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

The role of CEACAMs versus integrins in Helicobacter pylori CagA translocation: a systematic review

The delivery of Helicobacter pylori CagA into host cells was long believed to occur through the integrin cell surface receptors. However, the role of CEACAM receptors has recently been highlighted, instead. Here, we have categorized the existing experimental evidence according to whether deletion, upregulation, downregulation, or inhibition of the target ligands (T4SS or HopQ) or receptors (integrins or CEACAMs), result in alterations in CagA phosphorylation, cell elongation, or IL-8 production. According to our analysis, the statistics favor the essence of most of the T4SS constituents and the involvement of HopQ adhesin in all three functions. Concerning the integrin family, the collected data is controversial, but yielding towards it being dispensable or involved in CagA translocation. Yet, regarding cell elongation, more events are showing β1 integrin being involved, than αvβ4 being inhibitory. Concerning IL-8 secretion, again there are more events showing α5, β1 and β6 integrins to be involved, than those showing inhibitory roles for β1, β4 and β6 integrins. Finally, CEACAM 1, 3, and 5 are identified as mostly essential or involved in CagA phosphorylation, whereasCEACAM 4, 7, and 8 are found dispensable and CEACAM6 is under debate. Conversely, CEACAM1, 5 and 6 appear mostly dispensable for cell elongation. Noteworthy is the choice of cell type, bacterial strain, multiplicity and duration of infection, as well as the sensitivity of the detection methods, all of which can affect the variably obtained results.

ETS transcription factor ELF5 induces lumen formation in a 3D model of mammary morphogenesis and its expression is inhibited by Jak2 inhibitor TG101348

The loss of expression of a single gene can revert normal tissue to a malignant phenotype. For example, while normal breast has high lumenal expression of CEACAM1, the majority of breast cancers exhibit the early loss of this gene with the concurrent loss of their lumenal phenotype. MCF7 cells that lack CEACAM1 expression and fail to form lumena in 3D culture, regain the normal phenotype when transfected with CEACAM1. In order to probe the mechanism of this gain of function, we treated these cells with the clinically relevant Jak2 inhibitor TG101348 (TG), expecting that disruption of the prolactin receptor signaling pathway would interfere with the positive effects of transfection of MCF7 cells with CEACAM1. Indeed, lumen formation was inhibited, resulting in the down regulation of a set of genes, likely involved in the complex process of lumen formation. As expected, inhibition of the expression of many of these genes also inhibited lumen formation, confirming their involvement in a single pathway. Among the genes identified by the inhibition assay, ETS transcription factor ELF5 stood out, since it has been identified as a master regulator of mammary morphogenesis, and is associated with prolactin receptor signaling. When ELF5 was transfected into the parental MCF7 cells that lack CEACAM1, lumen formation was restored, indicating that ELF5 can replace CEACAM1 in this model system of lumenogenesis. We conclude that the event(s) that led to the loss of expression of CEACAM1 is epistatic in that multiple genes associated with a critical pathway were affected, but that restoration of the normal phenotype can be achieved with reactivation of certain genes at various nodal points in tissue morphogenesis.

Inhibition of cell invasion and migration by CEACAM1-4S in breast cancer

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), a cell-cell adhesion molecule, has been revealed to perform an important role in tumor progression. Although there are a number of studies on CEACAM1 in patients with breast cancer, there is limited information on the roles of CEACAM1 in breast cancer metastasis. The present study aimed to identify whether CEACAM1 is involved in breast cancer development and to investigate the underlying mechanisms. First, the expression of CEACAM1 was observed in patients with breast cancer, and the association between CEACAM1 expression levels and migration and invasion of breast cancer cells was analyzed. As there are 12 isoforms of CEACAM1, of which CEACAM1-4S dominates in the human breast epithelium, subsequent study focused on CEACAM1-4S as a representative of all the isoforms. Results of the present study demonstrated that CEACAM1-4S suppresses breast cancer cell invasion and migration in a manner that is dependent on the balance between matrix metalloproteinase 2/tissue inhibitor of metalloproteinase 2 and E-/N-cadherin expression. In addition, CEACAM1-4S was likely to cause reversal of epithelial-mesenchymal transition of breast cancer cells through repressing Smad2 and signal transducer and phosphorylation of activator of transcription 3. In conclusion, the present study demonstrated that CEACAM1-4S performs an inhibitory role in breast cancer metastasis, and restoring CEACAM1-4S expression may provide a novel strategy for therapy of patients with metastatic breast cancer.

CEACAM1 mediates B cell aggregation in central nervous system autoimmunity

B cell aggregates in the central nervous system (CNS) have been associated with rapid disease progression in patients with multiple sclerosis (MS). Here we demonstrate a key role of carcinoembryogenic antigen-related cell adhesion molecule1 (CEACAM1) in B cell aggregate formation in MS patients and a B cell-dependent mouse model of MS. CEACAM1 expression was increased on peripheral blood B cells and CEACAM1⁺ B cells were present in brain infiltrates of MS patients. Administration of the anti-CEACAM1 antibody T84.1 was efficient in blocking aggregation of B cells derived from MS patients. Along these lines, application of the monoclonal anti-CEACAM1 antibody mCC1 was able to inhibit CNS B cell aggregate formation and significantly attenuated established MS-like disease in mice in the absence of any adverse effects. CEACAM1 was co-expressed with the regulator molecule T cell immunoglobulin and mucin domain −3 (TIM-3) on B cells, a novel molecule that has recently been described to induce anergy in T cells. Interestingly, elevated coexpression on B cells coincided with an autoreactive T helper cell phenotype in MS patients. Overall, these data identify CEACAM1 as a clinically highly interesting target in MS pathogenesis and open new therapeutic avenues for the treatment of the disease.

miRNA-342 Regulates CEACAM1-induced Lumen Formation in a Three-dimensional Model of Mammary Gland Morphogenesis

Lumen formation of breast epithelium is rapidly lost during tumorigenesis along with expression of cell adhesion molecule CEACAM1. CEACAM1 induces lumena in a three-dimensional culture of MCF7/CEACAM1 cells that otherwise fail to form lumena. We hypothesized miRNAs may be involved because >400 genes were up- or down-regulated in MCF7/CEACAM1 cells and miRNAs may modify global expression patterns. Comparative analysis of miRNA expression in MCF7 versus MCF7/CEACAM1 cells revealed two miRNAs significantly down-regulated (hsa-miR-30a-3p by 6.73-fold and hsa-miR-342-5p by 5.68-fold). Location of miR-342 within an intron of the EVL gene, hypermethylated and involved in tumorigenesis, suggested that miR-342 overexpression may block lumen formation. In fact, overexpression of miR-342 in MCF7/CEACAM1 cells significantly blocked lumen formation (p < 0.001). ID4, a dominant-negative inhibitor of basic helix-loop-helix transcription factors, up-regulated in MCF7/CEACAM1 cells, down-regulated in breast cancer, and containing a miR-342 binding site, was tested as a potential target of miR-342. The ratio of ID4 to miR-342 increased from 1:2 in MCF7 cells to 30:1 in MCF7/CEACAM1 cells and a miR-342 inhibitor was able to induce 3'-UTR ID4 reporter activity in MCF7 cells. Because 5-methylcytosine methyltransferase DNMT1 is also a potential target of miR-342, we inhibited miR-342 in MCF7 cells and found DNMT1 was up-regulated with no change in EVL expression, suggesting that miR-342 regulates DNMT1 expression but DNMT1 does not affect the EVL expression in these cells. We conclude that the regulation of lumen formation by miR-342 involves at least two of its known targets, namely ID4 and DNMT1.

Induction of Lumen Formation in a Three-dimensional Model of Mammary Morphogenesis by Transcriptional Regulator ID4: ROLE OF CaMK2D IN THE EPIGENETIC REGULATION OF ID4 GENE EXPRESSION

Concomitant loss of lumen formation and cell adhesion protein CEACAM1 is a hallmark feature of breast cancer. In a three-dimensional culture model, transfection of CEACAM1 into MCF7 breast cells can restore lumen formation by an unknown mechanism. ID4, a transcriptional regulator lacking a DNA binding domain, is highly up-regulated in CEACAM1-transfected MCF7 cells, and when down-regulated with RNAi, abrogates lumen formation. Conversely, when MCF7 cells, which fail to form lumena in a three-dimensional culture, are transfected with ID4, lumen formation is restored, demonstrating that ID4 may substitute for CEACAM1. After showing the ID4 promoter is hypermethylated in MCF7 cells but hypomethylated in MCF/CEACAM1 cells, ID4 expression was induced in MCF7 cells by agents affecting chromatin remodeling and methylation. Mechanistically, CaMK2D was up-regulated in CEACAM1-transfected cells, effecting phosphorylation of HDAC4 and its sequestration in the cytoplasm by the adaptor protein 14-3-3. CaMK2D also phosphorylates CEACAM1 on its cytoplasmic domain and mutation of these phosphorylation sites abrogates lumen formation. Thus, CEACAM1 is able to maintain the active transcription of ID4 by an epigenetic mechanism involving HDAC4 and CaMK2D, and the same kinase enables lumen formation by CEACAM1. Because ID4 can replace CEACAM1 in parental MCF7 cells, it must act downstream from CEACAM1 by inhibiting the activity of other transcription factors that would otherwise prevent lumen formation. This overall mechanism may be operative in other cancers, such as colon and prostate, where the down-regulation of CEACAM1 is observed.

Signaling by epithelial members of the CEACAM family - mucosal docking sites for pathogenic bacteria

Carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) comprise a group of immunoglobulin-related vertebrate glycoproteins. Several family members, including CEACAM1, CEA, and CEACAM6, are found on epithelial tissues throughout the human body. As they modulate diverse cellular functions, their signaling capacity is in the focus of current research. In this review we will summarize the knowledge about common signaling processes initiated by epithelial CEACAMs and suggest a model of signal transduction by CEACAM family members lacking significant cytoplasmic domains. As pathogenic and non-pathogenic bacteria exploit these receptors during mucosal colonization, we try to highlight the connection between CEACAMs, microbes, and cellular responses. Special emphasis in this context is placed on the functional interplay between CEACAMs and integrins that influences matrix adhesion of epithelial cells. The cooperation between these two receptor families provides an intriguing example of the fine tuning of cellular responses and their manipulation by specialized microorganisms.

Role of CEACAM1 and CEACAM20 in an in vitro model of prostate morphogenesis

CEACAM20, a novel member of the CEACAM1 gene family with expression limited to the lumen of small intestine, testes, and prostate, is co-expressed with CEACAM1 in adult prostate tissue and down-regulated to the same extent as CEACAM1 in prostate cancer. Since prostate cancer often involves loss of epithelial lumen formation, we hypothesized that CEACAM20 and CEACAM1 play important roles in lumen formation of normal prostate epithelium. When prostate cells were grown on Matrigel as a source of extracellular matrix (ECM), they differentiated into acinar structures with single tubules and well-defined lumina closely resembling embryonic prostate organoids. Confocal microscopic analysis revealed restriction of CEACAM20 to acini and CEACAM1 to tubule structures, respectively. Inhibition of CEACAM1 with antibodies or soluble CEACAM1 or antisense oligonucleotides inhibited tubule formation by over 50% while the remaining tubules were stunted. Inhibition of CEACAM20 with antisense oligonucleotides completely inhibited tubule formation and stunted the growth of acini. We conclude that CEACAM20 and CEACAM1 not only mark the lumina of adult prostate tissue but also play a critical role in the vitro generation of prostate organoids.

CEACAM1 creates a pro-angiogenic tumor microenvironment that supports tumor vessel maturation

We have studied the effects of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) on tumor angiogenesis in murine ductal mammary adenocarcinomas. We crossed transgenic mice with whey acidic protein promoter-driven large T-antigen expression (WAP-T mice) with oncogene-induced mammary carcinogenesis with CEACAM1null mice, and with Tie2-Ceacam1 transgenics, in which the Tie2 promoter drives endothelial overexpression of CEACAM1 (WAP-T × CEACAM1(endo+) mice), and analyzed tumor vascularization, angiogenesis and vessel maturation in these mice. Using flat-panel volume computed tomography (fpVCT) and histology, we found that WAP-T × CEACAM1(endo+) mice exhibited enhanced tumoral vascularization owing to CEACAM1(+) vessels in the tumor periphery, and increased intratumoral angiogenesis compared with controls. In contrast, vascularization of CEACAM1null/WAP-T-derived tumors was poor, and tumor vessels were dilated, leaky and showed poor pericyte coverage. Consequently, the tumoral vasculature could not be visualized in CEACAM1null/WAP-T mice by fpVCT, and we observed poor organization of the perivascular extracellular matrix (ECM), accompanied by the accumulation of collagen IV-degrading matrix metalloproteinase 9(+) (MMP9(+)) leukocytes and stromal cells. Vascular instability and alterations in ECM structure were accompanied by a significant increase in pulmonary metastases in CEACAM1null/WAP-T mice, whereas only occasional metastases were observed in CEACAM1(+) hosts. In CEACAM1(+) hosts, intratumoral vessels did not express CEACAM1, but they were intact, extensively covered with pericytes and framed by a well-organized perivascular ECM. MMP9(+) accessory cells were largely absent. Orthotopic transplantation of primary WAP-T- and CEACAM1null/WAP-T tumors into all three mouse lines confirmed that a CEACAM1(+) host environment is a prerequisite for productive angiogenic remodeling of the tumor microenvironment. Hence, CEACAM1 expression in the tumor periphery determines the vascular phenotype in a tumor, whereas systemic absence of CEACAM1 interferes with the formation of an organized tumor matrix and intratumoral vessel maturation.

Human milk proteins: an interactomics and updated functional overview

Milk and milk fractions are characterized by a wide array of proteins, whose concentration spans across several orders of magnitude. By exploiting a combined approach based on functional gene ontology enrichment (FatiGO/Babelomics), hierarchical clustering, and pathway and network analyses, we merged data from literature dealing with protein-oriented studies on human milk. A total of 285 entries defined a nonredundant list upon comparison with the Ingenuity Knowledge Base from the Ingenuity Pathway Analysis software. Results were compared with an inventory of bovine milk proteins gathered from dedicated proteomic studies. A protein core of 106 proteins was found, with most of the entries associated to three main biological functions, namely nutrient transport/lipid metabolism, concretization of the immune system response and cellular proliferation processes. Our analyses confirm and emphasize that the biological role of the human milk proteins is not only limited to the provision of external nutrients and defense molecules against pathogens to the suckling but also to the direct stimulation of the growth of neonate tissues/organs and to the development of a proper independent immune system, both through the induction of a number of molecular cascades associated with cell proliferation/differentiation. The latter aspects were previously investigated by single-molecule dedicated studies, missing the holistic view that results from our analysis.

Ephrin-independent regulation of cell substrate adhesion by the EphB4 receptor

Receptor tyrosine kinases of the Eph family become tyrosine phosphorylated and initiate signalling events upon binding of their ligands, the ephrins. Eph receptors such as EphA2 and EphB4 are highly expressed but poorly tyrosine phosphorylated in many types of cancer cells, suggesting a limited interaction with ephrin ligands. Nevertheless, decreasing the expression of these receptors affects the malignant properties of cancer cells, suggesting that Eph receptors may influence cancer cells independently of ephrin stimulation. Ligand-independent activities of Eph receptors in cancer, however, have not been demonstrated. By using siRNA (small interfering RNA) to downregulate EphB4 in MCF7 and MDA-MB-435 cancer cells, we found that EphB4 inhibits integrin-mediated cell substrate adhesion, spreading and migration, and reduces beta1-integrin protein levels. Low expression of the EphB4 preferred ligand, ephrin-B2, and minimal contact between cells in these assays suggest that cell contact-dependent stimulation of EphB4 by the transmembrane ephrin-B2 ligand does not play a role in these effects. Indeed, inhibitors of ephrin-B2 binding to endogenous EphB4 did not influence cell substrate adhesion. Increasing EphB4 expression by transient transfection inhibited cell substrate adhesion, and this effect was also independent of ephrin stimulation because it was not affected by single amino acid mutations in EphB4 that impair ephrin binding. The overexpressed EphB4 was tyrosine phosphorylated, and we found that EphB4 kinase activity is important for inhibition of integrin-mediated adhesion, although several EphB4 tyrosine phosphorylation sites are dispensable. These findings demonstrate that EphB4 can affect cancer cell behaviour in an ephrin-independent manner.

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.

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.