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

A p53/LINC00324 positive feedback loop suppresses tumor growth by counteracting SET-mediated transcriptional repression

The p53 tumor suppressor exerts antitumor functions through its ability to regulate the transcription of its downstream targets. Long noncoding RNAs (lncRNAs) act as oncogenes or tumor suppressors implicated in tumorigenesis and tumor progression. Here, we identify the lncRNA LINC00324 (long intergenic noncoding RNA 00324) as a direct p53 transcriptional target. Knockdown of LINC00324 expression promotes tumor growth by reducing p53 transcriptional activity, whereas ectopic LINC00324 expression demonstrates a reverse effect. Notably, LINC00324 is present in the endogenous p53 complex in tumor cells and directly binds to the C-terminal domain of p53 in vitro. Mechanistically, LINC00324 enables p53 transactivation by competitively disrupting the p53-SET interaction, resulting in an increase of p300/CBP-mediated H3K18 and H3K27 acetylation on the p53 target promoters. Lower LINC00324 expression is associated with more aggressive disease status and predicts worse overall survival of patients with cancer. Our study identifies a p53/LINC00324 positive feedback loop that suppresses tumor growth by counteracting SET-mediated transcriptional repression.

Mechanisms of host manipulation by Neisseria gonorrhoeae

Neisseria gonorrhoeae (also known as gonococcus) has been causing gonorrhoea in humans since ancient Egyptian times. Today, global gonorrhoea infections are rising at an alarming rate, in concert with an increasing number of antimicrobial-resistant strains. The gonococcus has concurrently evolved several intricate mechanisms that promote pathogenesis by evading both host immunity and defeating common therapeutic interventions. Central to these adaptations is the ability of the gonococcus to manipulate various host microenvironments upon infection. For example, the gonococcus can survive within neutrophils through direct regulation of both the oxidative burst response and maturation of the phagosome; a concerning trait given the important role neutrophils have in defending against invading pathogens. Hence, a detailed understanding of how N. gonorrhoeae exploits the human host to establish and maintain infection is crucial for combating this pathogen. This review summarizes the mechanisms behind host manipulation, with a central focus on the exploitation of host epithelial cell signaling to promote colonization and invasion of the epithelial lining, the modulation of the host immune response to evade both innate and adaptive defenses, and the manipulation of host cell death pathways to both assist colonization and combat antimicrobial activities of innate immune cells. Collectively, these pathways act in concert to enable N. gonorrhoeae to colonize and invade a wide array of host tissues, both establishing and disseminating gonococcal infection.

Transfer RNA-derived fragment 5'tRF-Gly promotes the development of hepatocellular carcinoma by direct targeting of carcinoembryonic antigen-related cell adhesion molecule 1

Transfer RNA-derived fragments are a group of small noncoding single-stranded RNA that play essential roles in multiple diseases. However, their biological functions in carcinogenesis are not well understood. In this study, 5'tRF-Gly was found to have significantly high expression in hepatocellular carcinoma (HCC), and the upregulation of 5'tRF-Gly was positively correlated with tumor size and tumor metastasis. Overexpression of 5'tRF-Gly induced increased growth rate and metastasis in HCC cells in vitro and in nude mice, while knockdown showed the opposite effect. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) was confirmed to be a direct target of 5'tRF-Gly in HCC. In addition, the cytological effect of CEACAM1 knockdown proved to be similar to the overexpression of 5'tRF-Gly. Moreover, attenuation of CEACAM1 expression rescued the 5'tRF-Gly-mediated promoting effects on HCC cells. These data show that 5'tRF-Gly is a new tumor-promoting factor and could be a potential diagnostic biomarker or new therapeutic target for HCC.

Phosphorylation of human CEACAM1-LF by PKA and GSK3β promotes its interaction with β-catenin

CEACAM1-LF, a homotypic cell adhesion adhesion molecule, transduces intracellular signals via a 72 amino acid cytoplasmic domain that contains two immunoreceptor tyrosine-based inhibitory motifs (ITIMs) and a binding site for β-catenin. Phosphorylation of Ser503 by PKC in rodent CEACAM1 was shown to affect bile acid transport or hepatosteatosis via the level of ITIM phosphorylation, but the phosphorylation of the equivalent residue in human CEACAM1 (Ser508) was unclear. Here we studied this analogous phosphorylation by NMR analysis of the ¹⁵N labeled cytoplasmic domain peptide. Incubation with a variety of Ser/Thr kinases revealed phosphorylation of Ser508 by GSK3bβ but not by PKC. The lack of phosphorylation by PKC is likely due to evolutionary sequence changes between the rodent and human genes. Phosphorylation site assignment by mass spectrometry and NMR revealed phosphorylation of Ser472, Ser461 and Ser512 by PKA, of which Ser512 is part of a conserved consensus site for GSK3β binding. We showed here that only after phosphorylation of Ser512 by PKA was GSK3β able to phosphorylate Ser508. Phosphorylation of Ser512 by PKA promoted a tight association with the armadillo repeat domain of β-catenin at an extended region spanning the ITIMs of CEACAM1. The kinetics of phosphorylation of the ITIMs by Src, as well dephosphorylation by SHP2, were affected by the presence of Ser508/512 phosphorylation, suggesting that PKA and GSK3β may regulate the signal transduction activity of human CEACAM1-LF. The interaction of CEACAM1-LF with β-catenin promoted by PKA is suggestive of a tight association between the two ITIMs of CEACAM1-LF.

Immune checkpoint inhibition in syngeneic mouse cancer models by a silicasome nanocarrier delivering a GSK3 inhibitor

Checkpoint blocking antibodies that interfere in the PD-1/PD-L1 axis provide effective cancer immunotherapy for tumors that are immune inflamed or induced to become "hot". It has also been demonstrated that a small molecule inhibitor of the signaling hub kinase GSK3 can interfere in the PD-1/PD-L1 axis in T-cells by suppressing PD-1 expression. This provides an alternative approach to intervening in the PD-1/PD-L1 axis to provide cancer immunotherapy. In this communication, we demonstrate the remote loading of GSK3 inhibitor AZD1080 into the porous interior of mesoporous silica nanoparticles coated with a lipid bilayer (a.k.a. silicasomes). In a MC38 colon cancer model, intravenous injection (IV) of silicasome-encapsulated AZD1080 significantly improved biodistribution and drug delivery to the tumor site. The improved drug delivery was accompanied by cytotoxic MC38 tumor cell killing by perforin-releasing CD8⁺ T-cells, exhibiting reduced PD-1 expression. IV injection of encapsulated AZD1080 also resulted in significant tumor shrinkage in other syngeneic mouse tumor models, including another colorectal tumor (CT26), as well as pancreas (KPC) and lung (LLC) cancer models. Not only was the therapeutic efficacy of encapsulated AZD1080 similar or better than anti-PD-1 antibody, but the treatment was devoid of treatment toxicity. These results provide proof-of-principal demonstration of the feasibility of using encapsulated delivery of a GSK3 inhibitor to provide cancer immunotherapy, with the possibility to be used as a monotherapy or in combination with chemotherapy or other immunomodulatory agents.

Neisseria gonorrhoeae Blocks Epithelial Exfoliation by Nitric-Oxide-Mediated Metabolic Cross Talk to Promote Colonization in Mice

Several pathogens suppress exfoliation, a key defense of epithelia against microbial colonization. Common among these pathogens, exemplified by Neisseria gonorrhoeae, is their ability to bind carcinoembryonic antigen-related cell adhesion molecules (CEACAMs). Gonococcal CEACAM engagement triggers the expression of CD105, which is necessary to block epithelial exfoliation, whereas homotypic CEACAM-CEACAM interactions or antibody-mediated CEACAM clustering does not lead to CD105 expression. Here, we show that CEACAM-associated bacteria release nitric oxide (NO) during anaerobic respiration, and membrane-permeable NO initiates a eukaryotic signaling pathway involving soluble guanylate cyclase (sGC), protein kinase G, and the transcription factor CREB to upregulate CD105 expression. A murine vaginal infection model with N. gonorrhoeae reveals this metabolic cross communication allows bacterial suppression of epithelial exfoliation to facilitate mucosal colonization. Disrupting NO-initiated responses in host cells re-establishes epithelial exfoliation and inhibits mouse genital tract colonization by N. gonorrhoeae, suggesting a host-directed approach to prevent bacterial infections.

Astragaloside IV Inhibits the Progression of Non-Small Cell Lung Cancer Through the Akt/GSK-3β/β-Catenin Pathway

Astragaloside IV (AS-IV) is an active ingredient in Astragalus membranaceus and is involved in various biological processes, such as regulating the immune system, and counteracting inflammation and malignancy. The aim of this study was to explore the effect of AS-IV on non-small cell lung cancer (NSCLC) cells. Cell counting kit (CCK)-8 assay and flow cytometry were performed to investigate cell survival and cell death, and Western blotting was performed to assess protein expression. We found that AS-IV inhibited the migration and proliferation of NSCLC cells and caused a noticeable increase in cell death. Furthermore, the expression of Bax, a marker of cell death, was increased, whereas the expression of Bcl-2, an antiapoptotic protein, was reduced. AS-IV also promoted cleavage of caspase-3, another indication of apoptosis. Finally, the Akt/GSK-3β/β-catenin axis was suppressed in response to AS-IV. Taken together, these findings provide evidence that AS-IV inhibits NSCLC development via inhibition of the Akt/GSK-3β/β-catenin signaling axis. We therefore propose that AS-IV represents a promising novel agent for the treatment of NSCLC.

Prognostic Impact of CEACAM1 in Node-Negative Ovarian Cancer Patients

The underlying mechanisms of ovarian cancer (OvCa) dissemination are still poorly understood, and novel molecular markers for this cancer type are urgently needed. In search of adhesion molecules with prognostic relevance in OvCa, we compared tumors with good outcome (alive > 3 years) and those with poor outcome (dead < 2 years) within data from The Cancer Genome Atlas (TCGA). The carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) turned out as the only gene with differential expression in these groups. In order to further investigation on its role in OvCa, we analyzed CEACAM1 mRNA levels extracted from TCGA microarray data (n = 517) as well as CEACAM1 protein expression by Western blot analysis in a cohort of 242 tumor samples. Further, CEACAM1 localization in tumour tissue was evaluated by immunohistochemistry and CEACAM1 splice variants by RT-PCR in representative tumours. In Kaplan–Meier analysis, high CEACAM1 mRNA levels significantly correlated with longer survival (p = 0.008). By Western blot analysis in the second cohort, similar associations of high CEACAM1 protein levels with longer recurrence-free survival (RFS, p = 0.035) and overall survival (OAS, p = 0.004) were observed. In multivariate Cox regression analysis including clinical prognostic parameters, CEACAM1 mRNA or protein expression turned out as independent prognostic markers. Stratified survival analysis showed that high CEACAM1 protein expression was prognostic in node-negative tumors (p = 0.045 and p = 0.0002 for DFS and OAS) but lost prognostic significance in node-positive carcinomas. Similarly, high CEACAM1 mRNA expression did not show prognostic relevance in tumors with lymphatic invasion (L1) but was associated with longer survival in cases without lymphovascular involvement. Further analysis showed a predominance of 4S and 4L isoforms and mostly membraneous CEACAM1 localization in ovarian tumours. Our results suggest that CEACAM1 might be an independent favorable prognostic marker in OvCa, especially in the subgroup of patients with solely intraperitoneal metastasis.

SOX9 is an atypical intestinal tumor suppressor controlling the oncogenic Wnt/ß-catenin signaling

SOX9 inactivation is frequent in colorectal cancer (CRC) due to SOX9 gene mutations and/or to ectopic expression of MiniSOX9, a dominant negative inhibitor of SOX9. In the present study, we report a heterozygous L142P inactivating mutation of SOX9 in the DLD-1 CRC cell line and we demonstrate that the conditional expression of a wild type SOX9 in this cell line inhibits cell growth, clonal capacity and colonosphere formation while decreasing both the activity of the oncogenic Wnt/ß-catenin signaling pathway and the expression of the c-myc oncogene. This activity does not require SOX9 transcriptional function but, rather, involves an interaction of SOX9 with nuclear ß-catenin. Furthermore, we report that SOX9 inhibits tumor development when conditionally expressed in CRC cells injected either subcutaneous or intraperitoneous in BALB/c mice as an abdominal metastasis model. These observations argue in favor of a tumor suppressor activity for SOX9. As an siRNA targeting SOX9 paradoxically also inhibits DLD-1 and HCT116 CRC cell growth, we conclude that there is a critical level of endogenous active SOX9 needed to maintain CRC cell growth.

Co-expression of TIM-3 and CEACAM1 promotes T cell exhaustion in colorectal cancer patients

T-cell immunoglobulin domain and mucin domain-3(TIM-3) is an activation induced inhibitory molecule involved in immune tolerance and is recently reported to induce T cell exhaustion which is mediated by carcinoembryonic antigen cell adhesion molecule 1(CEACAM1), another well-known molecule expressed on activated T cells and involved in T cell inhibition. To investigate the expression of TIM-3 and CEACAM1 on circulating CD8⁺ T cells and tumor infiltrating lymphocytes (TILs), 65 diagnosed colorectal cancer (CRC) patients and 38 healthy controls were enrolled in this study and the results showed that TIM-3 and CEACAM1 were both highly expressed on circulating CD8⁺ T cells in CRC patients and elevated on TILs compared with paraneoplastic T cells. Furthermore, TIM-3⁺CEACAM1⁺ CD8⁺ T cells represented the most dysfunctional population with the least IFN-γ production. In addition, the expressions of TIM-3 and CEACAM1 were correlated with advanced stage and could be independent risk factors for CRC. We for the first time to our knowledge suggested that co-expression of TIM-3 and CEACAM1 can mediate T cell exhaustion and may be potential biomarkers for CRC prediction, highlighting the possibility of being immunotherapy targets.

The role of CEA-related cell adhesion molecule-1 (CEACAM1) in vascular homeostasis

Carcinoembryonic antigen (CEA)-related cell adhesion molecules belong to the immunoglobulin superfamily, are expressed in a broad spectrum of tissues and cell types and exert context-dependent activating as well as inhibitory effects. Among these molecules, the CEA-related cell adhesion molecule-1 (CEACAM1) is a transmembrane molecule with an extracellular, a transmembrane and a cytoplasmic domain. The latter contains immunoreceptor tyrosine-based inhibitory motifs and functions as a signaling molecule. CEACAM1 can form homo- and heterodimers which is relevant for its signaling activities. CEACAM1 acts as co-receptor that modulates the activity of different receptor types including VEGFR-2, and B and T cell receptors. CEACAM1 is expressed in endothelial cells, in pericytes of developing and newly formed immature blood vessels and in angiogenically activated adult vessels, e.g., tumor blood vessels. However, it is either undetectable or only weakly expressed in quiescent blood vessels. Recent studies indicated that CEACAM1 is involved in the regulation of the endothelial barrier function. In CEACAM1 ^-/- mice, increased vascular permeability and development of small atherosclerotic lesions was observed in the aortae. CEACAM1 is also detectable in activated lymphatic endothelial cells and plays a role in tumor lymphangiogenesis. This review summarizes the vascular effects of CEACAM1 and focuses on its role in vascular morphogenesis and endothelial barrier regulation.

CEACAM1 controls the EMT switch in murine mammary carcinoma in vitro and in vivo

We analyzed the molecular basis for carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1)-controlled inhibition of epithelial-mesenchymal transition (EMT) in a mouse model for mammary adenocarcinoma (WAP-T mice). We demonstrate that silencing of CEACAM1 in WAP-T tumor-derived G-2 cells induces epithelial-mesenchymal plasticity (EMP), as evidenced by typical changes of gene expression, morphology and increased invasion. In contrast, reintroduction of CEACAM1 into G-2 cells reversed up-regulation of genes imposing mesenchymal transition, as well as cellular invasion. We identified the Wnt-pathway as target for CEACAM1-mediated repression of EMT. Importantly, β-catenin phosphorylation status and transcriptional activity strongly depend on CEACAM1 expression: CEACAM1high G-2 cells displayed enhanced phosphorylation of β-catenin at S33/S37/T41 and decreased phosphorylation at Y86, thereby inhibiting canonical Wnt/β-catenin signaling. We identified Src-homology 2 domain-containing phosphatase 2 (SHP-2) as a critical binding partner of CEACAM1 that could modulate β-catenin Y86 phosphorylation. Hence, CEACAM1 serves as a scaffold that controls membrane proximal β-catenin signaling. In vivo, mammary tumors of WAP-T/CEACAM1null mice displayed increased nuclear translocation of β-catenin and a dramatically enhanced metastasis rate compared to WAP-T mice. Hence, CEACAM1 controls EMT in vitro and in vivo by site-specific regulation of β-catenin phosphorylation. Survival analyses of human mammary carcinoma patients corroborated these data, indicating that CEACAM1 is a prognostic marker for breast cancer survival.

Carcinoembryonic Antigen Cell Adhesion Molecule 1 long isoform modulates malignancy of poorly differentiated colon cancer cells

OBJECTIVE

Nearly 20%-29% of patients with colorectal cancer (CRC) succumb to liver or lung metastasis and there is a dire need for novel targets to improve the survival of patients with metastasis. The long isoform of the Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1-L or CC1-L) is a key regulator of immune surveillance in primary CRC, but its role in metastasis remains largely unexplored. We have examined how CC1-L expression impacts on colon cancer liver metastasis.

DESIGN

Murine MC38 transfected with CC1-L were evaluated in vitro for proliferation, migration and invasion, and for in vivo experimental liver metastasis. Using shRNA silencing or pharmacological inhibition, we delineated the role in liver metastasis of Chemokine (C-C motif) Ligand 2 (CCL2) and Signal Transducer and Activator of Transcription 3 (STAT3) downstream of CC1-L. We further assessed the clinical relevance of these findings in a cohort of patients with CRC.

RESULTS

MC38-CC1-L-expressing cells exhibited significantly reduced in vivo liver metastasis and displayed decreased CCL2 chemokine secretion and reduced STAT3 activity. Down-modulation of CCL2 expression and pharmacological inhibition of STAT3 activity in MC38 cells led to reduced cell invasion capacity and decreased liver metastasis. The clinical relevance of our findings is illustrated by the fact that high CC1 expression in patients with CRC combined with some inflammation-regulated and STAT3-regulated genes correlate with improved 10-year survival.

CONCLUSIONS

CC1-L regulates inflammation and STAT3 signalling and contributes to the maintenance of a less-invasive CRC metastatic phenotype of poorly differentiated carcinomas.

Stromal CEACAM1 expression regulates colorectal cancer metastasis

Colorectal cancer metastasis to Ceacam1-/- livers is significantly impaired, compared with wild type livers, due to decreased endothelial cell survival, reduced tumor cell proliferation, diminished immune infiltration and altered chemokine expression. Ceacam1-/- myeloid-derived suppressor cells diminish metastatic burden, as confirmed by bone marrow transplantation and adoptive transfer experiments.

Differentiation and loss of malignant character of spontaneous pulmonary metastases in patient-derived breast cancer models

Patient-derived human-in-mouse xenograft models of breast cancer (PDX models) that exhibit spontaneous lung metastases offer a potentially powerful model of cancer metastasis. In this study, we evaluated the malignant character of lung micrometastases that emerge in such models after orthotopic implantation of human breast tumor cells into the mouse mammary fat pad. Interestingly, relative to the parental primary breast tumors, the lung metastasis (met)-derived mammary tumors exhibited a slower growth rate and a reduced metastatic potential with a more differentiated epithelial status. Epigenetic correlates were determined by gene array analyses. Lung met-derived tumors displayed differential expression of negative regulators of cell proliferation and metabolism and positive regulators of mammary epithelial differentiation. Clinically, this signature correlated with breast tumor subtypes. We identified hsa-miR-138 (miR-138) as a novel regulator of invasion and epithelial-mesenchymal transition in breast cancer cells, acting by directly targeting the polycomb epigenetic regulator EZH2. Mechanistic investigations showed that GATA3 transcriptionally controlled miR-138 levels in lung metastases. Notably, the miR-138 activity signature served as a novel independent prognostic marker for patient survival beyond traditional pathologic variables, intrinsic subtypes, or a proliferation gene signature. Our results highlight the loss of malignant character in some lung micrometastatic lesions and the epigenetic regulation of this phenotype.

Murinization of internalin extends its receptor repertoire, altering Listeria monocytogenes cell tropism and host responses

Listeria monocytogenes (Lm) is an invasive foodborne pathogen that leads to severe central nervous system and maternal-fetal infections. Lm ability to actively cross the intestinal barrier is one of its key pathogenic properties. Lm crosses the intestinal epithelium upon the interaction of its surface protein internalin (InlA) with its host receptor E-cadherin (Ecad). InlA-Ecad interaction is species-specific, does not occur in wild-type mice, but does in transgenic mice expressing human Ecad and knock-in mice expressing humanized mouse Ecad. To study listeriosis in wild-type mice, InlA has been “murinized” to interact with mouse Ecad. Here, we demonstrate that, unexpectedly, murinized InlA (InlA^m) mediates not only Ecad-dependent internalization, but also N-cadherin-dependent internalization. Consequently, InlA^m-expressing Lm targets not only goblet cells expressing luminally-accessible Ecad, as does Lm in humanized mice, but also targets villous M cells, which express luminally-accessible N-cadherin. This aberrant Lm portal of entry results in enhanced innate immune responses and intestinal barrier damage, both of which are not observed in wild-type Lm-infected humanized mice. Murinization of InlA therefore not only extends the host range of Lm, but also broadens its receptor repertoire, providing Lm with artifactual pathogenic properties. These results challenge the relevance of using InlA^m-expressing Lm to study human listeriosis and in vivo host responses to this human pathogen.

Co-evolution of microbes with their hosts can select stringently specific host-microbe interactions at the cell, tissue and species levels. Listeria monocytogenes (Lm) is a foodborne pathogen that causes a deadly systemic infection in humans. Lm crosses the intestinal epithelium upon the interaction of its surface protein InlA with E-cadherin (Ecad). InlA-Ecad interaction is species-specific, does not occur in wild-type mice, but does in transgenic mice expressing human Ecad and knock-in mice expressing humanized mouse Ecad. To study listeriosis in wild-type mice, InlA has been “murinized” to interact with mouse Ecad. Here, we demonstrate that in addition to interacting with mouse Ecad, InlA^m also uses N-cadherin as a receptor, whereas InlA does not. This artifactual InlA^m-N-cadherin interaction promotes bacterial translocation across villous M cells, a cell type which is not targeted by InlA-expressing bacteria. This leads to intestinal inflammation and intestinal barrier damage, both of which are not seen in humans and humanized mouse models permissive to InlA-Ecad interaction. These results challenge the relevance of using InlA^m-expressing Lm as a model to study human listeriosis and host responses to this pathogen. They also illustrate that caution must be exercised before using “murinized” pathogens to study human infectious diseases.

CEACAM1 expression in oligodendrocytes of the developing rat brain shows a spatiotemporal relation to myelination and is altered in a model of encephalopathy of prematurity

CEACAM1 is the founder molecule of the family of 'carcinoembryonic antigen-related cell adhesion molecules' and part of the immunoglobulin superfamily. Due to its role as a coreceptor to many other receptors (e.g. Toll-like receptor 2, Toll-like receptor 4, T-cell receptor, B-cell receptor, epidermal growth factor receptor and vascular endothelial growth factor receptor) and its different isoforms, CEACAM1 is a multifunctional protein with an impact on proliferation and differentiation of multiple cell types. Although different modes of action in other tissues are described, the role of CEACAM1 in the developing brain remains elusive. Here we report for the first time that CEACAM1 is expressed ontogenetically in oligodendrocytes of the developing rat brain, and that CEACAM1 expression has a spatiotemporal relation to myelination. In addition, CEACAM1 expression is altered in a model of hyperoxia- and inflammation-induced encephalopathy of prematurity, a myelination disorder of children born preterm. Furthermore, primary oligodendrocytes stimulated with CEACAM1 show increased myelination. Therefore, we postulate that CEACAM1 is, at least in part, involved in hyperoxia- and inflammation-induced disruption of myelination, but may also play a role in intact myelination as it is ontogenetically expressed in myelinating oligodendrocytes.

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.

Loss of mammal-specific tectorial membrane component carcinoembryonic antigen cell adhesion molecule 16 (CEACAM16) leads to hearing impairment at low and high frequencies

The vertebrate-restricted carcinoembryonic antigen gene family evolves extremely rapidly. Among their widely expressed members, the mammal-specific, secreted CEACAM16 is exceptionally well conserved and specifically expressed in the inner ear. To elucidate a potential auditory function, we inactivated murine Ceacam16 by homologous recombination. In young Ceacam16(-/-) mice the hearing threshold for frequencies below 10 kHz and above 22 kHz was raised. This hearing impairment progressed with age. A similar phenotype is observed in hearing-impaired members of Family 1070 with non-syndromic autosomal dominant hearing loss (DFNA4) who carry a missense mutation in CEACAM16. CEACAM16 was found in interdental and Deiters cells and was deposited in the tectorial membrane of the cochlea between postnatal days 12 and 15, when hearing starts in mice. In cochlear sections of Ceacam16(-/-) mice tectorial membranes were significantly more often stretched out as compared with wild-type mice where they were mostly contracted and detached from the outer hair cells. Homotypic cell sorting observed after ectopic cell surface expression of the carboxyl-terminal immunoglobulin variable-like N2 domain of CEACAM16 indicated that CEACAM16 can interact in trans. Furthermore, Western blot analyses of CEACAM16 under reducing and non-reducing conditions demonstrated oligomerization via unpaired cysteines. Taken together, CEACAM16 can probably form higher order structures with other tectorial membrane proteins such as α-tectorin and β-tectorin and influences the physical properties of the tectorial membrane. Evolution of CEACAM16 might have been an important step for the specialization of the mammalian cochlea, allowing hearing over an extended frequency range.

Host-related carcinoembryonic antigen cell adhesion molecule 1 promotes metastasis of colorectal cancer

Liver metastasis is the predominant cause of colorectal cancer (CRC)-related mortality in developed countries. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a cell adhesion molecule with reduced expression in early phases of CRC development and thus functions as a tumor growth inhibitor. However, CEACAM1 is upregulated in metastatic colon cancer, suggesting a bimodal role in CRC progression. To investigate the role of this protein in the host metastatic environment, Ceacam1(-/-) mice were injected intrasplenically with metastatic MC38 mouse CRC cells. A significant reduction in metastatic burden was observed in Ceacam1(-/-) compared with wild-type (WT) livers. Intravital microscopy showed decreased early survival of MC38 cells in Ceacam1(-/-) endothelial environment. Metastatic cell proliferation within the Ceacam1(-/-) livers was also diminished. Bone marrow-derived cell recruitment, attenuation of immune infiltrates and diminished CCL2, CCL3 and CCL5 chemokine production participated in the reduced Ceacam1(-/-) metastatic phenotype. Transplantations of WT bone marrow (BM) into Ceacam1(-/-) mice fully rescued metastatic development, whereas Ceacam1(-/-) BM transfer into WT mice showed reduced metastatic burden. Chimeric immune cell profiling revealed diminished recruitment of CD11b(+)Gr1(+) myeloid-derived suppressor cells (MDSCs) to Ceacam1(-/-) metastatic livers and adoptive transfer of MDSCs confirmed the involvement of these immune cells in reduction of liver metastasis. CEACAM1 may represent a novel metastatic CRC target for treatment.

CEACAM1 deficiency delays important wound healing processes

Cutaneous wound healing is a complex process that requires the coordination of many cell types to achieve proper tissue repair. Four major overlapping processes have been identified in wound healing: hemostasis, inflammation, reepithelialization and granulation tissue formation, and tissue remodeling. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a glycoprotein expressed in epithelial, endothelial, lymphoid, and myeloid cells. Given its known roles in angiogenesis, cell migration, and immune functions, we hypothesized that CEACAM1 might also be involved in cutaneous wound healing and that a number of relevant CEACAM1-positive cell types might contribute to wound healing. To evaluate the role of CEACAM1 in these processes, 6-mm-diameter skin wounds were inflicted on Ceacam1(-/-) and wild-type mice. Herein, we demonstrate that CEACAM1 deletion indeed affects wound healing in three key ways. Infiltration of F4/80(+) macrophages was decreased in Ceacam1(-/-) wounds, altering inflammatory processes. Reepithelialization in Ceacam1(-/-) wounds was delayed. Furthermore, the vascular density of the granulation tissue in Ceacam1(-/-) wounds was significantly diminished. These results confirm CEACAM1's role as an important regulator of key processes in cutaneous wound healing, although whether this works via a specific cell type or alterations in the functioning of multiple processes remains to be determined.

Increased metabolic rate and insulin sensitivity in male mice lacking the carcino-embryonic antigen-related cell adhesion molecule 2

AIMS/HYPOTHESIS

The carcino-embryonic antigen-related cell adhesion molecule (CEACAM)2 is produced in many feeding control centres in the brain, but not in peripheral insulin-targeted tissues. Global Ceacam2 null mutation causes insulin resistance and obesity resulting from hyperphagia and hypometabolism in female Ceacam2 homozygous null mutant mice (Cc2 [also known as Ceacam2](-/-)) mice. Because male mice are not obese, the current study examined their metabolic phenotype.

METHODS

The phenotype of male Cc2(-/-) mice was characterised by body fat composition, indirect calorimetry, hyperinsulinaemic-euglycaemic clamp analysis and direct recording of sympathetic nerve activity.

RESULTS

Despite hyperphagia, total fat mass was reduced, owing to the hypermetabolic state in male Cc2(-/-) mice. In contrast to females, male mice also exhibited insulin sensitivity with elevated β-oxidation in skeletal muscle, which is likely to offset the effects of increased food intake. Males and females had increased brown adipogenesis. However, only males had increased activation of sympathetic tone regulation of adipose tissue and increased spontaneous activity. The mechanisms underlying sexual dimorphism in energy balance with the loss of Ceacam2 remain unknown.

CONCLUSIONS/INTERPRETATION

These studies identified a novel role for CEACAM2 in the regulation of metabolic rate and insulin sensitivity via effects on brown adipogenesis, sympathetic nervous outflow to brown adipose tissue, spontaneous activity and energy expenditure in skeletal muscle.

Ceacam1 separates graft-versus-host-disease from graft-versus-tumor activity after experimental allogeneic bone marrow transplantation

Background

Allogeneic bone marrow transplantation (allo-BMT) is a potentially curative therapy for a variety of hematologic diseases, but benefits, including graft-versus-tumor (GVT) activity are limited by graft-versus-host-disease (GVHD). Carcinoembryonic antigen related cell adhesion molecule 1 (Ceacam1) is a transmembrane glycoprotein found on epithelium, T cells, and many tumors. It regulates a variety of physiologic and pathological processes such as tumor biology, leukocyte activation, and energy homeostasis. Previous studies suggest that Ceacam1 negatively regulates inflammation in inflammatory bowel disease models.

Methods

We studied Ceacam1 as a regulator of GVHD and GVT after allogeneic bone marrow transplantation (allo-BMT) in mouse models. In vivo, Ceacam1^−/− T cells caused increased GVHD mortality and GVHD of the colon, and greater numbers of donor T cells were positive for activation markers (CD25^hi, CD62L^lo). Additionally, Ceacam1^−/− CD8 T cells had greater expression of the gut-trafficking integrin α₄β₇, though both CD4 and CD8 T cells were found increased numbers in the gut post-transplant. Ceacam1^−/− recipients also experienced increased GVHD mortality and GVHD of the colon, and alloreactive T cells displayed increased activation. Additionally, Ceacam1^−/− mice had increased mortality and decreased numbers of regenerating small intestinal crypts upon radiation exposure. Conversely, Ceacam1-overexpressing T cells caused attenuated target-organ and systemic GVHD, which correlated with decreased donor T cell numbers in target tissues, and mortality. Finally, graft-versus-tumor survival in a Ceacam1⁺ lymphoma model was improved in animals receiving Ceacam1^−/− vs. control T cells.

Conclusions

We conclude that Ceacam1 regulates T cell activation, GVHD target organ damage, and numbers of donor T cells in lymphoid organs and GVHD target tissues. In recipients of allo-BMT, Ceacam1 may also regulate tissue radiosensitivity. Because of its expression on both the donor graft and host tissues, this suggests that targeting Ceacam1 may represent a potent strategy for the regulation of GVHD and GVT after allogeneic transplantation.

Genetically modified mouse models of cancer invasion and metastasis

Tumor invasion and metastasis is a multi-step process that requires adaptation of cancer cells to conditions that they encounter during their journey to distant body sites. Understanding the molecular processes that underlie this adaptation is of exceeding importance because most cancer patients die because of metastases rather than primary tumors. In this review we assess genetically engineered mouse models (GEMMs) that have been established to investigate mechanisms of cancer invasion and metastasis.

Stat3 is a negative regulator of intestinal tumor progression in Apc(Min) mice

BACKGROUND AND AIMS

The transcription factor signal transducer and activator of transcription 3 (Stat3) has been considered to promote progression and metastasis of intestinal cancers.

METHODS

We investigated the role of Stat3 in intestinal tumors using mice with conditional ablation of Stat3 in intestinal epithelial cells (Stat3(DeltaIEC)).

RESULTS

In the Apc(Min) mouse model of intestinal cancer, genetic ablation of Stat3 reduced the multiplicity of early adenomas. However, loss of Stat3 promoted tumor progression at later stages, leading to formation of invasive carcinomas, which significantly shortened the lifespan of Stat3(DeltaIEC)Apc(Min/+) mice. Interestingly, loss of Stat3 in tumors of Apc(Min/+) mice had no significant impact on cell survival and angiogenesis, but promoted cell proliferation. A genome-wide expression analysis of Stat3-deficient tumors suggested that Stat3 might negatively regulate intestinal cancer progression via the cell adhesion molecule CEACAM1.

CONCLUSIONS

Our data suggest that Stat3 impairs invasiveness of intestinal tumors. Therefore, therapeutic targeting of the Stat3 signaling pathway in intestinal cancer should be evaluated for adverse effects on tumor progression.

Homophilic adhesion and CEACAM1-S regulate dimerization of CEACAM1-L and recruitment of SHP-2 and c-Src

Carcinoembryonic antigen (CEA)-related cell adhesion molecule 1 (CAM1 [CEACAM1]) mediates homophilic cell adhesion and regulates signaling. Although there is evidence that CEACAM1 binds and activates SHP-1, SHP-2, and c-Src, knowledge about the mechanism of transmembrane signaling is lacking. To analyze the regulation of SHP-1/SHP-2/c-Src binding, we expressed various CFP/YFP-tagged CEACAM1 isoforms in epithelial cells. The supramolecular organization of CEACAM1 was examined by cross-linking, coclustering, coimmunoprecipitation, and fluorescence resonance energy transfer. SHP-1/SHP-2/c-Src binding was monitored by coimmunoprecipitation and phosphotyrosine-induced recruitment to CEACAM1-L in cellular monolayers. We find that trans-homophilic CEACAM1 binding induces cis-dimerization by an allosteric mechanism transmitted by the N-terminal immunoglobulin-like domain. The balance of SHP-2 and c-Src binding is dependent on the monomer/dimer equilibrium of CEACAM1-L and is regulated by trans-binding, whereas SHP-1 does not bind under physiological conditions. CEACAM1-L homodimer formation is reduced by coexpression of CEACAM1-S and modulated by antibody ligation. These data suggest that transmembrane signaling by CEACAM1 operates by alteration of the monomer/dimer equilibrium, which leads to changes in the SHP-2/c-Src-binding ratio.

The CEACAM1 N-terminal Ig domain mediates cis- and trans-binding and is essential for allosteric rearrangements of CEACAM1 microclusters

Cell adhesion molecules (CAMs) sense the extracellular microenvironment and transmit signals to the intracellular compartment. In this investigation, we addressed the mechanism of signal generation by ectodomains of single-pass transmembrane homophilic CAMs. We analyzed the structure and homophilic interactions of carcinoembryonic antigen (CEA)-related CAM 1 (CEACAM1), which regulates cell proliferation, apoptosis, motility, morphogenesis, and microbial responses. Soluble and membrane-attached CEACAM1 ectodomains were investigated by surface plasmon resonance-based biosensor analysis, molecular electron tomography, and chemical cross-linking. The CEACAM1 ectodomain, which is composed of four glycosylated immunoglobulin-like (Ig) domains, is highly flexible and participates in both antiparallel (trans) and parallel (cis) homophilic binding. Membrane-attached CEACAM1 ectodomains form microclusters in which all four Ig domains participate. Trans-binding between the N-terminal Ig domains increases formation of CEACAM1 cis-dimers and changes CEACAM1 interactions within the microclusters. These data suggest that CEACAM1 transmembrane signaling is initiated by adhesion-regulated changes of cis-interactions that are transmitted to the inner phase of the plasma membrane.

[CEACAM1 as a central modulator of metabolism, tumor progression, angiogenesis and immunity]

CEACAM1 (carcinoembryonic antigen cell adhesion molecule 1), a member of the immunoglobulin (Ig) superfamily, is a heavily glycosylated protein. This glycoprotein exhibits an intracytoplasmic region that can be either long (71-73 amino acids) with two inhibitory tyrosine-phosphorylated motifs and several phosphorylated serine residues, or short (10 amino acid). CEACAM1 is a multifunctional protein that plays a role in intercellular adhesion, as an inhibitor of tumor development, as a bacterial adhesin, and as a receptor for the mouse hepatitis virus. Moreover, CEACAM1 is an active regulator of cell signaling, modulating the insulin or EGF receptor pathways in epithelial cells or the Zap-70 pathway in hematopoietic cells. The recent development of genetically modified mouse models altering the Ceacam1 gene corroborates most of these data, but also highlights CEACAM1's functional complexity. Thus, in addition to the functions identified previously, CEACAM1 is an important regulator of lipid metabolism, of tumor progression as a regulator of the Wnt signaling pathway, of normal and tumor neo-angiogenesis and of immunity.

A new mechanism of SOX9 action to regulate PKCalpha expression in the intestine epithelium

Variations of protein kinase C (PKC) expression greatly influence the proliferation-to-differentiation transition (PDT) of intestinal epithelial cells and might have an important impact on intestinal tumorigenesis. We demonstrate here that the expression of PKCalpha in proliferating intestinal epithelial cells is repressed both in vitro and in vivo by the SOX9 transcription factor. This repression does not require DNA binding of the SOX9 high-mobility group (HMG) domain but is mediated through a new mechanism of SOX9 action requiring the central and highly conserved region of SOXE members. Because SOX9 expression is itself upregulated by Wnt-APC signaling in intestinal epithelial cells, the present study points out this transcription factor as a molecular link between the Wnt-APC pathway and PKCalpha. These results provide a potential explanation for the decrease of PKCalpha expression in colorectal cancers with constitutive activation of the Wnt-APC pathway.