Progressive changes in adherens junction structure during intestinal adenoma formation in Apc mutant mice

A truncation mutant of adenomatous polyposis coli impairs apical cell extrusion through elevated epithelial tissue tension

Tissue tension encompasses the mechanical forces exerted on solid tissues within animal bodies, originating from various sources such as cellular contractility, interactions with neighboring cells and the extracellular matrix. Emerging evidence indicates that an imbalance in such forces can influence structural organization, homeostasis, and potentially contribute to disease. For instance, heightened tissue tension can impede apical cell extrusion, leading to the retention of apoptotic or transformed cells. In this study, we investigate the potential role of adenomatous polyposis coli (APC) in modulating tissue tension. Our findings reveal that expression of an APC truncation mutant elevates epithelial tension via the RhoA/ROCK pathway. This elevation induces morphological alterations and hampers apoptotic cell extrusion in cultured epithelial cells and organoids, both of which could be mitigated by pharmacologically restoring the tissue tension. This raises the possibility that APC mutations may exert pathogenetic effects by altering tissue mechanics.

LncRNA GAS5 Modulates the Progression of Glioma Through Repressing miR-135b-5p and Upregulating APC

Purpose

The main purpose of this paper is to explore the interaction between GAS5 and miR-135b-5p to understand their function in the metastasis, invasion, and proliferation of glioma. This may provide new ideas for the pathogenesis and treatment of glioma.

Patients and Methods

Western blotting assays and RT‑qPCR were employed to investigate the expression of related genes in glioma tissues or cell lines. CCK-8 was used to examine the impact of GAS5 on cell viability. Motile activities were adopted by the transwell and wound healing experiments. A double luciferase experiment was performed to elucidate transcriptional regulation.

Results

GAS5 showed low expression in glioma cells and tissues, and up-regulation of GAS5 could depress the invasion, proliferation, and metastasis of glioma. GAS5 negatively regulates miR-135b-5p, which can counteract the cellular effects caused by GAS5. APC was the target of miR-135b-5p, and GAS5 can regulate the expression of APC by sponging miR-135b-5p. APC overexpression reversed the effects of miR-135b-5p promotion on glioma cells, while miR-135b-5p has the opposite function. As a downstream target gene of GAS5, miR-135b-5p was negatively regulated by GAS5. The restoration of miR-135b-5p can remarkably reverse the impact of GAS5 on glioma cells. In addition, GAS5 increased the expression of APC in glioma cells by inhibiting miR-135b-5p.

Conclusion

GAS5 increased APC expression by restraining miR-135b-5p and partially blocked the progression of glioma, suggesting that it could be an advantageous therapeutic target for glioma intervention.

Genes regulating membrane-associated E-cadherin and proliferation in adenomatous polyposis coli mutant colon cancer cells: High content siRNA screen

Truncating mutations in the tumour suppressor gene APC occur frequently in colorectal cancers and result in the deregulation of Wnt signalling as well as changes in cell-cell adhesion. Using quantitative imaging based on the detection of membrane-associated E-cadherin, we undertook a protein coding genome-wide siRNA screen to identify genes that regulate cell surface E-cadherin in the APC-defective colorectal cancer cell line SW480. We identified a diverse set of regulators of E-cadherin that offer new insights into the regulation of cell-cell adhesion, junction formation and genes that regulate proliferation or survival of SW480 cells. Among the genes whose depletion promotes membrane-associated E-cadherin, we identified ZEB1, the microRNA200 family, and proteins such as a ubiquitin ligase UBE2E3, CDK8, sorting nexin 27 (SNX27) and the matrix metalloproteinases, MMP14 and MMP19. The screen also identified 167 proteins required for maintaining E-cadherin at cell-cell adherens junctions, including known junctional proteins, CTNND1 and CTNNA1, as well as signalling enzymes, DUSP4 and MARK2, and transcription factors, TEAD3, RUNX2 and TRAM2. A better understanding of the post-translational regulation of E-cadherin provides new opportunities for restoring cell-cell adhesion in APC-defective cells.

PAUF/ZG16B promotes colorectal cancer progression through alterations of the mitotic functions and the Wnt/β-catenin pathway

Pancreatic adenocarcinoma upregulated factor (PAUF), also known as ZG16B, was previously found in the secretome of metastatic colorectal cancer cells. Here, we demonstrated the presence of PAUF at the intracellular level and its multiple effects on cancer progression. An initial decline of PAUF expression was observed at early stages of colorectal cancer followed by an increase at the metastatic site. PAUF was located at different cellular compartments: membrane-associated vesicles, endosomes, microtubule-associated vesicles, cell growth cones and the cell nucleus. PAUF loss in two colorectal cancer cell lines caused severe alterations in the cell phenotype and cell cycle, including tetraploidy, extensive genomic alterations, micronuclei and increased apoptosis. An exhaustive analysis of the PAUF interactome using different proteomic approaches revealed the presence of multiple components of the cell cycle, mitotic checkpoint, Wnt pathway and intracellular transport. Among the interacting proteins we found ZW10, a moonlighting protein with a dual function in membrane trafficking and mitosis. In addition, PAUF silencing was associated to APC loss and increased β-catenin nuclear expression. Altogether, our results suggest that PAUF depletion increases aneuploidy, promotes apoptosis and activates the Wnt/β-catenin pathway in colorectal cancer cells facilitating cancer progression. In summary, PAUF behaves as a multifunctional protein, with different roles in cancer progression according to the extra- or intracellular expression, suggesting a therapeutic value for colorectal cancer.

Adaptogenic flower buds exert cancer preventive effects by enhancing the SCFA-producers, strengthening the epithelial tight junction complex and immune responses

Microbiome therapy has attracted a keen interest from both research and business sectors. Our lab has been applying this "second genome" platform to assess the functionality of herbal medicines with fulfilling results. In this study, we applied this platform to assess the potential cancer-preventive effects of three selected adaptogenic plants. The flower buds from these plants were used to constitute Preparations SL and FSP according to the receipts of two commonly consumed Chinese medicinal decoctions for gastrointestinal discomfort. Preparation SL contains Sophorae japonica and Lonicerae Japonicae, and Preparation FSP contains Sophorae japonica and Gardenia Jasminoides. SL and FSP extracts significantly (p < 0.001) lowered the polyp burden, as well as the expressions of oncogenic signaling molecules, such as MAPK/ERK, PI3K/AKT, and STAT3 in Apc^Min/+ mice. The inflamed gut was alleviated by shifting M1 to M2 macrophage phenotypes and the associated immune cytokines. The other remarkable change was on the extracellular tight junction protein complex, where the occludin, ZO-1, ICAM-1, E-cadherin were significantly (p < 0.05) upregulated while the N-cadherin and β-catenin were downregulated in the treated mice. The above physiological changes in the gut epithelial barrier were companied with the changes in gut microbiome. The 16S Sequencing data revealed a marked decrease in the potential pathogens (especially Helicobacter species and hydrogen sulfide producing-bacteria) and the increase in beneficial bacteria (especially for species from the genera of Akkermansia, Barnesiella, Coprococcus, Lachnoclostridium, and Ruminococcus). The majority of which were the short-chain fatty acids (SCFAs) producers. Meanwhile SCFAs-sensing G protein-coupled receptors (GPCRs), including GPR41, GPR43, and GPR109a were also significantly upregulated. In a recent report, we proved that the bacteria-derived SCFAs plays an essential role to the anti-cancer effects of the mushroom polysaccharides and saponins in Apc^Min/+ mice. In this study, we further demonstrated that butyrate treatment could enhance the extracellular tight junction protein complex as effective as the treatments with SL and FSP to the Apc^Min/+ mice. Our findings provide strong evidence of the vital role of the SCFA-producers and their metabolites to the cancer-preventive properties of the SL and FSP preparations.

Regulative Loop between β-catenin and Protein Tyrosine Receptor Type γ in Chronic Myeloid Leukemia

Protein tyrosine phosphatase receptor type γ (PTPRG) is a tumor suppressor gene, down-regulated in Chronic Myeloid Leukemia (CML) cells by the hypermethylation of its promoter region. β-catenin (CTNNB1) is a critical regulator of Leukemic Stem Cells (LSC) maintenance and CML proliferation. This study aims to demonstrate the antagonistic regulation between β-catenin and PTPRG in CML cells. The specific inhibition of PTPRG increases the activation state of BCR-ABL1 and modulates the expression of the BCR-ABL1- downstream gene β-Catenin. PTPRG was found to be capable of dephosphorylating β-catenin, eventually causing its cytosolic destabilization and degradation in cells expressing PTPRG. Furthermore, we demonstrated that the increased expression of β-catenin in PTPRG-negative CML cell lines correlates with DNA (cytosine-5)-methyl transferase 1 (DNMT1) over-expression, which is responsible for PTPRG promoter hypermethylation, while its inhibition or down-regulation correlates with PTPRG re-expression. We finally confirmed the role of PTPRG in regulating BCR-ABL1 and β-catenin phosphorylation in primary human CML samples. We describe here, for the first time, the existence of a regulative loop occurring between PTPRG and β-catenin, whose reciprocal imbalance affects the proliferation kinetics of CML cells.

Histone hypoacetylation contributes to CXCL12 downregulation in colon cancer: impact on tumor growth and cell migration

CXCL12 has been shown to be involved in colon cancer metastasis, but its expression level and molecular mechanisms regulating its expression remain controversial. We thus evaluated CXCL12 expression in a large cohort of colon adenomas and carcinomas, investigated for an epigenetic mechanism controlling its expression and evaluated the impact of CXCL12 levels on cell migration and tumor growth. CXCL12 expression was measured in human colon adenomas and carcinomas with transcriptome array and RT-qPCR. The promoter methylation was analyzed with whole-genome DNA methylation chips and protein expression by immunohistochemistry. We confirm a reduced expression of CXCL12 in 75% of MSS carcinomas and show that the decrease is an early event as already present in adenomas. The methylome analysis shows that the CXCL12 promoter is methylated in only 30% of microsatellite-stable tumors. In vitro, treatments with HDAC inhibitors, butyrate and valproate restored CXCL12 expression in three colon cell lines, increased acetylation of histone H3 within the CXCL12 promoter and inhibited cell migration. In vivo, valproate diminished (65%) the number of intestinal tumors in APC mutant mice, slowed down xenograft tumor growth concomitant to restored CXCL12 expression. Finally we identified loss of PCAF expression in tumor samples and showed that forced expression of PCAF in colon cancer cell lines restored CXCL12 expression. Thus, reduced PCAF expression may participate to CXCL12 promoter hypoacetylation and its subsequent loss of expression. Our study is of potential clinical interest because agents that promote or maintain histone acetylation through HDAC inhibition and/or HAT stimulation, may help to lower colon adenoma/carcinoma incidence, especially in high-risk families, or could be included in therapeutic protocols to treat advanced colon cancer.

Multiple Roles of APC and its Therapeutic Implications in Colorectal Cancer

Adenomatous polyposis coli (APC) is widely accepted as a tumor suppressor gene highly mutated in colorectal cancers (CRC). Mutation and inactivation of this gene is a key and early event almost uniquely observed in colorectal tumorigenesis. Alterations in the APC gene generate truncated gene products, leading to activation of the Wnt signaling pathway and deregulation of multiple other cellular processes. It has been a mystery why most patients with CRC retain a truncated APC protein, but accumulating evidence suggest that these C terminally truncated APC proteins may have gain of function properties beyond the well-established loss of tumor suppressive function. Here, we will review the evidence for both the loss of function and the gain of function of APC truncations and how together they contribute to CRC initiation and progression.

Cell proliferation within small intestinal crypts is the principal driving force for cell migration on villi

The functional integrity of the intestinal epithelial barrier relies on tight coordination of cell proliferation and migration, with failure to regulate these processes resulting in disease. It is not known whether cell proliferation is sufficient to drive epithelial cell migration during homoeostatic turnover of the epithelium. Nor is it known precisely how villus cell migration is affected when proliferation is perturbed. Some reports suggest that proliferation and migration may not be related while other studies support a direct relationship. We used established cell-tracking methods based on thymine analog cell labeling and developed tailored mathematical models to quantify cell proliferation and migration under normal conditions and when proliferation is reduced and when it is temporarily halted. We found that epithelial cell migration velocities along the villi are coupled to cell proliferation rates within the crypts in all conditions. Furthermore, halting and resuming proliferation results in the synchronized response of cell migration on the villi. We conclude that cell proliferation within the crypt is the primary force that drives cell migration along the villus. This methodology can be applied to interrogate intestinal epithelial dynamics and characterize situations in which processes involved in cell turnover become uncoupled, including pharmacological treatments and disease models.—Parker, A., Maclaren, O. J., Fletcher, A. G., Muraro, D., Kreuzaler, P. A., Byrne, H. M., Maini, P. K., Watson, A. J. M., Pin, C. Cell proliferation within small intestinal crypts is the principal driving force for cell migration on villi.

Differential RNA-seq analysis comparing APC-defective and APC-restored SW480 colorectal cancer cells

The adenomatous polyposis coli (APC) tumour suppressor gene is mutated in about 80% of colorectal cancers (CRC) Brannon et al. (2014) [1]. APC is a large multifunctional protein that regulates many biological functions including Wnt signalling (through the regulation of beta-catenin stability) Reya and Clevers (2005) [2], cell migration Kroboth et al. (2007), Sansom et al. (2004) [3], [4], mitosis Kaplan et al. (2001) [5], cell adhesion Faux et al. (2004), Carothers et al. (2001) [6], [7] and differentiation Sansom et al. (2004) [4]. Although the role of APC in CRC is often described as the deregulation of Wnt signalling, its other biological functions suggest that there are other factors at play that contribute to the onset of adenomas and the progression of CRC upon the truncation of APC. To identify genes and pathways that are dysregulated as a consequence of loss of function of APC, we compared the gene expression profiles of the APC mutated human CRC cell line SW480 following reintroduction of wild-type APC (SW480 + APC) or empty control vector (SW480 + vector control) Faux et al. (2004) . Here we describe the RNA-seq data derived for three biological replicates of parental SW480, SW480 + vector control and SW480 + APC cells, and present the bioinformatics pipeline used to test for differential gene expression and pathway enrichment analysis. A total of 1735 genes showed significant differential expression when APC was restored and were enriched for genes associated with cell polarity, Wnt signalling and the epithelial to mesenchymal transition. There was additional enrichment for genes involved in cell–cell adhesion, cell–matrix junctions, angiogenesis, axon morphogenesis and cell movement. The raw and analysed RNA-seq data have been deposited in the Gene Expression Omnibus (GEO) database under accession number GSE76307. This dataset is useful for further investigations of the impact of APC mutation on the properties of colorectal cancer cells.

Differences in the localization of the adenomatous polyposis coli-Asef/Asef2 complex between adenomatous polyposis coli wild-type and mutant cells

The tumor suppressor adenomatous polyposis coli (APC) is mutated in familial adenomatous polyposis and in many sporadic colorectal tumors. Adenomatous polyposis coli is known to negatively regulate Wnt signaling by inducing the degradation of β-catenin. Adenomatous polyposis coli also interacts with the guanine nucleotide exchange factors Asef and Asef2 and stimulates their activity, thereby regulating cell adhesion and migration. Here we show that in confluent, non-motile MDCK II cells, Asef/Asef2 are colocalized with APC at the sites of cell-cell adhesion at the apical and junctional levels. In contrast, in colorectal tumor cells containing mutated APC, significant amounts of Asef/Asef2 and the truncated mutant APCs are localized mainly in the cytoplasm. These results suggest that localization of the Asef/Asef2-APC complex at the sites of cell-cell contact is critical for the regulation of cell adhesion, and that the aberrant subcellular localization of these complexes in colorectal tumor cells may contribute to the cell's aberrant adhesive and migratory properties.

Tissue-dependent consequences of Apc inactivation on proliferation and differentiation of ciliated cell progenitors via Wnt and notch signaling

The molecular signals that control decisions regarding progenitor/stem cell proliferation versus differentiation are not fully understood. Differentiation of motile cilia from progenitor/stem cells may offer a simple tractable model to investigate this process. Wnt and Notch represent two key signaling pathways in progenitor/stem cell behavior in a number of tissues. Adenomatous Polyposis Coli, Apc is a negative regulator of the Wnt pathway and a well known multifunctional protein. Using the cre-LoxP system we inactivated the Apc locus via Foxj1-cre, which is expressed in cells committed to ciliated cell lineage. We then characterized the consequent phenotype in two select tissues that bear motile cilia, the lung and the testis. In the lung, Apc deletion induced β-catenin accumulation and Jag1 expression in ciliated cells and by lateral induction, triggered Notch signaling in adjacent Clara cells. In the bronchiolar epithelium, absence of Apc blocked the differentiation of a subpopulation of cells committed to the ciliogenesis program. In the human pulmonary adenocarcinoma cells, Apc over-expression inhibited Jag1 expression and promoted motile ciliogenic gene expression program including Foxj1, revealing the potential mechanism. In the testis, Apc inactivation induced β-catenin accumulation in the spermatogonia, but silenced Notch signaling and depleted spermatogonial stem cells, associated with reduced proliferation, resulting in male infertility. In sum, the present comparative analysis reveals the tissue-dependent consequences of Apc inactivation on proliferation and differentiation of ciliated cell progenitors by coordinating Wnt and Notch signaling.

E-cadherin and the cytoskeletal network in colorectal cancer development and metastasis

Abnormalities in the expression and functional activity of cell adhesion molecules are implicated in the development and progression of the majority of colorectal cancers (CRC). Cell-cell adhesion molecule E-cadherin regulates cell polarity, differentiation, proliferation and migration through its intimate association to the actin cytoskeletal network. During colorectal carcinogenesis changes in intercellular adhesion and dynamic rearrangements in the actin cytoskeleton result in altered signalling and migration with loss of contact inhibition. The adenomatous polyposis coli (APC) protein, besides its established role in the β catenin/Wnt signalling pathway, can coordinate microtubule and actin organization during cell migration. The actin-bundling protein Fascin promotes cell motility and is overexpressed in CRC. Based on recent molecular and pathological studies, this review focusses on the role of these molecules sharing the common feature of being associated with the cytoskeletal network during colorectal carcinogenesis and metastasis. The potential use of these molecules as prognostic markers and/or therapeutic targets will also be discussed.

Wnt signaling and colon tumorigenesis--a view from the periphery

In this brief overview we discuss the association between Wnt signaling and colon cell biology and tumorigenesis. Our current understanding of the role of Apc in the β-catenin destruction complex is compared with potential roles for Apc in cell adhesion and migration. The requirement for phosphorylation in the proteasomal-mediated degradation of β-catenin is contrasted with roles for phospho-β-catenin in the activation of transcription, cell adhesion and migration. The synergy between Myb and β-catenin regulation of transcription in crypt stem cells during Wnt signaling is discussed. Finally, potential effects of growth factor regulatory systems, Apc or truncated-Apc on crypt morphogenesis, stem cell localization and crypt fission are considered.

AP1B plays an important role in intestinal tumorigenesis with the truncating mutation of an APC gene

Recent evidence has suggested that carcinoma is accompanied by the loss of cell polarity. An epithelial cell-specific form of the AP-1 clathrin adaptor complex, AP1B, is involved in the polarized transport of membrane proteins to the basolateral surface of epithelial cells. In our study, we investigated whether AP1B is involved in intestinal tumorigenesis. The cellular polarity of intestinal tumor cells was examined using APC(Min/+) mice as an in vivo model and SW480 cells with a truncating mutation in the adenomatous polyposis coli (APC) gene as an in vitro model by confocal microscopy. Next, the expression of AP1B in intestinal tumor cells was examined by real-time polymerase chain reaction (PCR) and Western blotting. The localization of β-catenin and the expression of AP1B in the tumor tissue of patients with colorectal cancer were evaluated by confocal microscopy and real-time PCR, respectively, and the relationships among cell polarity, AP1B expression and intestinal tumorigenesis were examined. Cellular polarity was lost in intestinal tumor cells, and the expression of AP1B was downregulated. In addition, the reduction in the expression level of AP1B correlated with the nuclear localization of β-catenin in human colorectal cancer. Our study indicates the close associations between AP1B, intestinal tumorigenesis and mutations in the APC gene. This is the first report to reveal the relationships among AP1B, cellular polarity and intestinal tumorigenesis, and achieving a detailed understanding of AP1B will hopefully lead to discovery of therapeutic targets and novel biomarkers for intestinal cancer.

Corruption of homeostatic mechanisms in the guanylyl cyclase C signaling pathway underlying colorectal tumorigenesis

Colon cancer, the second leading cause of cancer-related mortality worldwide, originates from the malignant transformation of intestinal epithelial cells. The intestinal epithelium undergoes a highly organized process of rapid regeneration along the crypt-villus axis, characterized by proliferation, migration, differentiation and apoptosis, whose coordination is essential to maintaining the mucosal barrier. Disruption of these homeostatic processes predisposes cells to mutations in tumor suppressors or oncogenes, whose dysfunction provides transformed cells an evolutionary growth advantage. While sequences of genetic mutations at different stages along the neoplastic continuum have been established, little is known of the events initiating tumorigenesis prior to adenomatous polyposis coli (APC) mutations. Here, we examine a role for the corruption of homeostasis induced by silencing novel tumor suppressors, including the intestine-specific transcription factor CDX2 and its gene target guanylyl cyclase C (GCC), as early events predisposing cells to mutations in APC and other sequential genes that initiate colorectal cancer. CDX2 and GCC maintain homeostatic regeneration in the intestine by restricting cell proliferation, promoting cell maturation and adhesion, regulating cell migration and defending the intestinal barrier and genomic integrity. Elimination of CDX2 or GCC promotes intestinal tumor initiation and growth in aged mice, mice carrying APC mutations or mice exposed to carcinogens. The roles of CDX2 and GCC in suppressing intestinal tumorigenesis, universal disruption in their signaling through silencing of hormones driving GCC, and the uniform overexpression of GCC by tumors underscore the potential value of oral replacement with GCC ligands as targeted prevention and therapy for colorectal cancer.

Cox-2 expression, PGE(2) and cytokines production are inhibited by endogenously synthesized n-3 PUFAs in inflamed colon of fat-1 mice

There is great interest in the role of polyunsaturated fatty acids (PUFAs) in promoting (n-6 class) or inhibiting (n-3 class) inflammation. Mammalian cells are devoid of desaturase that converts n-6 to n-3 PUFAs. Consequently, essential n-3 fatty acids must be supplied with the diet. We have studied the effect of endogenously produced n-3 PUFAs on colitis development in fat-1 transgenic mice carrying the Caenorhabditis elegans fat-1 gene encoding n-3 desaturase. Colonic cell lipid profile was measured by capillary gas chromatography in fat-1 and wild-type (WT) littermates fed standard diet supplemented with 10% (w/w) safflower oil rich (76%) in n-6 polyunsaturated linoleic acid (LA). Experimental colitis was induced by administrating 3% dextran sodium sulphate (DSS). Colitis was scored by histopatological analysis. Cyclooxygenase-2 (Cox-2) expression was evaluated by real time polymerase chain reaction. Prostaglandin E(2) (PGE(2)) levels and cytokine production were determined by enzyme and microsphere-based immunoassays, respectively. The n-6/n-3 PUFA ratios in colonic cells of fat-1 mice were markedly lower (9.83±2.62) compared to WT (54.5±9.24, P<.001). Results also showed an attenuation of colonic acute and chronic inflammation in fat-1 mice with significant decreases in PGE(2) production (P<.01) and Cox-2 expression (P<.01). High levels of colitis-induced proinflammatory cytokines, interleukin (IL)-18, IL-1α, IL-1β, IL-6, monocytes chemotactic proteins 1, 2 and 3 (MCP 1,2,3), matrix metalloproteinase 9 and tumor necrosis factor α (TNF-α) were down-regulated in DSS acutely and chronically treated fat-1 mice. The expression of fat-1 gene in the colon was associated with endogenous n-3 PUFAs production, decreased Cox-2 expression, increased PGE(2) and cytokine production.

Persistent cyclooxygenase-2 inhibition downregulates NF-{kappa}B, resulting in chronic intestinal inflammation in the min/+ mouse model of colon tumorigenesis

Cyclooxygenase-2 (COX-2) inhibition prevents adenoma formation in humans and mouse models of colon cancer. The selective COX-2 inhibitor celecoxib reduces COX-2 and prostaglandin E(2) (PGE(2)) expression and adenomas in the intestine of Min/+ mice after treatment for several weeks, but prolonged treatment increases PGE(2) production, resulting in drug-resistant tumor formation and transforming growth factor beta (TGFbeta)-dependent intestinal fibrosis. In this study, we examined pathways that regulate COX-2 expression and suppress chronic intestinal inflammation. We show that NF-kappaB signaling was inhibited in the ileum of Min/+ mice receiving long-term treatment with celecoxib. This effect was associated with inhibition of TGFbeta-associated kinase-1 and IkappaB kinase alpha/beta activities and reduced expression of the Toll-like receptor (TLR) 2 and TLR4 that enhance colonic barrier function. Additionally, we observed reduced activities of protein kinases c-Jun NH(2)-terminal kinase 1 and protein kinase A and transcription factor cyclic AMP-responsive element binding protein, regulators of COX-2 expression, which cross-talk with NF-kappaB. In ileum subjected to long-term celecoxib treatment, we noted relatively higher expression of COX-2, vascular endothelial growth factor, and interleukin-1beta in Paneth cells, whereas NF-kappaB and COX-2 were more strongly expressed by an expanded population of stromal myofibroblasts. Our findings argue that celecoxib resistance is an acquired adaptation to changes in the crypt microenvironment that is associated with chronic intestinal inflammation and impaired acute wound-healing responsiveness.

Differential colorectal carcinogenesis: Molecular basis and clinical relevance

Colorectal cancer (CCR) is one of the most frequent cancers in developed countries. It poses a major public health problem and there is renewed interest in understanding the basic principles of the molecular biology of colorectal cancer. It has been established that sporadic CCRs can arise from at least two different carcinogenic pathways. The traditional pathway, also called the suppressor or chromosomal instability pathway, follows the Fearon and Vogelstein model and shows mutation in classical oncogenes and tumour suppressor genes, such as K-ras, adenomatous polyposis coli, deleted in colorectal cancer, or p53. Alterations in the Wnt pathway are also very common in this type of tumour. The second main colorectal carcinogenesis pathway is the mutator pathway. This pathway is present in nearly 15% of all cases of sporadic colorectal cancer. It is characterized by the presence of mutations in the microsatellite sequences caused by a defect in the DNA mismatch repair genes, mostly in hMLH1 or hMSH2. These two pathways have clear molecular differences, which will be reviewed in this article, but they also present distinct histopathological features. More strikingly, their clinical behaviours are completely different, having the “mutator” tumours a better outcome than the “suppressor” tumours.

Chronic cyclooxygenase-2 inhibition promotes myofibroblast-associated intestinal fibrosis

Anti-inflammatory drugs prevent intestinal tumor formation, an activity related to their ability to inhibit inflammatory pathway signaling in the target tissue. We previously showed that treatment of Min/(+) mice with the selective cyclooxygenase-2 (COX-2) inhibitor celecoxib induced rapid tumor regression; however, drug-resistant tumors appeared with long-term treatment. In this study, we investigated whole-tissue changes in inflammatory signaling by studying constituents of the tissue stroma and extracellular matrix. We found that celecoxib resistance was associated with changes in factors regulating autocrine transforming growth factor-beta (TGFbeta) signaling. Chronic drug treatment expanded the population of bone marrow-derived CD34(+) vimentin(+) alphaSMA(-) myofibroblast precursors and alphaSMA(+) vimentin(+) F4/80(-) myofibroblasts in the lamina propria and submucosa, providing a source of increased TGFbeta and COX-2 expression. Membrane constituents regulating TGFbeta availability, including syndecan-1 and heparanase-1, were also modified by chronic treatment in a manner promoting increased TGFbeta signaling. Finally, long-term celecoxib treatment induced tissue fibrosis, as indicated by increased expression of collagen, fibronectin, and laminin in the basement membrane. We conclude that chronic COX-2 inhibition alters TGFbeta signaling in the intestinal mucosa, producing conditions consistent with chronic inflammation.

APC and its modifiers in colon cancer

Colon cancer closely follows the paradigm of a single "gatekeeper gene." Mutations inactivating the APC (adenomatous polyposis coli) gene are found in approximately 80% of all human colon tumors and heterozygosity for such mutations produces an autosomal dominant colon cancer predisposition in humans and in murine models. However, this tight association between a single genotype and phenotype belies a complex association of genetic and epigenetic factors that together generate the broad phenotypic spectrum ofboth familial and sporadic colon cancers. In this Chapter, we give a general overview of the structure, function and outstanding issues concerning the role of Apc in human and experimental colon cancer. The availability of increasingly close models for human colon cancer in genetically tractable animal species enables the discovery and eventual molecular identification of genetic modifiers of the Apc-mutant phenotypes, connecting the central role of Apc in colon carcinogenesis to the myriad factors that ultimately determine the course of the disease.

Loss of EphA2 receptor tyrosine kinase reduces ApcMin/+ tumorigenesis

The Eph receptor A2 (EphA2) is overexpressed in a range of human epithelial cancers, a phenotype that is associated with cancer cell proliferation, progression and angiogenesis. Mouse models of mammary neoplasia have confirmed the role of EphA2 as mice carrying a knockout allele of EphA2 were resistant to breast cancer, a phenotype that was associated with interactions between EphA2 and ErbB2. We investigated in vivo the role of EphA2 in GI cancer. To determine whether EphA2 influences intestinal tumorigenesis, we used qRT-PCR to examine the mRNA expression levels of EphA2 in tumors from the small intestine and colon of Apc(Min/+) mice. We found that EphA2 was significantly up-regulated in tumors from both regions when compared with normal control tissues. We then evaluated the spatial expression patterns of EphA2 protein using immunohistochemistry in both the small intestine and colon and found that in normal tissues EphA2 was robustly expressed in highly differentiated cells, such as cells of the villi, but that EphA2 expression was largely absent from the stem cell niche and proliferative zones of intestinal crypts. In contrast, in tumors EphA2 was broadly expressed. Finally, we created a strain of Apc(Min/+) mice carrying a genetic knockout of the EphA2 gene. These mice developed significantly fewer and smaller tumors in both the small and large intestine. Overall, our results indicate that EphA2 plays an oncogenic role in the mammalian intestine suggesting that strategies to target EphA2 activity may offer new therapeutic modalities for colorectal cancer.

Adenomatous polyposis coli (APC): a multi-functional tumor suppressor gene

The adenomatous polyposis coli (APC) gene is a key tumor suppressor gene. Mutations in the gene have been found not only in most colon cancers but also in some other cancers, such as those of the liver. The APC gene product is a 312 kDa protein that has multiple domains, through which it binds to various proteins, including beta-catenin, axin, CtBP, Asefs, IQGAP1, EB1 and microtubules. Studies using mutant mice and cultured cells have demonstrated that APC suppresses canonical Wnt signalling, which is essential for tumorigenesis, development and homeostasis of a variety of cell types, such as epithelial and lymphoid cells. Further studies have suggested that APC plays roles in several other fundamental cellular processes. These include cell adhesion and migration, organization of the actin and microtubule networks, spindle formation and chromosome segregation. Deregulation of these processes caused by mutations in APC is implicated in the initiation and expansion of colon cancer.

Loss of Rassf1a cooperates with Apc(Min) to accelerate intestinal tumourigenesis

Promoter methylation of the RAS-association domain family 1, isoform A gene (RASSF1A) is one of the most frequent events found in human tumours. In this study we set out to test the hypothesis that loss of Rassf1a can cooperate with inactivation of the adenomatous polyposis coli (Apc) gene to accelerate intestinal tumourigenesis using the Apc-Min (Apc(Min/+)) mouse model, as mutational or deletional inactivation of APC is a frequent early event in the genesis of intestinal cancer. Further, loss of RASSF1A has also been reported to occur in premalignant adenomas of the bowel. RASSF1A has been implicated in an array of pivotal cellular processes, including regulation of the cell cycle, apoptosis, microtubule stability and most recently in the beta-catenin signalling pathway. By interbreeding isoform specific Rassf1a knockout mice with Apc(+/Min) mice, we showed that loss of Rassf1a results in a significant increase in adenomas of the small intestine and accelerated intestinal tumourigenesis leading to the earlier death of adenocarcinoma-bearing mice and decreased overall survival. Comparative genomic hybridization of adenomas from Rassf1a(-/-); Apc(+/Min) mice revealed no evidence of aneuploidy or gross chromosomal instability (no difference to adenomas from Rassf1a(+/+); Apc(+/Min) mice). Immunohistochemical analysis of adenomas revealed increased nuclear beta-catenin accumulation in adenomas from Rassf1a(-/-); Apc(+/Min) mice, compared to those from Rassf1a(+/+); Apc(+/Min) mice, but no differences in proliferation marker (Ki67) staining patterns. Collectively these data demonstrate cooperation between inactivation of Rassf1a and Apc resulting in accelerated intestinal tumourigenesis, with adenomas showing increased nuclear accumulation of beta-catenin, supporting a mechanistic link via loss of the known interaction of Rassf1 with beta-TrCP that usually mediates degradation of beta-catenin.

Alpha-catenin is essential in intestinal adenoma formation

A loss-of-function mutation in the APC gene initiates colorectal carcinogenesis. Although the molecular mechanism of tumor initiation is complex, several modifier genes have been identified using mouse models, including the ApcMin mouse. Among the familial adenomatous polyposis mouse lines carrying a truncation mutation at codon 580 in Apc (Apc580D), one line (line19-Apc(580D/+)) showed a remarkably reduced incidence of intestinal adenomas (<5% compared with other lines). Extensive genetic analysis identified a deletion in the alpha-catenin (Ctnna1) gene as the cause of this suppression. Notably, the suppression only occurred when the Ctnna1 deletion was in cis-configuration with the Apc580D mutation. In all adenomas generated in line19-Apc(580D/+), somatic recombination between the Apc and Ctnna1 loci retained the wild-type Ctnna1 allele. These data strongly indicate that simultaneous inactivation of alpha-catenin and Apc during tumor initiation suppresses adenoma formation in line19-Apc(580D/+), suggesting that alpha-catenin plays an essential role in the initiation of intestinal adenomas. Although accumulating evidence obtained from human colon tumors with invasive or metastatic potential has established a tumor-suppressive role for alpha-catenin in late-stage tumorigenesis, the role of alpha-catenin in the initiation of intestinal tumorigenesis is not well documented, especially compared with that of beta-catenin. A mouse model used in this study focused on the early stage of tumor initiation and clearly indicated an essential role for alpha-catenin. Thus, alpha-catenin has dual roles in intestinal tumorigenesis, a supporting role in tumor initiation, and a suppressive role in tumor progression.

Inulin results in increased levels of beta-catenin and cyclin D1 as the adenomas increase in size from small to large in the Min/+ mouse

The mechanism that drives the growth of some colonic adenomas towards malignancy, while permitting others to remain for decades in quiescence, remains unknown. Diets can alter the growth rate of intestinal tumours but it is still unknown whether diets are able to alter the molecular biology of these adenomas in a way that predicts further outcome. To address this issue we fed Min/+ mice with two diets known to lead to different adenoma outcomes: a high-fat control diet (n 15) or a high-fat inulin-enriched (10 % w/w) diet (n 13). To study the effect of diet on cell signalling during adenoma growth, the adenomas of each Min/+ mouse were divided into three size-categories, and the levels of beta-catenin, E-cadherin, cyclin D1 and matrix metalloproteinase-9, which are known to be involved in colon tumorigenesis, were determined. The growth-promoting inulin diet resulted in more large adenomas than the control feeding (P = 0.003) and doubled the total area of the adenomas (P = 0.008). The inulin diet increased the expression of nuclear beta-catenin (P = 0.004) and its target cyclin D1 (P = 0.017) as the adenomas increased in size from small to large, indicating the presence of an accelerated cancerous process. Neither phenomenon was seen in the control group during adenoma growth. Our results suggest that in addition to the number, size, and growth rate of adenomatous polyps, the signalling pattern of the adenomas should also be considered when evaluating preventive dietary strategies.

Three Nordic berries inhibit intestinal tumorigenesis in multiple intestinal neoplasia/+ mice by modulating beta-catenin signaling in the tumor and transcription in the mucosa

Berries contain a number of compounds that are proposed to have anticarcinogenic properties. We studied the effects and molecular mechanisms of wild berries with different phenolic profiles on intestinal tumorigenesis in multiple intestinal neoplasia/+ mice. The mice were fed a high-fat AIN93-G diet (Con) or AIN93-G diets containing 10% (w:w) freeze-dried bilberry, lingonberry (LB), or cloudberry (CB) for 10 wk. All 3 berries significantly inhibited the formation of intestinal adenomas as indicated by a 15-30% reduction in tumor number (P < 0.05). CB and LB also reduced tumor burden by over 60% (P < 0.05). Compared to Con, CB and LB resulted in a larger (P < 0.05) proportion of small adenomas (43, 69, and 64%, respectively) and a smaller proportion of large adenomas (56, 29, and 33%, respectively). Beta-catenin and cyclin D1 in the small and large adenomas and in the normal-appearing mucosa were measured by Western blotting and immunohistochemistry. CB resulted in decreased levels of nuclear beta-catenin and cyclin D1 and LB in the level of cyclin D1 in the large adenomas (P < 0.05). Early changes in gene expression in the normal-appearing mucosa were analyzed by Affymetrix microarrays, which revealed changes in genes implicated in colon carcinogenesis, including the decreased expression of the adenosine deaminase, ecto-5'-nucleotidase, and prostaglandin E2 receptor subtype EP4. Our results indicate that berries are potentially a rich source of chemopreventive components.

Epidermal growth factor receptor-directed enterocyte proliferation does not induce Wnt pathway transcription

BACKGROUND

Epidermal growth factor receptor (EGFR) stimulation enhances intestinal adaptation after massive small bowel resection (SBR), measured by taller villi, deeper crypts, and augmented enterocyte proliferation. Min mice with constitutively active beta-catenin signaling demonstrate enhanced villus growth after SBR, suggesting a role for the Wnt pathway during adaptation. Because there is crosstalk between EGFR signaling and the Wnt pathway, we hypothesized that beta-catenin is modulated by EGFR-induced enterocyte proliferation.

METHODS

Rat intestinal epithelial cells were stimulated with EGF and cytoplasmic to nuclear trafficking of beta-catenin was measured. Beta-catenin-directed transcription was also tested via transfection with a TOP/FOP luciferase reporter. Downstream transcriptional target expression was measured in murine intestine after SBR.

RESULTS

Epidermal growth factor-treated rat intestinal epithelial cells exhibited increased proliferation compared to serum-deficient cells in the face of no detectable accumulation of nuclear beta-catenin. The luciferase assay results showed minimal transcription activity in response to EGF. In vivo experiments revealed no significant difference in expression of beta-catenin targeted genes in crypt enterocytes after SBR.

CONCLUSIONS

The mechanism for EGFR-induced proliferation of enterocytes does not appear to involve a transcriptional role for beta-catenin. The effects of EGFR signaling on beta-catenin-mediated cell adhesion remain to be investigated.

Adenomatous polyposis coli localization is both cell type and cell context dependent

The adenomatous polyposis coli (APC) tumor suppressor protein is mutated in most colorectal carcinomas. In addition to its role in WNT signaling it is proposed to be involved in both cell migration and mitosis. Although a variety of studies have shown an APC localization along lateral membranes of adjacent epithelial cells the existence of a cortical APC localization in mammalian cells remains controversial. To address this we have used matched rat epithelial (NRK-52E) and fibroblast (NRK-49F) cell lines to investigate the localization of APC. Subconfluent cultures of NRK-52E and -49F cells displayed microtubule-associated APC populations by immunostaining. However, confluent NRK-52E, but not -49F monolayers, exhibited a cortical APC distribution. Cortical APC localized in close proximity to a number of cell junction proteins in a microtubule-independent manner while calcium switch experiments suggested that APC was recruited to the cortex only when junction assembly was complete. Confluent NRK-49F and -52E cells also showed contrasting APC localizations in response to monolayer wounding. Our data suggests APC cortical localization is a feature of confluent epithelioid cells and that the subcellular distribution of APC is therefore dependent upon both cell type and context.

Deficient E-cadherin adhesion in C57BL/6J-Min/+ mice is associated with increased tyrosine kinase activity and RhoA-dependent actomyosin contractility

The Min/+ mouse is a model for APC-dependent colorectal cancer (CRC). We showed that tumorigenesis in this animal was associated with decreased E-cadherin adhesion and increased epidermal growth factor receptor (Egfr) activity in the non-tumor intestinal mucosa. Here, we tested whether these abnormalities correlated with changes in the actin cytoskeleton due to increased Rho-ROCK signaling. We treated Apc+/+ (WT) littermate small intestine with EGTA, an inhibitor of E-cadherin, and with LPA, an RhoA activator; both induced effects on adhesion and kinase activity that mimicked the Min/+ phenotype. GTP-bound Rho was increased in Min/+ enterocytes relative to WT. Since RhoA activity is associated with actomyosin contractility, markers of this signaling cascade were assessed including phosphorylated myosin light chain (MLC), cofilin, Pyk2, Src, and MAPK kinases. The increased actomyosin contractility characterizing Min/+ intestinal tissue was suppressed by the ROCK inhibitor, Y27632, but was inducible in the WT by EGTA or LPA. Finally, ultrastructural imaging revealed changes consistent with actomyosin contractility in Min/+ enterocytes. Thus, the positive regulation of E-cadherin adhesion provided by Apc+ in vivo allows proper negative regulation of Egfr, Src, Pyk2, and MAPK, as well as RhoA activities.

Inhibition of intestinal tumorigenesis in Apcmin/+ mice by (-)-epigallocatechin-3-gallate, the major catechin in green tea

The present study was designed to investigate the effects of two main constituents of green tea, (-)-epigallocatechin-3-gallate (EGCG) and caffeine, on intestinal tumorigenesis in Apc(min/+) mice, a recognized mouse model for human intestinal cancer, and to elucidate possible mechanisms involved in the inhibitory action of the active constituent. We found that p.o. administration of EGCG at doses of 0.08% or 0.16% in drinking fluid significantly decreased small intestinal tumor formation by 37% or 47%, respectively, whereas caffeine at a dose of 0.044% in drinking fluid had no inhibitory activity against intestinal tumorigenesis. In another experiment, small intestinal tumorigenesis was inhibited in a dose-dependent manner by p.o. administration of EGCG in a dose range of 0.02% to 0.32%. P.o. administration of EGCG resulted in increased levels of E-cadherin and decreased levels of nuclear beta-catenin, c-Myc, phospho-Akt, and phospho-extracellular signal-regulated kinase 1/2 (ERK1/2) in small intestinal tumors. Treatment of HT29 human colon cancer cells with EGCG (12.5 or 20 micromol/L at different times) also increased protein levels of E-cadherin by 27% to 58%, induced the translocation of beta-catenin from nucleus to cytoplasm and plasma membrane, and decreased c-Myc and cyclin D1 (20 micromol/L EGCG for 24 hours). These results indicate that EGCG effectively inhibited intestinal tumorigenesis in Apc(min/+) mice, possibly through the attenuation of the carcinogenic events, which include aberrant nuclear beta-catenin and activated Akt and ERK signaling.

Non-traditional roles for the Adenomatous Polyposis Coli (APC) tumor suppressor protein

The Adenomatous Polyposis Coli (APC) tumor suppressor is a multifunctional protein that is mutated in a majority of colon cancers. The role of APC as an antagonist of the Wnt signaling pathway is well known and it is widely accepted that inappropriate activation of this pathway through loss of APC function contributes to the progression of colon cancers. However, a body of evidence is growing to support the idea that APC plays non-traditional functions outside of the Wnt pathway with roles in cell migration, adhesion, chromosome segregation, spindle assembly, apoptosis, and neuronal differentiation. This review highlights the research into alternate functions for APC beyond its role in Wnt signaling and discusses the possible contributions for these non-traditional functions of APC in tumor formation.

Promotion of adenoma growth by dietary inulin is associated with increase in cyclin D1 and decrease in adhesion proteins in Min/+ mice mucosa

We have earlier shown that dietary fructo-oligosaccharide inulin enhances adenoma growth in multiple intestinal neoplasia (Min/+) mice. To further explore inulin-induced early biochemical changes in the normal-appearing mucosa, Min/+ mice were fed from the age of 5 weeks to the ages of 8 and 15 weeks a control diet or an inulin-enriched diet (10% w/w). In addition, the wild-type littermates were fed with the same diets until the age of 8 weeks, in order to determine whether similar changes happen both in the wild-type and Min/+ mice. The mucosa without adenomas was collected and fractionated to nuclear, cytosolic and membrane pools. The protein levels of beta-catenin, cyclin D1 and E-cadherin were determined by Western blotting at both time points, and immunohistochemical stainings were done for 8-week-old mice. The promotion of adenoma growth by inulin (week 15, 1.3-fold increase, P=.0004) was associated with accumulation of cytosolic and nuclear beta-catenin, and increased amount of cytosolic cyclin D1 (1.5-fold increase, P=.003) in the normal-appearing mucosa of the Min/+ mice. Furthermore, inulin feeding reduced the membranous pools of beta-catenin and E-cadherin. Also in the wild-type mice the drop in membranous beta-catenin was clear (P=.015), and, moreover, a subset of crypts had enhanced nuclear beta-catenin staining. These data indicate that dietary inulin can already activate in the normal-appearing mucosa beta-catenin signaling, which in the presence of Apc mutation induces adenoma growth and even in the wild-type mice direction of the changes is similar.

Carnosol Inhibits -Catenin Tyrosine Phosphorylation and Prevents Adenoma Formation in the C57BL/6J/Min/+ (Min/+) Mouse

Carnosol, a constituent of the herb, rosemary, has shown beneficial medicinal and antitumor effects. Using the C57BL/6J/Min/+ (Min/+) mouse, a model of colonic tumorigenesis, we found that dietary administration of 0.1% carnosol decreased intestinal tumor multiplicity by 46%. Previous studies showed that tumor formation in the Min/+ mouse was associated with alterations in the adherens junctions, including an increased expression of tyrosine-phosphorylated β-catenin, dissociation of β-catenin from E-cadherin, and strongly reduced amounts of E-cadherin located at lateral plasma membranes of histologically normal enterocytes. Here, we confirm these findings and show that treatment of Min/+ intestinal tissue with carnosol restored both E-cadherin and β-catenin to these enterocyte membranes, yielding a phenotype similar to that of the Apc+/+ wild-type (WT) littermate. Moreover, treatment of WT intestine with the phosphatase inhibitor, pervanadate, removed E-cadherin and β-catenin from the lateral membranes of enterocytes, mimicking the appearance of the Min/+ tissue. Pretreatment of WT tissue with carnosol inhibited the pervanadate-inducible expression of tyrosine-phosphorylated β-catenin. Thus, the ApcMin allele produces adhesion defects that involve up-regulated expression of tyrosine-phosphorylated proteins, including β-catenin. Moreover, these data suggest that carnosol prevents Apc-associated intestinal tumorigenesis, potentially via its ability to enhance E-cadherin-mediated adhesion and suppress β-catenin tyrosine phosphorylation.

Interaction with IQGAP1 links APC to Rac1, Cdc42, and actin filaments during cell polarization and migration

Rho family GTPases, particularly Rac1 and Cdc42, are key regulators of cell polarization and directional migration. Adenomatous polyposis coli (APC) is also thought to play a pivotal role in polarized cell migration. We have found that IQGAP1, an effector of Rac1 and Cdc42, interacts directly with APC. IQGAP1 and APC localize interdependently to the leading edge in migrating Vero cells, and activated Rac1/Cdc42 form a ternary complex with IQGAP1 and APC. Depletion of either IQGAP1 or APC inhibits actin meshwork formation and polarized migration. Depletion of IQGAP1 or APC also disrupts localization of CLIP-170, a microtubule-stabilizing protein that interacts with IQGAP1. Taken together, these results suggest a model in which activation of Rac1 and Cdc42 in response to migration signals leads to recruitment of IQGAP1 and APC which, together with CLIP-170, form a complex that links the actin cytoskeleton and microtubule dynamics during cell polarization and directional migration.

A novel four transmembrane spanning protein, CLP24. A hypoxically regulated cell junction protein

A novel hypoxically regulated intercellular junction protein (claudin-like protein of 24 kDa, CLP24) has been identified that shows homology to the myelin protein 22/epithelial membrane protein 1/claudin family of cell junction proteins, which are involved in the modulation of paracellular permeability. The CLP24 protein contains four predicted transmembrane domains and a C-terminal protein-protein interaction domain. These domains are characteristic of the four transmembrane spanning (tetraspan) family of proteins, which includes myelin protein 22, and are involved in cell adhesion at tight, gap and adherens junctions. Expression profiling analyses show that CLP24 is highly expressed in lung, heart, kidney and placental tissues. Cellular studies confirm that the CLP24 protein localizes to cell-cell junctions and co-localizes with the beta-catenin adherens junction-associated protein but not with tight junctions. Over-expression of CLP24 results in decreased adhesion between cells, and functional paracellular flux studies confirm that over-expression of the CLP24 protein modulates the junctional barrier function. These data therefore suggest that CLP24 is a novel, hypoxically regulated tetraspan adherens junction protein that modulates cell adhesion, paracellular permeability and angiogenesis.

Apc deficiency is associated with increased Egfr activity in the intestinal enterocytes and adenomas of C57BL/6J-Min/+ mice

Overexpression of the epidermal growth factor receptor (EGFR) and its increased tyrosine kinase activity are implicated in colorectal cancer (CRC) development and malignant progression. The C57BL/6J-Min/+ (Min/+) mouse is a model for CRC and develops numerous intestinal adenomas. We analyzed the normal mucosa of Min/+ and Apc+/+ (WT) littermate mice together with Apc-null adenomas to gain insight into the roles of Egfr in these intestinal tissues. Protein analyses showed that Egfr activity was highest in the tumors, and also up-regulated in Min/+ relative to WT enterocytes. Expression of ubiquitylated Egfr (Egfr-Ub) was increased in Min/+ enterocytes and tumors. Tumors exhibited increased association of Egfr with clathrin heavy chain (CHC), Gab1, and p85alpha, the regulatory subunit of phosphoinositide 3-kinase (PI3K), and tumors also overexpressed c-Src, PDK1, and Akt. Immunohistochemistry for Akt-p-Ser473 revealed a low level of this active kinase in Min/+ and WT enterocytes and its strong presence in tumors. Prostaglandin E2 (PGE2) is a product of cyclooxygenase-2 (Cox-2) activity that is up-regulated in Min/+ tumors and transactivates Egfr. PGE2 expression was significantly higher in untreated Min/+ tumors and reduced by treatment with the Cox-2 inhibitor, celecoxib. Dietary administration of this NSAID also inhibited Egfr activity in tumors. Increased activation of the EGFR-PI3K-Akt signaling pathway in tumors relative to Apc+/+ and ApcMin/+ enterocytes provides potential opportunities for therapeutic interventions to differentially suppress tumor formation, promotion, progression, and/or recurrence.

Truncated mouse adenomatous polyposis coli reduces connexin32 content and increases matrilysin secretion from Paneth cells

Heterozygous mutations in adenomatous polyposis coli (APC) is an early event in inheritable and sporadic colon cancer development. We recently found reduced connexin (Cx43) expression in intestinal cell lines with heterozygous Apc mutation. In this study we investigated Cx expression and the role of one mutated Apc allele in epithelia of multiple intestinal neoplasia (Min) mouse intestines by immunohistochemistry. Cx43 was not expressed in intestinal epithelia of Min and wild-type mice. Cx32 was specifically expressed in enterochromaffin cells in both mice types, and in Paneth cells of wild-type mice. In contrast, Min mice had nearly undetectable level of Cx32 in Paneth cells. Isolated small intestinal crypts from Min mice had markedly increased secretion of both lysozyme and matrilysin compared with wild-type mice. Absence of matrilysin in Min mice reduces adenoma development. Reduced Cx32 and increased matrilysin secretion from Paneth cells could be important to neoplastic development in the intestine.

Cytokeratin deposits in lymph nodes show distinct clinical significance from lymph node micrometastasis in human esophageal cancers

BACKGROUND

Cytokeratin immunostaining is the most common method used to identify micrometastatic cancer cells from the lymph nodes. However, contamination with hyalinized cytokeratin particles, frequently observed in the lymph nodes of esophageal cancer patients, can lead to misinterpretation of cytokeratin immunostaining.

MATERIALS AND METHODS

Cytokeratin immunostaining (AE1/AE3) of surgically removed lymph nodes was performed for 41 cases of node-negative, but locally advanced (T3, T4), esophageal cancer patients. Cytokeratin immunoreactivity (CK) was classified as micrometastasis (MM) or cytokeratin deposit (CD) by the presence or absence of tumor nuclei in serial sections given hematoxylin-eosin staining.

RESULTS

CK (+) was observed in 18 patients (44%), including 11 with MM (+) (27%) and 10 with CD (+) (24%). There was no correlation between MM and CD, and neither was associated with clinicopathological factors, except for a high incidence of preoperative chemotherapy in CD (+) patients. The presence of CK did not affect postoperative survival of esophageal cancer patients at this limited stage, showing a 5-year survival rate of 57% for CK (+) and 64% for CK (-) (P = 0.6064). Interestingly, patients with MM (+) showed poorer prognosis than MM (-) (5-year survival: 28% vs 79%, P = 0.0188), while CD (+) patients tended to display better prognosis than CD (-) ones (5-year survival: 78% vs 56%, P = 0.1860).

CONCLUSIONS

Evaluation by cytokeratin immunostaining of lymph nodes requires careful discrimination of CD from MM, in order to allow MM to be used as a prognostic factor for esophageal cancer patients.