ß-Catenin signaling dosage dictates tissue-specific tumor predisposition in Apc-driven cancer.

Apc-driven tumor formation in patients and Apc-mutant mouse models is generally attributed to increased levels of ß-catenin signaling. We and others have proposed that a specific level of ß-catenin signaling is required to successfully initiate tumor formation, and that each tissue prefers different dosages of signaling. This is illustrated by APC genotype-tumor phenotype correlations in cancer patients, and by the different tumor phenotypes displayed by different Apc-mutant mouse models. Apc1638N mice, associated with intermediate ß-catenin signaling, characteristically develop intestinal tumors (<10) and extra-intestinal tumors, including cysts and desmoids. Apc1572T mice associated with lower levels of ß-catenin signaling are free of intestinal tumors, but instead develop mammary tumors. Although the concept of ß-catenin signaling dosage and its impact on tumor growth among tissues is gaining acceptance, it has not been formally proven. Additionally, alternative explanations for Apc-driven tumor formation have been proposed. To obtain direct evidence for the dominant role of ß-catenin dosage in tumor formation and tissue-specific tumor predisposition, we crossed Apc1638N mice with heterozygous ß-catenin knockout mice, thereby reducing ß-catenin levels. Whereas all the Apc1638N;Ctnnb1(+/+) mice developed gastrointestinal tumors, none were present in the Apc1638N;Ctnnb1(-/+) mice. Incidence of other Apc1638N-associated lesions, including desmoids and cysts, was strongly reduced as well. Interestingly, Apc1638N;Ctnnb1(-/+) females showed an increased incidence of mammary tumors, which are normally rarely observed in Apc1638N mice, and the histological composition of the tumors resembled that of Apc1572T-related tumors. Hereby, we provide in vivo genetic evidence confirming the dominant role of ß-catenin dosage in tumor formation and in dictating tumor predisposition among tissues in Apc-driven cancer.

Early morbidity encountered in the dietary-related mouse model of Barrett's esophagus: a question of zinc?

Recently, a mouse model for Barrett's esophagus based on a zinc-deficient diet supplemented with deoxycholic bile acids has been published. The aim of this study was to attempt to reproduce these data and extend them by employing genetically modified mice and intraperitoneal iron supplementation. The study design encompassed six experimental groups (wild type, Apc-mutant and Smad4-mutant mice, with or without iron injections), with all animals fed with the zinc-deficient diet supplemented with deoxycholic bile acids. All treatments were started at 3-5 weeks of age (the majority [78%] at 5 weeks). Animals were scheduled for euthanasia at two distinct time points, namely at 3 and 6 months of age. All mice showed signs of considerable distress already 4 weeks after the start of the modified diets, and had to be euthanized before the first evaluation time point (mean age 9.3 weeks, range 5-15 weeks). No differences were observed between wild type and genetically modified mice, or between animals with or without iron supplementation. On histological examination, we could not detect any lesions (Barrett's esophagus-like or tumors) other than esophagitis. In the currently presented experimental settings, we were not able to reproduce the mouse model according to which Barrett's-like lesions could be detected in animals fed with the zinc-deficient diet supplemented with deoxycholic bile acids.

Multiplicity in polyp count and extracolonic manifestations in 40 Dutch patients with MYH associated polyposis coli (MAP).

OBJECTIVE: To investigate the contribution of MYH associated polyposis coli (MAP) among polyposis families in the Netherlands, and the prevalence of colonic and extracolonic manifestations in MAP patients. METHODS: 170 patients with polyposis coli, who previously tested negative for APC mutations, were screened by denaturing gradient gel electrophoresis and direct sequencing to identify MYH germline mutations. RESULTS: Homozygous and compound heterozygous MYH mutations were identified in 40 patients (24%). No difference was found in the percentage of biallelic mutation carriers between patients with 10-99 polyps or 100-1000 polyps (29% in both groups). Colorectal cancer was found in 26 of the 40 patients with MAP (65%) within the age range 21 to 67 years (median 45). Complete endoscopic reports were available for 16 MAP patients and revealed five cases with gastro-duodenal polyps (31%), one of whom also presented with a duodenal carcinoma. Breast cancer occurred in 18% of female MAP patients, significantly more than expected from national statistics (standardised morbidity ratio = 3.75). CONCLUSIONS: Polyp numbers in MAP patients were equally associated with the attenuated and classical polyposis coli phenotypes. Two thirds of the MAP patients had colorectal cancer, 95% of whom were older than 35 years, and one third of a subset of patients had upper gastrointestinal lesions. Endoscopic screening of the whole intestine should be carried out every two years for all MAP patients, starting from age 25-30 years. The frequent occurrence of additional extraintestinal manifestations, such as breast cancer among female MAP patients, should be thoroughly investigated.

New mutations in the neuronal ceroid lipofuscinosis genes.

Thirty-eight mutations and seven polymorphisms have recently been reported in the genes underlying the neuronal ceroid lipofuscinoses (NCLs) including 11 new mutations described here. A total of 114 mutations and 28 polymorphisms have now been described in the five human genes identified which cause NCL. Thirty-eight mutations are recorded for CLN1/PPT; 40 for CLN2/TTP-1, 31 for CLN3, four for CLN5, one for CLN8. Two mutations have been described in animal genes (cln8/mnd, CTSD). All mutations in NCL genes are contained in the NCL Mutation Database (http://www.ucl.ac.uk/NCL).

First-trimester diagnosis of late-infantile neuronal ceroid lipofuscinosis (LINCL) by tripeptidyl peptidase I assay and CLN2 mutation analysis.

Late-infantile neuronal ceroid lipofuscinosis (LINCL) is a progressive neurodegenerative disorder caused by the deficiency of lysosomal tripeptidyl peptidase I (TPP-I) encoded by the CLN2 gene. We report the first case of early prenatal diagnosis of LINCL by combined enzyme and mutation analysis. TPP-I activity in chorionic villi (CV) was less than 2% of the mean normal control level and g.1946A > G and g.3670C > T mutations were demonstrated, as in the two previously affected children. After termination of pregnancy, TPP-I deficiency was confirmed in cultured CV cells and in the fetal skin fibroblasts. The expression of unequivocal TPP-I deficiency in CV demonstrates that enzyme assay is a reliable option for prenatal diagnosis of LINCL.

First-trimester diagnosis of infantile neuronal ceroid lipofuscinosis (INCL) using PPT enzyme assay and CLN1 mutation analysis.

Infantile neuronal ceroid lipofuscinosis (INCL) is a progressive neurodegenerative disorder in childhood which is caused by the deficiency of the lysosomal palmitoyl-protein thioesterase (PPT) encoded by the CLN1 gene. In a pregnancy at risk for INCL, chorionic villi (CV) were studied using a novel fluorometric PPT enzyme assay in combination with mutation-analysis of the CLN1 gene. The PPT activity in chorionic villi was found to be deficient and homozygosity for the C451T mutation in CLN1 was found. The pregnancy was terminated and the PPT deficiency was confirmed in cultured CV cells as well as in the cultured fetal skin fibroblasts. This report shows the first early prenatal diagnosis of INCL performed by fluorometric enzyme analysis and mutation analysis of the CLN1 gene.

Genetic heterogeneity of neuronal ceroid lipofuscinosis in The Netherlands.

An overview of patients in the Netherlands who are known to us with neuronal ceroid lipofuscinosis (NCL) is presented. Several CLN genes involved in NCL have been isolated or mapped. We have analyzed families with different types of NCL with polymorphic markers linked to CLN loci to investigate the genetic heterogeneity of NCL in the Netherlands. Haplotype analysis suggests that in addition to the CLN2 and CLN6 genes another gene is involved in at least one family with late infantile NCL in the Netherlands. The CLN2 and CLN6 loci have also been excluded in a family with protracted juvenile NCL.