Is there a role for CEA in innate immunity in the colon?

The correlation between pre-treatment CEA levels and the EGFR mutation status in advanced lung adenocarcinoma

BACKGROUND

The discovery of the epidermal growth factor receptor (EGFR) mutation, especially in adenocarcinoma, has led to a major change in the treatment of non-small-cell lung cancer (NSCLC). This study investigated the relationship between the EGFR mutation status and the carcinoembryonic antigen (CEA) levels at the time of diagnosis.

MATERIALS AND METHODS

A total of 102 patients with EGFR mutation and tested CEA levels were recruited for this study. Of the patients, 24 were EGFR mutants (23.5%), while 78 patients (76.5%) did not harbor any EGFR mutations.

RESULTS

The CEA levels did not differ across groups. Additionally, the CEA levels were analyzed between female and male patients separately due to EGFR mutations; no difference was observed. When the CEA levels were categorized as positive or negative based on different cut-off values, such as 5 and 10 ng/ml, no statistical difference was found between groups.

CONCLUSION

In this study, no relationship between EGFR mutation and pre-treatment CEA levels was observed. Despite positive trials having shown a predictive value of CEA levels for EGFR mutation, more clinical trials are needed to elucidate the racial, clinical, and pathological differences of the study populations. Most studies have been located in the Far East, but new trials in Caucasian, African, and Hispanic populations are still lacking.

CA19-9 and CEA biosensors in pancreatic cancer

Cancer is a complex pathophysiological condition causing millions of deaths each year. Early diagnosis is essential especially for pancreatic cancer. Existing diagnostic tools rely on circulating biomarkers such as Carbohydrate Antigen 19-9 (CA19-9) and Carcinoembryonic Antigen (CEA). Unfortunately, these markers are nonspecific and may be increased in a variety of disorders. Accordingly, diagnosis of pancreatic cancer generally involves more invasive approaches such as biopsy as well as imaging studies. Recent advances in biosensor technology have allowed the development of precise diagnostic tools having enhanced analytical sensitivity and specificity. Herein we examine these advances in the detection of cancer in general and in pancreatic cancer specifically. Furthermore, we highlight novel technologies in the measurement of CA19-9 and CEA and explore their future application in the early detection of pancreatic cancer.

Transcriptomic analysis identifies diagnostic genes in polycystic ovary syndrome and periodontitis

PURPOSE

To investigate underlying co-mechanisms of PCOS and periodontitis through transcriptomic approach.

METHODS

PCOS and periodontitis gene expression data were downloaded from the GEO database to identify differentially expressed genes. GO and KEGG pathway enrichment analysis and random forest algorithm were used to screen hub genes. GSEA analyzed the functions of hub genes. Correlations between hub genes and immune infiltration in two diseases were examined, constructing a TF-ceRNA regulatory network. Clinical samples were gathered from PCOS and periodontitis patients and RT-qPCR was performed to verify the connection.

RESULTS

There were 1661 DEGs in PCOS and 701 DEGs in periodontitis. 66 intersected genes were involved and were enriched in immune and inflammation-related biological pathways. 40 common genes were selected from the PPI network. RF algorithm demonstrated that ACSL5, NLRP12, CCRL2, and CEACAM3 were hub genes, and GSEA results revealed their close relationship with antigen processing and presentation, and chemokine signaling pathway. RT-qPCR results confirmed the upregulated gene expression in both PCOS and periodontitis.

CONCLUSION

The 4 hub genes ACSL5, NLRP12, CCRL2, and CEACAM3 may be diagnostic genes for PCOS and periodontitis. The created ceRNA network could provide a molecular basis for future studies on the association between PCOS and periodontitis.

Association of cigarette smoking with risk of colorectal cancer subtypes classified by gut microbiota

INTRODUCTION

Both cigarette smoking and gut microbiota play important roles in colorectal carcinogenesis. We explored whether the association between smoking and colorectal cancer (CRC) risk varies by gut microbial enterotypes and how smoking-related enterotypes promote colorectal carcinogenesis.

METHODS

A case-control study was conducted. Fecal microbiota was determined by 16S rDNA sequencing. The cases with CRC or adenoma were subclassified by gut microbiota enterotypes. Multivariate analyses were used to test associations between smoking and the odds of colorectal neoplasm subtypes. Mann-Whitney U tests were used to find differential genera, genes, and pathways between the subtypes.

RESULTS

Included in the study were 130 CRC patients (type I: n=77; type II: n=53), 120 adenoma patients (type I: n=66; type II: n=54), and 130 healthy participants. Smoking increased the odds for type II tumors significantly (all p for trend <0.05) but not for type I tumors. The associations of smoking with increased odds of colorectal neoplasm significantly differed by gut microbiota enterotypes (p<0.05 for heterogeneity). An increase in carcinogenic bacteria (genus Escherichia shigella) and a decrease in probiotics (family Lachnospiraceae and Ruminococcaceae) in type II tumors may drive disease progression by upregulating oncogenic signaling pathways and inflammatory/oxidative stress response pathways, as well as protein phospholipase D1/2, cytochrome C, and prostaglandin-endoperoxide synthase 2 expression.

CONCLUSIONS

Smoking was associated with a higher odds of type II colorectal neoplasms but not type I tumors, supporting a potential role for the gut microbiota in mediating the association between smoking and colorectal neoplasms.

Interactions of pathogenic Escherichia coli with CEACAMs

The pathogenic Escherichia coli can be parsed into specific variants (pathovars) depending on their phenotypic behavior and/or expression of specific virulence factors. These pathogens are built around chromosomally-encoded core attributes and through acquisition of specific virulence genes that direct their interaction with the host. Engagement of E. coli pathovars with CEACAMs is determined both by core elements common to all E. coli as well as extrachromosomally-encoded pathovar-specific virulence traits, which target amino terminal immunoglobulin variable-like (IgV) regions of CEACAMs. Emerging data suggests that engagement of CEACAMs does not unilaterally benefit the pathogen and that these interactions may also provide an avenue for pathogen elimination.

Generation and in vivo characterization of a novel high-affinity human antibody targeting carcinoembryonic antigen

There are no effective treatment options for most patients with metastatic colorectal cancer (mCRC). mCRC remains a leading cause of tumor-related death, with a five-year survival rate of only 15%, highlighting the urgent need for novel pharmacological products. Current standard drugs are based on cytotoxic chemotherapy, VEGF inhibitors, EGFR antibodies, and multikinase inhibitors. The antibody-based delivery of pro-inflammatory cytokines provides a promising and differentiated strategy to improve the treatment outcome for mCRC patients. Here, we describe the generation of a novel fully human monoclonal antibody (termed F4) targeting the carcinoembryonic antigen (CEA), a tumor-associated antigen overexpressed in colorectal cancer and other malignancies. The F4 antibody was selected by antibody phage display technology after two rounds of affinity maturation. F4 in single-chain variable fragment format bound to CEA in surface plasmon resonance with an affinity of 7.7 nM. Flow cytometry and immunofluorescence on human cancer specimens confirmed binding to CEA-expressing cells. F4 selectively accumulated in CEA-positive tumors, as evidenced by two orthogonal in vivo biodistribution studies. Encouraged by these results, we genetically fused murine interleukin (IL) 12 to F4 in the single-chain diabody format. F4-IL12 exhibited potent antitumor activity in two murine models of colon cancer. Treatment with F4-IL12 led to an increased density of tumor-infiltrating lymphocytes and an upregulation of interferon γ expression by tumor-homing lymphocytes. These data suggest that the F4 antibody is an attractive delivery vehicle for targeted cancer therapy.

Protective role of a melon superoxide dismutase combined with gliadin (GliSODin) on the status of lipid peroxidation and antioxidant defense against azoxymethane-induced experimental colon carcinogenesis

Background

Azoxymethane (AOM) is a potent carcinogenic agent commonly used to induce colon cancer in rats and mice, with the cytotoxicity of AOM mediated by oxidative stress.

Aim of Study

This study investigated the protective effect of a natural antioxidant (GliSODin) against AOM-induced oxidative stress and carcinogenesis in rat colon.

Methods

Twenty male Wistar rats were randomly divided into four groups (five rats/group). The control group was fed a basal diet. AOM-treated group (AOM) was fed a basal diet and received intraperitoneal injections of AOM for 2 weeks at a dose of 15 mg/kg. The GliSODin treatment group (superoxide dismutase [SOD]) received oral supplementation of GliSODin (300 mg/kg) for 3 months, and the fourth combined group received AOM and GliSODin (AOM + SOD). All animals were continuously fed ad libitum until the age of 16 weeks when all rats were sacrificed. The colon tissues were examined microscopically for pathological changes and aberrant crypt foci (ACF) development, oxidant status (lipid peroxidation-LPO), and enzyme antioxidant system (glutathione [GSH], GSH-S-transferase, catalase, and SOD).

Results

Our results showed that AOM induced ACF development and oxidative stress (GSH depletion and lipid peroxidation) in rat colonic cells. The concomitant treatment of AOM with GliSODin significantly ameliorated the cytotoxic effects of AOM.

Conclusion

The results of this study provide in vivo evidence that GliSODin reduced the AOM-induced colon cancer in rats, through their potent antioxidant activities.

Regulation of CEACAM Family Members by IBD-Associated Triggers in Intestinal Epithelial Cells, Their Correlation to Inflammation and Relevance to IBD Pathogenesis

Carcinoembryogenic antigen cellular adhesion molecules (CEACAMs) are intercellular adhesion molecules highly expressed in intestinal epithelial cells. CEACAM1, -3, -5, -6, -7 are altered in patients suffering from colon cancer and inflammatory bowel diseases (IBD), but their role in the onset and pathogenesis of IBD is not well known. Herein, we aim to correlate CEACAM1, -3, -5, -6, -7 expression to the degree of inflammation in pediatric and adult IBD colon biopsies and to examine the regulation of CEACAMs on human intestinal epithelial cell lines (C2BBe1/HT29) by different IBD-associated triggers (cytokines, bacteria/metabolites, emulsifiers) and IBD-drugs (6-Mercaptopurine, Prednisolone, Tofacitinib). Biopsies from patients with pediatric Crohn’s disease (CD) and adult ulcerative colitis (UC, active/inactive disease) showed a significant increase in CEACAM3, -5, -6 expression, while CEACAM5 expression was reduced in adult CD patients (active/inactive disease). Intestinal epithelial cells cultured with a pro-inflammatory cytokine cocktail and Adherent-invasive Escherichia coli (AIEC) showed a rapid induction of CEACAM1, -5, -7 followed by a reduced RNA and protein expression overtime and a constant expression of CEACAM3, correlating with IL-8 expression. Cells cultured with the emulsifier polysorbate-80 resulted in a significant induction of CEACAM3, -5, -6, -7 at a late time point, while SCFA treatment reduced CEACAM1, -5, -7 expression. No major alterations in expression of CEACAMs were noted on cells cultured with the commensal Escherichia coli K12 or the pathogen Salmonella typhimurium. IBD drugs, particularly Tofacitinib, significantly reduced cytokine-induced CEACAM1, -3, -5, -6, -7 expression associated with a reduced IL-8 secretion. In conclusion, we provide new evidence on the regulation of CEACAMs by different IBD-associated triggers, identifying a role of CEACAMs in IBD pathogenesis.

Enhanced E. coli LF82 Translocation through the Follicle-associated Epithelium in Crohn's Disease is Dependent on Long Polar Fimbriae and CEACAM6 expression, and Increases Paracellular Permeability

BACKGROUND AND AIMS

Patients with Crohn's disease [CD] harbour an increased number of adherent-invasive E. coli [AIEC]. The strain LF82, identified in the ileal mucosa of CD patients, has been extensively studied for pathogenic mechanisms. However, understanding of the interaction of LF82 with the intestinal mucosa of CD patients is lacking.

METHODS

Here, we investigated the importance of long polar fimbriae [LPF] type 1 pili and the carcinoembryonic antigen-related cell-adhesion molecule 6 [CEACAM6] for translocation of LF82 in an in vitro model of follicle-associated epithelium [FAE], and in the FAE and villus epithelium [VE] of patients with CD and controls, using Ussing chambers.

RESULTS

Significantly greater LF82 passage occurred in the FAE model compared with in the VE Caco-2cl1 mono-culture. Moreover, bacterial translocation was inhibited by either LPF disruption or pre-incubation with anti-CEACAM6 antibody. Tissue mounted in Ussing chambers showed significantly higher LF82 passage in FAE from patients with CD compared with control FAE, that was diminished in LF82 lacking LPF and by blocking host CEACAM6. Interestingly, addition of LF82 to the CD FAE tissues significantly increased paracellular permeability [of 51Chromium-EDTA] compared with baseline, and the increase was inhibited by anti-CEACAM6. Immunofluorescence and immunoblots showed higher expression of CEACAM6 in FAE of patients with CD compared with in FAE from controls.

CONCLUSIONS

These data suggest that the FAE of CD patients is a site of vulnerability for invasion by LF82 via a mechanism that requires both bacterial LPF and host CEACAM6. Further, LF82 has the ability to increase paracellular passage through the FAE of patients with CD. These data can help define novel therapeutic targets in CD for the prevention of clinical recurrence.

Mutual Regulation of TLR/NLR and CEACAM1 in the Intestinal Microvasculature: Implications for IBD Pathogenesis and Therapy

Background

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) displays multiple activities, among which pathogen binding and angiogenesis are particularly prominent. These same functions are also exerted by Toll- and NOD-like receptors (TLRs and NLRs), which are critical mediators of innate immune responses. We investigated whether a functional inter-relationship exists between CEACAM1 and TLRs and NLRs and its potential impact on induction of intestinal angiogenesis.

Methods

This hypothesis was tested using human intestinal microvascular endothelial cells, a unique cell population exposed to microbial products under physiological and pathological conditions.

Results

The results show that activation of TLR2/4, TLR4, NOD1, and NOD2 by specific bacterial ligands selectively and differentially upregulates the levels of cellular and soluble CEACAM1 produced by intestinal microvascular endothelial cells. The results also show that CEACAM1 regulates the migration, transmigration, and tube formation of these endothelial cells and mediates vessel sprouting induced by specific TLR and NLR bacterial ligands. Combined, these results demonstrate a close and reciprocal regulatory interaction between CEACAM1 and bacterial products in mediating multiple functions essential to new vessel formation in the gut mucosa.

Conclusions

A coordinated and reciprocal interaction of CEACAM1 and microbiota-derived factors is necessary to optimize angiogenesis in the gut mucosa. This suggests that a coordination of endogenous and exogenous innate immune responses is necessary to promote intestinal angiogenesis under physiological and inflammatory conditions such as inflammatory bowel disease.

The effect of polymeric formula on enterocyte differentiation

Exclusive enteral nutrition is established as an initial therapy to induce remission in active Crohn's disease (CD), especially in children, but the mechanisms of action of this therapy are yet to be fully defined. Intestinal alkaline phosphatase (IAP), a recognised marker of enterocyte differentiation, is implicated in the innate gut immune response to enteric pathogens. Using the Caco-2 human adenocarcinoma cell line, this study showed that the incubation of human cells with a polymeric formula (PF) resulted in a dose-dependent increase in the expression of IAP on the cell surface. While further investigation is required to determine the pathway(s) involved, this finding suggests that cell surface-associated IAP may be an aspect of the gut's innate immune response to pathogenic bacteria that is strengthened by PF in the setting of CD.

Inhibition of CEA release from epithelial cells by lipid A of Gram-negative bacteria

A number of bacterial species, both pathogenic and non-pathogenic, use the human CEACAM family members as receptors for internalization into epithelial cells. The GPI-linked CEA and CEACAM6 might play a role in the innate immune defense, protecting the colon from microbial invasion. Previous studies showed that CEA is released from epithelial cells by an endogenous GPI-PLD enzyme. GPI-PLD activity was reported to be inhibited by several synthetic and natural forms of lipid A. We hypothesized that CEA engagement by Gram-negative bacteria might attenuate CEA release from epithelial cells and that this might facilitate bacterial colonization. We tested the hypothesis by examining the effect of Escherichia coli on CEA release from colorectal cancer cells in a co-culture experiment. A subconfluent monolayer culture of colorectal cancer cells (LS-180, Caco-2 and HT29/219) was incubated with E. coli. While there was a significant reduction in CEA secretion from LS-180 and HT29/219 cells, we found only a small reduction of CEA shedding from Caco-2 cells compared to the level from the untreated control cells. Furthermore, lipid A treatment of LS-180 cells inhibited CEA release from the cells in a dosedependent manner. Western blot analysis of total lysates showed that CEA expression levels in cells co-cultured with bacteria did not differ from those in untreated control cells. These results suggest that lipid A of Gram-negative bacteria might play a role in preventing the release of CEA from mucosal surfaces and promote mucosal colonization by bacteria.

Pathogenesis of human diffusely adhering Escherichia coli expressing Afa/Dr adhesins (Afa/Dr DAEC): current insights and future challenges

The pathogenicity and clinical pertinence of diffusely adhering Escherichia coli expressing the Afa/Dr adhesins (Afa/Dr DAEC) in urinary tract infections (UTIs) and pregnancy complications are well established. In contrast, the implication of intestinal Afa/Dr DAEC in diarrhea is still under debate. These strains are age dependently involved in diarrhea in children, are apparently not involved in diarrhea in adults, and can also be asymptomatic intestinal microbiota strains in children and adult. This comprehensive review analyzes the epidemiology and diagnosis and highlights recent progress which has improved the understanding of Afa/Dr DAEC pathogenesis. Here, I summarize the roles of Afa/Dr DAEC virulence factors, including Afa/Dr adhesins, flagella, Sat toxin, and pks island products, in the development of specific mechanisms of pathogenicity. In intestinal epithelial polarized cells, the Afa/Dr adhesins trigger cell membrane receptor clustering and activation of the linked cell signaling pathways, promote structural and functional cell lesions and injuries in intestinal barrier, induce proinflammatory responses, create angiogenesis, instigate epithelial-mesenchymal transition-like events, and lead to pks-dependent DNA damage. UTI-associated Afa/Dr DAEC strains, following adhesin-membrane receptor cell interactions and activation of associated lipid raft-dependent cell signaling pathways, internalize in a microtubule-dependent manner within urinary tract epithelial cells, develop a particular intracellular lifestyle, and trigger a toxin-dependent cell detachment. In response to Afa/Dr DAEC infection, the host epithelial cells generate antibacterial defense responses. Finally, I discuss a hypothetical role of intestinal Afa/Dr DAEC strains that can act as "silent pathogens" with the capacity to emerge as "pathobionts" for the development of inflammatory bowel disease and intestinal carcinogenesis.

Influences of enteral nutrition upon CEACAM6 expression by intestinal epithelial cells

Exclusive enteral nutrition is established as an initial therapy to induce remission in active Crohn's disease (CD), especially in children, but the mechanisms of action of this therapy are yet to be fully defined. CEACAM6 protein is an adhesion molecule that is up-regulated in active CD and implicated in the attachment of adherent-invasive Escherichia coli (AIEC) to the gut epithelium. Using the Caco-2 human adenocarcinoma cell line, this study showed that the incubation of human cells with a polymeric formula (PF) resulted in a dose-dependent increase in the expression of CEACAM6, and that this effect was most noticeable on the cell surface. Further investigation revealed that PF doubled the release of CEACAM6 protein by Caco-2 cells exposed to PF, and that an increase in release of soluble CEACAM6 inversely correlated with the ability of AIEC to associate with the intestinal epithelial cells. Our findings suggest that the secretion of cell surface-associated proteins acting as releasable decoys may be an aspect of the gut's innate immune response to pathogenic bacteria that is strengthened by PF in the setting of CD.

Novel protein isoforms of carcinoembryonic antigen are secreted from pancreatic, gastric and colorectal cancer cells

Background

Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) is an oncofetal cell surface glycoprotein. Because of its high expression in cancer cells and secretion into serum, CEA has been widely used as a serum tumor marker. Although other members of CEACAM family were investigated for splice variants/variants-derived protein isoforms, few studies about the variants of CEACAM5 have been reported. In this study, we demonstrated the existence of novel CEACAM5 splice variants and splice variant-derived protein isoforms in gastrointestinal cancer cell lines.

Results

We identified two novel CEACAM5 splice variants in gastrointestinal (pancreatic, gastric, and colorectal) cancer cell lines. One of the variants possessed an alternative minor splice site that allowed generation of GC-AG intron. Furthermore, CEA protein isoforms derived from the novel splice variants were expressed in cancer cell lines and those protein isoforms were secreted into the culture medium. Although CEA protein isoforms always co-existed with the full-length protein, the secretion patterns of these isoforms did not correlate with the expression patterns.

Conclusions

This is the first study to identify the expression of CEA isoforms derived from the novel splice variants processed on the unique splice site. In addition, we also revealed the secretion of those isoforms from gastrointestinal cancer cell lines. Our findings suggested that discrimination between the full-length and identified protein isoforms may improve the clinical utility of CEA as a tumor marker.

CEA-Related CAMs

The carcinoembryonic antigen (CEA) family comprises a large number of cellular surface molecules, the CEA-related cell adhesion molecules (CEACAMs), which belong to the Ig superfamily. CEACAMs exhibit a complex expression pattern in normal and malignant tissues. The majority of the CEACAMs are cellular adhesion molecules that are involved in a great variety of distinct cellular processes, for example in the integration of cellular responses through homo- and heterophilic adhesion and interaction with a broad selection of signal regulatory proteins, i.e., integrins or cytoskeletal components and tyrosine kinases. Moreover, expression of CEACAMs affects tumor growth, angiogenesis, cellular differentiation, immune responses, and they serve as receptors for commensal and pathogenic microbes. Recently, new insights into CEACAM structure and function became available, providing further elucidation of their kaleidoscopic functions.

Ins and outs of microbial adhesion

Microbial adhesion is generally a complex process, involving multiple adhesins on a single microbe and their respective target receptors on host cells. In some situations, various adhesins of a microbe may co-operate in an apparently hierarchical and sequential manner whereby the first adhesive event triggers the target cell to express receptors for additional microbial adhesins. In other instances, adhesins may act in concert leading to high avidity interactions, often a prelude to cellular invasion and tissue penetration. Mechanisms used to target the host include both lectin-like interactions and protein-protein interactions; the latter are often highly specific for the host or a tissue within the host. This reflective chapter aims to offer a point of view on microbial adhesion by presenting some experiences and thoughts especially related to respiratory pathogens and explore if there can be any future hope of controlling bacterial infections via preventing adhesion or invasion stages of microbial pathogenesis.

Role of serum carcinoembryonic antigen in the detection of colorectal cancer before and after surgical resection

AIM: To determine whether serum levels of carcinoembryonic antigen (CEA) correlate with the presence of primary colorectal cancer (CRC), and/or recurrent CRC following radical resection.

METHODS: A total of 413 patients with CRC underwent radical surgery between January 1998 and December 2002 in our department and were enrolled in this study. The median follow-up period was 69 mo (range, 3-118 mo), and CRC recurrence was experienced by 90/413 (21.8%) patients. Serum levels of CEA were assayed preoperatively, and using a cutoff value of 5 ng/mL, patients were divided into two groups, those with normal serum CEA levels (e.g., ≤ 5 ng/mL) and those with elevated CEA levels (> 5 ng/mL).

RESULTS: The overall sensitivity of CEA for the detection of primary CRC was 37.0%. The sensitivity of CEA according to stage, was 21.4%, 38.9%, and 41.7% for stages I-III, respectively. Moreover, for stage II and stage III cases, the 5-year disease-free survival rates were reduced for patients with elevated preoperative serum CEA levels (P < 0.05). The overall sensitivity of CEA for detecting recurrent CRC was 54.4%, and sensitivity rates of 36.6%, 66.7%, and 75.0% were associated with cases of local recurrence, single metastasis, and multiple metastases, respectively. In patients with normal serum levels of CEA preoperatively, the sensitivity of CEA for detecting recurrence was reduced compared with patients having a history of elevated CEA prior to radical resection (32.6% vs 77.3%, respectively, P < 0.05).

CONCLUSION: CRC patients with normal serum CEA levels prior to resection maintained these levels during CRC recurrence, especially in cases of local recurrence vs cases of metastasis.

CEACAM1 recognition by bacterial pathogens is species-specific

BACKGROUND

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), an immunoglobulin (Ig)-related glycoprotein, serves as cellular receptor for a variety of Gram-negative bacterial pathogens associated with the human mucosa. In particular, Neisseria gonorrhoeae, N. meningitidis, Moraxella catarrhalis, and Haemophilus influenzae possess well-characterized CEACAM1-binding adhesins. CEACAM1 is typically involved in cell-cell attachment, epithelial differentiation, neovascularisation and regulation of T-cell proliferation, and is one of the few CEACAM family members with homologues in different mammalian lineages. However, it is unknown whether bacterial adhesins of human pathogens can recognize CEACAM1 orthologues from other mammals.

RESULTS

Sequence comparisons of the amino-terminal Ig-variable-like domain of CEACAM1 reveal that the highest sequence divergence between human, murine, canine and bovine orthologues is found in the beta-strands comprising the bacteria-binding CC'FG-face of the Ig-fold. Using GFP-tagged, soluble amino-terminal domains of CEACAM1, we demonstrate that bacterial pathogens selectively associate with human, but not other mammalian CEACAM1 orthologues. Whereas full-length human CEACAM1 can mediate internalization of Neisseria gonorrhoeae in transfected cells, murine CEACAM1 fails to support bacterial internalization, demonstrating that the sequence divergence of CEACAM1 orthologues has functional consequences with regard to bacterial recognition and cellular invasion.

CONCLUSIONS

Our results establish the selective interaction of several human-restricted bacterial pathogens with human CEACAM1 and suggest that co-evolution of microbial adhesins with their corresponding receptors on mammalian cells contributes to the limited host range of these highly adapted infectious agents.

Coevolution of activating and inhibitory receptors within mammalian carcinoembryonic antigen families

BACKGROUND

Most rapidly evolving gene families are involved in immune responses and reproduction, two biological functions which have been assigned to the carcinoembryonic antigen (CEA) gene family. To gain insights into evolutionary forces shaping the CEA gene family we have analysed this gene family in 27 mammalian species including monotreme and marsupial lineages.

RESULTS

Phylogenetic analysis provided convincing evidence that the primordial CEA gene family in mammals consisted of five genes, including the immune inhibitory receptor-encoding CEACAM1 (CEA-related cell adhesion molecule) ancestor. Our analysis of the substitution rates within the nucleotide sequence which codes for the ligand binding domain of CEACAM1 indicates that the selection for diversification is, perhaps, a consequence of the exploitation of CEACAM1 by a variety of viral and bacterial pathogens as their cellular receptor. Depending on the extent of the amplification of an ancestral CEACAM1, the number of CEACAM1-related genes varies considerably between mammalian species from less than five in lagomorphs to more than 100 in bats. In most analysed species, ITAM (immunoreceptor tyrosine-based activation motifs) or ITAM-like motif-containing proteins exist which contain Ig-V-like, ligand binding domains closely related to that of CEACAM1. Human CEACAM3 is one such protein which can function as a CEACAM1 decoy receptor in granulocytes by mediating the uptake and destruction of specific bacterial pathogens via its ITAM-like motif. The close relationship between CEACAM1 and its ITAM-encoding relatives appears to be maintained by gene conversion and reciprocal recombination. Surprisingly, secreted CEACAMs resembling immunomodulatory CEACAM1-related trophoblast-specific pregnancy-specific glycoproteins (PSGs) found in humans and rodents evolved only in a limited set of mammals. The appearance of PSG-like genes correlates with invasive trophoblast growth in these species.

CONCLUSIONS

These phylogenetic studies provide evidence that pathogen/host coevolution and a possible participation in fetal-maternal conflict processes led to a highly species-specific diversity of mammalian CEA gene families.

Pathogenic neisseriae: surface modulation, pathogenesis and infection control

Although renowned as a lethal pathogen, Neisseria meningitidis has adapted to be a commensal of the human nasopharynx. It shares extensive genetic and antigenic similarities with the urogenital pathogen Neisseria gonorrhoeae but displays a distinct lifestyle and niche preference. Together, they pose a considerable challenge for vaccine development as they modulate their surface structures with remarkable speed. Nonetheless, their host-cell attachment and invasion capacity is maintained, a property that could be exploited to combat tissue infiltration. With the primary focus on N. meningitidis, this Review examines the known mechanisms used by these pathogens for niche establishment and the challenges such mechanisms pose for infection control.

Contribution of intestinal epithelial cells to innate immunity of the human gut--studies on polarized monolayers of colon carcinoma cells

The aim was to establish an in vitro model for studies of innate defence mechanisms of human intestinal epithelium. Ultrastructural characterization and determination of mRNA expression levels for apical glycocalyx and mucous components showed that polarized, tight monolayers of the colon carcinoma cell lines T84 and Caco2 acquire the features of mature- and immature columnar epithelial cells, respectively. Polarized monolayers were challenged with non-pathogenic Gram+ and Gram- bacteria from the apical side and the proinflammatory cytokines interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) from the basolateral side. Immune responses were estimated as changes in mRNA expression levels for the mucous component mucin-2 (MUC2), the glycocalyx components carcinoembryonic antigen (CEA), CEA-related cell adhesion molecule-1 (CEACAM1), CEACAM6, CEACAM7 and MUC3, the antimicrobial factors human beta-defensin-1 (hBD1), hBD2, hBD3 and lysozyme, the chemokine IL-8 and the cytokines IL-6 and TNF-alpha. Tight monolayer cells were generally unresponsive to bacterial challenge, but increased their hBD2 levels when challenged with Bacillus megaterium. T84 cells also increased their TNF-alpha levels upon bacterial challenge. Tight monolayer cells responded to cytokine challenge suggesting awareness of basolateral attack. TNF-alpha induced significantly increased levels of IL-8 and TNF-alpha itself in both cell lines suggesting recruitment and activation of immune cells in the underlying mucosa in vivo. Cytokine challenge also increased levels of CEACAM1, which includes two functionally different forms, CEACAM1-L and CEACAM1-S. In T84 cells, IFN-gamma was selective for CEACAM1-L while TNF-alpha upregulated both forms. Increased CEACAM1 expression may influence epithelial function and communication between epithelial cells and intraepithelial lymphocytes.

Serum carcinoembryonic antigen level is associated with epidermal growth factor receptor mutations in recurrent lung adenocarcinomas

BACKGROUND

The presence of epidermal growth factor receptor (EGFR) gene mutations is a good indicator of the clinical efficacy of gefitinib in patients with nonsmall cell lung cancer. It was recently reported that the serum carcinoembryonic antigen (CEA) level could be a predictive factor for the efficacy of gefitinib treatment; therefore, it is suggested that the EGFR gene mutation is associated with the serum CEA level. The current study analyzed the association between EGFR gene mutations and clinical features, including the serum CEA level, in patients with recurrent lung adenocarcinomas.

METHODS

A total of 48 lung adenocarcinoma patients with postoperative disease recurrence who underwent chemotherapy were investigated. EGFR gene mutations at exons 18, 19, and 21 were measured using surgical specimens taken from the primary tumor.

RESULTS

Mutations of the EGFR gene were detected in 25 of the 48 patients and the abnormal serum CEA concentration at the time of disease recurrence was found to be significantly associated with the incidence of EGFR gene mutations (P = .045). The rate of EGFR gene mutations significantly increased as the serum CEA level increased (serum CEA level; <5 vs > or =5 <20 vs > or =20 = 35% vs 55% vs 87.5%, respectively, P = .040). A multivariate analysis revealed that a higher serum CEA level at the time of disease recurrence is independently associated with EGFR gene mutations (P = .036) with an odds ratio of 4.70 (95% confidence interval, 1.1-21.1).

CONCLUSIONS

The serum CEA level appears to be closely associated with the presence of EGFR gene mutations in patients with pulmonary adenocarcinomas.

Haplotypic diversity in human CEACAM genes: effects on susceptibility to meningococcal disease

Adhesion between the opacity-associated adhesin (Opa) proteins of Neisseria meningitidis and human carcino-embryonic antigen cell adhesion molecule (CEACAM) proteins is an important stage in the pathogenesis of meningococcal disease, a globally important bacterial infection. Most disease is caused by a small number of meningococcal genotypes known as hyperinvasive lineages. As these are also carried asymptomatically, acquisition of them alone cannot explain why only some hosts develop meningococcal disease. Our aim was to determine whether genetic diversity in CEACAM is associated with susceptibility to meningococcal disease. Frequency distributions of alleles, genotypes and haplotypes were compared in four CEACAM genes in 384 case samples and 190 controls. Linkage disequilibrium among polymorphic sites, haplotype structures and relationships were also analysed. A number of polymorphisms were observed in CEACAM genes but the diversity of CEACAM1, to which most Opa proteins bind, was lower, and a small number of high-frequency haplotypes were detected. Dose-dependent associations of three CEACAM haplotypes with meningococcal disease were observed, with the effect of carrying these haplotypes amplified in homozygous individuals. Two haplotypes were protective while one haplotype in CEACAM6 was associated with a twofold increase in disease susceptibility. These data imply that human CEACAM may be one determinant of human susceptibility to meningococcal disease.

IFN-gamma amplifies NFkappaB-dependent Neisseria meningitidis invasion of epithelial cells via specific upregulation of CEA-related cell adhesion molecule 1

Temporal relationship between viral and bacterial infections has been observed, and may arise via the action of virus-induced inflammatory cytokines. These, by upregulating epithelial receptors targeted by bacteria, may encourage greater bacterial infiltration. In this study, human epithelial cells exposed to interferon-gamma but not tumour necrosis factor-alpha or interleukin 1-beta supported increased meningococcal adhesion and invasion. The increase was related to Opa but not Opc or pili adhesin expression. De novo synthesis of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), a major Opa receptor, occurred in epithelial cells exposed to the cytokine, or when infected with Opa-expressing bacteria. Cell line-dependent differences in invasion that were observed could be correlated with CEACAM expression levels. There was also evidence for Opa/pili synergism leading to high levels of monolayer infiltration by capsulate bacteria. The use of nuclear factor-kappa B (NFkappaB) inhibitors, diferuloylmethane (curcumin) and SN50, abrogated bacterial infiltration of both untreated and interferon-gamma-treated cells. The studies demonstrate the importance of CEACAMs as mediators of increased cellular invasion under conditions of inflammation and bring to light the potential role of NFkappaB pathway in Opa-mediated invasion by meningococci. The data imply that cell-surface remodelling by virally induced cytokines could be one factor that increases host susceptibility to bacterial infection.

Co-ordinate action of bacterial adhesins and human carcinoembryonic antigen receptors in enhanced cellular invasion by capsulate serum resistant Neisseria meningitidis

Neisseria meningitidis (Nm) is a human specific opportunistic pathogen that occasionally penetrates mucosal barriers via the action of adhesins and invasins and evades host immune mechanisms during further dissemination via capsule expression. From in vitro studies, the primary adhesion of capsulate bacteria is believed to be mediated by polymeric pili, followed by invasion via outer membrane adhesins such as Opa proteins. As the latter requires the surface capsule to be down-modulated, invading bacteria would be serum sensitive and thus avirulent. However, there is recent evidence that capsulate bacteria may interact via Opa proteins when host cells express high levels of carcinoembryonic antigen-related cell adhesion molecules (CEACAMs), their target receptors. Such a situation may arise following increased circulation of inflammatory cytokines that upregulate certain adhesion molecules on host cells. In this study, using a tetracycline controlled expression system, we have developed cell lines with inducible CEACAM expression to mimic post-inflammation state of target tissues and analysed the interplay between the three surface components capsule, pili and Opa proteins in cellular interactions. With two distinct cell lines, not only the level but also the rate of adhesion of capsulate Opa-expressing Nm increased concurrently with CEACAM density. Moreover, when threshold levels of receptor were reached, cellular invasion ensued in an Opa-dependent manner. In studies with cell lines intrinsically expressing pilus receptors, notable synergism in cellular interactions between pili and Opa of several meningococcal strains was observed and was independent of capsule type. A number of internalized bacteria were shown to express capsule and when directly isolated from host cells, these bacteria were as serum resistant as the inoculated phenotype. Furthermore, we observed that agents that block Opa-CEACAM binding substantially reduced cellular invasion, while maintaining a low level of cellular adhesion. These studies highlight some of the factors that may determine increased host susceptibility to infection by serum resistant phenotypes; and demonstrate the potential of selective inhibition of key interactions in preventing target tissue penetration while maintaining a level of colonization.

Gene expression profiles of normal proliferating and differentiating human intestinal epithelial cells: a comparison with the Caco-2 cell model

cDNA microarray technology enables detailed analysis of gene expression throughout complex processes such as differentiation. The aim of this study was to analyze the gene expression profile of normal human intestinal epithelial cells using cell models that recapitulate the crypt-villus axis of intestinal differentiation in comparison with the widely used Caco-2 cell model. cDNA microarrays (19,200 human genes) and a clustering algorithm were used to identify patterns of gene expression in the crypt-like proliferative HIEC and tsFHI cells, and villus epithelial cells as well as Caco-2/15 cells at two distinct stages of differentiation. Unsupervised hierarchical clustering analysis of global gene expression among the cell lines identified two branches: one for the HIEC cells versus a second comprised of two sub-groups: (a) the proliferative Caco-2 cells and (b) the differentiated Caco-2 cells and closely related villus epithelial cells. At the gene level, supervised hierarchical clustering with 272 differentially expressed genes revealed distinct expression patterns specific to each cell phenotype. We identified several upregulated genes that could lead to the identification of new regulatory pathways involved in cell differentiation and carcinogenesis. The combined use of microarray analysis and human intestinal cell models thus provides a powerful tool for establishing detailed gene expression profiles of proliferative to terminally differentiated intestinal cells. Furthermore, the molecular differences between the normal human intestinal cell models and Caco-2 cells clearly point out the strengths and limitations of this widely used experimental model for studying intestinal cell proliferation and differentiation.

Deglycosylation to obtain stable and homogeneous Pichia pastoris-expressed N–A1 domains of carcinoembryonic antigen

Carcinoembryonic antigen (CEA) is a seven domain membrane glycoprotein widely used as a tumour marker for adenocarcinomas and as a target for antibody-directed therapies. Structural models have proposed that the first two domains of CEA (the N terminal and adjoining A1 domains) bind MFE-23, a single chain Fv antibody in experimental clinical use. We aimed to produce recombinant N-A1 to test this hypothesis. The N-A1 domains were expressed as soluble protein with a C-terminal hexahistidine tag (His6-tag) in the yeast Pichia pastoris. His6-tagged N-A1 was captured from the supernatant by batch purification with copper-loaded Streamline Chelating, an immobilised metal affinity chromatography (IMAC) matrix usually utilised in expanded bed techniques. Purified N-A1 was heterogeneous with a molecular weight range from 38 to 188 kDa. Deglycosylation with endoglycosidase H (Endo H) resulted in three discrete molecular weight forms of N-A1, one partially mannosylated, one fully Endo H-digested and one fully Endo H-digested but lacking the His6-tag. These were separated by concanavalin A chromatography followed by HiTrap IMAC. The procedure resulted in single-band-purity, mannose-free N-A1. The binding interaction of MFE-23 to N-A1 was analysed by surface plasmon resonance. The affinity constants retrieved were KD = 4.49 x 10(-9)M for the P. pastoris expressed, native N-A1, and 5.33 x 10(-9) M for the Endo H-treated N-A1. To our knowledge this is the first time that two consecutive domains of CEA have been stably expressed and purified from P. pastoris. This work confirms that the CEA epitope recognised by MFE-23 resides in N-A1.

Environmental signals implicated in Dr fimbriae release by pathogenic Escherichia coli

Afa/Dr diffusely adhering Escherichia coli have been shown to cause urinary tract infections and enteric infections. Virulence of Dr-positive IH11128 bacteria is associated with the presence of Dr fimbriae. In this report, we show for the first time that the Dr fimbriae are released in the extracellular medium in response to multiple environmental signals. Production and secretion of Dr fimbriae are clearly thermoregulated. A comparison of the amounts of secreted fimbriae showed that the secretion is drastically increased during anaerobic growth in minimal medium. The effect of anaerobiosis on secretion seemed to depend on both the growth phase and the culture medium. The secretion was maximal during the logarithmic-phase growth and corresponded to 27 and 57% of total Dr fimbriae produced by bacteria grown in mineral medium+glucose and LB broth, respectively. Thus, the anaerobic environment of the colon would favour the secretion of Dr fimbriae during bacterial multiplication. The controlled release of the Dr fimbriae, which is carried out in the absence of cellular lysis, appears independent of the action of proteases or a process of maturation. The mechanism employed in the liberation of Dr fimbriae thus seems different from that described for the adhesins FHA and Hap of Bordetella pertussis and Haemophilus influenzae.

Interactions of DC-SIGN with Mac-1 and CEACAM1 regulate contact between dendritic cells and neutrophils

Early during infection neutrophils are the most important immune cells that are involved in killing of pathogenic bacteria and regulation of innate immune responses at the site of infection. It has become clear that neutrophils also modulate adaptive immunity through interactions with dendritic cells (DCs) that are pivotal in the induction of T cell responses. Upon activation, neutrophils release TNF-alpha and induce maturation of DCs that enables these antigen-presenting cells to stimulate T cell proliferation and to induce T helper 1 polarization. DC maturation by neutrophils also requires cellular interactions that are mediated by binding of the DC-specific receptor DC-SIGN to Mac-1 on the neutrophil. Here, we demonstrate that also CEACAM1 is an important ligand for DC-SIGN on neutrophils. Binding of DC-SIGN to both CEACAM1 and Mac-1 is required to establish cellular interactions with neutrophils. DC-SIGN is a C-type lectin that has specificity for Lewis(x), and we show that DC-SIGN mediates binding to CEACAM1 through Lewis(x) moieties that are specifically expressed on CEACAM1 derived from neutrophils. This indicates that glycosylation-driven binding of both Mac-1 and CEACAM1 to DC-SIGN is essential for interactions of neutrophils with DCs and enables neutrophils to modulate T cell responses through interactions with DCs.

CEACAM engagement by human pathogens enhances cell adhesion and counteracts bacteria-induced detachment of epithelial cells

Exfoliation, which is the detachment of infected epithelial cells, is an innate defense mechanism to prevent bacterial colonization. Indeed, infection with Neisseria gonorrhoeae induced epithelial detachment from an extracellular matrix (ECM) substrate in vitro. Surprisingly, variants of N. gonorrhoeae that bind to human carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) failed to induce detachment and, instead, promoted enhanced host cell adhesion to the ECM. Microarray analysis revealed that CEACAM engagement by several human pathogens triggers expression of CD105. Blockage of CD105 expression by antisense oligonucleotides abolished infection-induced cell adhesion. The expression of full-length CD105 promoted cell adhesion to the ECM and was sufficient to prevent infection-induced detachment. The CD105-mediated increase in cell adhesion was dependent on the presence and function of integrin β1. CD105 expression did not elevate cellular integrin levels but caused a dramatic increase in the ECM-binding capacity of the cells, suggesting that CD105 affects integrin activity. The exploitation of CEACAMs to trigger CD105 expression and to counteract infection-induced cell detachment represents an intriguing adaptation of pathogens that are specialized to colonize the human mucosa.

Pathogenesis of Afa/Dr diffusely adhering Escherichia coli

Over the last few years, dramatic increases in our knowledge about diffusely adhering Escherichia coli (DAEC) pathogenesis have taken place. The typical class of DAEC includes E. coli strains harboring AfaE-I, AfaE-II, AfaE-III, AfaE-V, Dr, Dr-II, F1845, and NFA-I adhesins (Afa/Dr DAEC); these strains (i) have an identical genetic organization and (ii) allow binding to human decay-accelerating factor (DAF) (Afa/Dr(DAF) subclass) or carcinoembryonic antigen (CEA) (Afa/Dr(CEA) subclass). The atypical class of DAEC includes two subclasses of strains; the atypical subclass 1 includes E. coli strains that express AfaE-VII, AfaE-VIII, AAF-I, AAF-II, and AAF-III adhesins, which (i) have an identical genetic organization and (ii) do not bind to human DAF, and the atypical subclass 2 includes E. coli strains that harbor Afa/Dr adhesins or others adhesins promoting diffuse adhesion, together with pathogenicity islands such as the LEE pathogenicity island (DA-EPEC). In this review, the focus is on Afa/Dr DAEC strains that have been found to be associated with urinary tract infections and with enteric infection. The review aims to provide a broad overview and update of the virulence aspects of these intriguing pathogens. Epidemiological studies, diagnostic techniques, characteristic molecular features of Afa/Dr operons, and the respective role of Afa/Dr adhesins and invasins in pathogenesis are described. Following the recognition of membrane-bound receptors, including type IV collagen, DAF, CEACAM1, CEA, and CEACAM6, by Afa/Dr adhesins, activation of signal transduction pathways leads to structural and functional injuries at brush border and junctional domains and to proinflammatory responses in polarized intestinal cells. In addition, uropathogenic Afa/Dr DAEC strains, following recognition of beta(1) integrin as a receptor, enter epithelial cells by a zipper-like, raft- and microtubule-dependent mechanism. Finally, the presence of other, unknown virulence factors and the way that an Afa/Dr DAEC strain emerges from the human intestinal microbiota as a "silent pathogen" are discussed.

Expression of the carcinoembryonic antigen gene is inhibited by SOX9 in human colon carcinoma cells

The human carcinoembryonic antigen (CEA) is overexpressed in many types of human cancers and is commonly used as a clinical marker. In colon cancer, this overexpression protects cells against apoptosis and contributes to carcinogenesis. Therefore, CEA-expressing cells as well as CEA expression itself constitute potential therapeutic targets. In this report, we show that the transcription factor SOX9 down-regulates CEA gene expression and, as a probable consequence, induces apoptosis in the human colon carcinoma cell line HT29Cl.16E.

Monoclonal Anti-idiotype Antibody 6G6.C4 Fused to GM-CSF Is Capable of Breaking Tolerance to Carcinoembryonic Antigen (CEA) in CEA–Transgenic Mice

Internal image anti-idiotypic antibodies are capable of mimicking tumor-associated antigens and thus may serve as surrogate for vaccination strategies in cancer patients. The monoclonal antibody (mAb) 6G6.C4 mimics an epitope specific for the human carcinoembryonic antigen (CEA) and generates a CEA-specific response (Ab3) in various experimental animals. In humans, however, 6G6.C4 only yields a very limited humoral anti-CEA reaction presumably due to tolerance against the CEA autoantigen. In this study, we investigated the CEA-specific Ab3 response in mice transgenic for the human CEA and tested whether the antigen tolerance could be overcome by fusing a recombinant single-chain variable fragment of 6G6.C4 (scFv6G6.C4) to the murine granulocyte macrophage colony-stimulating factor (GM-CSF). Like mAb 6G6.C4, the fusion protein (scFv6G6.C4/GM-CSF) retained binding to the CEA-specific idiotype mAb T84.66. Also, scFv6G6.C4/GM-CSF was biologically active as measured by proliferation of the GM-CSF-dependent murine FDC-P1 cells in vitro. After immunization with the scFv6G6.C4/GM-CSF fusion protein, CEA-transgenic animals showed significantly enhanced Ab3 antibody responses to scFv6G6.C4 (P=0.005) and to CEA (P=0.012) compared with the scFV6G6.C4 alone. Sera from mice immunized with the fusion protein specifically recognized CEA in Western blot analyses with no cross-reaction to CEA-related antigens. Finally, the Ab3 antisera detected single CEA-expressing tumor cells in suspension as shown by flow cytometry. Taken together, these data show in a model antigenically related to the human system that vaccination with scFv6G6.C4/GM-CSF improves vaccination against an endogenous tumor-associated antigen resulting in a highly specific humoral Ab3 response in vivo that is capable of bind single circulating CEA-positive tumor cells.

Granulocyte CEACAM3 is a phagocytic receptor of the innate immune system that mediates recognition and elimination of human-specific pathogens

Carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) are used by several human pathogens to anchor themselves to or invade host cells. Interestingly, human granulocytes express a specific isoform, CEACAM3, that participates together with CEACAM1 and CEACAM6 in the recognition of CEACAM-binding microorganisms. Here we show that CEACAM3 can direct efficient, opsonin-independent phagocytosis of CEACAM-binding Neisseria, Moraxella, and Haemophilus species. CEACAM3- but not CEACAM6-mediated uptake is blocked by dominant-negative versions of the small GTPase Rac. Moreover, CEACAM3 engagement triggers membrane recruitment and increased GTP loading of Rac that are not observed upon bacterial binding to CEACAM6. Internalization and Rac stimulation are also inhibited by compromising the integrity of an immunoreceptor tyrosine-based activation motif (ITAM)–like sequence in the cytoplasmic tail of CEACAM3 or by interference with Src family protein tyrosine kinases that phosphorylate CEACAM3. In contrast to interfering with CEACAM6, blockage of CEACAM3-mediated events reduces the ability of primary human granulocytes to internalize and eliminate CEACAM-binding bacteria, indicating an important role of CEACAM3 in the control of human-specific pathogens by the innate immune system.

Tumor markers and colorectal cancer: utility in management

Colorectal cancer (CRC) is a leading cause of morbidity and mortality. Although genetic testing can screen for rare hereditary CRC syndromes, there is no ideal means of screening for sporadic forms of CRC. This review will focus on markers that are currently used in the management of sporadic CRC and their limitations, as well as possible future clinical applications.

Carcinoembryonic antigen (CEA) and CEA-related cell adhesion molecule 1 (CEACAM1), apically expressed on human colonic M cells, are potential receptors for microbial adhesion

In the human gut mucosa, specialized M cells deliver intact foreign macromolecules and commensal bacteria from the lumen to organized mucosal lymphoid tissues triggering immune responses. M cells are also major sites of adhesion and invasion for enteric pathogens. The molecular features of M cell apical surfaces that promote microbial normal attachment are still largely unknown. We have demonstrated previously that in the human colonic epithelium, carcinoembryonic antigen (CEA) and CEA-related cell adhesion molecule 1 (CEACAM1) are integral components of the apical glycocalyx which participate in epithelial-microbial interactions. In this study, based on the reactivity of specific monoclonal antibodies and on immunoelectron microscopy, we show that M cells of human colonic solitary lymphoid follicles express CEA and CEACAM1 on the apical surface. Recently these highly glycosylated molecules have been characterized as protein receptors for different bacteria. This leads us to propose a role for CEA and CEACAM1 in the adherence of enteric bacteria to the apical membrane of colonic M cells. We also hypothesize that, unlike colonic enterocytes, M cells lack the defense mechanism that eliminates CEA and CEACAM1 upon microbial binding and which is based on vesiculation of microvillus plasma membrane.

Interferon-gamma Tempers the Expression of Carcinoembryonic Antigen Family Molecules in Human Colon Cells: a Possible Role in Innate Mucosal Defence

Four carcinoembryonic antigen-related cell adhesion molecule (CEACAM)s, i.e. CEA, CEACAM1, CEACAM6 and CEACAM7, are localized to the apical glycocalyx of normal colonic epithelium and have been suggested to play a role in innate immunity. The expression of these molecules in colon carcinoma cells was studied at the mRNA and protein levels after treatment with interferon-gamma (IFN-gamma), interleukin-1beta, live bacteria or lipopolysaccharide. The colon carcinoma cell lines LS174T and HT-29 were studied in detail using real-time quantitative reverse transcriptase-polymerase chain reaction, immunoflow cytometry and immunoelectron microscopy. IFN-gamma, but not the other agents, modified expression of CEA, CEACAM1 and CEACAM6. None of the agents upregulated CEACAM7 expression. Two expression patterns were seen. HT-29 cells, which initially showed low quantities of mRNAs and proteins, displayed marked upregulation of both mRNAs and proteins. LS174T cells transcribed stable high levels of mRNA before and after treatment. Additionally, IFN-gamma induced increased cell surface expression of CEA, CEACAM1 and CECAM6. IFN-gamma has two important effects on the expression levels of the CEA family molecules in colon epithelial cells: direct upregulation of CEACAM1 and promotion of cell differentiation resulting in increased expression of CEA and CEACAM6 and decreased expression of CEACAM7.

Salivary carcinoembryonic antigen as an inflammatory marker

In this study we examined concentration of carcinoembryonic antigen (CEA) in paired saliva and serum samples from healthy individuals and patients with periodontal disease. CEA concentration was determined immunoradiometrically using highly specific anti-CEA antibodies. The salivas from periodontally healthy subjects revealed CEA concentrations with median value of 62 mg/L. Distribution of salivary CEA concentrations in patients with periodontal diseases were very broad with median values: 74 mg/L (stage I), 84 mg/L (stage II), 240 mg/L (stage III) and 412 mg/L (necrotizing ulcerative periodontitis-NUP). Analysis of the obtained values indicated statistically significant increase in salivary CEA, in subjects with periodontal diseases. Metronisadole treatment in patients with NUP leads to statistically significant decrease in salivary CEA. The results obtained suggested salivary CEA as a potential marker of the alterations of periodontium.

Increased expression of antimicrobial peptides and lysozyme in colonic epithelial cells of patients with ulcerative colitis

The impact of chronic inflammation on the expression of human alpha-defensins 5 and 6 (HD-5, HD-6), beta-defensins 1 and 2 (hBD-1, hBD-2) and lysozyme in epithelial cells of small and large intestine was investigated. Intestinal specimens from 16 patients with ulcerative colitis (UC), 14 patients with Crohn's disease (CD) and 40 controls with no history of inflammatory bowel disease were studied. mRNA expression levels of the five defence molecules were determined in freshly isolated epithelial cells by real-time quantitative RT-PCR. Specific copy standards were used allowing comparison between the expression levels of the different defensins. HD-5 and lysozyme protein expression was also studied by immunohistochemistry. Colonic epithelial cells from patients with UC displayed a significant increase of hBD-2, HD-5, HD-6 and lysozyme mRNA as compared to epithelial cells in controls. Lysozyme mRNA was expressed at very high average copy numbers followed by HD-5, HD-6, hBD-1 and hBD-2 mRNA. HD-5 and lysozyme protein was demonstrated in metaplastic Paneth-like cells in UC colon. There was no correlation between hBD-2 mRNA levels and HD-5 or HD-6 mRNA levels in colon epithelial cells of UC patients. Colonic epithelial cells of Crohn's colitis patients showed increased mRNA levels of HD-5 and lysozyme mRNA whereas ileal epithelial cells of Crohn's patients with ileo-caecal inflammation did not. Chronic inflammation in colon results in induction of hBD-2 and alpha-defensins and increased lysozyme expression. hBD-1 expression levels in colon remain unchanged in colitis. The high antimicrobial activity of epithelial cells in chronic colitis may be a consequence of changes in the epithelial lining, permitting adherence of both pathogenic bacteria and commensals directly to the epithelial cell surface.

A carcinoembryonic antigen-specific diabody produced in tobacco

The feasibility of using tobacco for production of a recombinant antibody (T84.66/GS8 diabody) directed against the carcinoembryonic antigen (CEA) and used for tumor imaging was investigated. Two constructs were generated for targeting the protein either to the apoplast or to the endoplasmic reticulum. Expression of the diabody in tobacco leaves after vacuum-assisted infiltration of engineered Agrobacteria (agro-infiltration) and in regenerated transgenic tobacco plants was analyzed and compared. Results in terms of protein expression and accumulation between both systems showed a good correlation. His6-tagged T84.66 diabody was readily purified from agro-infiltrated tobacco leaves and from transgenic plants by immobilized metal ion affinity chromatography. The purified protein was analyzed by polyacrylamide gel electrophoresis, Western blot, gel filtration, electrospray mass spectrometry, direct and competition ELISA, electrophoretic mobility shift assay, and staining of CEA-positive colon adenocarcinoma cell line LS174T. Our results demonstrate that tobacco is a competent production system for this clinically relevant diabody.