Hubert Mörk

Expression Profiling and Genetic Alterations of the Selenoproteins GI-GPx and SePP in Colorectal Carcinogenesis

The trace element selenium is discussed as a chemopreventive agent in colorectal carcinogenesis. Selenocysteine-containing proteins, so-called selenoproteins, represent potential molecular targets for nutritive selenium supplementation. Due to their antioxidative potential, the selenoproteins gastrointestinal glutathione peroxidase (GI-GPx) and selenoprotein P (SePP) are considered to provide protection against reactive oxygen species (ROS), thereby reducing DNA damage and preventing development of colon cancer. GI-GPx and SePP are abundantly expressed in normal colon mucosa. Recently, we demonstrated both reduced SePP expression and increased GI-GPx expression in colorectal adenomas. In this study, we investigated the expression of SePP and GI-GPx in colorectal cancers compared with corresponding normal mucosa. Further, the occurrence of genetic alterations within the SePP and GI-GPx genes was analyzed. We observed a significant reduction or loss of SePP mRNA expression in colon cancers, whereas GI-GPx mRNA and protein expression varied between different tumor samples. In addition, we identified novel polymorphisms within the SePP and GI-GPx genes with so far unknown relevance for protein function. Our results argue against a general decrease of selenoprotein expression in colorectal carcinogenesis but imply specific differential regulation of expression of individual selenoproteins.

Reconstitution of Squamous Epithelium in Barrett's Oesophagus with Endoscopic Argon Plasma Coagulation: A Prospective Study

Background: Barretts oesophagus is a premalignant condition. Recent reports have suggested that laser coagulation or photodynamic therapy combined with acid suppression may induce reconstitution of squamous mucosa. However, a high percentage of residual glands remain in cases treated with both techniques. Argon plasma coagulation (APC) appears to be an attractive alternative to other thermoablative techniques. The aim of this study was to investigate the reconstitution of squamous epithelium in Barretts oesophagus after APC. Methods: Fifteen patients with histologically proven Barretts oesophagus were included in a prospective study. After base-line documentation by videotaping and biopsies, Barretts epithelium was treated by repeated APC at intervals of 4-6 weeks until complete squamous restoration was achieved. All patients were kept under high-dose proton pump inhibitor therapy. Results: In 13 patients complete reconstitution of squamous epithelium was achieved. Buried glands after squamous restora...

Compliance with Therapy in Patients with Chronic Hepatitis C: Associations with Psychiatric Symptoms, Interpersonal Problems, and Mode of Acquisition

Tolerance of interferon-α therapy for hepatitis C is often poor and medication is expensive. Compliance with diagnostic procedures and, even more important, with medical treatment is obviously critical to minimize the rate of dropouts and to maximize cost efficiency. Moreover, a good concordance with scheduled follow-ups is important for early recognition and treatment of interferon-associated side effects. Therefore, we investigated psychiatric symptoms, interpersonal problems, different modes of acquisition, and sociodemographic factors in HCV-infected patients as possible predictor variables of good versus poor compliance. In a longitudinal study, 74 patients with chronic hepatitis C (CHC) who fulfilled the criteria for treatment with interferon (IFN)-α-2b with or without ribavirin were investigated prospectively to identify those at risk for poor compliance during IFN medication. To assess predictive factors, we used both IIP-C (Inventory of Interpersonal Problems) and SCL-90-R (Symptom Check List 90 Items Revised) as psychometric instruments. Sociodemographic and somatic variables as well as compliance during IFN therapy were also evaluated. Poor compliance before or during medication was demonstrated by 23% (N = 17) of HCV patients. Sociodemographic factors and mode of acquisition, particularly former intravenous drug (IVD) abuse were not significantly linked with compliance. Logistic regression analysis demonstrated that the subgroup of patients with compliance problems was best identified by both pretherapeutic psychiatric symptoms and interpersonal problems. Predictive value was best and significant for anger-hostility (P = 0.009), intrusive (P = 0.014), depression (P = 0.015), and phobic anxiety (P = 0.049). Adopting this statistical prediction model, sensitivity was 47.1%, but specificity reached 98.3%. In total, 86.5% of cases were classified correctly. In situations of unclear indication for IFN therapy, psychological variables assessment of before the beginning of treatment may represent an additional decision-making factor.

Inverse mRNA expression of the selenocysteine-containing proteins GI-GPx and SeP in colorectal adenomas compared with adjacent normal mucosa

Four selenocysteine-containing proteins (gastrointestinal glutathione peroxidase, plasma glutathione peroxidase, selenoprotein P, and thioredoxin reductase-α) are expressed in the colonic mucosa. Because of their antioxidant functions, a protective role in colon carcinogenesis is discussed. The aim of this study was to elucidate an involvement of gastrointestinal selenoproteins during the adenoma-carcinoma sequence. Matched pairs of biopsies of colorectal adenomas and adjacent normal mucosa from 11 patients were analyzed for mRNA expression, protein expression, or enzyme activity of selenoproteins by Northern blot, Western blot, or enzymatic tests. All adenomas revealed a marked reduction of selenoprotein P and a variable increase of gastrointestinal glutathione peroxidase mRNA compared with adjacent tissue. Thioredoxin reductase-α and plasma glutathione peroxidase mRNA expression were not altered in adenomas. The Northern blot results were confirmed by Western blot analysis or enzyme activity measurement, respectively. We conclude that gastrointestinal glutathione peroxidase and selenoprotein P play a complementary role in the antioxidative cell defense along the adenoma-carcinoma sequence. It remains to be shown whether upregulation of gastrointestinal glutathione peroxidase in adenomas represents a compensatory mechanism to reduce susceptibility for oxidative damage resulting from the loss of selenoprotein P.

Hypereosinophilic syndrome resembling chronic inflammatory bowel disease with primary sclerosing cholangitis.

Surgical patient who presented with chronic inflammation of the colon, and initially also the terminal ileum, accompanied by marked diarrhea, is described. Repeated high-dose steroid therapy was only temporarily successful, and symptoms recurred upon dose reduction. During the further course of the disease, a marked elevation of alkaline phosphatase and transaminases, as well as soft tissues swelling occurred. Clinically, the diagnosis of inflammatory bowel disease with primary sclerosing cholangitis was made. Irregularities in the walls of the common bile duct and the intrahepatic ducts seen at endoscopic retrograde cholangiopancreatography were consistent with the latter diagnosis. However, extreme eosinophilia of peripheral blood, bone marrow and bowel mucosa was present, and liver histology showed eosinophilic cholangiohepatitis. Under the diagnosis of hypereosinophilic syndrome with involvement of bowel, liver and biliary system, therapy with hydroxyurea was initiated. The patients condition improved promptly. Eosinophil count and liver enzymes have remained normal under long-term medication with 1.0 g per day of this drug.

Analysis of neuroendocrine tumour metastases in the liver using contrast enhanced ultrasonography

Background. Imaging of liver tumours might be improved by contrast-enhanced ultrasonography, which allows much better demonstration of the microvascular system. The aim of this study was to assess the sonographic morphology and vascularity of neuroendocrine liver metastases. Methods. Forty-eight patients with histologically proven neuroendocrine tumours (NET) and suspected liver metastases – as well as 50 consecutive patients with liver metastases of other origins – were included in a prospective study to evaluate tumour characteristics using B-mode, colour Doppler (CDI) and contrast-enhanced ultrasound (CEUS). Results. In 4/48 patients with NET, liver biopsy revealed hemangiomas. The typical B-mode appearance was that of both echo-rich and echo-poor combined, also inhomogeneous depending on the size, and often centrally cystic. With CDI, neuroendocrine metastases appeared hypervascular (66%) or isovascular (34%). Metastases of another origin were hypovascular in 82%. With CEUS, neuroendocrine metastases showed increased arterial enhancement in 38 patients and hypoechoic appearance in the portalvenous phase in 39 patients. In liver metastases of another origin, the sensitivity for malignancy due to a hypoechoic appearance during the portalvenous phase was 100%. In liver metastases of NET origin the sensitivity for malignancy was 39/48 (82%). Conclusions. Neuroendocrine tumour metastases might show characteristics which are similar to hemangiomas. In patients with liver cirrhosis and severe fatty liver disease the identification of NET with CEUS as a malignant lesion is more difficult. The sensitivity of CEUS in identifying malignancy based on the lack of portalvenous enhancement is higher for metastases of other origin.

Glutathione peroxidase isoforms as part of the local antioxidative defense system in normal and Barrett's esophagus

The development of an oesophageal adenocarcinoma arising in Barretts mucosa is associated with a multistep process of genetic lesions that may be triggered by persistent oxidative damage. The glutathione peroxidase isoforms pGPx and GI‐GPx, which were identified recently in the mucosa of the esophagus, may play a role as defense factors to prevent such oxidative injury. To determine alterations of the expression of pGPx and GI‐GPx in Barretts mucosa as compared to primary and regenerative squamous epithelium. Biopsy samples of oesophageal mucosa of patients with Barretts esophagus (n = 12), patients with squamous restoration after thermal ablation (n = 10), and healthy controls (n = 5) were analyzed for pGPx and GI‐GPx mRNA expression by Northern blot and for glutathione peroxidase activity by enzymatic assay. Squamous regeneration was induced by argon plasma coagulation (APC) combined with proton pump inhibitor therapy. In Barretts epithelium mRNA levels of pGPx (the secreted isoform) were significantly reduced and of GI‐GPx (the intracellular isoform) significantly increased as compared to normal squamous mucosa. In squamous mucosa that had regenerated after APC, no significant differences compared to the expression pattern of primary squamous mucosa were found. Compared to squamous mucosa, Barretts metaplasia shows a different mRNA expression of pGPx and GI‐GPx that may be associated with increased susceptibility to oxidative damage.

Expression pattern of gastrointestinal selenoproteins— targets for selenium supplementation

There is experimental and epidemiological evidence for an association between low selenium levels and gastrointestinal cancer incidence, prevalence, and mortality. To identify targets for selenium supplementation in the human digestive tract, we examined mRNA expression of various selenocysteine-containing proteins in normal mucosa biopsy specimens. Tissue samples from the esophagus and from different sites of the stomach, small bowel, and colon were obtained during endoscopies of the upper and lower gastrointestinal tract. Northern blot analyses revealed a lack of cytosolic glutathione peroxidase mRNA but a differential mRNA expression pattern of gastrointestinal and plasma glutathione peroxidase, selenoprotein P, and thioredoxin reductase. Glutathione peroxidase and thioredoxin reductase activities were detected in the mucosa of all biopsies, but the differential pattern did not reflect the differential mRNA steady-state levels. In addition to gastrointestinal glutathione peroxidase, which was found to play a role in colon cancer resistance, we identified further gastrointestinal selenoproteins, which may be involved in gastrointestinal cell defense and cell differentiation.

High recurrence rate of Barrett's epithelium during long-term follow-up after argon plasma coagulation

Objective. Several studies have shown that argon plasma coagulation (APC) combined with proton-pump inhibitor (PPI) therapy is a suitable procedure to eradicate Barretts epithelium for a short-term follow-up. The real impact of this kind of management with respect to cancer risk and durability of squamous regeneration remains unclear. We present the follow-up data for up to 51 months after eradication of Barretts mucosa. Material and methods. In 1998–2001, 25 patients with Barretts esophagus were included in a prospective study. After baseline documentation, Barretts epithelium was treated with repeated APC until complete squamous restoration was reached. Thereafter, all patients were continuously treated with high-dose PPIs. Results. Each patient underwent a median of four APC sessions. Twenty-one (84%) of the patients had complete squamous regeneration at the end of treatment. During a follow-up of up to 51 months, Barretts epithelium was found to have recurred in 14/21 (66%) patients. Including the patients with initially incomplete squamous restoration, a long-lasting and complete effect was achieved in only 7 patients (28%) after a mean follow-up period of 30 months. Conclusions. So far, it is still not proven whether coagulation-induced squamous regeneration reduces the risk of Barretts carcinoma. Furthermore, the high relapse rate, the procedure-related risk, and the high costs incurred preclude the routine use of APC for the treatment of non-dysplastic Barretts esophagus. The different recurrence rates between published studies may be due to technical differences and PPI schedule. We suggest that optimal conditions for the procedure must be defined before further studies are undertaken.

A complex DNA-repeat structure within the Selenoprotein P promoter contains a functionally relevant polymorphism and is genetically unstable under conditions of mismatch repair deficiency

Epidemiological data, animal studies and interventional studies provide evidence for a potential chemopreventive effect of selenium during development of colorectal cancer. The human glycoprotein Selenoprotein P (SeP) contains up to 50% of plasma selenium content. SeP is expressed in the gastrointestinal tract and the liver, where its expression is downregulated by various proinflammatory cytokines (Il1β, TGFβ, IFNγ). Previously, we have demonstrated dramatically reduced SeP expression in human colon adenomas. Here, we have identified a complex (A)4-C-(A)4-GG-(A)8-GCT-(TC)5-(T)17 (bp −429 to bp − 477) repeat structure within the SeP promoter and we have analysed this regulatory DNA sequence with respect to polymorphisms, genomic instability and functional relevance to promoter activity. As opposed to the (TC)5 variant we identified a novel (TC)3 polymorphism within this repeat in the general population, which conferred significantly reduced basal promoter activity to reporter gene constructs in HepG2 cells. Allelic distribution of this (TC)n element was similar in colon carcinoma patients and healthy controls. Additionally, we observed genetic instability within the (T)17 repeat motif in colon cancers of the mutator phenotype. This instability of the (T)17 repeat had no effect on basal promoter activity in reporter gene assays. In conclusion, we characterised a complex repeat structure within the SeP promoter that may be of functional relevance to SeP gene expression. Further studies on the effect of different SeP promoter genotypes on SeP protein expression and disease susceptibility are needed.