Carcinoembryonic antigens: alternative splicing accounts for the multiple mRNAs that code for novel members of the carcinoembryonic antigen family

Recent developments on nanomaterial-based optical biosensor as potential Point-of-Care Testing (PoCT) probe in carcinoembryonic antigen detection: A review

For the past decades, several cancer biomarkers have been exploited for rapid and accurate prognosis or diagnosis purposes. In this review, the optical biosensor is targeted for carcinoembryonic antigen (CEA) detection. The CEA level is a prominent parameter currently used in clinical cases for the prognosis of cancer-related diseases. Many nanomaterial-based biosensors are invented as alternatives for the commonly used enzyme-linked immunosorbent assays (ELISA) immunoassay method in CEA detection as the traditional approach but they possess certain drawbacks such as tedious procedure, high technical demand, and costly. Nevertheless, the effort appears to be wasted as none of them are being actualised. Generally, the sensor function was carried out by converting bio-signals generated upon the interface of the receptor into light signals. These sensors were popular due to specific advantages such as sensitivity, being free from chemical and electromagnetic interferences, wide dynamic range, and being easy to be monitored. The features of PoC diagnostics are discussed and associated with the various applications of colorimetric-based and chemiluminescent-based biosensors. The roles of nanomaterials in each application were also summarised by comparing the modification, incubation period, lowest detection limit (LOD) and linear range of detection amount. The challenges and future perspectives were highlighted at the end of the review.

Carcinoembryonic antigen-related cell adhesion molecule 1: a key regulatory protein involved in leiomyoma growth

OBJECTIVE

To assess and characterize the role of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) in the development of uterine leiomyoma.

DESIGN

Laboratory study.

SETTING

Academic research center.

PATIENT(S)

Not applicable.

INTERVENTION(S)

Laboratory investigation. In vitro assessment of human leiomyoma and myometrial tissue specimens as well as immortalized leiomyoma and myometrial cell lines.

MAIN OUTCOME MEASURE(S)

Western blotting and immunohistochemical analyses were performed to assess differences in CEACAM1 content between leiomyoma and myometrial samples. Small interfering RNA silencing experiments and transient transfection experiments were performed to characterize the regulatory role of CEACAM1 on downstream signaling cascades.

RESULT(S)

Analysis of RNA sequencing data revealed decreased CEACAM1 expression in human uterine leiomyoma specimens compared with that in myometrial samples. This translated to a significant down-regulation in CEACAM1 protein content in human leiomyoma compared with patient-matched myometrial tissue samples (0.236 ± 0.05-fold). A similar decrease in CEACAM1 protein content was observed in matched immortalized leiomyoma cell (ILC) and immortalized myometrial cell lines (0.21 ± 0.07). Immunohistochemical analysis revealed decreased staining intensity in leiomyoma surgical specimens compared with the matched myometrium of placebo patients. Lower CEACAM1 levels in leiomyoma were associated with increased activation of both the mitogen-activated protein kinase (MAPK) and the phosphoinositide 3-kinase/protein kinase B pathways compared with that in myometrial cells. This is significant because activation of these pathways plays an important role in leiomyoma growth. Treatment of myometrial cells with CEACAM1 small interfering RNA resulted in a significant down-regulation of CEACAM1 at the protein level (0.272 ± 0.06-fold) and was associated with increased activation of the MAPK (1.62 ± 0.21-fold) and phosphoinositide 3-kinase/protein kinase B (1.79 ± 0.35-fold) pathways, as well as increased collagen production (2.1 ± 0.49-fold). Rescue of CEACAM1 expression in leiomyoma cells by transient transfection restored regulatory control and resulted in lower activation of the MAPK pathway (0.58 ± 0.37-fold).

CONCLUSION(S)

CEACAM1 is an important protein involved in regulating many signal transduction pathways. Decreased CEACAM1 expression in leiomyoma allows permissive uncontrolled overactivation and up-regulation of downstream pathways that may contribute to leiomyoma growth.

Association of circulating CEACAM1 levels and insulin sensitivity in gestational diabetes mellitus

BACKGROUND

The aim of this study was to estimate the levels of circulating carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) in subjects with gestational diabetes mellitus (GDM) and investigate the relationships between CEACAM1 and GDM.

METHODS

Circulating CEACAM1 levels were measured by ELISA kit in 70 women with GDM and 70 normal glucose tolerance (NGT) pregnant women. Blood samples were collected to detect fasting plasma glucose (FPG), fasting insulin (FINS) and glycosylated hemoglobin (HbA1c) levels in all participants. Insulin sensitivity index (ISOGTT) was calculated to assess insulin sensitivity. Correlation analysis was performed between serum CEACAM1 levels and other parameters.

RESULTS

Circulating CEACAM1 levels were higher in the GDM group than that in the NGT pregnant group, however, the difference showed no statistical significance (1889.82 ± 616.14 vs 1758.92 ± 433.15 pg/ml, p > 0.05). In GDM group, CEACAM1 was positively correlated with ISOGTT (R = 0.39, P = 0.001), while negatively with 1 h post-meal plasma insulin level (1hPINS) (R = -0.32, P = 0.008), 2 h post-meal plasma insulin level (2hPINS) (R = -0.33, P = 0.006) and area under curve of insulin (AUCI) (R = -0.36, P = 0.002) when adjusting for maternal age and gestational age.

CONCLUSIONS

The present study showed that circulating CEACAM1 levels did not differ in both GDM and NGT groups. However, we found a significant positively correlation between CEACAM1 and insulin sensitivity in the GDM group.

Reactivities of an anti-CEA peptide monoclonal antibody

Synthetic peptides representing different areas of the CEA molecule were used as immunogens for the development of anti-CEA antibodies. Both polyclonal and monoclonal antibodies were generated using peptides composed of CEA amino acid positions 99–128 and 585–613, respectively. One MAb, designated CP4, generated using the CEA peptide 99–128, was chosen for a more detailed analysis of reactivity. MAb CP4 reacts in solid phase RIAs with CEA peptide 99–128 immunogen and purified native CEA. CP4 did not react with purified non- specific cross reacting antigen (NCA), even though there were two single amino acid differences between NCA and CEA in the 29 amino acid peptide. The affinity constants of CP4 for the CEA peptide 99–128 and native CEA are 4.07 × 109M−1and 5.75 × 108M−1, respectively. When CP4 was reacted with purified CEA in Western blotting experiments, the Mr 180,000 glycoprotein characteristic of CEA was detected, but CP4 reacted to various size entities in tumor cell extracts. The results of liquid competition RIAs showed that the epitope that MAb CP4 recognized on native CEA is not available for binding when CEA is in solution. Physical (adsorption to a solid matrix) or chemical (deglycosylation or formalin-fixation) alteration of CEA is required for binding of CP4 to CEA. MAb CP4 reacted approximately 1,000-fold greater to deglycosylated CEA than native CEA. Immunohistochemical studies using formalin-fixed paraffin-embedded tissue sections demonstrated that, among carcinomas, CP4 reacts selectively with colorectal carcinomas, while normal colon is negative. Although stomach carcinoma is negative, dysplastic lesions and areas of intestinal metaplasia are reactive. Two of 7 normal stomach tissues showed focal cytoplasmic reactivity of the surface epithelium. CP4, therefore, appears to react with an epitope with highly restricted expression in colorectal carcinoma. These studies demonstrate the complexities in dealing with an anti-peptide MAb with reactivity to an epitope which is accessible only under certain conditions.

Alternative splicing after gene duplication drives CEACAM1-paralog diversification in the horse

Background

The CEA gene family is one of the most rapidly evolving gene families in the human genome. The founder gene of the family is thought to be an ancestor of the inhibitory immune checkpoint molecule CEACAM1. Comprehensive analyses of mammalian genomes showed that the CEA gene family is subject to tremendous gene family expansion and contraction events in different mammalian species. While in some species (e.g. rabbits) less than three CEACAM1 related genes exist, were in others (certain microbat species) up to 100 CEACAM1 paralogs identified. We have recently reported that the horse has also an extended CEA gene family. Since mechanisms of gene family expansion and diversification are not well understood we aimed to analyze the equine CEA gene family in detail.

Results

We found that the equine CEA gene family contains 17 functional CEACAM1-related genes. Nine of them were secreted molecules and eight CEACAMs contain transmembrane and cytoplasmic domain exons, the latter being in the focus of the present report. Only one (CEACAM41) gene has exons coding for activating signaling motifs all other CEACAM1 paralogs contain cytoplasmic exons similar to that of the inhibitory receptor CEACAM1. However, cloning of cDNAs showed that only one CEACAM1 paralog contain functional immunoreceptor tyrosine-based inhibitory motifs in its cytoplasmic tail. Three receptors have acquired a stop codon in the transmembrane domain and two have lost their inhibitory motifs due to alternative splicing events. In addition, alternative splicing eliminated the transmembrane exon sequence of the putative activating receptor, rendering it to a secreted molecule. Transfection of eukaryotic cells with FLAG-tagged alternatively spliced CEACAMs indicates that they can be expressed in vivo. Thus detection of CEACAM41 mRNA in activated PBMC suggests that CEACAM41 is secreted by lymphoid cells upon activation.

Conclusions

The results of our study demonstrate that alternative splicing after gene duplication is a potent mechanism to accelerate functional diversification of the equine CEA gene family members. This potent mechanism has created novel CEACAM receptors with unique signaling capacities and secreted CEACAMs which potentially enables equine lymphoid cells to control distantly located immune cells.

The CEA Family: A System in Transitional Evolution?

The CEA family consists of two structurally and functionally distinct subgroups; the group including CEA, NCA and CGM-6 which are cell surface-bound by phosphatidylinositol (PI) linkages, and the group of BGP splice variants which have transmembrane and cytoplasmic domains. Although all CEA family members mediate intercellular adhesion in vitro, the PI-linked group show Ca++ and temperature independent adhesion whereas the BGP group show rapidly reversible Ca++ and temperature dependent adhesion. From the close alignment in cDNA nucleotide sequences between family members and between repeated domains in one family member, it is apparent that the CEA family is now rapidly evolving; in fact, analogs of only the transmembrane BGP group have been found so far in the mouse. The addition of a new group of potent adhesion molecules to complex species at some time after the rodent radiation has strong evolutional implications, which are discussed.

CEACAM1 is associated with recurrence after hepatectomy for colorectal liver metastasis

BACKGROUND

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is re-expressed at the invasion front of colorectal cancer. CEACAM1 expression at metastatic sites remains to be investigated. The current study aims to clarify the association between CEACAM1 expression and recurrence after hepatectomy of colorectal liver metastasis and to address whether CEACAM1 induces tumor-initiating properties needed for growth at metastatic sites.

METHODS

Immunohistochemical analyses for CEACAM1 were performed in 67 patients with liver metastasis of colorectal cancer who had undergone curative hepatectomy. The risk factors for postoperative recurrence were calculated based on a CEACAM1 cytoplasmic domain isoform at the primary tumor invasion front. To investigate the effects of CEACAM1 cytoplasmic isoforms on HT29 and HCT116 colorectal cancer cells, Western blotting for CD44 and CD133, flow cytometry for ALDH1 activity, and soft-agar colony formation assay were performed.

RESULTS

CEACAM1 long (CEACAM1-L) and short (CEACAM1-S) cytoplasmic domain isoforms are strongly expressed on cancer cells in the liver metastases. Enhanced CEACAM1-S expression in the state of CEACAM1-L dominance at the primary tumor invasion front was an independent factor for colorectal cancer recurrence after curative hepatectomy. CEACAM1-4S-transfected HT29 and HCT116 cells had significantly higher CD44 expression and ALDH1 activity and increased the growth in anchorage-independent condition.

CONCLUSIONS

High expression of CEACAM1-S at the primary lesion invasion front is associated with recurrence and prognosis of patients with colorectal liver metastasis after curative hepatectomy. The expression of CEACAM1-4S enhances the tumor-initiating property of colorectal cancer cells.

CEACAM1 is overexpressed in oral tumors and related to tumorigenesis

Carcinoembryonic antigen-related adhesion molecule 1 (CEACAM1) is a type 1 transmembrane glycoprotein belonging to the CEA family, which has been known to exist as either soluble forms in body fluids or membrane-bound forms on the cell surface. Aberrant CEACAM1 expression is associated with tumorigenesis and has been reported in a variety of human tumors, especially malignancies. The aim of this study is to determine the expression of CEACAM1 in oral tumors, trying to study CEACAM1 different expressions as a function of histotype. CEACAM1 expression was observed by immunohistochemistry (IHC) with mouse anti-human antibody for CEACAM1. IHC was performed using avidin-biotin-diaminobenzidine staining. The results were expressed as average score ± SD (0 = negative/8 = highest) for each histotype. Oral tumors expressed more CEACAM1 than normal tissues including squamous and salivary epithelia (P < 0.05). In malignancies, the squamous cell carcinoma overexpressed CEACAM1, compared to well-differentiated squamous cell with more membranous expression; the intermediately and poorly differentiated squamous cell carcinoma showed more cytoplasmic expression (P < 0.05). In addition, the salivary tumors significantly expressed more CEACAM1 than squamous cell carcinoma (P < 0.05). So, we thought oral tumors overexpressed CEACAM1 and the cytoplasmic CEACAM1 might be involved in tumorigenesis, and also CEACAM1 might be regarded as a marker of salivary glandular tumors.

The human antibody fragment DIATHIS1 specific for CEACAM1 enhances natural killer cell cytotoxicity against melanoma cell lines in vitro

Supplemental Digital Content is available in the text.

Several lines of evidence show that de novo expression of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is strongly associated with reduced disease-free survival of patients affected by metastatic melanoma. Previously published investigations report that homophilic interactions between CEACAM1 expressed on natural killer (NK) cells and tumors inhibit the NK cell-mediated killing independently of major histocompatibility complex class I recognition. This biological property can be physiologically relevant in metastatic melanoma because of the increased CEACAM1 expression observed on NK cells from some patients. Moreover, this inhibitory mechanism in many cases might hinder the efficacy of immunotherapeutic treatments of CEACAM1⁺ malignancies because of tumor evasion by activated effector cells. In the present study, we designed an in vitro experimental model showing that the human single-chain variable fragment (scFv) DIATHIS1 specific for CEACAM1 is able to enhance the lytic machinery of NK cells against CEACAM1⁺ melanoma cells. The coincubation of the scFv DIATHIS1 with CEACAM1⁺ melanoma cells and NK-92 cell line significantly increases the cell-mediated cytotoxicity. Moreover, pretreatment of melanoma cells with scFv DIATHIS1 promotes the activation and the degranulation capacity of in vitro–expanded NK cells from healthy donors. It is interesting to note that the melanoma cell line MelC and the primary melanoma cells STA that respond better to DIATHIS1 treatment, express higher relative levels of CEACAM1-3L and CEACAM1-3S splice variants isoforms compared with Mel501 cells that are less responsive to DIATHIS1-induced NK cell–mediated cytotoxicity. Taken together, our results suggest that the fully human antibody fragment DIATHIS1 originated by biopanning approach from a phage antibody library may represent a relevant biotechnological platform to design and develop completely human antimelanoma therapeutics of biological origin.

Determination of a Comprehensive Alternative Splicing Regulatory Network and Combinatorial Regulation by Key Factors during the Epithelial-to-Mesenchymal Transition

The epithelial-to-mesenchymal transition (EMT) is an essential biological process during embryonic development that is also implicated in cancer metastasis. While the transcriptional regulation of EMT has been well studied, the role of alternative splicing (AS) regulation in EMT remains relatively uncharacterized. We previously showed that the epithelial cell-type-specific proteins epithelial splicing regulatory proteins 1 (ESRP1) and ESRP2 are important for the regulation of many AS events that are altered during EMT. However, the contributions of the ESRPs and other splicing regulators to the AS regulatory network in EMT require further investigation. Here, we used a robust in vitro EMT model to comprehensively characterize splicing switches during EMT in a temporal manner. These investigations revealed that the ESRPs are the major regulators of some but not all AS events during EMT. We determined that the splicing factor RBM47 is downregulated during EMT and also regulates numerous transcripts that switch splicing during EMT. We also determined that Quaking (QKI) broadly promotes mesenchymal splicing patterns. Our study highlights the broad role of posttranscriptional regulation during the EMT and the important role of combinatorial regulation by different splicing factors to fine tune gene expression programs during these physiological and developmental transitions.

Carcinoembryonic antigen-related cell adhesion molecule 1 is expressed and as a function histotype in ovarian tumors

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a cell-cell adhesion receptor and is implicated in several cellular functions. It is rarely reported in ovarian tumors. The aim of this study is to determine the expression of CEACAM1 in ovarian tumors, trying to see whether CEACAM1 has different expression patterns as a function of histotype. Antigen expression was examined by immunohistochemistry with mouse anti-human antibody for CEACAM1. Immunohistochemistry was performed using avidin-biotin-diaminobenzide staining. The results were expressed as average score ± SD (0, negative; 8, highest) for each histotype. In ovarian tumors, the benign serous and mucinous cystadenoma negatively or weakly expressed CEACAM1, the malignant epithelial tumors strongly expressed CEACAM1, and there was significant difference between benign epithelial tumor and adenocarcinoma (P < .05). The well-differentiated serous adenocarcinoma expressed CEACAM1 mainly with membrane pattern, and the intermediately and poorly differentiated serous adenocarcinomas expressed CEACAM1 mainly with cytoplasmic pattern (P < .05). In addition, CEACAM1 expression is elevated in solid tumors of ovary but variable as a function of histotype. Compared with membranous expression, the cytoplasmic expression was observed almost in metastatic carcinoma that might decrease the adhesive interactions of the carcinoma cells with the surrounding cells, especially with tumor cells, and this could facilitate the tumor cells to metastasize to distant regions. So, we thought that cytoplasmic CEACAM1 might play an important role in tumor progression, especially in tumor metastasis.

Evaluation of VEGF-C and tumor markers in bronchoalveolar lavage fluid for lung cancer diagnosis

A total of 87 patients were enrolled and bronchoalveolar lavage fluid (BALF) samples were obtained from all subjects. A significant difference was found in BALF VEGF-C level between patients with squamous cell carcinoma and benign diseases (P = 0.043). In addition, the concentration of NSE in BALF form the malignant group was significantly higher compared with that of the benign groups (P = 0.018). However, no statistical difference was observed in BALF CEA (P = 0.375) or CYFRA21-1 (P = 0.838) between lung cancer patients and nonmalignant controls. With a cut-off value of 2.06 ng/ml, NSE had a sensitivity of 72.9%, a specificity of 69.2%, respectively, in predicting the malignant nature of pulmonary mass. Our study observed that the level of VEGF-C was increased in BALF of patients with squamous cell carcinoma. Moreover, we found that NSE was significantly higher in BALF of lung cancer patients than in benign diseases.

Inside-out signaling promotes dynamic changes in the carcinoembryonic antigen-related cellular adhesion molecule 1 (CEACAM1) oligomeric state to control its cell adhesion properties

Cell-cell contacts are fundamental to multicellular organisms and are subject to exquisite levels of control. The carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) can engage in both cis-homophilic (parallel) oligomerization and trans-homophilic (anti-parallel) binding. In this study, we establish that the CEACAM1 transmembrane domain has a propensity to form cis-dimers via the transmembrane-embedded (432)GXXXG(436) motif and that this basal state is overcome when activated calmodulin binds to the CEACAM1 cytoplasmic domain. Although mutation of the (432)GXXXG(436) motif reduced CEACAM1 oligomerization, it did not affect surface localization of the receptor or influence CEACAM1-dependent cellular invasion by the pathogenic Neisseria. The mutation did, however, have a striking effect on CEACAM1-dependent cellular aggregation, increasing both the kinetics of cell-cell association and the size of cellular aggregates formed. CEACAM1 association with tyrosine kinase c-Src and tyrosine phosphatases SHP-1 and SHP-2 was not affected by the (432)GXXXG(436) mutation, consistent with their association with the monomeric form of wild type CEACAM1. Collectively, our results establish that a dynamic oligomer-to-monomer shift in surface-expressed CEACAM1 facilitates trans-homophilic binding and downstream effector signaling.

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.

The CEACAM1 expression is decreased in the liver of severely obese patients with or without diabetes

BACKGROUND

Type 2 diabetes is mainly caused by insulin resistance. The carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is an important candidate for causing insulin resistance.

METHODS

The CEACAM1 expression was evaluated immunohistochemically in the liver tissues of 99 severely obese or non-obese subjects with or without diabetes. The CEACAM1 expression was classified into two categories: a normal expression or a decreased expression.

RESULTS

The CEACAM1 expression was markedly decreased in the hepatocytes with macrovesicular steatosis. A decreased CEACAM1 expression was noted in 29 (29%) of 99 cases. The incidence of a decreased CEACAM1 expression was significantly higher in high grade fatty liver as well as severe obesity with or without diabetes (p < 0.05). The incidence of a decreased CEACAM1 expression was not different between the diabetic and non-diabetic groups.

CONCLUSIONS

This data supports that a decreased CEACAM1 expression is related to obesity and a fatty liver.

Interdependency of CEACAM-1, -3, -6, and -8 induced human neutrophil adhesion to endothelial cells

Members of the carcinoembryonic antigen family (CEACAMs) are widely expressed, and, depending on the tissue, capable of regulating diverse functions including tumor promotion, tumor suppression, angiogenesis, and neutrophil activation. Four members of this family, CEACAM1, CEACAM8, CEACAM6, and CEACAM3 (recognized by CD66a, CD66b, CD66c, and CD66d mAbs, respectively), are expressed on human neutrophils. CD66a, CD66b, CD66c, and CD66d antibodies each increase neutrophil adhesion to human umbilical vein endothelial cell monolayers. This increase in neutrophil adhesion caused by CD66 antibodies is blocked by CD18 mAbs and is associated with upregulation of CD11/CD18 on the neutrophil surface. To examine potential interactions of CEACAMs in neutrophil signaling, the effects on neutrophil adhesion to human umbilical vein endothelial cells of a set of CD66 mAbs was tested following desensitization to stimulation by various combinations of these mAbs. Addition of a CD66 mAb in the absence of calcium results in desensitization of neutrophils to stimulation by that CD66 mAb. The current data show that desensitization of neutrophils to any two CEACAMs results in selective desensitization to those two CEACAMs, while the cells remain responsive to the other two neutrophil CEACAMs. In addition, cells desensitized to CEACAM-3, -6, and -8 were still responsive to stimulation of CEACAM1 by CD66a mAbs. In contrast, desensitization of cells to CEACAM1 and any two of the other CEACAMs left the cells unresponsive to all CD66 mAbs. Cells desensitized to any combination of CEACAMs remained responsive to the unrelated control protein CD63. Thus, while there is significant independence of the four neutrophil CEACAMs in signaling, CEACAM1 appears to play a unique role among the neutrophil CEACAMs. A model in which CEACAMs dimerize to form signaling complexes could accommodate the observations. Similar interactions may occur in other cells expressing CEACAMs.

Cytokine-induced CEACAM1 expression on keratinocytes is characteristic for psoriatic skin and contributes to a prolonged lifespan of neutrophils

Carcinoembryonic antigen-related cellular adhesion molecule 1 (CEACAM1) is a cell-surface glycoprotein, belonging to the carcinoembryonic antigen family, expressed by human neutrophils, epithelial cells, activated T and NK cells. CEACAM1 is expressed as a cell-surface molecule with different isoforms or can be secreted as a soluble protein. Here, we show that keratinocytes in the outer epidermal layer of psoriatic skin express CEACAM1, unlike those in healthy skin or in cutaneous lesions of patients with atopic or nummular dermatitis. Stimulation of primary human keratinocytes or in vitro reconstituted epidermis with culture supernatants of activated psoriatic lesion-infiltrating T cells, IFN-gamma or oncostatin M, but not IL-17, induced the expression of transcripts for the CEACAM1-long and -short isoforms and cell-surface CEACAM1, whereas soluble CEACAM1 was not produced. The uppermost layers of the epidermis in psoriatic lesions also contain neutrophils, a cell type with inflammatory and antimicrobial properties. Coculture of CEACAM1-expressing keratinocytes or CHO transfectants with neutrophils delayed spontaneous apoptosis of the latter cells. These results show that cytokine-induced cell-surface expression of CEACAM1 by keratinocytes in the context of a psoriatic environment might contribute to the persistence of neutrophils and thus to ongoing inflammation and the decreased propensity for skin infection, typical for patients with psoriasis.

Differential cell fates induced by all-trans retinoic acid-treated HL-60 human leukemia cells

HL-60 human leukemia cells, differentiated into a neutrophil lineage by all-trans retinoic acid (ATRA) treatment, express three members of the carcinoembryonic antigen (CEA) gene family, CEA-related cell adhesion molecule 1 (CEACAM1; CD66a), CEACAM3 (CD66d), and CEACAM6 (CD66c). CD66d is a neutrophil lineage-specific marker, and CD66a and CD66c are found on epithelial and other cells. HL-60 cells continuously treated with ATRA underwent apoptosis, and cells transiently treated for 1 day underwent cell-cycle arrest, entered into senescence, and exhibited reduced apoptosis with CD66-positive cells accounting for the majority of live cells. CD66 antigens were also induced in NB4 leukemic cells upon continuous treatment with ATRA. NB4 cells underwent apoptosis with a higher frequency in transient versus continuous-treated cells (38% vs. 19% at Day 5), in contrast to HL-60 cells that underwent cell-cycle arrest and senescence when transiently treated with ATRA. CD66 antigens were not induced in transient, ATRA-treated NB4 cells compared with HL-60 cells. Cell-cycle arrest in HL-60 cells involved reduction in expression levels of p21, cyclins D and E, while Rb1 exhibited reduction in protein levels without changes in mRNA levels over the time course of ATRA treatment. Analysis of several proapoptotic proteins implicated the activation of calpain and cleavage of Bax in the intrinsic apoptotic pathway, similar to published studies about the apoptosis of neutrophils. CD1d expression was also induced by ATRA in HL-60 cells and ligation with anti-CD1d antibody-induced apoptosis. In contrast, CD1d-positive primary monocytes were protected from spontaneous apoptosis by CD1d ligation. These studies demonstrate distinct cell fates for ATRA-treated HL-60 cells that provide new insights into ATRA-induced cell differentiation.

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.

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.

Expression Pattern of Osteopontin in Endometrial Carcinoma: Correlation With Expression of the Adhesion Molecule CEACAM1

Osteopontin (OPN) and CEACAM1 have diverse biological functions in the uterus and placenta throughout the estrous cycle and pregnancy and have been shown to interact with integrin beta3. OPN is a glycoprotein of the extracellular matrix, which has been shown to mediate cellular migration and invasion and to contribute to tumorigenesis in several types of cancers. Recently we showed the expression pattern of OPN in gestational trophoblastic tumors. CEACAM1 is an adhesion molecule of the carcinoembryonic antigen family that we have recently found to be expressed in endometrial cancer and that has been shown to be down-regulated in colorectal, prostate, and breast cancer. In this study, immunohistochemistry and immunofluorescence with specific antibodies were performed on a series of 20 normal endometrial samples, 17 endometrial hyperplasias, and 43 endometrial carcinomas (28 endometrioid, 10 serous, and 5 clear cell carcinomas) to investigate the expression pattern and cell-type specific localization of OPN and to correlate it with the expression of CEACAM1. In addition, Western blot was performed on normal human endometrium and endometrial neoplasia. Strong OPN expression with a consistent cytoplasmic localization in epithelial glandular cells was observed in the normal human endometrium in 80% of the samples of the proliferative and secretory phase (score 8-12). Similar results could be found in endometrial hyperplasias. Strong expression of OPN could be observed in 29 (67.4%) of the 43 analyzed endometrial carcinomas. Of the 43 analyzed tumors, 18 (41.8%) were in the high score (8-12) category with a strong OPN expression level; 11 of 43 (25.5%) showed a moderate score (4-7) category. In endometrioid carcinoma with increasing malignancy grade, increasing areas with low OPN expression level or complete loss of OPN expression could be observed. In contrast, serous tumors showed a strong OPN expression level. Similar results could be found in Western blot analysis. CEACAM1 showed similar results and could be found to be coexpressed with OPN in normal human endometrium and in endometrial neoplasia as we showed using immunofluorescence. In this study, the different expression patterns of OPN in endometrial tumors could additionally support the biological diversity of endometrioid and serous carcinomas together with other markers. We suggest that OPN might play a different role in the pathogenesis of endometrial cancer (possibly as a functional complex with CEACAM1) and could be relevant for invasive growth of such lesions.

Corticotropin-releasing hormone modulates human trophoblast invasion through carcinoembryonic antigen-related cell adhesion molecule-1 regulation

Abnormalities in the process of trophoblast invasion may result in abnormal placentation. Both the embryonic trophoblast and maternal decidua produce corticotropin-releasing hormone (CRH), which promotes implantation. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), which is expressed in extravillous trophoblasts (EVTs) of normal human placenta, may also function in tro-phoblast/endometrial interactions. We investigated whether locally produced CRH plays a role in trophoblast invasion, primarily by regulating CEACAM1 expression. We examined cultures of freshly isolated human EVTs, which express CEACAM1, and an EVT-based hybridoma cell line, which is devoid of endogenous CEACAM1. CRH inhibited EVT invasion in Matrigel invasion assays, and this effect was blocked by the CRH receptor type 1 (CRHR1)-specific antagonist antalarmin. Additionally, CRH decreased CEACAM1 expression in EVTs in a dose-dependent manner. After transfection of the hybridoma cell line with a CEACAM1 expression vector, the invasiveness of these cells was strongly enhanced. This effect was inhibited by addition of blocking monoclonal antibody against CEACAM1. Furthermore, blocking of endogenous CEACAM1 in EVTs inhibited the invasive potential of these cells. Taken together these findings suggest that CRH inhibits trophoblast invasion by decreasing the expression of CEACAM1 through CRHR1, an effect that might be involved in the pathophysiology of clinical conditions, such as preeclampsia and placenta accreta.

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.

Osteopontin Expression in Gestational Trophoblastic Diseases: Correlation With Expression of the Adhesion Molecule, CEACAM1

The human placenta is a complex tissue with multiple endocrine and nutritional functions and a unique capacity for rapid proliferation but tightly controlled invasion, differentiating it from malignant tumors. Osteopontin (OPN) is a glycoprotein of the extracellular matrix, which has been shown to mediate cellular migration and invasion and to contribute to tumorigenesis in several types of cancers. OPN also could be implicated in regulating implantation and placentation by promoting cellular migration and invasion in a placenta-specific fashion. We could demonstrate the expression pattern of OPN in the normal human placenta in which it is localized in the extravillous (intermediate) trophoblast and the villous cytotrophoblast. CEACAM1 is an adhesion molecule, which we have recently found to be expressed at the maternal-fetal interface of the normal placenta with a localization to the extravillous (invasive) trophoblast and in gestational trophoblastic disease (GTD) and also to be potentially implicated in trophoblast invasion and tumorigenesis. Both OPN and CEACAM1 have been shown to interact with integrin beta3. The purpose of this study was to investigate the expression pattern of OPN in GTD and to correlate it with the expression of CEACAM1. To analyze the expression of OPN, we performed immunohistochemistry on a total of 27 cases of GTD, including 21 hydatidiform moles and 6 choriocarcinomas, which had previously been characterized with respect to their CEACAM1 expression. Hydatidiform moles showed a positivity for OPN in villous cytotrophoblast and in the trophoblast proliferations on the villous surface. The strongest OPN expression could be observed in the choriocarcinomas with a heterogenous OPN expression pattern. CEACAM1 had shown similar results and was found to be expressed in choriocarcinoma. The expression pattern of osteopontin in gestational trophoblastic diseases indicates that it might play a role in the pathogenesis of GTD (possibly as a functional complex with CEACAM1 and integrin beta3) and might be useful as an additional diagnostic marker for such lesions.

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.

The Cell-Cell Adhesion Molecule Carcinoembryonic Antigen-Related Cellular Adhesion Molecule 1 Inhibits IL-2 Production and Proliferation in Human T Cells by Association with Src Homology Protein-1 and Down-Regulates IL-2 Receptor

The cell adhesion molecule, carcinoembryonic Ag-related cellular adhesion molecule 1, shown by others to both activate and inhibit T cell proliferation, exhibits a reciprocal relationship to IL-2R expression over the time course of activation of PBMCs, and upon Ab ligation, inhibits both the production of IL-2 and cell proliferation. Carcinoembryonic Ag-related cellular adhesion molecule 1 associates with CD3 and is found in lipid rafts of PBMCs, is phosphorylated on the immunoreceptor tyrosine-based inhibitory motifs (ITIMs) of the -4L isoform, and associates with Src homology protein-1, providing an explanation for its inhibitory activity. When the ITIM-containing -4L and non-ITIM-containing -4S isoforms are transfected into Jurkat cells that produce, but do not depend on IL-2 for growth, both IL-2 production and cell proliferation are differentially inhibited, demonstrating that the two isoforms signal via different pathways. When the two isoforms are transfected into Kit-225 cells that depend on IL-2 for growth, IL-2Rbeta and gamma, but not alpha subunits are down-regulated, and the -4L, but not the -4S isoform inhibits cell proliferation by 6-fold in an IL-2 dose-response study.

CEACAM1-4S, a cell-cell adhesion molecule, mediates apoptosis and reverts mammary carcinoma cells to a normal morphogenic phenotype in a 3D culture

In a 3D model of breast morphogenesis, CEACAM1 (carcinoembryonic antigen-related cell adhesion molecule 1) plays an essential role in lumen formation in a subline of the nonmalignant human breast cell line (MCF10A). We show that mammary carcinoma cells (MCF7), which do not express CEACAM1 or form lumena when grown in Matrigel, are restored to a normal morphogenic program when transfected with CEACAM1-4S, the short cytoplasmic isoform of CEACAM1 that predominates in breast epithelia. During the time course of lumen formation, CEACAM1-4S was found initially between the cells, and in mature acini, it was found exclusively in an apical location, identical to its expression pattern in normal breast. Lumena were formed by apoptosis as opposed to necrosis of the central cells within the alveolar structures, and apoptotic cells within the lumena expressed CEACAM1-4S. Dying cells exhibited classical hallmarks of apoptosis, including nuclear condensation, membrane blebbing, caspase activation, and DNA laddering. Apoptosis was mediated by Bax translocation to the mitochondria and release of cytochrome c into the cytoplasm, and was partially inhibited by culturing cells with caspase inhibitors. The dynamic changes in CEACAM1 expression during morphogenesis, together with studies implicating extracellular matrix and integrin signaling, suggest that a morphogenic program integrates cell-cell and cell-extracellular matrix signaling to produce the lumena in mammary glands. This report reveals a function of CEACAM1-4S relevant to cellular physiology that distinguishes it from its related long cytoplasmic domain isoform.

Deregulated expression of the human tumor marker CEA and CEA family member CEACAM6 disrupts tissue architecture and blocks colonocyte differentiation

Human carcinoembryonic antigen (CEA) and the CEA family member CEACAM6 (formerly nonspecific cross-reacting antigen [NCA]) function in vitro, at least, as homotypic intercellular adhesion molecules and, in model systems, can block the terminal differentiation and anoikis of several different cell types. We have recently demonstrated that the increased cell surface levels of CEA and CEACAM6 in purified human colonocytes from freshly excised, well to poorly differentiated colon carcinomas are inversely correlated with the degree of cellular differentiation. Thus, deregulated expression of CEA/CEACAM6 could directly contribute to colon tumorigenesis by the inhibition of terminal differentiation and anoikis. Evidence against this view includes the common observation of increased CEA/CEACAM6 expression as normal colonocytes differentiate in their migration up colonic crypt walls. We report here the direct effects of deregulated overexpression of CEA/CEACAM6, at levels observed in colorectal carcinomas, on the differentiation of two human colonic cell lines, SW-1222 and Caco-2. Stable transfectants of both of these cell lines that constitutively express 10- to 30-fold higher cell surface levels of CEA/CEACAM6 than endogenous levels failed to polarize and differentiate into glandular structures in monolayer or 3D culture or to form colonic crypts in a tissue architecture assay in nude mice. In addition, these transfectants were found to exhibit increased tumorigenicity in nude mice. These results thus support the contention that deregulated overexpression of CEA and CEACAM6 could provide a tumorigenic contribution to colon carcinogenesis.

Carcinoembryonic antigen-related cell adhesion molecule 1 expression and signaling in human, mouse, and rat leukocytes: evidence for replacement of the short cytoplasmic domain isoform by glycosylphosphatidylinositol-linked proteins in human leukocytes

Carcinoembryonic Ag-related cell adhesion molecule 1 (CEACAM1), the primordial carcinoembryonic Ag gene family member, is a transmembrane cell adhesion molecule expressed in leukocytes, epithelia, and blood vessel endothelia in humans and rodents. As a result of differential splicing, CEACAM1 occurs as several isoforms, the two major ones being CEACAM1-L and CEACAM1-S, that have long (L) or short (S) cytoplasmic domains, respectively. The L:S expression ratios vary in different cells and tissues. In addition to CEACAM1, human but not rodent cells express GPI-linked CEACAM members (CEACAM5-CEACAM8). We compared the expression patterns of CEACAM1-L, CEACAM1-S, CEACAM6, and CEACAM8 in purified populations of neutrophilic granulocytes, B lymphocytes, and T lymphocytes from rats, mice, and humans. Human granulocytes expressed CEACAM1, CEACAM6, and CEACAM8, whereas human B lymphocytes and T lymphocytes expressed only CEACAM1 and CEACAM6. Whereas granulocytes, B cells, and T cells from mice and rats expressed both CEACAM1-L and CEACAM1-S in ratios of 2.2-2.9:1, CEACAM1-S expression was totally lacking in human granulocytes, B cells, and T cells. Human leukocytes only expressed the L isoforms of CEACAM1. This suggests that the GPI-linked CEACAM members have functionally replaced CEACAM1-S in human leukocytes. Support for the replacement hypothesis was obtained from experiments in which the extracellular signal-regulated kinases (Erk)1/2 were activated by anti-CEACAM Abs. Thus, Abs against CEACAM1 activated Erk1/2 in rat granulocytes, but not in human granulocytes. Erk1/2 in human granulocytes could, however, be activated by Abs against CEACAM8. We demonstrated that CEACAM1 and CEACAM8 are physically associated in human granulocytes. The CEACAM1/CEACAM8 complex in human cells might accordingly play a similar role as CEACAM1-L/CEACAM1-S dimers known to occur in rat cells.

Deregulated expression of the human tumor marker CEA and CEA family member CEACAM6 disrupts tissue architecture and blocks colonocyte differentiation

Human carcinoembryonic antigen (CEA) and the CEA family member CEACAM6 (formerly nonspecific cross-reacting antigen [NCA]) function in vitro, at least, as homotypic intercellular adhesion molecules and, in model systems, can block the terminal differentiation and anoikis of several different cell types. We have recently demonstrated that the increased cell surface levels of CEA and CEACAM6 in purified human colonocytes from freshly excised, well to poorly differentiated colon carcinomas are inversely correlated with the degree of cellular differentiation. Thus, deregulated expression of CEA/CEACAM6 could directly contribute to colon tumorigenesis by the inhibition of terminal differentiation and anoikis. Evidence against this view includes the common observation of increased CEA/CEACAM6 expression as normal colonocytes differentiate in their migration up colonic crypt walls. We report here the direct effects of deregulated overexpression of CEA/CEACAM6, at levels observed in colorectal carcinomas, on the differentiation of two human colonic cell lines, SW-1222 and Caco-2. Stable transfectants of both of these cell lines that constitutively express 10- to 30-fold higher cell surface levels of CEA/CEACAM6 than endogenous levels failed to polarize and differentiate into glandular structures in monolayer or 3D culture or to form colonic crypts in a tissue architecture assay in nude mice. In addition, these transfectants were found to exhibit increased tumorigenicity in nude mice. These results thus support the contention that deregulated overexpression of CEA and CEACAM6 could provide a tumorigenic contribution to colon carcinogenesis.

Activation-induced expression of carcinoembryonic antigen-cell adhesion molecule 1 regulates mouse T lymphocyte function

Carcinoembryonic Ag cell adhesion molecule 1 (CEACAM1) consists of highly related homologs in humans and rodents that are characterized by significant alternate splicing generating isoforms capable of negative intracellular signaling by virtue of two immunoreceptor tyrosine-based inhibition motifs in its cytoplasmic (cyt) tail. Although human T cells have been recently observed to express CEACAM1, the expression and function of CEACAM1 in mouse T cells have not been defined. Although resting mouse spleen T cells exhibited no evidence of CEACAM1 on the cell surface, CEACAM1 was rapidly up-regulated on CD4+ and CD8+ T cells after activation with either Con A or anti-CD3 without a requirement for either de novo transcription or translation due to the fact that CEACAM1 was present intracellularly before activation. Using a GST-CEACAM1-cytoplasmic tail fusion protein, it was shown that the cytoplasmic tail of CEACAM1 bound the src homology domain-containing phosphatase 1 and adaptor protein 1 complex in its phosphorylated and nonphosphorylated states, respectively. CEACAM1 ligation with an anti-CEACAM1 mAb resulted in inhibition of an allogeneic MLR and anti-CD3 plus anti-CD28 Ab-induced proliferation of spleen T cells in vitro and inhibition of a delayed-type hypersensitivity response to oxazolone in vivo. Inhibition of the delayed-type hypersensitivity response required that the anti-CEACAM1-specific mAb be present at the time of T cell sensitization. These studies support a role for CEACAM1 as a novel class of immunoreceptor tyrosine-based inhibition motif-bearing regulatory molecules on T cells that are active during early phases of the immune response in mice.

Carcinoembryonic antigen cell adhesion molecule 1 directly associates with cytoskeleton proteins actin and tropomyosin

CEA cell adhesion molecule 1 (CEACAM1), a type 1 transmembrane and homotypic cell adhesion protein belonging to the carcinoembryonic antigen (CEA) gene family and expressed on epithelial cells, is alternatively spliced to produce four major isoforms with three or four Ig-like ectodomains and either long (CEACAM1-L) or short (CEACAM1-S) cytoplasmic domains. When murine MC38 (methylcholanthrene-induced adenocarcinoma 38) cells were transfected with human CEACAM1-L and stimulated with sodium pervanadate, actin was found to co-localize with CEACAM1-L at cell-cell boundaries but not in untreated cells. When CEACAM1-L was immunoprecipitated from pervanadate-treated MC38/CEACAM1-L cells and the associated proteins were analyzed by two-dimensional gel analysis and mass spectrometry, actin and tropomyosin, among other proteins, were identified. Whereas a glutathione S-transferase (GST) fusion protein containing the l-isoform (GST-Cyto-L) bound poorly to F-actin in a co-sedimentation assay, the S-isoform fusion protein (GST-Cyto-S) co-sedimented with F-actin, especially when incubated with G-actin during polymerization (K(D) = 7.0 microm). Both GST-Cyto-S and GST-Cyto-L fusion proteins bind G-actin and tropomyosin by surface plasmon resonance studies with binding constants of 0.7 x 10(-8) and 1.0 x 10(-7) m for GST-Cyto-L to G-actin and tropomyosin, respectively, and 3.1 x 10(-8) and 1.3 x 10(-7) m for GST-Cyto-S to G-actin and tropomyosin, respectively. Calmodulin or EDTA inhibited binding of the GST-Cyto-L fusion protein to G-actin, whereas calmodulin and G-actin, but not EDTA, stimulated binding to tropomyosin. A biotinylated 14-amino acid peptide derived from the juxtamembrane portion of the cytoplasmic domain of CEACAM1-L associated with both G-actin and tropomyosin with K(D) values of 1.3 x 10(-5) and 1.8 x 10(-5) m, respectively. These studies demonstrate the direct interaction of CEACAM1 isoforms with G-actin and tropomyosin and the direct interaction of CEACAM1-S with F-actin.

Targeted disruption of the Ceacam1 (MHVR) gene leads to reduced susceptibility of mice to mouse hepatitis virus infection

The CEACAM1 glycoproteins (formerly called biliary glycoproteins; BGP, C-CAM, CD66a, or MHVR) are members of the carcinoembryonic antigen family of cell adhesion molecules. In the mouse, splice variants of CEACAM1 have either two or four immunoglobulin (Ig) domains linked through a transmembrane domain to either a short or a long cytoplasmic tail. CEACAM1 has cell adhesion activity and acts as a signaling molecule, and long-tail isoforms inhibit the growth of colon and prostate tumor cells in rodents. CEACAM1 isoforms serve as receptors for several viral and bacterial pathogens, including the murine coronavirus mouse hepatitis virus (MHV) and Haemophilus influenzae, Neisseria gonorrhoeae, and Neisseria meningitidis in humans. To elucidate the mechanisms responsible for the many biological activities of CEACAM1, we modified the expression of the mouse Ceacam1 gene in vivo. Manipulation of the Ceacam1 gene in mouse embryonic stem cells that contained the Ceacam1a allele yielded a partial knockout. We obtained one line of mice in which the insert in the Ceacam1a gene had sustained a recombination event. This resulted in the markedly reduced expression of the two CEACAM1a isoforms with four Ig domains, whereas the expression of the two isoforms with two Ig domains was doubled relative to that in wild-type BALB/c (+/+) mice. Homozygous (p/p) Ceacam1a-targeted mice (Ceacam1aDelta4D) had no gross tissue abnormalities and were viable and fertile; however, they were more resistant to MHV A59 infection and death than normal (+/+) mice. Following intranasal inoculation with MHV A59, p/p mice developed markedly fewer and smaller lesions in the liver than +/+ or heterozygous (+/p) mice. The titers of virus produced in the livers were 50- to 100-fold lower in p/p mice than in +/p or +/+ mice. p/p mice survived a dose 100-fold higher than the lethal dose of virus for +/+ mice. +/p mice were intermediate between +/+ and p/p mice in susceptibility to liver damage, virus growth in liver, and susceptibility to killing by MHV. Ceacam1a-targeted mice provide a new model to study the effects of modulation of receptor expression on susceptibility to MHV infection in vivo.

Expression pattern of the adhesion molecule CEACAM1 (C-CAM, CD66a, BGP) in gestational trophoblastic lesions

CEACAM1 (CD66a, BGP, C-CAM) is an adhesion molecule of the carcinoembryonic antigen (CEA) family which has been shown to be normally expressed at the apical pole of epithelial cells and to show a dysregulated expression pattern in tumors derived from the latter. The purpose of the present study was to investigate the expression pattern of CEACAM1 in gestational trophoblastic lesions and to compare this expression with the one observed in the normal trophoblast. For this purpose, we performed immunohistochemistry using the 4D1/C2 monoclonal antibody which specifically recognizes CEACAM1 and does not interact with other members of the CEA family. Immunohistochemistry was performed on a total of 20 cases of gestational trophoblastic lesions including complete hydatidiform moles, one placental site trophoblastic nodule (PSN), one placental site trophoblastic tumor (PSTT), and three choriocarcinomas. Immunostaining for cytokeratin, hPL, hCG, and Ki-67 was also performed. Normal placental samples served as a control. CEACAM1 was absent from villous cyto- and syncytiotrophoblast in both normal placenta and hydatidiform molar samples. It was present in the benign extravillous trophoblast, with stronger expression in the proximal extravillous trophoblast of anchoring villi, but was also observed in interstitial and endovascular intermediate trophoblast and chorionic intermediate-like trophoblast. Partial expression was observed in the trophoblast proliferating from the surface of molar villi. In choriocarcinomas, areas of weak expression could be observed along with large areas without CEACAM1 expression. In the PSN and especially in the PSTT, CEACAM1 expression was stronger and more diffuse. The specific localization to extravillous trophoblast and its expression pattern in gestational trophoblastic lesions indicate that CEACAM1 can potentially be a helpful additional diagnostic marker in the differential diagnosis of such lesions.

The carcinoembryonic antigen (CEA) gene family in non-human primates

Carcinoembryonic antigen (CEA) is a tumor marker of wide clinical use though its function remains unknown. The CEA counterpart and some related macromolecules cannot be demonstrated in mice, thus prohibiting studies of CEA function by gene disruption strategies. In an attempt to find a relevant animal model for functional studies of CEA we have investigated the occurrence of CEA subgroup members in baboon and African green monkey at the genomic and mRNA levels. The investigation was focused on the characteristic immunoglobulin-variable region-like (IgV-like) N-terminal domain of the family members. Based on N-domain sequences 3 and 4 different CEA subgroup genes, respectively, were identified. One sequence in each monkey species corresponded to human CEACAM8, while it was not possible to assign an obvious human counterpart for the other N-domain sequences. However, studies of cDNAs from African green monkey COS-1 cells identified one of the sequences as CEACAM1. Expression of CEACAM1 mRNA and protein was upregulated by IFNgamma as has previously been demonstrated for human CEACAM1. Presence of GPI-linked CEA subgroup members in African green monkey was suggested by sequencing. Both monkey species would thus seem suitable for functional studies of selected CEA subgroup members.

The CEACAM1-L Ser503 residue is crucial for inhibition of colon cancer cell tumorigenicity

CEACAM1 (also known as biliary glycoprotein, C-CAM or CD66a) is a cell adhesion molecule of the immunoglobulin family behaving as a tumor inhibitory protein in colon, prostate, liver, endometrial and breast cancers. Inhibition of tumor development is dependent upon the presence of the long 71-73 amino acid cytoplasmic domain of the CEACAM1 protein (CEACAM1-L). We have recently defined a number of cis-acting motifs within the long cytoplasmic domain participating in tumor cell growth inhibition. These are Tyr488, corresponding to an Immunoreceptor Tyrosine-based Inhibition Motif, as well as the three terminal lysine residues of the protein. In this study, we provide evidence that treatment with phorbol esters leads to increased phosphorylation of in vivo (32)P-labeled CEACAM1-L in mouse CT51 carcinoma cells, in the mouse 1MEA 7R.1 liver carcinoma cells and in 293 human embryonic kidney cells transfected with the Ceacam1-L cDNA. Basal level Ser phosphorylation was abrogated by treatment with the staurosporine inhibitor, but not by the protein kinase C-specific inhibitor calphostin C or other inhibitors such as H7 or sphingosine. Specific inhibitors of protein kinase A or calmodulin kinase had only minimal effects on the levels of basal or PMA-induced Ser phosphorylation. Furthermore, PMA treatment of the CT51 cells induced cell spreading and cellular relocalization of the CEACAM1-L protein. Since Ser503 has been described as a PMA-induced phosphorylation site in other cell systems, we investigated whether Ser503 was involved in these responses in mouse intestinal cells. No differences were noticed in the basal or the PMA-induced phosphorylation levels, kinase inhibitor sensitivity or the PMA-induced relocalization of the protein between the wild-type and the Ser503Ala mutant CEACAM1-L. However, we provide evidence that Ser503 participates in CEACAM1-L-mediated tumor inhibition as its mutation to an Ala led to in vivo tumor development, contrary to the tumor inhibitory phenotype observed with the wild-type CEACAM1-L protein.

Angiogenic properties of the carcinoembryonic antigen-related cell adhesion molecule 1

The carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), a member of the immunoglobulin superfamily, is expressed in microvessels of proliferating tissues such as endometrium, in tissues after wounding, and in solid human tumors. In microvascular human endothelial cells, purified native and recombinant CEACAM1 stimulates proliferation, chemotaxis, and tube formation. In the chorioallantoic membrane of the chicken, CEACAM1 induces angiogenesis. The angiogenic effects of CEACAM1 are additive to those of the vascular endothelial growth factor (VEGF). The expression of CEACAM1 is up-regulated by VEGF, and VEGF-induced in vitro tube formation is blocked completely by a monoclonal CEACAM1 antibody. These findings indicate that CEACAM1 is an angiogenic factor and an effector of VEGF.

Cell adhesion molecule CEACAM1 associates with paxillin in granulocytes and epithelial and endothelial cells

CEACAM1 functions as an epithelial tumor suppressor and as an angiogenic growth factor. In the present study, utilizing differentially (serine/threonine or tyrosine) phosphorylated cytoplasmic domains of CEACAM1 and CEACAM3 as bait to isolate associated proteins from granulocyte extracts, we have identified human paxillin as a binding partner of the tyrosine-phosphorylated cytoplasmic CEACAM1 domain. CEACAM1-paxillin complexes were coimmunoprecipitated from extracts of granulocytes, the colonic cell line HT29, and HUVECs. We identified phosphorylated Tyr-488-a residue in the cytoplasmic CEACAM1 domain known to be essential for the tumor suppressive effect-to be necessary for this association. The CEACAM1-paxillin interaction was confirmed using laser scanning confocal microscopy analyses in granulocytes and HT29 cells, where CEACAM1 colocalizes with paxillin at the plasma membrane. In HUVECs a highly polarized expression pattern and colocalization of paxillin and CEACAM1 was observed. These findings support the findings that CEACAM1 is linked to the actin-based cytoskeleton.

Soluble isoforms of CEACAM1 containing the A2 domain: increased serum levels in patients with obstructive jaundice and differences in 3-fucosyl-N-acetyl-lactosamine moiety

CEACAM1 (biliary glycoprotein or CD66a) is a member of the carcinoembryonic antigen (CEA) subgroup of the CEA family. Eleven RNA isoforms derived from the splicing of a single CEACAM1 gene have been described. Some of the CEACAM1 isoforms have been recognized by the CD66 antibodies in T and B lymphocytes, natural killer cells, granulocytes and epithelial cells in several human tissues. Although it is also present in soluble form in bile and serum, and elevated levels have been found in the serum of patients with liver diseases, it is not known which isoforms are primarily involved. In order to learn more about the distribution and properties of particular CEACAM1 isoforms, we have prepared a monoclonal antibody specific for the A2 domain of CEACAM1, designated TEC-11. This antibody does not cross-react with other members of the CEA family. Immunoblotting analysis revealed that the TEC-11 epitope was present in all cell types expressing CEACAM1 containing the A2 domain [CEACAM1(A2)], including granulocytes (160 000 MW isoform) and sperm cells (140 000 MW isoform). A 115 000 MW isoform of CEACAM1(A2) was present in human serum, bile, saliva and seminal fluid. Human bile, saliva and seminal fluid also contained the 160 000 MW CEACAM1(A2) isoform. Significantly higher serum levels of the 115 000 MW CEACAM1(A2) isoform were detected in patients with obstructive jaundice. The 160 000 MW isoform of CEACAM1(A2) in bile, but not a 115 000 MW isoform in serum and bile, carried the 3-fucosyl-N-acetyl-lactosamine moiety. The combined data indicate that various isoforms of CEACAM1(A2) are present in different body fluids where they could take part in different CEACAM1-mediated functions.

The adhesion molecule CEACAM1 (CD66a, C-CAM, BGP) is specifically expressed by the extravillous intermediate trophoblast

CEACAM1 (CD66a, C-CAM, BGP) is an adhesion molecule of the carcinoembryonic antigen family which has been shown to be normally expressed at the apical pole of epithelial cells, including the apical pole of endometrial surface and glandular epithelia. The purpose of the present study was to investigate its expression pattern at the maternal-fetal interface, and thus to determine whether CEACAM1 could be implicated in the human implantation process. For this purpose, we performed immunohistochemistry using the 4D1/C2 monoclonal antibody (mAb) as well as flow cytometry and Western blot on isolated trophoblast populations. On the maternal side of the maternal-fetal interface, CEACAM1 was present in epithelial cells of pregnancy endometrium as well as in small endometrial vessels, whereas it was absent from decidual cells. On the fetal side, CEACAM1 was strongly expressed by the extravillous (intermediate) trophoblast at the implantation site, as well as by extravillous trophoblast cells with invasive phenotype in primary culture, as shown by flow cytometry and Western blot. Expression was also observed in placental villous core vessels but was absent from both villous cyto- and syncytiotrophoblasts throughout the pregnancy. We conclude that, given its specific expression pattern, CEACAM1 can be a useful marker for extravillous intermediate trophoblast and might be functionally implicated in mediating trophoblast/endometrial and/or trophoblast/endothelial interactions during the trophoblastic invasion of the endometrium.

Expression of Ep-CAM in normal, regenerating, metaplastic, and neoplastic liver

Ep-CAM is a homophilic, Ca2+-independent cell-cell adhesion molecule that is expressed in many human epithelial tissues. Its increased expression is closely associated with active cell proliferation. Furthermore, in epithelial cell types that in adults lack Ep-CAM (i. e. squamous epithelia), up-regulation of Ep-CAM coincides with the early stages of neoplastic change. This study has analysed the expression of Ep-CAM in liver, in the hepatocytes and cells of the biliary duct system, in relation to proliferative diseases and carcinogenesis. Adult hepatocytes are Ep-CAM negative, with only bile duct epithelium being positive in the liver tissue. However, in the 8-week embryonic liver, the majority of hepatocytes express Ep-CAM. During regeneration and repair of liver tissues associated with focal nodular hyperplasia and (biliary) cirrhosis, activation of Ep-CAM expression was observed, with high expression levels in so-called 'ductular proliferations'-regenerating stem cells. During precursor cell differentiation into mature hepatocytes, several intermediate morphological stages could be observed, all Ep-CAM positive, including cells morphologically close to mature hepatocytes. Full maturation of the precursor resulted in the disappearance of Ep-CAM expression. The results suggest that expression of Ep-CAM is a prerequisite of the proliferative phenotype during differentiation of hepatocyte precursors. In liver neoplasia, Ep-CAM was expressed in almost all cholangiocarcinomas (10/11), whereas the majority of hepatocellular carcinomas (8/10) were negative, suggesting that malignant proliferation of hepatocellular carcinoma cells is not related to expression of Ep-CAM and that hepatocellular carcinoma originates from a highly differentiated precursor. The results indicate that Ep-CAM can be used as an additional immunohistochemical marker to distinguish cholangiocarcinoma from hepatocellular carcinoma due to the differential expression of Ep-CAM in these tumours.

The CEACAM1-L glycoprotein associates with the actin cytoskeleton and localizes to cell-cell contact through activation of Rho-like GTPases

Associations between plasma membrane-linked proteins and the actin cytoskeleton play a crucial role in defining cell shape and determination, ensuring cell motility and facilitating cell-cell or cell-substratum adhesion. Here, we present evidence that CEACAM1-L, a cell adhesion molecule of the carcinoembryonic antigen family, is associated with the actin cytoskeleton. We have delineated the regions involved in actin cytoskeleton association to the distal end of the CEACAM1-L long cytoplasmic domain. We have demonstrated that CEACAM1-S, an isoform of CEACAM1 with a truncated cytoplasmic domain, does not interact with the actin cytoskeleton. In addition, a major difference in subcellular localization of the two CEACAM1 isoforms was observed. Furthermore, we have established that the localization of CEACAM1-L at cell-cell boundaries is regulated by the Rho family of GTPases. The retention of the protein at the sites of intercellular contacts critically depends on homophilic CEACAM1-CEACAM1 interactions and association with the actin cytoskeleton. Our results provide new evidence on how the Rho family of GTPases can control cell adhesion: by directing an adhesion molecule to its proper cellular destination. In addition, these results provide an insight into the mechanisms of why CEACAM1-L, but not CEACAM1-S, functions as a tumor cell growth inhibitor.

Essential role of biliary glycoprotein (CD66a) in morphogenesis of the human mammary epithelial cell line MCF10F

Normal mammary epithelial cells express the cell surface protein biliary glycoprotein (BGP or CD66a) in a polarized manner, suggesting that this protein may play a role in the formation of mammary acini. In order to test this hypothesis, we interrupted the expression of BGP in the mammary epithelial line MCF10F when cultured in or on Matrigel, a source of extracellular matrix (ECM). When analyzed by immunofluorescence confocal microscopy, the BGP staining is confined to the lumenal surface and colocalizes with actin. Sequential scanning electron microscopy demonstrates that the MCF10F cells migrate to form clusters, followed by apoptotic cell death within the center, resulting in lumen formation. Transmission electron micrographs reveal the presence of tight junctions and desmosomes between the cells, microvilli along the lumenal surface, and typical apoptotic bodies within the lumen. When the MCF10F cells are transfected with the BGP antisense gene and grown in Matrigel, they exhibit reduced acini formation (12% and 20%) compared to untransfected cells (52%) or to cells transfected with vector only (62%). Acini formation is also significantly reduced when MCF10F cells grown in Matrigel are treated with anti-BGP antibody (18% at 100 microgram/ml), or recombinant soluble BGP (18% at 0.4 microM). In contrast, the BGP-negative MCF7 breast tumor cell line, which does not form acini when grown in matrigel, exhibits &gt;60% cell death with the occasional formation of acini, when transfected with the BGP sense gene and grown in Matrigel. These results support the hypothesis that BGP plays a role in the normal differentiation program of mammary epithelial cells, indicating that its expression is essential to the formation of the lumen. Furthermore, and as shown by others, the differentiation program depends on the presence of ECM. The lack of expression of BGP in the MCF7 breast cancer cell line suggests that the downregulation of BGP expression confers a growth advantage to these cells in ECM. In addition, we found that the MCF10F cells could be separated into a BGP-positive epithelial fraction (MCF10F-e), and a BGP-negative myoepithelial fraction (MCF10F-m). When the myoepithelial cell-enriched fraction is grown on Matrigel, web-like structures are formed. These cells have a typical spindle shape cell morphology and express keratin, alpha-smooth muscle actin and vimentin, markers of the myoepithelial cell phenotype. When MCF10F-m cells are treated with IFNgamma, they express CEA (carcinoembryonic antigen) but not BGP. Since breast carcinomas, especially in situ carcinomas, express CEA, this finding may suggest a heretofore unappreciated relationship between myoepithelial cells and breast cancer.

cis-Determinants in the cytoplasmic domain of CEACAM1 responsible for its tumor inhibitory function

CEACAM1, also known as C-CAM, BGP and CD66a, is a member of the carcinoembryonic antigen (CEA) family which is itself part of the immunoglobulin supergene family. CEACAM1 is involved in intercellular adhesion, signal transduction and tumor cell growth regulation. CEACAM1 is down-regulated in colon and prostate carcinomas, as well as in endometrial, bladder and hepatic tumors, and 30% of breast cancers. We have shown in a mouse colon tumor model that CEACAM1 with a long cytoplasmic domain inhibited the development of tumors whereas a splice variant lacking the cytoplasmic domain did not. In this study, we define the subregions of the long cytoplasmic domain participating in the tumor inhibition phenotype of CEACAM1. We show that a single point mutation of Tyr488, conforming to an Immunoreceptor Tyrosine Inhibition Motif (ITIM), was sufficient to reverse the in vivo tumor cell growth inhibition. Substitution or deletion of residues in the C-terminal region of the CEACAM1 cytoplasmic domain also led to reversal of tumor cell growth inhibition. This result is in agreement with our previous studies demonstrating the C-terminal region of the cytoplasmic domain influences the levels of CEACAM1 Tyr phosphorylation and its association with the protein Tyr phosphatases SHP-1 and SHP-2. Furthermore, removal of the N-terminal domain of CEACAM1, essential for intercellular adhesion, did not impair the tumor inhibitory effect. These results suggest that Tyr phosphorylation or dephosphorylation of the CEACAM1 cytoplasmic domain represents a crucial step in the control of epithelial cell proliferation.

Expression of Ep-CAM in normal, regenerating, metaplastic, and neoplastic liver

Ep-CAM is a homophilic, Ca2+-independent cell-cell adhesion molecule that is expressed in many human epithelial tissues. Its increased expression is closely associated with active cell proliferation. Furthermore, in epithelial cell types that in adults lack Ep-CAM (i. e. squamous epithelia), up-regulation of Ep-CAM coincides with the early stages of neoplastic change. This study has analysed the expression of Ep-CAM in liver, in the hepatocytes and cells of the biliary duct system, in relation to proliferative diseases and carcinogenesis. Adult hepatocytes are Ep-CAM negative, with only bile duct epithelium being positive in the liver tissue. However, in the 8-week embryonic liver, the majority of hepatocytes express Ep-CAM. During regeneration and repair of liver tissues associated with focal nodular hyperplasia and (biliary) cirrhosis, activation of Ep-CAM expression was observed, with high expression levels in so-called 'ductular proliferations'-regenerating stem cells. During precursor cell differentiation into mature hepatocytes, several intermediate morphological stages could be observed, all Ep-CAM positive, including cells morphologically close to mature hepatocytes. Full maturation of the precursor resulted in the disappearance of Ep-CAM expression. The results suggest that expression of Ep-CAM is a prerequisite of the proliferative phenotype during differentiation of hepatocyte precursors. In liver neoplasia, Ep-CAM was expressed in almost all cholangiocarcinomas (10/11), whereas the majority of hepatocellular carcinomas (8/10) were negative, suggesting that malignant proliferation of hepatocellular carcinoma cells is not related to expression of Ep-CAM and that hepatocellular carcinoma originates from a highly differentiated precursor. The results indicate that Ep-CAM can be used as an additional immunohistochemical marker to distinguish cholangiocarcinoma from hepatocellular carcinoma due to the differential expression of Ep-CAM in these tumours.

The carcinoembryonic antigen (CEA) family: structures, suggested functions and expression in normal and malignant tissues

The human CEA family has been fully characterized. It comprises 29 genes of which 18 are expressed; 7 belonging to the CEA subgroup and 11 to the pregnancy specific glycoprotein subgroup. CEA is an important tumor marker for colorectal and some other carcinomas. The CEA subgroup members are cell membrane associated and show a complex expression pattern in normal and cancerous tissues with notably CEA showing a selective epithelial expression. Several CEA subgroup members possess cell adhesion properties and the primordial member, biliary glycoprotein, seems to function in signal transduction or regulation of signal transduction possibly in association with other CEA sub-family members. A modified ITAM/ITIM motif is identified in the cytoplasmatic domain of BGP. A role of CEA in innate immunity is envisioned.