Laminin α1 orchestrates VEGFA functions in the ecosystem of colorectal carcinoma.

Background Information: Tumor stroma remodeling is a key feature of malignant tumors and can promote cancer progression. Laminins are major constituents of basement membranes that physically separate the epithelium from the underlying stroma.

Results: By employing mouse models expressing high and low levels of the laminin α1 chain (LMα1), we highlighted its implication in a tumor-stroma crosstalk, thus leading to increased colon tumor incidence, angiogenesis and tumor growth.

Hemidesmosome integrity protects the colon against colitis and colorectal cancer.

Objective: Epidemiological and clinical data indicate that patients suffering from IBD with long-standing colitis display a higher risk to develop colorectal high-grade dysplasia. Whereas carcinoma invasion and metastasis rely on basement membrane (BM) disruption, experimental evidence is lacking regarding the potential contribution of epithelial cell/BM anchorage on inflammation onset and subsequent neoplastic transformation of inflammatory lesions. Herein, we analyse the role of the α6β4 integrin receptor found in hemidesmosomes that attach intestinal epithelial cells (IECs) to the laminin-containing BM.

The laminin response in inflammatory bowel disease: protection or malignancy?

Laminins (LM), basement membrane molecules and mediators of epithelial-stromal communication, are crucial in tissue homeostasis. Inflammatory Bowel Diseases (IBD) are multifactorial pathologies where the microenvironment and in particular LM play an important yet poorly understood role in tissue maintenance, and in cancer progression which represents an inherent risk of IBD. Here we showed first that in human IBD colonic samples and in murine colitis the LMα1 and LMα5 chains are specifically and ectopically overexpressed with a concomitant nuclear p53 accumulation.

Abnormal Wnt and PI3Kinase signaling in the malformed intestine of lama5 deficient mice.

Laminins are major constituents of basement membranes and are essential for tissue homeostasis. Laminin-511 is highly expressed in the intestine and its absence causes severe malformation of the intestine and embryonic lethality. To understand the mechanistic role of laminin-511 in tissue homeostasis, we used RNA profiling of embryonic intestinal tissue of lama5 knockout mice and identified a lama5 specific gene expression signature.

Dysregulation of laminins in intestinal inflammation.

Laminins are structural components of basement membranes that regulate and control many cellular functions. Changes in basement membrane composition play significant roles in etiology of diseases. Inflammatory bowel diseases are conditions that lead to defects in the mucosal barrier which includes the basement membrane underlying the epithelium.

Histologic characteristics of non-microsatellite-instable colon adenomas correlate with distinct molecular patterns.

Colon carcinogenesis encompasses the stepwise accumulation of genomic aberrations correlated with the transition of aberrant crypt-adenoma-carcinoma. Recent data have revealed that, in addition to the microsatellite-instable phenotype, the chromosome instability pathway, representing four fifth of the colon carcinoma, could be involved in heterogeneous molecular alterations. Our project was aimed at determining the existence of distinct molecular subtypes in 159 non-microsatellite-instable colon polyps and their correlation with histology and dysplasia, using allelotyping, MGMT promoter gene methylation status, and K-RAS mutation analyses.

The role of the basement membrane as a modulator of intestinal epithelial-mesenchymal interactions.

Intestinal development is a process of continuous dynamic bidirectional crosstalk between epithelial and underlying mesenchymal cells. This crosstalk is mediated by well-dissected signaling pathways. Another crucial actor in the epithelio-mesenchymal interactions is the stromal microenvironment, which is composed of extracellular matrix molecules.

Loss of enteroendocrine cells in mice alters lipid absorption and glucose homeostasis and impairs postnatal survival.

At least 10 enteroendocrine cell types have been identified, and the peptide hormones they secrete have diverse functions that include regulation of glucose homeostasis, food intake, and gastric emptying. Mice lacking individual enteroendocrine hormones, their receptors, or combinations of these have shed light on the role of these hormones in the regulation of energy homeostasis. However, because enteroendocrine hormones have partially overlapping functions, these loss-of-function studies produced only minor phenotypes, and none of the enteroendocrine hormones was shown to be essential for life.

Evidence for various 20q status using allelotyping, CGH arrays, and quantitative PCR in distal CIN colon cancers.

The genomic aberration profile of chromosome 20q in distal CIN colon carcinomas was analysed using allelotyping and CGH arrays. Allelotyping revealed carcinomas with allelic imbalance along the full long arm, and carcinomas with fully non-aberrant 20q. Oligonucleotide-based CGH showed that among the carcinomas without allelic imbalance, 47% had in fact a gain.

Tissue recombinants to study extracellular matrix targeting to basement membranes.

Several techniques have been used to study the expression of basement membranes molecules but none of them allow distinguishing the cellular origin of the deposition of a single molecule at the subepithelial basement membrane. For this purpose, we designed an experimental model using recombinants between chick and mouse embryonic intestines. Following constructions of interspecies endodermal/mesenchymal associations in culture, developmental growth was achieved by in vivo transplantation in the chick embryo.

Multiple regulatory regions control the complex expression pattern of the mouse Cdx2 homeobox gene.

Background & Aims: The Cdx2 homeobox gene exerts multiple functions including trophectoderm specification, antero-posterior patterning, and determination of intestinal identity. The aim of this study was to map genomic regions that regulate the transcription of Cdx2, with a particular interest in the gut.

Methods: Genomic fragments covering 13 kilobase (kb) of the mouse Cdx2 locus were analyzed in transgenic mice and in cell assays.

Cdx1, a dispensable homeobox gene for gut development with limited effect in intestinal cancer.

The homeobox gene Cdx1 is involved in anteroposterior patterning in embryos and its expression selectively persists in the intestinal epithelium throughout life. In human colon cancers, Cdx1 is overexpressed in few cases and lost in the majority of adenocarcinomas. We used mouse models of gain and loss-of-function to investigate the role of Cdx1 in intestinal development and cancers.

Sprouty2 inhibits BDNF-induced signaling and modulates neuronal differentiation and survival.

Sprouty (Spry) proteins are ligand-inducible inhibitors of receptor tyrosine kinases-dependent signaling pathways, which control various biological processes, including proliferation, differentiation and survival. Here, we investigated the regulation and the role of Spry2 in cells of the central nervous system (CNS). In primary cultures of immature neurons, the neurotrophic factor BDNF (brain-derived neurotrophic factor) regulates spry2 expression.

The intestine-specific homeobox gene Cdx2 decreases mobility and antagonizes dissemination of colon cancer cells.

The gravity of colorectal cancer is mainly due to the capacity of tumor cells to migrate out of the tumor mass to invade the stroma and disseminate as metastases. The acquisition of a migratory phenotype also occurs during wound healing. Here, we show that several features characterizing invasive colon tumor cells are shared by migrating cells during wound repair in vitro.

Different effects of the Cdx1 and Cdx2 homeobox genes in a murine model of intestinal inflammation.

Aims: The CDX1 and CDX2 homeoproteins are intestine-specific transcription factors regulating homeostasis. We investigated their relevance in experimentally-induced intestinal inflammation.

Methods: The response to intestinal inflammation induced by dextran sodium sulfate (DSS) was compared in wild type, Cdx1(-/-) and Cdx2(+/-) mice.

The microenvironment controls CDX2 homeobox gene expression in colorectal cancer cells.

The homeobox gene CDX2 plays a major role in development, especially in the gut, and it also acts as a tumor suppressor in the adult colon. Using orthotopic and heterotopic xenografts of human primary colorectal tumor cells and cell lines in nude mice, we addressed the effect of the microenvironment on CDX2 expression. In cells expressing CDX2 at a high level in culture, this level was maintained in subcutaneous grafts but was reduced when implanted into the cecum wall.

Essential role of the JAK/STAT1 signaling pathway in the expression of inducible nitric-oxide synthase in intestinal epithelial cells and its regulation by butyrate.

Nitric oxide (NO) is a highly reactive free radical that modulates tumorigenesis through its ability to regulate cell proliferation, cell death, migration and angiogenesis. Although the role of NO has been well studied in inflammatory cells, much less is known about the regulation of NO production in epithelial cells. We demonstrated that in intestinal epithelial cells the expression of inducible NO synthase (iNOS), the critical enzyme in the synthesis of NO, is synergistically stimulated by bacterial lipopolysaccharide (LPS) and interferon gamma (IFNgamma) or by the combination of tumor necrosis factor (TNF) and IFNgamma at the transcriptional level.

Morphological and biochemical alterations in the jejunum following iodoacetamide-induced colitis in rats.

This study aims to describe the morphological alterations in the small and large intestines as well as the expression of some enterocyte enzymes and carriers in a rat model of iodoacetamide-induced colitis. Biopsies from the large and small intestines were taken at 1, 2, 4, 8, and 16 days postinduction and studied by light microscopy. The expressions of lactase, sucrase, aminopeptidase, and Glut-5 in the jejunum were studied by immunohistochemistry.

In vitro models of intestinal epithelial cell differentiation.

The intestinal epithelium is a particularly interesting tissue as (1) it is in a constant cell renewal from a stem cell pool located in the crypts which form, with the underlying fibroblasts, a stem cell niche and (2) the pluripotent stem cells give rise to four main cell types: enterocytes, mucus, endocrine, and Paneth cells. The mechanisms leading to the determination of phenotype commitment and cell-specific expressions are still poorly understood. Although transgenic mouse models are powerful tools for elucidating the molecular cascades implicated in these processes, cell culture approaches bring easy and elegant ways to study cellular behavior, cell interactions, and cell signaling pathways for example.

Functional interaction between the homeoprotein CDX1 and the transcriptional machinery containing the TATA-binding protein.

We have previously reported that the CDX1 homeoprotein interacts with the TATA-box binding protein (TBP) on the promoter of the glucose-6-phosphatase (G6Pase) gene. We show here that CDX1 interacts with TBP via the homeodomain and that the transcriptional activity additionally requires the N-terminal domain upstream of the homeodomain. CDX1 interacting with TBP is connected to members of the TFIID and Mediator complexes, two major elements of the general transcriptional machinery.

Allelotyping analyses of synchronous primary and metastasis CIN colon cancers identified different subtypes.

In colorectal cancer, the molecular alterations that lead to metastasis are not clearly established, probably because of their high genetic complexity. To identify combinations of genetic changes involved in tumor progression and metastasis, we focused on chromosome instable (CIN) colon cancers. We compared by allelotyping of 33 microsatellites, the genomic alterations of 38 primary colon tumors with the synchronously resected matched liver metastases (CLM).

Cytokine expression in rat colon during postnatal development: regulation by glucocorticoids.

Objectives: Cytokine expression and regulation by glucocorticoids and retinoic acid were investigated in the colon during postnatal development.

Materials And Methods: Gene expression of the transforming growth factors (TGFs) TGF-beta1, TGF-beta2 and TGF-alpha and the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) was evaluated by reverse transcription-polymerase chain reaction (RT-PCR) in rat colon mucosa during weaning and in adult rats. Protein expression and distribution of TGF-betas was analysed in the colon from 14- and 60-day-old animals.

DCC regulates cell adhesion in human colon cancer derived HT-29 cells and associates with ezrin.

The deleted in colorectal cancer (DCC) gene encodes a 170- to 190-kDa protein of the Immunoglobulin superfamily. Firstly identified as a tumor suppressor gene in human colorectal carcinomas, the main function for DCC has been described in the nervous system as part of a receptor complex for netrin-1. Moreover, roles in mucosecretory cell differentiation and as inducer of apoptosis have also been reported.

Frequent rearrangements and amplification of the CDX2 homeobox gene in human sporadic colorectal cancers with chromosomal instability.

The expression of the CDX2 gene, a crucial regulator of gut homeostasis, is altered in human colorectal cancers in parallel with de-differentiation. Here, we have investigated the chromosomal status of CDX2 in human sporadic colorectal cancers with the phenotype of chromosomal instability. Allelic imbalance determination showed frequent rearrangements at the CDX2 locus.

Primary tumour genetic alterations and intra-tumoral heterogeneity are maintained in xenografts of human colon cancers showing chromosome instability.

Evaluation of the role of clonal heterogeneity in colon tumour sensitivity/resistance to drugs and/or in conferring metastatic potential requires an adequate experimental model in which the tumour cells maintain the initial genetic alterations and intra-tumoral heterogeneity through maintenance of the genetic clones present in the initial tumour. Therefore, we xenografted subcutaneously into nude mice seven human colonic tumours (from stages B1 to D) that showed chromosome instability and transplanted them sequentially for up to 14 passages. Maintenance after xenografting of the genetic alterations present in the initial tumours was scored by allelotype studies targeting 45 loci localized on 18 chromosomes.