.3%) left-sided colitis and 119 (28.6%) pancolitis. Proximal disease extension was observed in 120 (28.8%) patients during follow-up (51 proctitis to left-sided colitis, 39 proctitis to extensive colitis and 30 left-sided to extensive colitis). Disease behaviour was evaluable in 378 patients, of whom 244 (64.6%) had less than one relapse per year. Younger age at diagnosis (HR 0.98, 95% CI 0.96-0.99) and continuous active disease (HR 2.18, 95% CI 1.27-3.73) were independent risk factors for proximal disease extension. The cumulative risk of colectomy did not change over time between patients diagnosed before and after the year 2000 (p = 0.341). Continuous active disease (HR 7.05, 95% CI 4.23-11.77), systemic steroids (HR 3.25, 95% CI 1.37-7.71) and cyclosporine treatment (HR 2.80, 95% CI 1.66-4.72) were independent risk factors for colectomy, whereas proctitis at diagnosis (HR 0.43, 95% CI 0.22-0.86) carried a lower risk.

CONCLUSION

In one-third of UC patients, left-sided disease at diagnosis will extend proximally during 10 years of follow-up. Proximal disease extension was not a risk factor for colectomy, but the risk of colectomy is rather determined by continuous disease activity, and use of systemic steroids and cyclosporine.

Induction of endoplasmic reticulum stress by deletion of Grp78 depletes Apc mutant intestinal epithelial stem cells

Intestinal epithelial stem cells are highly sensitive to differentiation induced by endoplasmic reticulum (ER) stress. Colorectal cancer develops from mutated intestinal epithelial stem cells. The most frequent initiating mutation occurs in Apc, which results in hyperactivated Wnt signalling. This causes hyperproliferation and reduced sensitivity to chemotherapy, but whether these mutated stem cells are sensitive to ER stress induced differentiation remains unknown. Here we examined this by generating mice in which both Apc and ER stress repressor chaperone Grp78 can be conditionally deleted from the intestinal epithelium. For molecular studies, we used intestinal organoids derived from these mice. Homozygous loss of Apc alone resulted in crypt elongation, activation of the Wnt signature and accumulation of intestinal epithelial stem cells, as expected. This phenotype was however completely rescued on activation of ER stress by additional deletion of Grp78. In these Apc-Grp78 double mutant animals, stem cells were rapidly lost and repopulation occurred by non-mutant cells that had escaped recombination, suggesting that Apc-Grp78 double mutant stem cells had lost self-renewal capacity. Although in Apc-Grp78 double mutant mice the Wnt signature was lost, these intestines exhibited ubiquitous epithelial presence of nuclear β-catenin. This suggests that ER stress interferes with Wnt signalling downstream of nuclear β-catenin. In conclusion, our findings indicate that ER stress signalling results in loss of Apc mutated intestinal epithelial stem cells by interference with the Wnt signature. In contrast to many known inhibitors of Wnt signalling, ER stress acts downstream of β-catenin. Therefore, ER stress poses a promising target in colorectal cancers, which develop as a result of Wnt activating mutations.

Endogenous c-Myc is essential for p53-induced apoptosis in response to DNA damage in vivo

Recent studies have suggested that C-MYC may be an excellent therapeutic cancer target and a number of new agents targeting C-MYC are in preclinical development. Given most therapeutic regimes would combine C-MYC inhibition with genotoxic damage, it is important to assess the importance of C-MYC function for DNA damage signalling in vivo. In this study, we have conditionally deleted the c-Myc gene in the adult murine intestine and investigated the apoptotic response of intestinal enterocytes to DNA damage. Remarkably, c-Myc deletion completely abrogated the immediate wave of apoptosis following both ionizing irradiation and cisplatin treatment, recapitulating the phenotype of p53 deficiency in the intestine. Consistent with this, c-Myc-deficient intestinal enterocytes did not upregulate p53. Mechanistically, this was linked to an upregulation of the E3 Ubiquitin ligase Mdm2, which targets p53 for degradation in c-Myc-deficient intestinal enterocytes. Further, low level overexpression of c-Myc, which does not impact on basal levels of apoptosis, elicited sustained apoptosis in response to DNA damage, suggesting c-Myc activity acts as a crucial cell survival rheostat following DNA damage. We also identify the importance of MYC during DNA damage-induced apoptosis in several other tissues, including the thymus and spleen, using systemic deletion of c-Myc throughout the adult mouse. Together, we have elucidated for the first time in vivo an essential role for endogenous c-Myc in signalling DNA damage-induced apoptosis through the control of the p53 tumour suppressor protein.

Role of mast cells in colorectal cancer development, the jury is still out

The link between inflammation and colorectal cancer development is becoming increasingly clear. It had long been recognized that patients with inflammatory bowel disease are at an increased risk of colon cancer. Evidence from experimental animals now also implicates the innate immune system in the development of sporadically occurring intestinal adenomas, the precursors to colorectal cancer. Here we discuss the interaction between the immune system and the adenoma to carcinoma sequence with a special emphasis on the role of mast cells which may play a key role in adenoma development. This article is part of a Special Issue entitled: Mast cells in inflammation.

Key elements of the BMP/SMAD pathway co-localize with CDX2 in intestinal metaplasia and regulate CDX2 expression in human gastric cell lines

Helicobacter pylori infection induces intestinal metaplasia of the stomach, a preneoplastic lesion associated with an increased risk for gastric cancer development. Intestinal metaplasia is induced by the intestine-specific transcription factor CDX2 but the mechanisms responsible for this ectopic expression have never been described. We hypothesized that the BMP/SMAD pathway has a role in CDX2 regulation, in this context, for the following reasons: (1) the BMP pathway is crucial for normal intestinal differentiation and (2) there is an influx of BMP2 and BMP4-producing cells to the stomach upon Helicobacter pylori infection. We evaluated the expression of key elements of the BMP pathway in human stomach specimens with IM. Growth factor treatments, with BMP2 and BMP4, were performed in cultured cells and a knock-down experiment of SMAD4 was done using RNAi. We showed overexpression in IM of BMP2/4, BMPR1A, and SMAD4 in 56% of IM foci, and pSMAD1/5/8 in 100% of IM foci as compared to adjacent mucosa. In vitro, treatment of AGS cells with BMP2 and BMP4 increased endogenous CDX2 expression as well as the intestinal differentiation markers MUC2 and LI-cadherin. On the other hand, SMAD4 knock-down led to decreased endogenous CDX2, MUC2, and LI-cadherin in AGS. Treatment of the SMAD4 knock-down cells had no influence on CDX2 expression as opposed to wild-type cells. A 9.3 kb CDX2 promoter could be transactivated by SMAD4 and SMAD1 in a cell-dependent manner. In conclusion, we identified for the first time that the BMP pathway is active in intestinal metaplasia and that BMP2 and BMP4 regulate CDX2 expression and promote intestinal differentiation through the canonical signal transducers.

Altered bone morphogenetic protein signalling in the Helicobacter pylori-infected stomach

Morphogens regulate epithelial cell fate decisions in the adult gastrointestinal tract. The authors hypothesized that influx of inflammatory cells into the lamina propria may disturb the normal expression gradients of morphogens (morphogenetic landscape) in gastrointestinal epithelia. Changes in the activity of the bone morphogenetic protein (BMP) pathway in normal and Helicobacter pylori-infected gastric mucosa were therefore examined. It is shown that BMP receptors, the activated (phosphorylated) form of the intracellular BMP signal transduction protein SMAD1, and BMP target ID2 all localize to gastric epithelial cells that are at the end of the axis of epithelial renewal in normal mucosa. Colonization of human gastric mucosa with H. pylori was associated with an increase in BMP2 expression due to influx of inflammatory cells that produce BMP2. Furthermore, whereas no BMP4 was detected in the normal antrum, focal infiltrates of BMP4-expressing cells were found in the H. pylori-infected stomach. This influx of BMP-expressing cells was associated with an increase in epithelial BMP signalling. Interestingly, a shift in activity of the BMP pathway was observed towards the precursor cell compartment (isthmus) of the gastric units. Thus, H. pylori infection results in an influx of inflammatory cells that disturb the normal activity gradient of a morphogenetic pathway with an established role in epithelial cell fate regulation. The data suggest that morphological changes in epithelial histology may result from alterations in the morphogenetic landscape secondary to changes in the cellular composition of the lamina propria.

Effect of aspirin on the Wnt/beta-catenin pathway is mediated via protein phosphatase 2A

Nonsteroidal anti-inflammatory drugs show chemopreventive efficacy in colon cancer, but the mechanism behind this remains unclear. Elucidating this mechanism is seen as vital to the development of new chemopreventive agents. We studied the effects of aspirin on the oncogenic Wnt/beta-catenin pathway activity in colorectal cancer cell lines and observed that aspirin dose-dependently decreased the activity of this pathway, as judged by TCF-driven luciferase activity, reduced Wnt target gene expression and increased phosphorylation of beta-catenin by immunoblotting. Furthermore, the ubiquitination and cytoplasmic levels of beta-catenin were assessed by immunoblotting, and also the localization of beta-catenin was shown by green fluorescent protein-tagged beta-catenin and time-lapse fluorescent imaging. Importantly, aspirin treatment caused increased phosphorylation of protein phosphatase 2A (PP2A), an event associated with inhibition of PP2A enzymatic activity, which was confirmed by a reduction in enzymatic PP2A activity. Moreover, this inhibition of PP2A enzymatic activity was essential for the effects of aspirin on the Wnt/beta-catenin pathway as shown by transient transfection with PP2A constructs. The findings in this article provide a molecular explanation for the efficacy of aspirin in chemoprevention of colorectal cancer and shows biochemical evidence that PP2A is an important regulator of Wnt/beta-catenin pathway activity in these cells.

Hedgehog Wnteraction in colorectal cancer

The Hedgehog pathway was recently shown to antagonise constitutive activity of the Wnt pathway that drives proliferation of colorectal cancer cells. Studies in this issue of Gut refine our understanding of the underlying mechanism and provide evidence for such antagonism in colorectal cancers in vivo

Development and differentiation of the intestinal epithelium

The gastrointestinal tract develops from a simple tube to a complex organ with patterns of differentiation along four axes of asymmetry. The organ is composed of all three germ layers signaling to each other during development to form the adult structure. The gut epithelium is a constitutively developing tissue, constantly differentiating from a stem cell in a progenitor pool throughout the life of the organism. Signals from the adjacent mesoderm and between epithelial cells are required for normal orderly development/differentiation, homeostasis, and apoptosis. Embryonically important patterning factors are used during adult stages for these processes. Such critical pathways as the hedgehog, bone morphogenetic protein, Notch, Sox, and Wnt systems are used both in embryologic and adult times of gut development. We focus on and review the roles of these factors in gut epithelial cell development and differentiation.

Sonic hedgehog expression correlates with fundic gland differentiation in the adult gastrointestinal tract

BACKGROUND

Sonic hedgehog (Shh) is an important endodermal morphogenetic signal during the development of the vertebrate gut. It controls gastrointestinal patterning in general, and gastric gland formation in particular. We have previously shown that Shh regulates gastric gland proliferation in the adult but detailed analysis of its expression along the adult gastrointestinal tract has never been undertaken. We therefore studied Shh expression along the normal human and rodent adult gastrointestinal tract as well as in intestinal metaplasia of the stomach, gastric and intestinal metaplasia of the oesophagus, and gastric heterotopia in Meckel's diverticulum.

METHODS

The studies were performed with in situ hybridisation and by immunohistochemistry using an antibody that recognises the Shh precursor form.

RESULTS

We found that in the normal gastrointestinal tract, high levels of Shh were expressed in the fundic glands of the stomach. Shh expression was also found in fundic gland metaplasia and heterotopia. However, Shh expression was lost in intestinal metaplasia of the stomach.

CONCLUSION

We found a strong correlation between Shh expression and fundic gland differentiation. Our current study therefore provides evidence that in addition to its role in gastric epithelial development, Shh plays a unique role in gastric epithelial differentiation in adults.

Sonic hedgehog regulates gastric gland morphogenesis in man and mouse

BACKGROUND & AIMS

Gastric epithelial renewal is an asymmetric process. A stem cell located halfway up the tubular unit gives rise to both a basal gland region and a luminal pit compartment, but the mechanisms responsible for the maintenance of this asymmetry are obscure. We investigated whether Sonic hedgehog (Shh), an established polarizing signal protein during development, is expressed and functional in the adult human and murine stomach.

METHODS

Expression of Shh and putative transcriptional targets was investigated using immunoblot and immunohistochemistry. Mice were treated with the Shh inhibitor cyclopamine and examined for expression levels of Shh targets and proliferation of gastric epithelial cells.

RESULTS

Shh was expressed in the stomach. In cyclopamine-treated mice, we observed decreased expression of HNF3beta, Islet (Isl)-1 and BMP4, 3 putative Shh target genes. Inhibition of Shh markedly enhanced gastric epithelial proliferation and affected the cell cycle of gastric epithelial gland cells, whereas pit cells remained unaffected.

CONCLUSIONS

Shh controls the expression of at least 3 factors important for epithelial differentiation and is a negative regulator of gastric gland cell proliferation. Shh is a candidate polarizing signal in the maintenance of gastric pit-gland asymmetry.

NF-kappaB, p38 MAPK and JNK are highly expressed and active in the stroma of human colonic adenomatous polyps

The factors that govern the progression from colonic adenomatous polyp to colon cancer are poorly understood. The observation that NSAIDs act as chemopreventative agents and reduce the size of colonic polyps suggests the involvement of inflammatory signalling, but inflammatory signalling in colonic polyps has not been studied. We investigated the expression of the active forms of NF-kappaB, JNK and p38 MAPK using immunohistochemistry with activation specific antibodies in human colonic adenomas. We show that active NF-kappaB is seen in stromal macrophages that also express COX-2 and TNF-alpha, active JNK is seen in stromal and intraepithelial T-lymphocytes and periendothelial cells of new blood vessels, and active p38 MAPK is most highly expressed in macrophages and other stromal cells. These results demonstrate the presence of active inflammatory signal transduction in colonic polyps and that these are predominantly in the stroma. In the case of NF-kappaB this coincides with the cellular localisation of COX-2. These results support evidence that NSAIDs may act through effects on stromal cells rather than epithelial cells.

A new phosphospecific cell-based ELISA for p42/p44 mitogen-activated protein kinase (MAPK), p38 MAPK, protein kinase B and cAMP-response-element-binding protein

Assaying activation of signal transduction is laborious and does not allow the study of large numbers of samples, essential for high-throughput drug screens or for large groups of patients. Using phosphospecific antibodies, we have developed ELISA techniques enabling non-radioactive semi-quantitative assessment of the activation state of p42/p44 mitogen-activated protein kinase (MAPK), p38 MAPK, protein kinase B and the transcription factor cAMP-response-element-binding protein (CREB) in 96-well plates. This assay has been termed PACE (phosphospecific antibody cell-based ELISA) and was used successfully for both adherent and suspension cells. Various stimuli induced dose-dependent enzymic activity of which the kinetics closely correlated with those measured via classical methodology. Using PACE we have now characterized for the first time the concentration-dependent effects of various inflammatory prostaglandins on CREB phosphorylation in macrophages. PACE is a straightforward and novel technique enabling the large-scale analysis of signal transduction.

Leptin signaling in human peripheral blood mononuclear cells, activation of p38 and p42/44 mitogen-activated protein (MAP) kinase and p70 S6 kinase

The adipocyte-derived hormone leptin plays an important role as a relayer of nutritional status to several organ systems. Evidence is accumulating that leptin plays an important role in the adequate functioning and maintenance of the immune system. Here we show that leptin induces sustained phosphorylation of p38 MAP kinase in human peripheral blood mononuclear cells (PBMCs). We show furthermore that leptin induces two routes to phosphorylation of the 40S ribosomal protein S6, one is activation of the p90 ribosomal S6 kinase (RSK) via the MEK/p42/p44 MAP kinase pathway, the other is via activation of p70 S6 kinase. Thus, these results give new insight in the mechanism that underlies the immunomodulatory effects of leptin.

Treatment of bile duct lesions after laparoscopic cholecystectomy

From January 1990 to June 1994, 53 patients who sustained bile duct injuries during laparoscopic cholecystectomy were treated at the Amsterdam Academic Medical Centre. There were 16 men and 37 women with a mean age of 47 years. Follow up was established in all patients for a median of 17 months. Four types of ductal injury were identified. Type A (18 patients) had leakage from cystic ducts or peripheral hepatic radicles, type B (11 patients) had major bile duct leakage, type C (nine patients) had an isolated ductal stricture, and type D (15 patients) had complete transection of the bile duct. Endoscopic retrograde cholangiopancreatography (ERCP) established the diagnosis in all type A, B, and C lesions. In type D lesions percutaneous cholangiography was required to delineate the proximal extent of the injury. Initial treatment (until resolution of symptoms and discharge from hospital) comprised endoscopy in 36 patients and surgery in 26 patients. Endoscopic treatment was possible and successful in 16 of 18 of type A lesions, five of seven of type B lesions, and three of nine of type C lesions. Most failures resulted from inability to pass strictures or leaks at the initial endoscopy. During initial treatment additional surgery was required in seven patients. Fourteen patients underwent percutaneous or surgical drainage of bile collections, or both. After endoscopic treatment early complications occurred in three patients, with a fatal outcome in two (not related to the endoscopic therapy). During follow up six patients developed late complications. All 15 patients with complete transection and four patients with major bile duct leakage were initially treated surgically. During initial treatment additional endoscopy was required in two patients. Early complications occurred in eight patients. During follow up seven patients developed stenosis of the anastomosis or bile duct. Reconstructive surgery in the early postoperative phase was associated with more complications than elective reconstructive surgery. Most type A and B bile duct injuries after laparoscopic cholecystectomy (80%) can be treated endoscopically. In patients with more severe ductal injury (type C and D) reconstructive surgery is eventually required in 70%. Multidisciplinary approach to these lesions is advocated and algorithms for treatment are proposed.