Gerhard Faller

The ZEB1/miR‐200 feedback loop controls Notch signalling in cancer cells

Notch signalling is important for development and tissue homeostasis and activated in many human cancers. Nevertheless, mutations in Notch pathway components are rare in solid tumours. ZEB1 is an activator of an epithelial–mesenchymal transition (EMT) and has crucial roles in tumour progression towards metastasis. ZEB1 and miR‐200 family members repress expression of each other in a reciprocal feedback loop. Since miR‐200 members target stem cell factors, ZEB1 indirectly induces stemness maintenance and associated drug resistance. Here, we link ZEB1 and its cancer promoting properties to Notch activation. We show that miR‐200 members target Notch pathway components, such as Jagged1 (Jag1) and the mastermind‐like coactivators Maml2 and Maml3, thereby mediating enhanced Notch activation by ZEB1. We further detected a coordinated upregulation of Jag1 and ZEB1, associated with reduced miR‐200 expression in two aggressive types of human cancer, pancreatic adenocarcinoma and basal type of breast cancer. These findings explain increased Notch signalling in some types of cancers, where mutations in Notch pathway genes are rare. Moreover, they indicate an additional way how ZEB1 exerts its tumour progressing functions.

The gastric H+,K+-ATPase is a major autoantigen in chronic Helicobacter pylori gastritis with body mucosa atrophy ☆ ☆☆ ★ ★★

BACKGROUND & AIMS A subgroup of Helicobacter pylori-infected patients develops autoantibodies to gastric parietal cell canaliculi. The aim of this study was to define the unknown autoantigen. METHODS We screened 72 H. pylori-infected patients, 5 patients with autoimmune gastritis, and 36 healthy controls for immunoglobulin G autoantibodies to canaliculi by immunohistochemistry. The antigen specificity was determined by immunoprecipitation of the murine gastric H+,K+-adenosine triphosphatase (H+,K+-ATPase) expressed in oocytes and by immunoblotting on human gastric membranes from the body mucosa. RESULTS Autoantibodies specific for the conformational peptides of the H+,K+-ATPase were detected in 3% (1/36) of controls, in all patients with autoimmune gastritis (5/5), in 25% (18/72) of H. pylori-infected patients, and in 47% (15/32) of the infected patients with anticanalicular autoantibodies. No other major autoantigen was identified. Atrophy in the gastric body mucosa was found in 60% (9/15) of infected patients with both anticanalicular and anti-H+,K+-ATPase antibodies, but only in 13% (5/37) of infected patients lacking both autoantibodies (P < 0.01). CONCLUSIONS The gastric H+,K+-ATPase is a major autoantigen in H. pylori-associated antigastric autoimmunity. Thus, anti-H+,K+-ATPase autoantibodies, which are closely linked to classical autoimmune gastritis, are also significant indicators for body mucosa atrophy in chronic H. pylori gastritis.

Expression of Nuclear β-Catenin and c-myc Is Correlated with Tumor Size but Not with Proliferative Activity of Colorectal Adenomas

Most colorectal cancers have loss-of-function mutations in the adenomatosis polyposis coli (APC) tumor suppressor gene. This leads to the accumulation of nuclear beta-catenin, which, together with the DNA-binding protein TCF-4, functions as a transcriptional activator. The recently defined target genes c-myc, cyclin D1, and matrilysin are responsible for tumor proliferation or malignant progression and explain the oncogenic potential of nuclear beta-catenin. To investigate its role in early colon carcinogenesis, we analyzed the expression of beta-catenin, its target gene c-myc, and the proliferative activity in 88 colorectal adenomas of varying size and grade of dysplasia. The results revealed i) the most significant correlation of nuclear beta-catenin and c-myc expression was not with the grade of dysplasia but with the size of the colon adenoma; ii) perfect correlation of nuclear beta-catenin and c-myc expression; iii) no significant correlation of adenoma size with the proliferative activity; and iv) no significant correlation of proliferative activity and the nuclear expression of beta-catenin and c-myc. These results imply that APC mutations have additional beta-catenin-independent functions; APC mutations alone are not sufficient for nuclear overexpression of beta-catenin; and nuclear beta-catenin has additional important functions for exceeding a threshold tumor size.

Lewis X structures in the O antigen side‐chain promote adhesion of Helicobacter pylori to the gastric epithelium

Helicobacter pylori NCTC11637 expresses a lipopolysaccharide (LPS) that comprises an O antigen side‐chain with structural homology to the human blood group antigen Lewis X (Lex). The role of this molecule in adhesion of H. pylori to gastric epithelial cells was investigated. Mutants expressing truncated LPS structures were generated through insertional mutagenesis of rfbM and galE; genes encode GDP mannose pyrophosphorylase and galactose epimerase respectively. Compositional and structural analysis revealed that the galE mutant expressed a rough LPS that lacked an O antigen side‐chain. In contrast, an O antigen side‐chain was still synthesized by the rfbM mutant, but it lacked fucose and no longer reacted with anti‐Lex monoclonal antibodies (Mabs). The ability of these mutants to bind to paraffin‐embedded sections from the antrum region of a human stomach was assessed. Adhesion of the wild type was characterized by tropic binding to the apical surface of mucosal epithelial cells and cells lining gastric pits. In contrast, both the rfbM and galE mutants failed to demonstrate tropic binding and adhered to the tissue surface in a haphazard manner. These results indicate that LPS and, more specifically, LeX structures in the O antigen side‐chain play an important role in targeting H. pylori to specific cell lineages within the gastric mucosa. The role of LeX in this interaction was confirmed by the tropic binding of synthetic Lex, conjugated to latex beads, to gastric tissue. The observed pattern of adhesion was indistinguishable from that of wild‐type H. pylori.

Bugs on trial: the case of Helicobacter pylori and autoimmunity

Abstract Helicobacter pylori infection induces autoantibodies to gastric H + K + -ATPase similar to those found in autoimmune gastritis and pernicious anaemia (AIG/PA). Here, Ben Appelmelk and colleagues consider the possibility that H. pylori infection triggers an autoimmune process that leads to gastric atrophy and AIG/PA.

Down-Regulation of the Homeodomain Factor Cdx2 in Colorectal Cancer by Collagen Type I: An Active Role for the Tumor Environment in Malignant Tumor Progression

The homeobox transcription factor Cdx2 specifies intestinal development and homeostasis and is considered a tumor suppressor in colorectal carcinogenesis. However, Cdx2 mutations are rarely found. Invasion of colorectal cancer is characterized by a transient loss of differentiation and nuclear accumulation of the oncoprotein β-catenin in budding tumor cells. Strikingly, this is reversed in growing metastases, indicating that tumor progression is a dynamic process that is not only driven by genetic alterations but also regulated by the tumor environment. Here we describe a transient loss of Cdx2 in budding tumor cells at the tumor host interface, and reexpression of Cdx2 in metastases. Cell culture experiments show that collagen type I, through β1 integrin signaling, triggers a transient transcriptional down-regulation of Cdx2 and its intestine-specific target gene sucrase isomaltase, associated with a loss of differentiation. These data indicate an active role for the tumor environment in malignant tumor progression.

Antigastric autoantibodies in Helicobacter pylori gastritis: prevalence, in-situ binding sites and clues for clinical relevance.

Colonization of human gastric mucosa with Helicobacter pylori leads to chronic active gastritis and induces the occurrence of an acquired mucosa-associated lymphoid tissue (MALT) in the stomach. This remodelling of the gastric mucosa together with chronic antigen persistence may induce autoimmune reactions. The aim of this study was to investigate humoral autoimmune reactions to human gastric mucosa in H. pylori gastritis and their clinical relevance. Sera from patients with dyspeptic symptoms were tested for presence of IgG immunoglobulins against H. pylori. Gastric infection with H. pylori and alterations of gastric mucosa were demonstrated by histological examination of gastric biopsy specimens. All sera were tested for reactivity against human gastric mucosa by immunohistochemistry. Two different in-situ binding sites of antigastric autoantibodies were observed. Binding to canalicular structures within parietal cells was significantly correlated with antibodies to H. pylori, elevated basal gastrin levels and atrophy of gastric corpus glands. Our data indicate that autoimmune reactions to antigens in the human gastric mucosa occur in H. pylori gastritis and that they may play a role in the pathogenesis of the disease.

Expression of the extracellular matrix signaling molecule Cyr61 is downregulated in prostate cancer

Prostate cancer (CaP) is one of the most common neoplasms in the USA and Europe. We used differential display PCR (DD‐PCR) to identify genes related to the development of prostate cancer.

Helicobacter pylori Induces Apoptosis in Gastric Mucosa through an Upregulation of Bax Expression in Humans

BACKGROUND Maintenance of gastric mucosal integrity depends on the balance between cell loss due to apoptosis and cell proliferation. Helicobacter pylori induces apoptosis in gastric epithelial cells, but the regulation of this process has been little studied. The Bcl-2 proteins are the best-studied family of proteins involved in the mechanism of apoptotic death. Some members of this family, such as Bcl-2, inhibit apoptosis, whereas others, such as Bax, induce it. The present study was performed to determine the apoptosis rate and mRNA and protein expression for Bax and Bcl-2 in the gastric mucosa of duodenal ulcer (DU) patients with H. pylori infection before and after H. pylori eradication. We recruited 8 H. pylori-negative control subjects and 20 DU patients (H. pylori-positive) given a 1-week triple therapy to eradicate H. pylori. The apoptosis was analyzed by means of terminal deoxyribonucleotide transferase-mediated digoxigenin-11-deoxyuridine triphosphate biotin nick-end labeling (TUNEL) staining, and the expression of mRNA for Bax and Bcl-2 by reverse transcription polymerase chain reaction (RT-PCR) and Southern blot. In all patients gastritis was assessed histologically on the basis of the Sydney classification, the presence of H. pylori, and analysis of cagA status. RESULTS All 20 DU patients were H. pylori-positive, and 18 (90%) were CagA-positive. The apoptotic cells were infrequently identified in gastric surface epithelium by TUNEL histochemistry in H. pylori-negative controls. In DU patients infected with H. pylori, apoptotic cells were more numerous and seen deep in the gastric glands. The infection was associated with significantly upregulated expression of mRNA and protein for Bax and suppressed mRNA and protein expression for Bcl-2, as determined using RT-PCR and Western blot analysis. The Bax overexpression was significantly stronger in the antrum than in the corpus of H. pylori-infected patients. Four weeks after the eradication a marked decrease of neutrophil infiltration, an improvement of the grade of gastritis (mononuclear infiltration), and significant reduction in apoptosis rate were observed. After eradication the Bax mRNA expression was still at an increased level, whereas the Bcl-2 mRNA expression remained suppressed. CONCLUSIONS 1) H. pylori induces apoptosis in the gastric epithelium, at least in part, due to an upregulation of proapoptotic Bax and downregulation of antiapoptotic Bcl-2, and 2) Bax mRNA and protein expression was higher in the antrum than in the corpus, and this was probably due to greater inflammatory changes observed in the antrum than in the corpus.

Transcription of sonic hedgehog, a potential factor for gastric morphogenesis and gastric mucosa maintenance, is up-regulated in acidic conditions

Gastric body mucosa atrophy predisposes one to gastric cancer. Disturbances in the gastric differentiation process might play a role in the evolution of gastric atrophy. Sonic hedgehog (Shh) has recently been implicated as a crucial factor in gastric organogenesis and gland differentiation. In this study we investigated the expression of key factors in the Shh pathway, namely Shh and its receptor Patched (Ptc), in normal and pathologic stomach mucosa. Furthermore, the potential role of pH for Shh dysregulation was analyzed. Ten gastric biopsy specimens each from normal gastric mucosa, chronic nonatrophic gastritis, atrophic gastritis, and gastric cancer were included. Expression of Shh and Ptc was analyzed by immunohistochemistry. In normal body mucosa and in nonatrophic body gastritis, Shh was strongly expressed in parietal cells. Ptc was also expressed in gastric chief cells. Shh expression was almost completely lost in atrophic gastritis and in gastric cancer and absent in intestinal metaplasia. Ptc was markedly reduced in atrophy and only weakly positive in intestinal metaplasia and gastric cancer. In in vitro experiments, gastric cancer cell line 23132 was found positive for Shh. In long-term culture as well as in culture conditions with low pH, transcription of Shh in 23132 was significantly increased in quantitative reverse transcription PCR analyses. We concluded that the decreased expression of the Shh pathway in atrophic gastritis and gastric cancer might reflect altered differentiation processes within the gastric unit and contributes to the development of gastric atrophy. The increase of gastric pH might play a role in the development of gastric mucosa atrophy via reduction of Shh transcription.