Wnt/beta-catenin/Tcf signaling: A critical pathway in gastrointestinal tumorigenesis

Cancers of the gastrointestinal tract, including the liver, bile ducts, and pancreas, constitute the largest group of malignant tumors. Colorectal cancer is one of the most common neoplastic diseases in Western countries and one of the leading causes of cancer-related deaths. Inactivation of the adenomatous polyposis coli (APC) tumor-suppressor gene during early adenoma formation is thought to be the first genetic event in the process of colorectal carcinogenesis followed by mutations in oncogenes like K-Ras and tumor-suppressor genes like p53. Identification of the interaction of APC with the proto-oncogene beta-catenin has linked colorectal carcinogenesis to the Wnt-signal transduction pathway. The main function of APC is thought to be the regulation of free beta-catenin in concert with the glycogen synthase kinase 3beta (GSK-3beta) and Axin proteins. Loss of APC function, inactivation of Axin or activating beta-catenin mutations result in the cellular accumulation of beta-catenin. Upon translocation to the nucleus beta-catenin serves as an activator of T-cell factor (Tcf)-dependent transcription leading to an increased expression of several specific target genes including c-Myc, cyclin D1, MMP-7, and ITF-2. While APC mutations are almost exclusively found in colorectal cancers, deregulation of Wnt/beta-catenin/Tcf signaling is also common in other gastrointestinal and extra-gastrointestinal human cancers. In a fraction of hepatocellular carcinomas the Writ pathway is deregulated by inactivation of Axin or stabilizing mutations of beta-catenin. The majority of hepatoblastomas and a group of gastric cancers also carry beta-catenin mutations. Clearly, this pathway harbors great potential for future applications in cancer diagnostics, staging, and therapy. Copyright (C) 2002 S. Karger AG, Basel

Waldränder und Knicks als Lebensräume von Schmetterlingszönosen in der Agrarlandschaft

The habitat quality of different from human impact influenced forest edges and hedges for butterflies and moths is investigated. For this purpose a comparison of the species occurring on trees and bushes is made. In addition two light-traps are operated continuously to get an overview about the Lepidoptera fauna in this area. The results can be used to optimise forest edges and hedges in agricultural land-scapes as habitats for butterflies and moths

Attitude to Secondary Prevention and Concerns about Colonoscopy Are Independent Predictors of Acceptance of Screening Colonoscopy

Background: Colonoscopy in combination with endoscopic polypectomy has been shown to be an efficient measure for reducing colorectal cancer incidence. In Germany, a colorectal cancer screening program based on colonoscopy for individuals aged 55 and above was introduced in 2002. However, for largely unknown reasons, participation rates remain low. The purpose of this study was to identify factors influencing compliance with colorectal cancer screening. Methods: A structured survey of 239 individuals aged 55-79 years ;was performed. Statistical analysis included chi(2) test, t test, principal component analysis, and logistic regression. Results: 56% of previously screened, but only 26% of non-screened individuals had received a recommendation to undergo screening colonoscopy. 50% of the non-screened believed a screening colonoscopy should only be performed in case of complaints. Univariate analysis identified participation in any secondary prevention measures (p < 0.001), concerns about colonoscopy (p < 0.012), and knowledge about colorectal cancer (p < 0.001) as critical issues distinguishing between groups. Multivariate analysis revealed that secondary prevention (p < 0.001) and concerns about colonoscopy (p = 0.026) were independent predictors of compliance with screening recommendations. Conclusion: Our survey has identified critical factors deterring compliance with colorectal cancer screening recommendations. This will help to direct future campaigns in order to increase participation in colorectal cancer screening. Copyright (C) 2010 S. Karger AG, Base

Risk of advanced colorectal neoplasia according to age and gender.

Colorectal cancer (CRC) is one of the leading causes of cancer related morbidity and death. Despite the fact that the mean age at diagnosis of CRC is lower in men, screening by colonoscopy or fecal occult blood test (FOBT) is initiated at same age in both genders. The prevalence of the common CRC precursor lesion, advanced adenoma, is well documented only in the screening population. The purpose of this study was to assess the risk of advanced adenoma at ages below screening age. We analyzed data from a census of 625,918 outpatient colonoscopies performed in adults in Bavaria between 2006 and 2008. A logistic regression model to determine gender- and age-specific risk of advanced neoplasia was developed. Advanced neoplasia was found in 16,740 women (4.6%) and 22,684 men (8.6%). Male sex was associated with an overall increased risk of advanced neoplasia (odds ratio 1.95; 95% confidence interval, CI, 1.91 to 2.00). At any age and in any indication group, more colonoscopies were needed in women than in men to detect advanced adenoma or cancer. At age 75 14.8 (95% CI, 14.4-15.2) screening, 18.2 (95% CI, 17.7-18.7) diagnostic, and 7.9 (95% CI, 7.6-8.2) colonoscopies to follow up on a positive FOBT (FOBT colonoscopies) were needed to find advanced adenoma in women. At age 50 39.0 (95% CI, 38.0-40.0) diagnostic, and 16.3 (95% CI, 15.7-16.9) FOBT colonoscopies were needed. Comparable numbers were reached 20 and 10 years earlier in men than in women, respectively. At any age and independent of the indication for colonoscopy, men are at higher risk of having advanced neoplasia diagnosed upon colonoscopy than women. This suggests that starting screening earlier in life in men than in women might result in a relevant increase in the detection of asymptomatic preneoplastic and neoplastic colonic lesions

Genetic targeting of B-Raf(V600E) affects survival and proliferation and identifies selective agents against BRAF-mutant colorectal cancer cells

Background: Colorectal cancers carrying the B-Raf V600E-mutation are associated with a poor prognosis. The purpose of this study was to identify B-Raf(V600E)-mediated traits of cancer cells in a genetic in vitro model and to assess the selective sensitization of B-Raf(V600E)-mutant cancer cells towards therapeutic agents. Methods: Somatic cell gene targeting was used to generate subclones of the colorectal cancer cell line RKO containing either wild-type or V600E-mutant B-Raf kinase. Cell-biologic analyses were performed in order to link cancer cell traits to the BRAF-mutant genotype. Subsequently, the corresponding tumor cell clones were characterized pharmacogenetically to identify therapeutic agents exhibiting selective sensitivity in B-Raf(V600E)-mutant cells. Results: Genetic targeting of mutant BRAF resulted in restoration of sensitivity to serum starvation-induced apoptosis and efficiently inhibited cell proliferation in the absence of growth factors. Among tested agents, the B-Raf inhibitor dabrafenib was found to induce a strong V600E-dependent shift in cell viability. In contrast, no differential sensitizing effect was observed for conventional chemotherapeutic agents (mitomycin C, oxaliplatin, paclitaxel, etoposide, 5-fluorouracil), nor for the targeted agents cetuximab, sorafenib, vemurafenib, RAF265, or for inhibition of PI3 kinase. Treatment with dabrafenib efficiently inhibited phosphorylation of the B-Raf downstream targets Mek 1/2 and Erk 1/2. Conclusion: Mutant BRAF alleles mediate self-sufficiency of growth signals and serum starvation-induced resistance to apoptosis. Targeting of the BRAF mutation leads to a loss of these hallmarks of cancer. Dabrafenib selectively inhibits cell viability in B-Raf(V600E) mutant cancer cells