Biliary glycoprotein, a potential human cell adhesion molecule, is down-regulated in colorectal carcinomas

The transmembrane domain of CEACAM1-4S is a determinant of anchorage independent growth and tumorigenicity

CEACAM1 is a multifunctional Ig-like cell adhesion molecule expressed by epithelial cells in many organs. CEACAM1-4L and CEACAM1-4S, two isoforms produced by differential splicing, are predominant in rat liver. Previous work has shown that downregulation of both isoforms occurs in rat hepatocellular carcinomas. Here, we have isolated an anchorage dependent clone, designated 253T-NT that does not express detectable levels of CEACAM1. Stable transfection of 253-NT cells with a wild type CEACAM1-4S expression vector induced an anchorage independent growth in vitro and a tumorigenic phenotype in vivo. These phenotypes were used as quantifiable end points to examine the functionality of the CEACAM1-4S transmembrane domain. Examination of the CEACAM1 transmembrane domain showed N-terminal GXXXG dimerization sequences and C-terminal tyrosine residues shown in related studies to stabilize transmembrane domain helix-helix interactions. To examine the effects of transmembrane domain mutations, 253-NT cells were transfected with transmembrane domain mutants carrying glycine to leucine or tyrosine to valine substitutions. Results showed that mutation of transmembrane tyrosine residues greatly enhanced growth in vitro and in vivo. Mutation of transmembrane dimerization motifs, in contrast, significantly reduced anchorage independent growth and tumorigenicity. 253-NT cells expressing CEACAM1-4S with both glycine to leucine and tyrosine to valine mutations displayed the growth-enhanced phenotype of tyrosine mutants. The dramatic effect of transmembrane domain mutations constitutes strong evidence that the transmembrane domain is an important determinant of CEACAM1-4S functionality and most likely by other proteins with transmembrane domains containing dimerization sequences and/or C-terminal tyrosine residues.

Re-expression of CEACAM1 long cytoplasmic domain isoform is associated with invasion and migration of colorectal cancer

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is known to be downregulated at the transcriptional level in adenoma and carcinoma. Recent reports have shown that CEACAM1 is overexpressed at protein level in colorectal cancer and correlated with clinical stage. The reason why colorectal cancer cells re-expressed CEACAM1 remains unclear. The aim of our study was to clarify the implication of CEACAM1 re-expression in colorectal cancer. Immunohistochemical analyses were conducted with CEACAM1 long (CEACAM1-L) or short (CEACAM1-S) cytoplasmic domain-specific antibodies on clinical samples from 164 patients with colorectal cancer. The risk factors for metastasis and survival were calculated for clinical implication of CEACAM1 re-expression. Invasion chamber and wound healing assays were performed for the effect of CEACAM1 expression on invasion and migration of colorectal cancer cells. CEACAM1-L and CEACAM1-S stained with greater intensity at the invasion front than at the luminal surface of tumors. Differences between the long and short cytoplasmic isoform expression levels were observed at the invasion front. Multivariate analysis showed that CEACAM1-L dominance was an independent risk factor for lymph node metastasis, hematogenous metastasis and short survival. The Kaplan-Meier evaluation demonstrated that CEACAM1-L dominance was associated with shorter survival time (p < 0.0001). In the invasion chamber and wound healing assays, CEACAM1-L promoted invasion and migration. Re-expression of CEACAM1 is observed at the invasion front of colorectal cancer. CEACAM1-L dominance is associated with metastasis and shorter survival of the patients with colorectal cancer. CEACAM1-L dominance is important for colorectal cancer cells invasion and migration.

Hollow spheroids beyond the invasive margin indicate the malignant potential of colorectal cancer

Objective Tumour budding formed by histologically undifferentiated cancer cells beyond the border of the tumour margin is associated with lymph node metastasis. However, hollow tumour nests, a possible histologically advanced phenotype of tumour budding, have not been discussed. We examined whether hollow spheroids exist beyond the border of the invasive margin and are associated with metastasis and prognosis. Moreover, we suggest that carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) isoform balance is associated with hollow spheroid formation. Methods Immunohistochemical analyses with CEACAM1 and M30 as an apoptosis marker were performed to examine the importance of hollow spheroid CEACAM1 expression and central cell apoptosis in hollow spheroid formation. The correlations between the presence of hollow spheroids beyond the invasive margin and the clinicopathological characteristics of 314 patients with colorectal cancer were retrospectively evaluated. A 3D culture with colorectal cancer cells transfected with CEACAM1 cDNA or shRNA was used to determine whether CEACAM1 isoform balance controls colorectal hollow spheroid formation. Results Hollow spheroid formation accompanying central cell apoptosis was confirmed by M30 staining and serial section with CEACAM1 staining. Of the 314 patients, 96 (30.4%) were classified as having hollow spheroids. The presence of hollow spheroids is an independent risk factor for metastases and shorter survival. In 3D culture, CEACAM1 isoform balance modulated hollow spheroid formation of colorectal cancer cells. Conclusions Hollow spheroid formation beyond the border of the tumour margin in colorectal cancer is more important than tumour budding for the prediction of malignant potential.

Vitamin D inhibits CEACAM1 to promote insulin/IGF-I receptor signaling without compromising anti-proliferative action

Population studies suggest putative links between vitamin D (VD)-deficiency and risk of cancer and diabetes. The insulin/IGF-I receptor represents a signaling target of the carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) that is implicated in both diabetes and cancer, therefore we hypothesized that VD actions may be mediated through this adhesion molecule. In this study, we show that 1,25 vitamin D3 and its analogues EB1089 and KH1060 potently inhibit CEACAM1 expression in cancer cells. This effect was associated with significant reductions in mRNA and protein levels, resulting from transcriptional and posttranslational actions respectively. Insulin/IGF-I-mediated IRS-1 and Akt activation were enhanced by VD treatment. Similarly, CEACAM1 downregulation significantly upregulated the insulin and IGF-I receptors and mimicked the effect of VD-mediated enhanced insulin/IGF-I receptor signaling. Despite improved insulin/IGF-I signaling, the anti-proliferative actions of VD were preserved in the absence or presence of forced CEACAM1 expression. Forced CEACAM1, however, abrogated the anti-invasive actions of VD. Our findings highlight CEACAM1 as a target of VD action. The resulting inhibition of CEACAM1 has potentially beneficial effects on metabolic disorders without necessarily compromising the anticancer properties of this vitamin.

Regulation of CEACAM1 transcription in human breast epithelial cells

BACKGROUND

Carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1) is a transmembrane protein with multiple functions in different cell types. CEACAM1 expression is frequently mis-regulated in cancer, with down-regulation reported in several tumors of epithelial origin and de novo expression of CEACAM1 in lung cancer and malignant melanoma. In this report we analyzed the regulation of CEACAM1 expression in three breast cancer cell lines that varied in CEACAM1 expression from none (MCF7) to moderate (MDA-MB-468) to high (MCF10A, comparable to normal breast).

RESULTS

Using in vivo footprinting and chromatin immunoprecipitation experiments we show that the CEACAM1 proximal promoter in breast cells is bound in its active state by SP1, USF1/USF2, and IRF1/2. When down-regulated the CEACAM1 promoter remains accessible to USF2 and partially accessible to USF1. Interferon-γ up-regulates CEACAM1 mRNA by a mechanism involving further induction of IRF-1 and USF1 binding at the promoter. As predicted by this analysis, silencing of IRF1 and USF1 but not USF2 by RNAi resulted in a significant decrease in CEACAM1 protein expression in MDA-MB-468 cells. The inactive CEACAM1 promoter in MCF7 cells exhibits decreased histone acetylation at the promoter region, with no evidence of H3K9 or H3K27 trimethylation, histone modifications often linked to condensed chromatin structure.

CONCLUSIONS

Our data suggest that transcription activators USF1 and IRF1 interact to modulate CEACAM1 expression and that the chromatin structure of the promoter is likely maintained in a poised state that can promote rapid induction under appropriate conditions.

DC-SIGN and SRCL bind glycans of carcinoembryonic antigen (CEA) and CEA-related cell adhesion molecule 1 (CEACAM1): recombinant human glycan-binding receptors as analytical tools

Members of the family of carcinoembryonic antigen (CEA)-related cell adhesion molecules (CEACAMs) belonging to the immunoglobulin (Ig) superfamily are expressed in a variety of normal and malignant human tissues. As components of the cell membrane, these glycoproteins can make contact with adjacent cells. CEACAM1 and CEACAM5 (CEA) express Lewis(x) (Le(x)) structures. As shown by mass spectrometry in conjunction with enzymatic digestion, CEACAM1 contains at least seven Le(x) residues. Fucosyltransferase IX is the main fucosyltransferase responsible for attachment of terminal fucose, the key feature of the Le(x) structure, to CEA and CEACAM1. The Le(x) residues of both, CEACAM1 and CEA, interact with the human Le(x)-binding glycan receptors DC-SIGN and SRCL. Since subpopulations of human macrophages express DC-SIGN or SRCL, Le(x)-carrying CEACAMs may modulate the immune response in normal tissues such as the human placenta or in malignant tumours, for example in colorectal, pancreatic or lung carcinomas.

Deregulation of the CEACAM expression pattern causes undifferentiated cell growth in human lung adenocarcinoma cells

CEACAM1, CEA/CEACAM5, and CEACAM6 are cell adhesion molecules (CAMs) of the carcinoembryonic antigen (CEA) family that have been shown to be deregulated in lung cancer and in up to 50% of all human cancers. However, little is known about the functional impact of these molecules on undifferentiated cell growth and tumor progression. Here we demonstrate that cell surface expression of CEACAM1 on confluent A549 human lung adenocarcinoma cells plays a critical role in differentiated, contact-inhibited cell growth. Interestingly, CEACAM1-L, but not CEACAM1-S, negatively regulates proliferation via its ITIM domain, while in proliferating cells no CEACAM expression is detectable. Furthermore, we show for the first time that CEACAM6 acts as an inducer of cellular proliferation in A549 cells, likely by interfering with the contact-inhibiting signal triggered by CEACAM1-4L, leading to undifferentiated anchorage-independent cell growth. We also found that A549 cells expressed significant amounts of non-membrane anchored variants of CEACAM5 and CEACAM6, representing a putative source for the increased CEACAM5/6 serum levels frequently found in lung cancer patients. Taken together, our data suggest that post-confluent contact inhibition is established and maintained by CEACAM1-4L, but disturbances of CEACAM1 signalling by CEACAM1-4S and other CEACAMs lead to undifferentiated cell growth and malignant transformation.

The roles of cell adhesion molecules in tumor suppression and cell migration: a new paradox

In addition to mediating cell adhesion, many cell adhesion molecules act as tumor suppressors. These proteins are capable of restricting cell growth mainly through contact inhibition. Alterations of these cell adhesion molecules are a common event in cancer. The resulting loss of cell-cell and/or cell-extracellular matrix adhesion promotes cell growth as well as tumor dissemination. Therefore, it is conventionally accepted that cell adhesion molecules that function as tumor suppressors are also involved in limiting tumor cell migration. Paradoxically, in 2005, we identified an immunoglobulin superfamily cell adhesion molecule hepaCAM that is able to suppress cancer cell growth and yet induce migration. Almost concurrently, CEACAM1 was verified to co-function as a tumor suppressor and invasion promoter. To date, the reason and mechanism responsible for this exceptional phenomenon remain unclear. Nevertheless, the emergence of these intriguing cell adhesion molecules with conflicting roles may open a new chapter to the biological significance of cell adhesion molecules.

CEACAM1 expression in pancreatic endocrine tumors

The aim of this study was to examine the expression of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) in pancreatic endocrine tumors (PETs) and to correlate it with clinicopathologic parameters. Sixty-nine PETs were examined for tumor size, necrosis, local peripancreatic invasion and lymphovascular invasion, lymph node, and liver metastasis. The mitotic count, expressed per 10 high-power fields (HPF) and MIB1 index were assessed and tumors were classified according to the World Health Organization classification. A tissue microarray was constructed and stained with an extensive panel of endocrine markers and CEACAM1. Twenty-nine tumors were from males and 40 from females, age range: 23 to 80 years (mean 52.4 y), tumor size ranged from 0.8 to 11 cm (mean 3.5 cm), 8 patients had multiple endocrine neoplasia 1 syndrome, and 1 had von Hippel-Lindau disease. Twenty tumors demonstrated local invasion, 32 had lymphovascular invasion, 16 had lymph node metastasis, and 10 had liver metastasis. CEACAM1 was positive in 47 cases and negative in 22 cases (31.9%). Ninety percent of the CEACAM1-negative cases had a MIB1 index <or=2%, whereas 88.9% of CEACAM1-positive cases had a MIB1 index >2% (P=0.02). 86.4% of the CEACAM1-negative PETs had a mitotic count <or=2/10 HPF, whereas 75% of the CEACAM-positive PETs had a mitotic count >2/10 HPF. In addition, 80% of tumors >or=2 cm in diameter were CEACAM positive (P<0.05). CEACAM1-positive tumors were more frequently insulin negative (9 of 10 cases) (P=0.005) and vasoactive intestinal peptide-positive PETs were all CEACAM1 immunopositive (7 of 7 cases) (P=0.005). Benign tumors and PETs of uncertain malignant behavior were more frequently CEACAM1-negative and low-grade malignant cases were CEACAM1 positive (27 of 29 cases) (P=0.001). In addition, CEACAM1-positive tumors were statistically correlated with cytokeratin 19-positive tumors (P<0.05). PETs showing CEACAM1 positivity have a statistically significant correlation with several of the pathologic parameters of aggressive behavior and its overexpression is seen in those cases with increased invasiveness.

Whole genome exon arrays identify differential expression of alternatively spliced, cancer-related genes in lung cancer

Alternative processing of pre-mRNA transcripts is a major source of protein diversity in eukaryotes and has been implicated in several disease processes including cancer. In this study we have performed a genome wide analysis of alternative splicing events in lung adenocarcinoma. We found that 2369 of the 17 800 core Refseq genes appear to have alternative transcripts that are differentially expressed in lung adenocarcinoma versus normal. According to their known functions the largest subset of these genes (30.8%) is believed to be cancer related. Detailed analysis was performed for several genes using PCR, quantitative RT-PCR and DNA sequencing. We found overexpression of ERG variant 2 but not variant 1 in lung tumors and overexpression of CEACAM1 variant 1 but not variant 2 in lung tumors but not in breast or colon tumors. We also identified a novel, overexpressed variant of CDH3 and verified the existence and overexpression of a novel variant of P16 transcribed from the CDKN2A locus. These findings demonstrate how analysis of alternative pre-mRNA processing can shed additional light on differences between tumors and normal tissues as well as between different tumor types. Such studies may lead to the development of additional tools for tumor diagnosis, prognosis and therapy.

Altered splicing of CEACAM1 in breast cancer: identification of regulatory sequences that control splicing of CEACAM1 into long or short cytoplasmic domain isoforms

Background

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), a cell adhesion molecule expressed in a variety of cell types is a putative tumor suppressor gene. Alternative splicing of CEACAM1 generates 11 different splice variants, which include 1–4 ectodomains with either short or long cytoplasmic domain generated by the exclusion (CEACAM1-S) or inclusion (CEACAM1-L) of exon 7. Studies in rodents indicate that optimal ratios of CEACAM1 splice variants are required to inhibit colonic tumor cell growth.

Results

We show that CEACAM1 is expressed in a tissue specific manner with significant differences in the ratios of its short (CEACAM1-S) and long (CEACAM1-L) cytoplasmic domain splice variants. Importantly, we find dramatic differences between the ratios of S:L isoforms in normal breast tissues versus breast cancer specimens, suggesting that altered splicing of CEACAM1 may play an important role in tumorogenesis. Furthermore, we have identified two regulatory cis-acting elements required for the alternative splicing of CEACAM1. Replacement of these regulatory elements by human β-globin exon sequences resulted in exon 7-skipped mRNA as the predominant product. Interestingly, while insertion of exon 7 in a β-globin reporter gene resulted in its skipping, exon 7 along with the flanking intron sequences recapitulated the alternative splicing of CEACAM1.

Conclusion

Our results indicate that a network of regulatory elements control the alternative splicing of CEACAM1. These findings may have important implications in therapeutic modalities of CEACAM1 linked human diseases.

Intestinal tumor progression is promoted by decreased apoptosis and dysregulated Wnt signaling in Ceacam1-/- mice

The carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1) is downregulated in colonic and intestinal hyperplastic lesions as well as in other cancers, where it functions as a tumor suppressor. To investigate the functions of CEACAM1 in the normal intestine and in intestinal tumors, we generated a compound knockout mouse model and examined both Ceacam1(-/-) and Apc(1638N/+):Ceacam1(-/-) mice. Ceacam1(-/-) intestinal cells exhibited a significant decrease in apoptosis, with no change in proliferation or migration, however. Compound Apc(1638N/+):Ceacam1(-/-) mice demonstrated an increase in intestinal tumor multiplicity and tumor progression. Increases in intussusceptions and desmoid lesions were also observed. We have shown that CEACAM1-L associates with beta-catenin by co-immunoprecipitation and colocalization in CEACAM1-L-transfected CT26 and CT51 mouse colon carcinoma cells. Ceacam1(-/-) enterocytes displayed decreased glycogen synthase kinase 3-beta activity with corresponding nuclear localization of beta-catenin. Increased T-cell factor/Lef transcriptional activity was observed in CEACAM1-null CT51 colonic cells and in Caco2 colon cancer cells in which CEACAM1 was downregulated. A significant increased expression in c-Myc and cyclin D1 targets of the Wnt signaling pathway was also revealed in the Ceacam1(-/-) intestine. CEACAM1 therefore actively participates in Wnt signaling in intestinal cells and its downregulation in intestinal tissue contributes to malignancy by augmenting tumor multiplicity and progression.

Direct interaction of tumor suppressor CEACAM1 with beta catenin: identification of key residues in the long cytoplasmic domain

CEACAM1-4L (carcinoembryonic antigen cell adhesion molecule 1, with 4 extracellular Ig-like domains and a long, 71 amino acid cytoplasmic domain) is expressed in epithelial cells and activated T-cells, but is down-regulated in most epithelial cell cancers and T-cell leukemias. A highly conserved sequence within the cytoplasmic domain has ca 50% sequence homology with Tcf-3 and -4, transcription factors that bind beta-catenin, and to a lesser extent (32% homology), with E-cadherin that also binds beta-catenin. We show by quantitative yeast two-hybrid, BIAcore, GST-pull down, and confocal analyses that this domain directly interacts with beta-catenin, and that H-469 and K-470 are key residues that interact with the armadillo repeats of beta-catenin. Jurkat cells transfected with CEACAM1-4L have 2-fold less activity in the TOPFLASH reporter assay, and in MCF7 breast cancer cells that fail to express CEACAM1, transfection with CEACAM1 and growth in Ca2+ media causes redistribution of beta-catenin from the cytoplasm to the cell membrane, demonstrating a functional role for the long cytoplasmic domain of CEACAM1 in regulation of beta-catenin activity.

The CEACAM1-mediated apoptosis pathway is activated by CEA and triggers dual cleavage of CEACAM1

Marked reduction in apoptosis is a hallmark of early colon tumour growth and the vast majority of these tumours exhibit a loss of expression of the glycoprotein carcinoembryonic-antigen-related cell adhesion molecule 1 (CEACAM1). We recently reported that the CEACAM1 functions as a mediator of apoptosis implicating this cell surface protein in early tumour development. However, the mechanistic involvement of CEACAM1 in cell death pathways is unclear. Here, we show that apoptosis triggers cleavage of the long form of CEACAM1 (CEACAM1-4L) at intracellular and extracellular sites in Jurkat cells and HEK293 cells. Signalling through CEACAM1 leads to caspase activation including caspase-1 and -3 and also involves non-caspase proteases. Moreover, we provide evidence that the naturally occurring CEACAM family member CEA is an inducer of CEACAM1-mediated apoptosis in HT29 colon cancer cells, an effect that depends on the abundance of CEACAM1 on the cell surface. Together, our results demonstrate that the CEACAM1-dependent cell death pathway involves dual cleavage of CEACAM1 and caspase activation and can be activated by CEA.

Elevated expression of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM-1) is associated with increased angiogenic potential in non-small-cell lung cancer

Recent studies have challenged the previously postulated concept of a tumor-suppressive effect of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM-1). A possible angiogenic influence of CEACAM-1 in non-small-cell lung cancer (NSCLC) has not been investigated so far. Therefore, we examined microvessel density (MVD) and CEACAM-1 expression in primary NSCLC and analyzed their possible correlations under consideration of their prognostic effects. Specimens from 82 consecutive patients with completely resected NSCLC were stained immunohistochemically using the monoclonal anti-CEACAM-1 antibody 4D1/C2 and the monoclonal anti-CD31 antibody JC70A. The prognostic relevance of CEACAM-1 expression and MVD was evaluated by univariate Kaplan-Meier and multivariate Cox regression analysis. The median follow-up period was 75 months (range 10-156 months). A high MVD (i.e., > or =31microvessels/400x microscopic field) was observed more frequently in tumors with high CEACAM-1 expression (i.e., >/=66% stained tumor cells) than in tumors with low CEACAM-1 expression (61.8% vs. 33.3%, respectively; p=0.01). In univariate survival analyses, high CEACAM-1 expression and high MVD were associated with development of distant metastasis (p=0.011 and 0.022, respectively) and decreased cancer-related survival (p=0.046 and 0.006, respectively). Multivariate Cox regression analysis demonstrated that the prognostic impact of CEACAM-1 depended on the prognostic influence of MVD, while MVD itself represented an independent prognosticator for unfavorable cancer-related survival (p=0.021; relative risk 2.1; 95% confidence interval, 1.1-4.0). Here we show for the first time that high CEACAM-1 expression is associated with an increased angiogenic activity in NSCLC, and that the prognostic influence of CEACAM-1 might be derived from this association.

Lymphatic reprogramming of microvascular endothelial cells by CEA-related cell adhesion molecule-1 via interaction with VEGFR-3 and Prox1

Here, we demonstrate that carcinoembryonic antigen-related cell adhesion molecule-1 (CEACAM1) is expressed and co-localized with podoplanin in lymphatic endothelial cells (LECs) of tumor but not of normal tissue. CEACAM1 overexpression in human dermal microvascular endothelial cells (HDMECs) results in a significant increase of podoplanin-positive cells in fluorescence-activated cell sorting analyses, while such effects are not observed in CEACAM1 overexpressing human umbilical vein endothelial cell (HUVECs). This effect of CEACAM1 is ceased when HDMECs are transfected with CEACAM1/y− missing the tyrosine residues in its cytoplasmic domain. CEACAM1 overexpression in HDMECs leads to an up-regulation of vascular endothelial growth factor C, -D (VEGF-C, -D) and their receptor vascular endothelial growth factor receptor 3 (VEGFR-3) at mRNA and protein levels. HDMECs transfected with CEACAM1 but not those with CEACAM1/y− show enhanced expression of the lymphatic markers Prox1, podoplanin, and LYVE-1. Furthermore, Prox1 silencing in HDMECs via small interfering RNA blocks the CEACAM1-induced increase of VEGFR-3 expression. Number and network of endothelial tubes induced by VEGF-C and -D are enhanced in CEACAM1-overexpressing HDMECs. Moreover, VEGF-A treatment of CEACAM1-silenced HDMECs restores their survival but not that with VEGF-C and VEGF-D. These data imply that the interaction of CEACAM1 with Prox1 and VEGFR-3 plays a crucial role in tumor lymphangiogenesis and reprogramming of vascular endothelial cells to LECs. CEACAM1-induced signaling effects appear to be dependent on the presence of tyrosine residues in the CEACAM1 cytoplasmic domain.

Role of CEACAM1 isoforms in an in vivo model of mammary morphogenesis: mutational analysis of the cytoplasmic domain of CEACAM1-4S reveals key residues involved in lumen formation

CEACAM1 (carcinoembryonic antigen-related cell adhesion molecule 1) is a type I transmembrane glycoprotein expressed in epithelial cells with three or four extracellular domains (ECDs) and either long or short cytoplasmic domain isoforms. We have previously shown that the four extracellular domains, short cytoplasmic domain isoform, CEACAM1-4S, plays an essential role in lumen formation in an in vitro model of mammary morphogenesis. In this study, we transfected MCF-7 cells with either the long or short cytoplasmic domain isoforms of CEACAM1, and grew the cells in humanized mammary mouse fat pads in NOD/SCID mice. In this in vivo model, only the long cytoplasmic domain isoform, CEACAM1-4L, formed glands with lumen. On the basis of other studies that revealed phosphorylation of key Thr and Ser residues in the short cytoplasmic domain, we introduced phosphorylation mimic (for example, Thr or Ser to Asp) or null (Thr or Ser to Ala) mutations into the cytoplasmic domain of CEACAM1-4S and tested them in the in vivo model. Mutation of either Thr or Ser to Asp or the double mutant Thr+Ser to Asp, but not the null mutants, induced gland formation with a central lumen-containing apoptotic cells. Moreover, the phosphorylation mimic mutants of CEACAM1-4S induced downregulation of beta1-integrin, overexpression of beta2-integrin, inhibited phosphorylation of focal adhesion kinase (pTyr-397) and resulted in myofibroblast differentiation as characterized by expression of vimentin, alpha-smooth muscle actin and beta2-integrin, as well as the production of abundant extracellular matrix.

The expression of CD66a and possible roles in colorectal adenoma and adenocarcinoma

BACKGROUND

The aim of our study was to analyze the expression and possible role of CD66a in colorectal adenoma and adenocarcinoma and the relationship between its expression and pre-operation serum carcinoembryonic antigen (CEA) level and tumor stage in patients with colorectal adenocarcinomas.

METHODS

Paraffin-embedded sections from 184 patients including 42 colorectal adenomas with low-grade dysplasia, 43 adenomas with high-grade dysplasia, and 99 adenocarcinomas were collected for this study. Immunohistochemical analysis was performed, and the expression and the location of CD66a were evaluated and were correlated with beta-catenin nuclear expression.

RESULTS

The expression of CD66a was found not only in the apical membrane of neoplastic glands but also in secretion within the lumen of the neoplastic glands including adenomas and adenocarcinomas. Expressions of secreted CD66a were of higher level in adenocarcinoma than in adenoma with high-grade dysplasia and adenoma with low-grade dysplasia (p < 0.0001). High expression of secreted CD66a was also associated with tumor stage, invasion, and pre-operation serum CEA level of patients with colorectal adenocarcinoma.

CONCLUSIONS

This study implied that CD66a can function both as an epithelial cell adhesion protein or alternatively as secreted CD66a. In addition, a high expression of CD66a was significantly correlated with tumor invasion, stage, and pre-operation serum CEA level.

CEACAM5 and CEACAM6 are major target genes for Smad3-mediated TGF-β signaling

The carcinoembryonic antigen (CEAs) family consists of a large group of evolutionarily and structurally divergent glycoproteins. The transforming growth factor-beta (TGF-beta) signaling pathway has been implicated in the stimulation of CEA secretion in TGF-beta-sensitive colon cells, thereby possibly modulating cell adhesion and differentiation. However, the specific CEAs targeted by TGF-beta signaling or underlying mechanism of the expression of CEAs has not yet been clarified. In this study, we investigated the specific CEAs targeted by the TGF-beta signaling pathway. In nine human gastric cancer cell lines examined, TGF-beta-responsive cell lines showed positive expression of CEAs. Expression patterns of CEA proteins correlated well with the level of CEA (CEACAM5) and CEACAM6 transcripts in these cell lines, but CEACAM1 expression was not observed in all of these cells. To investigate the role of TGF-beta signaling in CEA expression, we selected two TGF-beta unresponsive gastric cancer cell lines; SNU638 cells that contain a mutation in the TGF-beta type II receptor and SNU484 cells that express low to undetectable level of the TGF-beta pathway intermediate protein, Smad3. Restoration of TGF-beta signaling in these cells induced expression of the CEAs and increased activity of both CEA (CEACAM5) and CEACAM6 promoters. CEA expression was observed in the epithelium of the stomach of wild-type mice, but was markedly decreased in Smad3 null mice. These findings suggest that CEA (CEACAM5) and CEACAM6 are major target genes for Smad3-mediated TGF-beta signaling.

Tumor suppressor carcinoembryonic antigen-related cell adhesion molecule 1 potentates the anchorage-independent growth of human hepatoma HepG2 cells

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), an adhesion molecule of the immunoglobulin superfamily, has been characterized as a putative tumor suppressor because it is frequently down-regulated in aggressive types of cancer cells. Recently, however, several studies have shown that CEACAM1 actively contributes to malignant progression or migration in some types of tumor cells, suggesting that the role of CEACAM1 might be diverse among different types of cancer cells. To investigate the functional consequences of CEACAM1 expression in hepatocellular carcinoma, we analyzed the status of CEACAM1 in hepatoma cell lines HLF, PLC/PRF/5, HepG2 and KYN-2. We found that CEACAM1 was only expressed in HepG2 cells, which show a unique property for enhanced anchorage-independent growth. When HepG2 cells were treated with small interfering RNA targeted against CEACAM1, the growth rate in monolayer culture was increased. In contrast, when HepG2 cells were cultured in suspension, inhibition of CEACAM1 expression significantly decreased the growth rate, and the speed of cell-cell attachment was repressed. Hyaluronidase treatment attenuated the growth rate of HepG2 cells in suspension culture, indicating that cell-cell attachment is a requisite for anchorage-independent growth. Our data may reveal the dual role of CEACAM1 on hepatocarcinogenesis, by showing that CEACAM1 acts as a tumor suppressor in HepG2 cells in anchorage-dependent growth conditions, while in anchorage-independent growth conditions, it augments cell proliferation by potentiating the cell-cell attachment.

Carcinoembryonic antigen inhibits anoikis in colorectal carcinoma cells by interfering with TRAIL-R2 (DR5) signaling

Carcinoembryonic antigen (CEA) is a tumor marker that is associated with metastasis, poor response to chemotherapy of colorectal cancer (CRC), and anoikis, a form of apoptosis caused by cell detachment from matrix that is dependent on TRAIL-R2 (DR5) and caspase-8 activation in CRC. Although CEA is a homophilic binding protein that may provide survival signals through homotypical cell aggregation, we now report that CEA binds TRAIL-R2 (DR5) directly in two-hybrid assays to decrease anoikis through the extrinsic pathway. Deletion of the PELPK sequence (delPELPK) of CEA (delPELPK CEA) restores sensitivity to anoikis while it maintains its cell aggregation function. Wild-type (WT) CEA also increases experimental hepatic metastasis, whereas the delPELPK CEA does not. Thus, membrane CEA interacts with DR5 to inhibit anoikis and increase metastatic potential in CRC.

CEACAM6 acts as a receptor for adherent-invasive E. coli, supporting ileal mucosa colonization in Crohn disease

The ileal mucosa of Crohn disease (CD) patients is abnormally colonized by adherent-invasive E. coli (AIEC) that are able to adhere to and invade intestinal epithelial cells. Here, we show that CD-associated AIEC strains adhere to the brush border of primary ileal enterocytes isolated from CD patients but not controls without inflammatory bowel disease. AIEC adhesion is dependent on type 1 pili expression on the bacterial surface and on carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) expression on the apical surface of ileal epithelial cells. We report also that CEACAM6 acts as a receptor for AIEC adhesion and is abnormally expressed by ileal epithelial cells in CD patients. In addition, our in vitro studies show that there is increased CEACAM6 expression in cultured intestinal epithelial cells after IFN-gamma or TNF-alpha stimulation and after infection with AIEC bacteria, indicating that AIEC can promote its own colonization in CD patients.

CEACAM1, a novel serum biomarker for pancreatic cancer

OBJECTIVES

Serum biomarkers for early diagnosis of pancreatic adenocarcinoma are not currently available. We recently observed elevated expression of CEACAM1 in pancreatic adenocarcinomas and sought to determine whether serum CEACAM1 levels were elevated in pancreatic cancer patients.

METHODS

CEACAM1 messenger RNA levels were measured in pancreatic tissue samples using quantitative reverse transcription-polymerase chain reaction. CEACAM1 was localized by immunohistochemistry in adenocarcinomas and in pancreatic intraductal neoplasia lesions. CEACAM1 serum levels were assessed by a double determinant enzyme-linked immunosorbent assay and compared with serum levels of CA19-9.

RESULTS

CEACAM1 had higher expression levels in pancreatic adenocarcinomas compared with noncancerous pancreas (P < 0.0001) and was localized to neoplastic cells (95% (45/47) of adenocarcinomas and 85% (17/20) of pancreatic intraductal neoplasia 3 lesions. CEACAM1 was expressed in the sera of 91% (74/81) of pancreatic cancer patients, 24% (15/61) of normal patients, and 66% (35/53) of patients with chronic pancreatitis, with a sensitivity and specificity superior to CA19-9. The combination of CEACAM1 and CA19-9 had significantly higher diagnostic accuracy than CA19-9.

CONCLUSIONS

CEACAM1 is expressed in pancreatic adenocarcinoma, and serum levels of CEACAM1 serve as a useful indicator for the presence of pancreatic cancer. Additional validation studies on the use of serum CEACAM1 as a diagnostic marker in pancreatic cancer are warranted.

CEACAM1 impedes thyroid cancer growth but promotes invasiveness: a putative mechanism for early metastases

CEACAM1, also known as biliary glycoprotein (BGP), CD66a, pp120 and C-CAM1, is a member of the CEA immunoglobulin superfamily. CEACAM1 is a putative tumor suppressor based on diminished expression in some solid neoplasms such as colorectal carcinoma. However, CEACAM1 is overexpressed in some tumors such as non-small cell lung cancer. To clarify the mechanism of action of this cell adhesion molecule, we studied thyroid carcinoma that has a spectrum of morphologies and variable behavior allowing separation of proliferation from invasion and metastasis. CEACAM1 is expressed in thyroid carcinoma cell lines derived from tumors that exhibit aggressive behavior. Introduction of CEACAM1 into endogenously deficient WRO cells resulted in reduced cell cycle progression associated with p21 upregulation and diminished Rb phosphorylation. Forced CEACAM1 expression enhanced cell-matrix adhesion and migration and promoted tumor invasiveness. Conversely, small interfering RNA (siRNA)-mediated downregulation of CEACAM1 expression in MRO cells accelerated cell cycle progression and significantly enhanced tumor size in xenografted mice. CEACAM1 is not appreciably expressed in normal thyroid tissue or benign thyroid tumors. In a human thyroid tissue array, CEACAM1 reactivity was associated with metastatic spread but not with increased tumor size. These findings identify CEACAM1 as a unique mediator that restricts tumor growth whereas increasing metastatic potential. Our data highlight a complex repertoire of actions providing a putative mechanism underlying the spectrum of biologic behaviors associated with thyroid cancer.

Evolution of a tumorigenic property conferred by glycophosphatidyl-inositol membrane anchors of carcinoembryonic antigen gene family members during the primate radiation

GPI membrane anchors of cell surface glycoproteins have been shown to confer functional properties that are different from their transmembrane (TM)-anchored counterparts. For the human carcinoembryonic antigen (CEA) family, a subfamily of the immunoglobulin superfamily, conversion of the mode of membrane linkage from TM to GPI confers radical changes in function: from tumor suppression or neutrality toward inhibition of differentiation and anoikis and distortion of tissue architecture, thereby contributing to tumorigenesis. We show here that GPI anchorage in the CEA family evolved twice independently in primates, very likely from more primitive TM anchors, by different packages of mutations. Both mutational packages, one package found in many primates, including humans, and a second, novel package found only in the Cebidae radiation of New World monkeys, give rise to efficiently processed GPI-linked proteins. Both types of GPI anchors mediate inhibition of cell differentiation. The estimated rate of nonsynonymous mutations (Ka) in the anchor-determining domain for conversion from TM to GPI anchorage in the CEA family that were fixed during evolution in these primates is 7 times higher than the average Ka in primates, indicating positive selection. These results suggest therefore that the functional changes mediated by CEA GPI anchors, including the inhibition of differentiation and anoikis, could be adaptive and advantageous.

Mutation Analysis of the Short Cytoplasmic Domain of the Cell-Cell Adhesion Molecule CEACAM1 Identifies Residues That Orchestrate Actin Binding and Lumen Formation

CEACAM1-4S (carcinoembryonic antigen cell adhesion molecule 1, with 4 ectodomains and a short, 12-14 amino acid cytoplasmic domain) mediates lumen formation via an apoptotic and cytoskeletal reorganization mechanism when mammary epithelial cells are grown in a three-dimensional model of mammary morphogenesis. We show by quantitative yeast two-hybrid, BIAcore, NMR HSQC and STD, and confocal analyses that amino acids phenylalanine (Phe(454)) and lysine (Lys(456)) are key residues that interact with actin orchestrating the cytoskeletal reorganization. A CEACAM1 membrane model based on vitamin D-binding protein that predicts an interaction of Phe(454) at subdomain 3 of actin was supported by inhibition of binding of actin to vitamin D-binding protein by the cytoplasmic domain peptide. We also show that residues Thr(457) and/or Ser(459) are phosphorylated in CEACAM1-transfected cells grown in three-dimensional culture and that mutation analysis of these residues (T457A/S459A) or F454A blocks lumen formation. These studies demonstrate that a short cytoplasmic domain membrane receptor can directly mediate substantial intracellular signaling.

ES1, a new lung carcinoma antibody? an immunohistochemical study

AIMS

To characterize a single domain antibody (sdAb), AFAI, obtained by panning a naive phage display library of single domain antibodies against the non-small cell lung carcinoma cell line A549. AFAI recognizes a variant form of carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6 or CEA6).

METHODS AND RESULTS

Various normal tissues and 139 neoplastic lesions from lung and other organs were immunostained with ES1 antibody, a pentameric and highly avid form of AFAI. ES1 was immunoreactive with 34 of 35 non-squamous large cell lung carcinomas with staining intensities ranging from focal to extensive and from moderate to strong. Importantly, ES1 stained poorly differentiated lung adenocarcinomas and many undifferentiated large cell lung carcinomas that typically show negative immunoreactivity with an antibody specific for thyroid transcription factor-1. Non-lung adenocarcinomas showed more focal and weaker immunoreactivity than for lung adenocarcinoma. Other carcinomas showed negative or weak immunoreactivity and normal tissues showed no immunoreactivity.

CONCLUSIONS

Compared with other antibodies used in the clinical evaluation of lung adenocarcinomas, ES1 is more lung carcinoma sensitive, more sensitive in immunostaining of poorly differentiated adenocarcinomas that are usually associated with distant metastasis and less immunoreactive with normal tissues.

CEACAM1 (CD66a) promotes human monocyte survival via a phosphatidylinositol 3-kinase- and AKT-dependent pathway

CEACAM1 (also known as CD66a) is a transmembrane glycoprotein that mediates homophilic intercellular interactions that influence cellular growth, immune cell activation, and tissue morphogenesis. Various studies have suggested a link between CEACAM1 and cellular apoptosis, including a recent demonstration that ERK1/2 signaling is triggered downstream of CEACAM1. In this study, we reveal that CEACAM1-long binding confers survival signals to human peripheral blood mononuclear cells. CEACAM-specific antibodies effectively protected peripheral blood mononuclear cells from apoptosis, with this effect being particularly dramatic for primary monocytes that undergo spontaneous apoptosis during in vitro culture. This protective effect was reiterated when using soluble CEACAM1, which binds to cell-surface CEACAM1 via homophilic interactions. Monocyte survival correlated with a CEACAM1-dependent up-regulation of the cellular inhibitor of apoptosis Bcl-2 and the abrogation of caspase-3 activation. CEACAM1 binding triggered a phosphatidylinositol 3-kinase-dependent activation of the protein kinase Akt without influencing the activity of extracellular signal-related kinase ERK, whereas the phosphatidylinositol 3-kinase-specific inhibitor LY294002 effectively blocked the protective effect of CEACAM1. Together, this work indicates that CEACAM1 confers a phosphatidylinositol 3-kinase- and Akt-dependent survival signal that inhibits mitochondrion-dependent apoptosis of monocytes. By controlling both ERK/MEK and PI3K/Akt pathways, CEACAM1 functions as a key regulator of contact-dependent control of cell survival, differentiation, and growth.

CEACAMs: their role in physiology and pathophysiology

Carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) belong to a group of mammalian immunoglobulin-related glycoproteins. They are involved in cell–cell recognition and modulate cellular processes that range from the shaping of tissue architecture and neovascularization to the regulation of insulin homeostasis and T-cell proliferation. CEACAMs have also been identified as receptors for host-specific viruses and bacteria in mice and humans, respectively, making these proteins an interesting example of pathogen–host co-evolution. Forward and reverse genetics in the mouse now provide powerful novel models to elucidate the action of CEACAM family members in vivo.

Glycoconjugate profiling of primary melanoma and its sentinel node and distant metastases: implications for diagnosis and pathophysiology of metastases

Aiming at more precise detection of melanoma cells in sentinel lymph nodes and better understanding of the mechanisms underlying metastatic spread, expression of L1, CEACAM1, and binding of the lectins HPA, ML-I and PNA, was assessed in benign nevi (n=12), primary melanomas (PTs: n=67), their corresponding sentinel lymph nodes (SLNs: n=40), and distant metastases (DMs: n=35). Sensitivity and specificity of CEACAM1 (95-97%; 66%) and L1 (90-93%; 100%) exceeded that of the standard markers MelanA, S100, and HMB45 in single marker use. Lectin binding was found in PTs and DMs (HPA: 69% and 77%; ML-I: 82% and 77%, respectively), but rarely in SLNMs (HPA: 20%, ML-I: 20%, PNA: 5%, respectively). The highly specific and sensitive L1-11A against L1 and 4D1/C2 against CEACAM1 antibodies are a worthy completion to standard antibody panels for diagnosis of melanoma cells. Both CAMs seem to be functionally involved in lymphatic and haematogenous spread, and are thus promising target molecules for immunotoxins.

Biomarker selection for detection of occult tumour cells in lymph nodes of colorectal cancer patients using real-time quantitative RT-PCR

Accurate identification of lymph node involvement is critical for successful treatment of patients with colorectal carcinoma (CRC). Real-time quantitative RT–PCR with a specific probe and RNA copy standard for biomarker mRNA has proven very powerful for detection of disseminated tumour cells. Which properties of biomarker mRNAs are important for identification of disseminated CRC cells? Seven biomarker candidates, CEA, CEACAM1-S/L, CEACAM6, CEACAM7-1/2, MUC2, MMP7 and CK20, were compared in a test-set of lymph nodes from 51 CRC patients (Dukes' A–D) and 10 controls. Normal colon epithelial cells, primary tumours, and different immune cells were also analysed. The biomarkers were ranked according to: (1) detection of haematoxylin/eosin positive nodes, (2) detection of Dukes' A and B patients, who developed metastases during a 54 months follow-up period and (3) identification of patients with Dukes' C and D tumours using the highest value of control nodes as cutoff. The following properties appear to be of importance; (a) no expression in immune cells, (b) relatively high and constant expression in tumour tissue irrespective of Dukes' stage and (c) no or weak downregulation in tumours compared to normal tissue. CEA fulfilled these criteria best, followed by CK20 and MUC2.

CEACAM1: contact-dependent control of immunity

The carcinoembryonic-antigen-related cell-adhesion molecule (CEACAM) family of proteins has been implicated in various intercellular-adhesion and intracellular-signalling-mediated effects that govern the growth and differentiation of normal and cancerous cells. Recent studies show that there is an important role for members of the CEACAM family in modulating the immune responses associated with infection, inflammation and cancer. In this Review, we consider the evidence for CEACAM involvement in immunity, with a particular emphasis on CEACAM1, which functions as a regulatory co-receptor for both lymphoid and myeloid cell types.

Deletion of the carcinoembryonic antigen-related cell adhesion molecule 1 (Ceacam1) gene contributes to colon tumor progression in a murine model of carcinogenesis

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a glycoprotein that is part of the carcinoembryonic antigen and the immunoglobulin superfamilies. We have shown that it functions as a tumor suppressor and that this function depends upon the presence of the longer CEACAM1 cytoplasmic domain. In this report, we describe the generation of a Ceacam1-/- mouse. The Ceacam1-/- colon exhibits increased in vivo proliferation relative to the wild-type counterpart with a corresponding decreased expression of the p21(Cip1) and p27(Kip1) Cyclin D kinase inhibitors. The colonic villi undergo decreased apoptosis. Out of 35 litters of mice, no spontaneous tumors in any tissues normally expressing CEACAM1 were found over the lifespan of the animals, suggesting that CEACAM1 may not be involved in initiation of tumor development. However, when mice are treated with azoxymethane to induce colonic tumors, we find that Ceacam1-/- mice developed a significantly greater number of tumors than their littermate controls. Moreover, the tumor size was greater in the knockout mice relative to that in the wild-type mice. These results indicate that deletion of CEACAM1 favors progression of colon tumorigenesis.

CEA-related cell adhesion molecule-1 is involved in angiogenic switch in prostate cancer

We demonstrate here that epithelial carcinoembryonic antigen (CEA)-related cell adhesion molecule-1 (CEACAM1) downregulation in prostate intraepithelial neoplasia (PIN) is inversely correlated with its upregulation in adjacent blood vessels. CEACAM1 silencing in prostate cancer cell line DU-145 via small interfering ribonucleic acid (siRNA) increased but its overexpression suppressed the expression of angiogenic/lymphangiogenic factors such as vascular endothelial growth factor (VEGF)-A, -C and -D, and angiogenic inhibitor collagen 18/endostatin. Furthermore, CEACAM1 overexpression in DU-145 cells increased but CEACAM1 silencing reduced angiopoietin-1 expression. Inverse relation was found for angiopoietin-2. Supernatant of CEACAM1-overexpressing DU-145 suppressed but that of CEACAM1-silenced increased the VEGF-induced endothelial tubes. Electron microscopically the majority of PIN-associated blood vessels was structurally destabilized exhibiting endothelial fenestration, trans- and inter-endothelial gaps. In some PIN areas, invasion of single tumor cells into the destabilized blood vessels was observed. These data show that disappearance of epithelial CEACAM1 in PIN is accompanied by its upregulation in adjacent vasculature which apparently correlates with vascular destabilization and increased vascularization of prostate cancer. Strategies to either conserve the epithelial CEACAM1 or to target endothelial CEACAM1 might be useful for an anti-angiogenic therapy of prostate cancer.

GPI-anchored CEA family glycoproteins CEA and CEACAM6 mediate their biological effects through enhanced integrin α5β1-fibronectin interaction

Carcinoembryonic antigen (CEA) and CEA family member CEACAM6 are glycophosphatidyl inositol (GPI)-anchored, intercellular adhesion molecules that are up-regulated in a wide variety of human cancers, including colon, breast, and lung. When over-expressed in a number of cellular systems, these molecules are capable of inhibiting cellular differentiation and anoikis, as well as disrupting cell polarization and tissue architecture, thus increasing tumorigenicity. The present study shows that perturbation of the major fibronectin receptor, integrin alpha5beta1, underlies some of these biological effects. Using confocal microscopy and specific antibodies, CEA and CEACAM6 were demonstrated to co-cluster with integrin alpha5beta1 on the cell surface. The presence of CEA and CEACAM6 was shown to lead to an increase in the binding of the integrin alpha5beta1 receptor to its ligand fibronectin, without changing its cell surface levels, resulting in increased adhesion of CEA/CEACAM6-expressing cells to fibronectin. More tenacious binding of free fibronectin to cells led to enhanced fibronectin matrix assembly and the formation of a polymerized fibronectin "cocoon" around the cells. Disruption of this process with specific monoclonal antibodies against either fibronectin or integrin alpha5beta1 led to the restoration of cellular differentiation and anoikis in CEA/CEACAM6 producing cells.

Carcinoembryonic Antigen–Related Cell Adhesion Molecule 1a-4L Suppression of Rat Hepatocellular Carcinomas

Carcinoembryonic antigen (CEA)–related cell adhesion molecule 1 (CEACAM1) is a member of the CEA family of immunoglobulin-like adhesion molecules with two major splice variants, CEACAM1a-4L and CEACAM1b-4S, differing in the length of their COOH-terminal cytoplasmic tail. Both forms are down-regulated in prostate and liver carcinomas relative to normal tissues. We have previously shown in a nude mouse xenograft model that restoration of CEACAM1a-4L expression in human prostate carcinoma cells (PC-3) suppresses tumorigenicity, an effect observed with carcinomas from several other tissues but never established for hepatocellular carcinomas. In this report, we have examined the effect of CEACAM1a-4L on tumorigenicity of 1682A, a rat hepatocellular carcinoma that grows on the omentum when injected into the peritoneal cavity. Results show that restoration of CEACAM1a-4L expression at levels 13- and 0.45-fold compared with negative controls or normal hepatocytes, respectively, completely suppressed the formation of 1682A tumor nodules on the omentum at 3 weeks after injection. In contrast, 1682A cells infected with CEACAM1b-4S or an empty retroviral vector formed multiple clusters of tumor nodules. Although tumor nodules of 1682A cells positive and negative for CEACAM1a-4L did not display significant differences in histologic organization, aggregates formed in vitro by 1682A-L were smaller in size and displayed enlarged intercellular spaces relative to their 1682A-V counterparts. Restoration of CEACAM1a-4L expression did not elevate levels of apoptosis but seemed to cause an increase in the length of G1. This is the first demonstration of CEACAM1a-4L–induced tumor suppression in liver carcinomas using a quantifiable i.p. syngeneic transplantation model.

CEACAM1 functionally interacts with filamin A and exerts a dual role in the regulation of cell migration

The carcinoembryonic antigen-related cell adhesion molecule CEACAM1 (CD66a) and the scaffolding protein filamin A have both been implicated in tumor cell migration. In the present study we identified filamin A as a novel binding partner for the CEACAM1-L cytoplasmic domain in a yeast two-hybrid screen. Direct binding was shown by surface plasmon resonance analysis and by affinity precipitation assays. The association was shown for human and rodent CEACAM1-L in endogenous CEACAM1-L expressing cells. To address functional aspects of the interaction, we used a well-established melanoma cell system. We found in different migration studies that the interaction of CEACAM1-L and filamin A drastically reduced migration and cell scattering, whereas each of these proteins when expressed alone, acted promigratory. CEACAM1-L binding to filamin A reduced the interaction of the latter with RalA, a member of the Ras-family of GTPases. Furthermore, co-expression of CEACAM1-L and filamin A led to a reduced focal adhesion turnover. Independent of the presence of filamin A, the expression of CEACAM1-L led to an increased phosphorylation of focal adhesions and to altered cytoskeletal rearrangements during monolayer wound healing assays. Together, our data demonstrate a novel mechanism for how CEACAM1-L regulates cell migration via its interaction with filamin A.

Dendritic cells recognize tumor-specific glycosylation of carcinoembryonic antigen on colorectal cancer cells through dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin

Dendritic cells play a pivotal role in the induction of antitumor immune responses. Immature dendritic cells are located intratumorally within colorectal cancer and intimately interact with tumor cells, whereas mature dendritic cells are present peripheral to the tumor. The majority of colorectal cancers overexpress carcinoembryonic antigen (CEA), and malignant transformation changes the glycosylation of CEA on colon epithelial cells, resulting in higher levels of Lewis(x) and de novo expression of Lewis(y) on tumor-associated CEA. Dendritic cells express the C-type lectin dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN) that has high affinity for nonsialylated Lewis antigens, so we hypothesized that DC-SIGN is involved in recognition of colorectal cancer cells by dendritic cells. We show that immature dendritic cells within colorectal cancer express DC-SIGN and that immature dendritic cells but not mature dendritic cells interact with tumor cells. DC-SIGN mediates these interactions through binding of Lewis(x) and Lewis(y) carbohydrates on CEA of colorectal cancer cells. In contrast, DC-SIGN does not bind CEA expressed on normal colon epithelium that contains low levels of Lewis antigens. This indicates that dendritic cells may recognize colorectal cancer cells through binding of DC-SIGN to tumor-specific glycosylation on CEA. Similar to pathogens that target DC-SIGN to escape immunosurveillance, tumor cells may interact with DC-SIGN to suppress dendritic cell functions.

Modelling glandular epithelial cancers in three-dimensional cultures

Little is known about how the genotypic and molecular abnormalities associated with epithelial cancers actually contribute to the histological phenotypes observed in tumours in vivo. 3D epithelial culture systems are a valuable tool for modelling cancer genes and pathways in a structurally appropriate context. Here, we review the important features of epithelial structures grown in 3D basement membrane cultures, and how such models have been used to investigate the mechanisms associated with tumour initiation and progression.

Cloning and characterization of hepaCAM, a novel Ig-like cell adhesion molecule suppressed in human hepatocellular carcinoma

BACKGROUND/AIMS

Previously, we reported on gene HEPN1 that was silenced in hepatocellular carcinoma (HCC) and its capability of arresting cell growth. In this study, we identified another novel gene hepaCAM from the liver, which contains the full-length HEPN1 on its antisense strand in the 3'-noncoding region, and assessed its expression, characteristics and functions in HCC.

METHODS

Full-length hepaCAM cDNA was isolated by rapid amplification of cDNA ends. The gene expression was examined by semi-quantitative RT-PCR in 23 paired HCC liver specimens and 5 HCC cell lines. Transfection studies, coupled with immunocytochemistry, cellular interaction analyses, colony formation and microtetrazolium assay, were employed to elucidate the localization and functions of hepaCAM.

RESULTS

The expression of hepaCAM decreased in 20/23 of HCC samples and was undetectable in 5 HCC cell lines tested. The gene product consisting of 416 amino acids displayed the typical structure of Ig-like cell adhesion molecules. The protein was glycosylated and predominantly localized on the cytoplasmic membrane. When re-expressed in HepG2, hepaCAM accelerated cell spreading (P<0.001), increased cell motility (P=0.0011), reduced colony formation (P=0.0022), and inhibited cell growth (P<0.001).

CONCLUSIONS

Gene hepaCAM, frequently silenced in HCC, encodes an Ig-like transmembrane glycoprotein and is involved in cell adhesion and growth control.

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.

The human tumor suppressor CEACAM1 modulates apoptosis and is implicated in early colorectal tumorigenesis

Defects in the adenomatous polyposis coli (APC) tumor suppressor pathway are sufficient for neoplastic transformation as the initiating step in colorectal carcinogenesis. In contrast, hyperplastic tumors possess normal APC function, and it is unclear whether they represent significant precursor lesion in cancer development. CEACAM1 is a tumor suppressor whose expression is known to be lost in the great majority of early adenomas and carcinomas. We found that loss of CEACAM1 expression is more common in neoplastic tumors than APC mutations. While APC function was normal in hyperplastic aberrant cypt foci and hyperplastic polyps, loss of CEACAM1 was observed as frequently as in the neoplasias. Moreover, the presence or absence of CEACAM1 expression in the hyperplastic tumors correlates with normal or reduced apoptosis, respectively. In vitro, CEACAM1 acts as a regulator of apoptosis in CEACAM1-transfected Jurkat cells. Finally, in human HT29 colon cancer cells, apoptosis can be specifically restored by induction of CEACAM1 expression. These data suggest an oncodevelopmental link between neoplasia and hyperplasia and demonstrate that CEACAM1 acts as a regulator of apoptosis in the colonic epithelium. Thus, failure of the maturing colon cell to express CEACAM1 is likely to contribute to the development of hyperplastic lesions, which may eventually pave the way to neoplastic transformation and colon cancer development.

Adhesion molecules: opportunities for modulation and a paradigm for novel therapeutic approaches in cancer

In the past decade, there have been major advances in the elucidation of processes underlying tumour invasion and metastasis, in which adhesion molecules play a critical role. These advances have revolutionised our ability to devise novel approaches for cancer treatment. This review gives an insight into the adhesion pathways, and highlights the current status of adhesion molecules as potential therapeutic targets.

Cell-cell adhesion molecule CEACAM1 is expressed in normal breast and milk and associates with beta1 integrin in a 3D model of morphogenesis

CEA cell adhesion molecule-1 (CEACAM1) is a cell–cell adhesion molecule that, paradoxically, is expressed in an apical location in normal breast epithelium. Strong lumenal membrane staining is observed in 100% of normal glands (11/11), low in atypical hyperplasia (2/6), high in cribiform ductal carcinoma in situ (DCIS) (8/8), but low in other types of DCIS (2/15). Although most invasive ductal carcinomas express CEACAM1 (21/26), the staining pattern tends to be weak and cytoplasmic in tumours with minimal lumena formation (grades 2–3), while there is membrane staining in well-differentiated tumours (grade 1). The 'normal' breast epithelial line MCF10F forms acini with lumena in Matrigel with apical membrane expression of CEACAM1. MCF7 cells that do not express CEACAM1 and fail to form lumena in Matrigel, revert to a lumen forming phenotype when transfected with the CEACAM1-4S but not the -4L isoform. CEACAM1 directly associates with and down-regulates the expression of β1-integrin. Immuno-electron microscopy reveals numerous vesicles coated with CEACAM1 within the lumena, and as predicted by this finding, CEACAM1 is found in the lipid fraction of breast milk. Thus, CEACAM1 is a critical molecule in mammary morphogenesis and may play a role in the absorption of the lipid vesicles of milk in the infant intestinal tract.

Loss of carcinoembryonic antigen-related cell adhesion molecule 1 expression is an adverse prognostic factor in hepatocellular carcinoma

BACKGROUND

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a negative regulator of tumor cell growth, and may function as a tumor suppressor. CEACAM1 expression is down-regulated with increasing histologic grade in a number of malignancies. The authors hypothesized that loss of CEACAM1 expression in hepatocellular carcinoma (HCC) cells may function as an adverse prognostic factor.

METHODS

A retrospective analysis was conducted of 139 consecutive patients who underwent resection for HCC, with a median follow-up period of 83 months. Immunohistochemistry of the resected specimens was conducted using a monoclonal anti-CEACAM1 antibody. CEACAM1 expression in HCC was classified into two categories: diffuse expression, characterized by positive staining throughout the tumor specimen, or loss of expression, in which there were distinct areas of negative staining within the tumor specimen.

RESULTS

Of the 139 patients, 113 were classified as having tumors with diffuse expression and 26 had loss-of-expression tumors. Loss of CEACAM1 expression was more frequent in tumor specimens with Edmondson-Steiner Grades III or IV (21 of 32 [66%]) than in tumor specimens with Grades I or II (5 of 107 [5%]; P < 0.001) and was always seen in areas with the highest histologic grade. Loss of CEACAM1 expression was significantly associated with large tumor size, multiplicity of the tumor, portal vein invasion, and satellite nodules and affected survival adversely, according to univariate (P < 0.0001) and multivariate analyses (relative risk, 5.737; P < 0.001).

CONCLUSIONS

Loss of CEACAM1 expression reflects aggressive tumor biology and thus indicates a poor prognosis for patients with HCC.