CEACAM1 dampens antitumor immunity by down-regulating NKG2D ligand expression on tumor cells

The emerging role of Fusobacteria in carcinogenesis

The Fusobacterium genus comprises Gram-negative, obligate anaerobic bacteria that typically reside in the periodontium of the oral cavity, gastrointestinal tract, and female genital tract. The association of Fusobacterial spp. with colorectal tumours is widely accepted, with further evidence that this pathogen may also be implicated in the development of other malignancies. Fusobacterial spp. influence malignant cell behaviours and the tumour microenvironment in various ways, which can be related to the multiple surface adhesins expressed. These adhesins include Fap2 (fibroblast-activated protein 2), CpbF (CEACAM binding protein of Fusobacteria), FadA (Fusobacterium adhesin A) and FomA (Fusobacterial outer membrane protein A). This review outlines the influence of Fusobacteria in promoting cancer initiation and progression, impacts of therapeutic outcomes and discusses potential therapeutic interventions where appropriate.

Carcinoembryonic antigen-related cell adhesion molecule 1 in cancer: Blessing or curse?

The Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1, also CD66a), a transmembrane glycoprotein of the immunoglobulin superfamily, is a pivotal mediator of various physiological and pathological processes, including oncologic disorders. However, its precise role in tumorigenicity is contradictory discussed by several clinical studies. This review aims to elucidate the clinical significance of CEACAM1 in different cancer entities focusing on tumour formation, progression and metastasis as well as on CEACAM1-mediated treatment resistance. Furthermore, we discuss the contribution of CEACAM1 to cancer immunity and modulation of the inflammatory microenvironment and finally provide a comprehensive review of treatment regimens targeting this molecule.

CEACAM1-engineered MSCs have a broad spectrum of immunomodulatory functions and therapeutic potential via cell-to-cell interaction

Mesenchymal stem cells (MSCs) have garnered attention for their regenerative and immunomodulatory capabilities in clinical trials for various diseases. However, the effectiveness of MSC-based therapies, especially for conditions like graft-versus-host disease (GvHD), remains uncertain. The cytokine interferon (IFN)-γ has been known to enhance the immunosuppressive properties of MSCs through cell-to-cell interactions and soluble factors. In this study, we observed that IFN-γ-treated MSCs upregulated the expression of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), associated with immune evasion through the inhibition of natural killer (NK) cell cytotoxicity. To co-opt this immunomodulatory function, we generated MSCs overexpressing CEACAM1 and found that CEACAM1-engineered MSCs significantly reduced NK cell activation and cytotoxicity via cell-to-cell interaction, independent of NKG2D ligand regulation. Furthermore, CEACAM1-engineered MSCs effectively inhibited the proliferation and activation of T cells along with the inflammatory responses of monocytes. In a humanized GvHD mouse model, CEACAM1-MSCs, particularly CEACAM1-4S-MSCs, demonstrated therapeutic potential by improving survival and alleviating symptoms. These findings suggest that CEACAM1 expression on MSCs contributes to MSC-mediated regulation of immune responses and that CEACAM1-engineered MSC could have therapeutic potential in conditions involving immune dysregulation.

The immunosuppressive landscape in tumor microenvironment

Recent advances in cancer immunotherapy, especially immune checkpoint inhibitors (ICIs), have revolutionized the clinical outcome of many cancer patients. Despite the fact that impressive progress has been made in recent decades, the response rate remains unsatisfactory, and many patients do not benefit from ICIs. Herein, we summarized advanced studies and the latest insights on immune inhibitory factors in the tumor microenvironment. Our in-depth discussion and updated landscape of tumor immunosuppressive microenvironment may provide new strategies for reversing tumor immune evasion, enhancing the efficacy of ICIs therapy, and ultimately achieving a better clinical outcome.

The Biological Significance of Trogocytosis

Trogocytosis is the intercellular transfer of membrane and membrane-associated proteins between cells. Trogocytosis is an underappreciated phenomenon that has historically routinely been dismissed as an artefact. With a greater understanding of the process and the implications it has on biological systems, trogocytosis has the potential to become a paradigm changer. The presence on a cell of molecules they don't endogenously express can alter the biological activity of the cell and could also lead to the acquisition of new functions. To better appreciate this phenomenon, it is important to understand how these intercellular membrane exchanges influence the function and activity of the donor and the recipient cells. In this chapter, we will examine how the molecules acquired by trogocytosis influence the biology of a variety of systems including mammalian fertilization, treatment of hemolytic disease of the newborn, viral and parasitic infections, cancer immunotherapy, and immune modulation.

The role of carcinoembryonic antigen-related cell adhesion molecule 1 in cancer

The Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), also known as CD66a, is a member of the immunoglobulin superfamily. CEACAM1 was shown to be a prognostic marker in patients suffering from cancer. In this review, we summarize pre-clinical and clinical evidence linking CEACAM1 to tumorigenicity and cancer progression. Furthermore, we discuss potential CEACAM1-based mechanisms that may affect cancer biology.

The Role and Regulation of the NKG2D/NKG2D Ligand System in Cancer

The family of human NKG2D ligands (NKG2DL) consists of eight stress-induced molecules. Over 80% of human cancers express these ligands on the surface of tumour cells and/or associated stromal elements. In mice, NKG2D deficiency increases susceptibility to some types of cancer, implicating this system in immune surveillance for malignancy. However, NKG2DL can also be shed, released via exosomes and trapped intracellularly, leading to immunosuppressive effects. Moreover, NKG2D can enhance chronic inflammatory processes which themselves can increase cancer risk and progression. Indeed, tumours commonly deploy a range of countermeasures that can neutralise or even corrupt this surveillance system, tipping the balance away from immune control towards tumour progression. Consequently, the prognostic impact of NKG2DL expression in human cancer is variable. In this review, we consider the underlying biology and regulation of the NKG2D/NKG2DL system and its expression and role in a range of cancer types. We also consider the opportunities for pharmacological modulation of NKG2DL expression while cautioning that such interventions need to be carefully calibrated according to the biology of the specific cancer type.

Inhibitory innate receptors and their potential role in transplantation

The regulatory arm of the immune system plays a crucial role in maintaining immune tolerance and preventing excessive immune responses. Immune regulation comprises various regulatory cells and molecules that work together to suppress or regulate immune responses. The programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4) are examples of inhibitory receptors that counteract activating signals and fine-tune immune responses. While most of the discoveries of immune regulation have been related to T cells and the adaptive immune system, the innate arm of the immune system also has a range of inhibitory receptors that can counteract activating signals and suppress the effector immune responses. Targeting these innate inhibitory receptors may provide a complementary therapeutic approach in several immune-related conditions, including transplantation. In this review, we will explore the potential role of innate inhibitory receptors in controlling alloimmunity during solid organ transplantation.

Appearance of tuft cells during prostate cancer progression

Tuft cells are chemosensory epithelial cells that increase in number following infection or injury to robustly activate the innate immune response to alleviate or promote disease. Recent studies of castration resistant prostate cancer and its subtype, neuroendocrine prostate cancer, revealed Pou2f3+ populations in mouse models. The transcription factor Pou2f3 is a master regulator of the tuft cell lineage. We show that tuft cells are upregulated early during prostate cancer development, and their numbers increase with progression. Cancer-associated tuft cells in the mouse prostate express DCLK1, COX1, COX2, while human tuft cells express COX1. Mouse and human tuft cells exhibit strong activation of signaling pathways including EGFR and SRC-family kinases. While DCLK1 is a mouse tuft cell marker, it is not present in human prostate tuft cells. Tuft cells that appear in mouse models of prostate cancer display genotype-specific tuft cell gene expression signatures. Using bioinformatic analysis tools and publicly available datasets, we characterized prostate tuft cells in aggressive disease and highlighted differences between tuft cell populations. Our findings indicate that tuft cells contribute to the prostate cancer microenvironment and may promote development of more advanced disease. Further research is needed to understand contributions of tuft cells to prostate cancer progression.

The Wheel of p53 Helps to Drive the Immune System

The p53 tumor suppressor protein is best known as an inhibitor of the cell cycle and an inducer of apoptosis. Unexpectedly, these functions of p53 are not required for its tumor suppressive activity in animal models. High-throughput transcriptomic investigations as well as individual studies have demonstrated that p53 stimulates expression of many genes involved in immunity. Probably to interfere with its immunostimulatory role, many viruses code for proteins that inactivate p53. Judging by the activities of immunity-related p53-regulated genes it can be concluded that p53 is involved in detection of danger signals, inflammasome formation and activation, antigen presentation, activation of natural killer cells and other effectors of immunity, stimulation of interferon production, direct inhibition of virus replication, secretion of extracellular signaling molecules, production of antibacterial proteins, negative feedback loops in immunity-related signaling pathways, and immunologic tolerance. Many of these p53 functions have barely been studied and require further, more detailed investigations. Some of them appear to be cell-type specific. The results of transcriptomic studies have generated many new hypotheses on the mechanisms utilized by p53 to impact on the immune system. In the future, these mechanisms may be harnessed to fight cancer and infectious diseases.

Novel strategies for cancer immunotherapy: counter-immunoediting therapy

The advent of immunotherapy has made an indelible mark on the field of cancer therapy, especially the application of immune checkpoint inhibitors in clinical practice. Although immunotherapy has proven its efficacy and safety in some tumors, many patients still have innate or acquired resistance to immunotherapy. The emergence of this phenomenon is closely related to the highly heterogeneous immune microenvironment formed by tumor cells after undergoing cancer immunoediting. The process of cancer immunoediting refers to the cooperative interaction between tumor cells and the immune system that involves three phases: elimination, equilibrium, and escape. During these phases, conflicting interactions between the immune system and tumor cells result in the formation of a complex immune microenvironment, which contributes to the acquisition of different levels of immunotherapy resistance in tumor cells. In this review, we summarize the characteristics of different phases of cancer immunoediting and the corresponding therapeutic tools, and we propose normalized therapeutic strategies based on immunophenotyping. The process of cancer immunoediting is retrograded through targeted interventions in different phases of cancer immunoediting, making immunotherapy in the context of precision therapy the most promising therapy to cure cancer.

CEACAMS 1, 5, and 6 in disease and cancer: interactions with pathogens

The CEA family comprises 18 genes and 11 pseudogenes located at chromosome 19q13.2 and is divided into two main groups: cell surface anchored CEA-related cell adhesion molecules (CEACAMs) and the secreted pregnancy-specific glycoproteins (PSGs). CEACAMs are highly glycosylated cell surface anchored, intracellular, and intercellular signaling molecules with diverse functions, from cell differentiation and transformation to modulating immune responses associated with infection, inflammation, and cancer. In this review, we explore current knowledge surrounding CEACAM1, CEACAM5, and CEACAM6, highlight their pathological significance in the areas of cancer biology, immunology, and inflammatory disease, and describe the utility of murine models in exploring questions related to these proteins.

miR-221-5p and miR-186-5p Are the Critical Bladder Cancer Derived Exosomal miRNAs in Natural Killer Cell Dysfunction

Bladder cancer (BC) is the tenth most commonly diagnosed cancer worldwide, and its carcinogenesis mechanism has not been fully elucidated. BC is able to induce natural killer (NK) cell dysfunction and escape immune surveillance. The present study found that exosomes derived from the urinary bladder cancer cell line (T24 cell) contribute in generating NK cell dysfunction by impairing viability, and inhibiting the cytotoxicity of the NK cell on target cells. Meanwhile, T24 cell-derived exosomes inhibited the expression of the important functional receptors NKG2D, NKp30, and CD226 on NK cells as well as the secretion of perforin and granzyme-B. The critical miRNAs with high expression in T24 cell-derived exosomes were identified using high-throughput sequencing. Furthermore, following dual-luciferase reporter assay and transfection experiments, miR-221-5p and miR-186-5p were confirmed as interfering with the stability of the mRNAs of DAP10, CD96, and the perforin gene in NK cells and may be potential targets used in the therapy for BC.

The mechanisms on evasion of anti-tumor immune responses in gastric cancer

The immune system and the tumor have been at each other's throats for so long that the neoplasm has learned to avoid detection and avoid being attacked, which is called immune evasion. Malignant tumors, such as gastric cancer (GC), share the ability to evade the body's immune system as a defining feature. Immune evasion includes alterations to tumor-associated antigens (TAAs), antigen presentation mechanisms (APMs), and the tumor microenvironment (TME). While TAA and APM are simpler in nature, they both involve mutations or epigenetic regulation of genes. The TME is comprised of numerous cell types, cytokines, chemokines and extracellular matrix, any one of which might be altered to have an effect on the surrounding ecosystem. The NF-kB, MAPK, PI3K/AKT, JAK/STAT, Wnt/β-catenin, Notch, Hippo and TGF-β/Smad signaling pathways are all associated with gastric cancer tumor immune evasion. In this review, we will delineate the functions of these pathways in immune evasion.

SOX10 requirement for melanoma tumor growth is due, in part, to immune-mediated effects

Developmental factors may regulate the expression of immune modulatory proteins in cancer, linking embryonic development and cancer cell immune evasion. This is particularly relevant in melanoma because immune checkpoint inhibitors are commonly used in the clinic. SRY-box transcription factor 10 (SOX10) mediates neural crest development and is required for melanoma cell growth. In this study, we investigate immune-related targets of SOX10 and observe positive regulation of herpesvirus entry mediator (HVEM) and carcinoembryonic-antigen cell-adhesion molecule 1 (CEACAM1). Sox10 knockout reduces tumor growth in vivo, and this effect is exacerbated in immune-competent models. Modulation of CEACAM1 expression but not HVEM elicits modest effects on tumor growth. Importantly, Sox10 knockout effects on tumor growth are dependent, in part, on CD8+ T cells. Extending this analysis to samples from patients with cutaneous melanoma, we observe a negative correlation with SOX10 and immune-related pathways. These data demonstrate a role for SOX10 in regulating immune checkpoint protein expression and anti-tumor immunity in melanoma.

The Potential Role of RP105 in Regulation of Inflammation and Osteoclastogenesis During Inflammatory Diseases

Inflammatory diseases have a negative impact on bone homeostasis via exacerbated local and systemic inflammation. Bone resorbing osteoclasts are mainly derived from hematopoietic precursors and bone marrow monocytes. Induced osteoclastogenesis during inflammation, autoimmunity, metabolic diseases, and cancers is associated with bone loss and osteoporosis. Proinflammatory cytokines, pathogen-associated molecular patterns, or endogenous pathogenic factors induce osteoclastogenic differentiation by binding to the Toll-like receptor (TLR) family expressed on surface of osteoclast precursors. As a non-canonical member of the TLRs, radioprotective 105 kDa (RP105 or CD180) and its ligand, myeloid differentiation protein 1 (MD1), are involved in several bone metabolic disorders. Reports from literature had demonstrated RP105 as an important activator of B cells, bone marrow monocytes, and macrophages, which regulates inflammatory cytokines release from immune cells. Reports from literature had shown the association between RP105 and other TLRs, and the downstream signaling mechanisms of RP105 with different “signaling-competent” partners in immune cells during different disease conditions. This review is focused to summarize: (1) the role of RP105 on immune cells’ function and inflammation regulation (2) the potential regulatory roles of RP105 in different disease-mediated osteoclast activation and the underlying mechanisms, and (3) the different “signaling-competent” partners of RP105 that regulates osteoclastogenesis.

Myeloid Cells Are Enriched in Tonsillar Crypts, Providing Insight into the Host Tropism of Human Papillomavirus

Viruses are the second leading cause of cancer worldwide, and human papillomavirus (HPV)-associated head and neck cancers are increasing in incidence in the United States. HPV preferentially infects the crypts of the tonsils rather than the surface epithelium. The present study sought to characterize the unique microenvironment within the crypts to better understand the host tropism of HPV to a lymphoid-rich organ. Laser-capture microdissection of distinct anatomic areas (crypts, surface epithelium, and germinal centers) of the tonsil, coupled with transcriptional analysis and multiparameter immunofluorescence staining, was performed and demonstrated that the tonsillar crypts are enriched with myeloid populations that co-express multiple canonical and noncanonical immune checkpoints, including PD-L1, CTLA-4, HAVCR2 (TIM-3), ADORA2A, IDO1, BTLA, LGALS3, CDH1, CEACAM1, PVR, and C10orf54 (VISTA). The resident monocytes may foster a permissive microenvironment that facilitates HPV infection and persistence. Furthermore, the myeloid populations within HPV-associated tonsil cancers co-express the same immune checkpoints, providing insight into potential novel immunotherapeutic targets for HPV-associated head and neck cancers.

Natural Killer Cells: Tumor Surveillance and Signaling

Natural killer (NK) cells play a pivotal role in cancer immunotherapy due to their innate ability to detect and kill tumorigenic cells. The decision to kill is determined by the expression of a myriad of activating and inhibitory receptors on the NK cell surface. Cell-to-cell engagement results in either self-tolerance or a cytotoxic response, governed by a fine balance between the signaling cascades downstream of the activating and inhibitory receptors. To evade a cytotoxic immune response, tumor cells can modulate the surface expression of receptor ligands and additionally, alter the conditions in the tumor microenvironment (TME), tilting the scales toward a suppressed cytotoxic NK response. To fully harness the killing power of NK cells for clinical benefit, we need to understand what defines the threshold for activation and what is required to break tolerance. This review will focus on the intracellular signaling pathways activated or suppressed in NK cells and the roles signaling intermediates play during an NK cytotoxic response.

Neutrophil Extracellular Trap-Associated CEACAM1 as a Putative Therapeutic Target to Prevent Metastatic Progression of Colon Carcinoma

Neutrophils promote tumor growth and metastasis at multiple stages of cancer progression. One mechanism through which this occurs is via release of neutrophil extracellular traps (NETs). We have previously shown that NETs trap tumor cells in both the liver and the lung, increasing their adhesion and metastasis following postoperative complications. Multiple studies have since shown that NETs play a role in tumor progression and metastasis. NETs are composed of nuclear DNA-derived web-like structures decorated with neutrophil-derived proteins. However, it is unknown which, if any, of these NET-affiliated proteins is responsible for inducing the metastatic phenotype. In this study, we identify the NET-associated carcinoembryonic Ag cell adhesion molecule 1 (CEACAM1) as an essential element for this interaction. Indeed, blocking CEACAM1 on NETs, or knocking it out in a murine model, leads to a significant decrease in colon carcinoma cell adhesion, migration and metastasis. Thus, this work identifies NET-associated CEACAM1 as a putative therapeutic target to prevent the metastatic progression of colon carcinoma.

EpCAM-high liver cancer stem cells resist natural killer cell-mediated cytotoxicity by upregulating CEACAM1

BACKGROUND

Natural killer (NK) cells can recognize and kill cancer cells directly, but their activity can be attenuated by various inhibitory molecules expressed on the surface. The expression of epithelial cell adhesion molecule (EpCAM), a potential marker for cancer stem cells (CSCs), is known to be strongly associated with poor clinical outcomes in hepatocellular carcinoma (HCC). NK cells targeting CSCs may be a promising strategy for anti-tumor therapy, but little is known about how they respond to EpCAMhigh CSCs in HCC.

METHODS

EpCAM expression was assessed by immunohistochemistry in 280 human HCC tissues obtained from curative surgery. To investigate the functional activity of NK cells against liver CSCs, EpCAMhigh and EpCAMlow Huh-7 cells were sorted by flow cytometry. The functional role of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), which is related to NK cells, was determined by in vitro co-culture of NK cells and hepatoma cells using Hepa1-6 mouse hepatoma cells, as well as in vivo experiments using C57/BL6 mice.

RESULTS

The frequency of recurrence after curative surgery was higher in patients with positive EpCAM expression than in those with negative EpCAM expression. In subsequent analysis based on the anatomical location of EpCAM expression, patients with peritumoral EpCAM expression showed worse prognosis than those with pantumoral EpCAM expression. Co-culture experiments demonstrated that CEACAM1 was upregulated on the surface of EpCAMhigh HCC cells, resulting in resistance to NK cell-mediated cytotoxicity. Inversely, silencing CEACAM1 restored cytotoxicity of NK cells against EpCAMhigh Huh-7 cells. Moreover, neutralizing CEACAM1 on the NK cell surface enhanced killing of Huh-7 cells, suggesting that homophilic interaction of CEACAM1 is responsible for attenuated NK cell-mediated killing of CEACAM1high cells. In mouse experiments with Hepa1-6 cells, EpCAMhigh Hepa1-6 cells formed larger tumors and showed higher CEACAM1 expression after NK cell depletion. NK-mediated cytotoxicity was enhanced after blocking CEACAM1 expression using the anti-CEACAM1 antibody, thereby facilitating tumor regression. Moreover, CEACAM1 expression positively correlated with EpCAM expression in human HCC tissues, and serum CEACAM1 levels were also significantly higher in patients with EpCAM+ HCC.

CONCLUSION

Our data demonstrated that EpCAMhigh liver CSCs resist NK cell-mediated cytotoxicity by upregulation of CEACAM1 expression.

Low-Dose Gemcitabine Treatment Enhances Immunogenicity and Natural Killer Cell-Driven Tumor Immunity in Lung Cancer

Gemcitabine has been used as first-line chemotherapy against lung cancer, but many patients experience cancer recurrence. Activation of anti-tumor immunity in vivo has become an important way to prevent recurrence. Anti-tumor immune responses are often dependent upon the immunogenicity of tumors. In our study, we observed that low-dose gemcitabine treatment enhanced the immunogenicity of lung cancer by increasing the exposure of calreticulin, high mobility group box 1, and upregulating expression of NKG2D ligands. Further studies demonstrated that low-dose gemcitabine treatment increased interferon-γ expression and NK-cell activation in mice. Low-dose gemcitabine treatment was sufficient for inhibiting tumor growth with few side effects in vivo. These data suggest that low-dose gemcitabine-induced immunochemotherapy activated antitumor immunity in immunocompetent patients.

The Monoclonal Antibody NEO-201 Enhances Natural Killer Cell Cytotoxicity Against Tumor Cells Through Blockade of the Inhibitory CEACAM5/CEACAM1 Immune Checkpoint Pathway

Background: Natural killer (NK) cells are essential to innate immunity and participate in cancer immune surveillance. Heterophilic interactions between carcinoembryonic antigen (CEA) on tumor cells and carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) on NK cells inhibit NK cell cytotoxicity against tumor cells. NEO-201 is a humanized IgG1 monoclonal antibody that recognizes members of CEACAM family, expressed specifically on a variety of human carcinoma cell lines and tumor tissues. This investigation was designed to determine whether the binding of NEO-201 with CEACAM5 on tumor cells can block the CEACAM5/CEACAM1 interaction to restore antitumor cytotoxicity of NK cells. Materials and Methods: In vitro functional assays, using various human tumor cell lines as target cells and NK-92 cells as effectors, were conducted to assess the ability of NEO-201 to block the interaction between CEACAM5 on tumor cells and CEACAM1 on NK cells to enhance the in vitro killing of tumor cells by NK-92. NK-92 cells were used as a model of direct NK killing of tumor cells because they lack antibody-dependent cellular cytotoxicity activity. Results: Expression profiling revealed that various human carcinoma cell lines expressed different levels of CEACAM5⁺ and NEO-201⁺ cells. Addition of NEO-201 significantly enhanced NK-92 cell cytotoxicity against highly CEACAM5⁺/NEO-201⁺ expressing tumor cells, suggesting that its activity is correlated with the level of CEACAM5⁺/NEO-201⁺ expression. Conclusions: These findings demonstrate that NEO-201 can block the interaction between CEACAM5 on tumor cells and CEACAM1 on NK cells to reverse CEACAM1-dependent inhibition of NK cytotoxicity.

CEACAM1 structure and function in immunity and its therapeutic implications

The type I membrane protein receptor carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) distinctively exhibits significant alternative splicing that allows for tunable functions upon homophilic binding. CEACAM1 is highly expressed in the tumor environment and is strictly regulated on lymphocytes such that its expression is restricted to activated cells where it is now recognized to function in tolerance pathways. CEACAM1 is also an important target for microbes which have co-opted these attributes of CEACAM1 for the purposes of invading the host and evading the immune system. These properties, among others, have focused attention on CEACAM1 as a unique target for immunotherapy in autoimmunity and cancer. This review examines recent structural information derived from the characterization of CEACAM1:CEACAM1 interactions and heterophilic modes of binding especially to microbes and how this relates to CEACAM1 function. Through this, we aim to provide insights into targeting CEACAM1 for therapeutic intervention.

Size Matters: The Functional Role of the CEACAM1 Isoform Signature and Its Impact for NK Cell-Mediated Killing in Melanoma

Malignant melanoma is the most aggressive and treatment resistant type of skin cancer. It is characterized by continuously rising incidence and high mortality rate due to its high metastatic potential. Various types of cell adhesion molecules have been implicated in tumor progression in melanoma. One of these, the carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), is a multi-functional receptor protein potentially expressed in epithelia, endothelia, and leukocytes. CEACAM1 often appears in four isoforms differing in the length of their extracellular and intracellular domains. Both the CEACAM1 expression in general, and the ratio of the expressed CEACAM1 splice variants appear very dynamic. They depend on both the cell activation stage and the cell growth phase. Interestingly, normal melanocytes are negative for CEACAM1, while melanomas often show high expression. As a cell–cell communication molecule, CEACAM1 mediates the direct interaction between tumor and immune cells. In the tumor cell this interaction leads to functional inhibitions, and indirectly to decreased cancer cell immunogenicity by down-regulation of ligands of the NKG2D receptor. On natural killer (NK) cells it inhibits NKG2D-mediated cytolysis and signaling. This review focuses on novel mechanistic insights into CEACAM1 isoforms for NK cell-mediated immune escape mechanisms in melanoma, and their clinical relevance in patients suffering from malignant melanoma.

CEACAM1 regulates the IL-6 mediated fever response to LPS through the RP105 receptor in murine monocytes

Background

Systemic inflammation and the fever response to pathogens are coordinately regulated by IL-6 and IL-1β. We previously showed that CEACAM1 regulates the LPS driven expression of IL-1β in murine neutrophils through its ITIM receptor.

Results

We now show that the prompt secretion of IL-6 in response to LPS is regulated by CEACAM1 expression on bone marrow monocytes. Ceacam1^−/− mice over-produce IL-6 in response to an i.p. LPS challenge, resulting in prolonged surface temperature depression and overt diarrhea compared to their wild type counterparts. Intraperitoneal injection of a ⁶⁴Cu-labeled LPS, PET imaging agent shows confined localization to the peritoneal cavity, and fluorescent labeled LPS is taken up by myeloid splenocytes and muscle endothelial cells. While bone marrow monocytes and their progenitors (CD11b⁺Ly6G⁻) express IL-6 in the early response (< 2 h) to LPS in vitro, these cells are not detected in the bone marrow after in vivo LPS treatment perhaps due to their rapid and complete mobilization to the periphery. Notably, tissue macrophages are not involved in the early IL-6 response to LPS. In contrast to human monocytes, TLR4 is not expressed on murine bone marrow monocytes. Instead, the alternative LPS receptor RP105 is expressed and recruits MD1, CD14, Src, VAV1 and β-actin in response to LPS. CEACAM1 negatively regulates RP105 signaling in monocytes by recruitment of SHP-1, resulting in the sequestration of pVAV1 and β-actin from RP105.

Conclusion

This novel pathway and regulation of IL-6 signaling by CEACAM1 defines a novel role for monocytes in the fever response of mice to LPS.

Electronic supplementary material

The online version of this article (10.1186/s12865-019-0287-y) contains supplementary material, which is available to authorized users.

Carcinoembryonic antigen cell adhesion molecule 1 inhibits the antitumor effect of neutrophils in tongue squamous cell carcinoma

Carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1), a transmembrane glycoprotein, has multiple functions. In tongue squamous cell carcinoma (TSCC), CEACAM1 overexpression is correlated with neutrophil infiltration, and both are associated with poor clinical outcomes. However, the mechanism underlying CEACAM1's effect on neutrophil function in TSCC remains unclear. We cocultured tongue carcinoma cells overexpressing CEACAM1‐4L, CEACAM1‐4S and differentiated HL‐60 cells. This significantly upregulated the expression of MMP‐9, interleukin 8, and VEGF‐A in the differentiated HL‐60 cells and downregulated the expression of TNF‐α, relative to vector and blank control groups (P < 0.05). Additionally, CEACAM1 overexpression in tongue carcinoma cells weakened the cytotoxicity of differentiated HL‐60 cells in the coculture system (P < 0.05). Thus, CEACAM1 expression in TSCC may induce an antitumor to protumor transformation of neutrophils. We performed qRT‐PCR and ELISA to evaluate the underlying mechanism, and found that CEACAM1 expression in tongue carcinoma cells upregulated transforming growth factor β1 (TGF‐β1) expression, while blocking of TGF‐β1 inhibited the neutrophils’ changes in the coculture system. Immunohistochemical analysis of clinical specimens revealed strong expression of TGF‐β1 protein in TSCC. TGF‐β1 expression was positively correlated with CEACAM1 expression, lymph node metastasis, and tumor recurrence. Double immunofluorescence results revealed colocalization of CEACAM1 and TGF‐β1 protein in TSCC. A xenograft nude mouse model revealed that CEACAM1 overexpression in TSCC promoted tumor formation and growth, and was associated with more neutrophils infiltration. Our results indicate that CEACAM1 overexpression in TSCC may induce transformation of neutrophils from antitumor to protumor type via TGF‐β1, which may further promote tumor progression.

Prognostic implication of CEACAM1 expression in squamous cell carcinoma of the larynx: Pilot study

BACKGROUND

CEACAM1, a valuable biomarker for several cancers, have remained unexplored up to the present in laryngeal squamous cell carcinoma (LSCC). We aimed to examine CEACAM1 expression and evaluate its combinational clinical significance for the diagnosis or prognosis and treatment decision making in LSCC.

METHODS

CEACAM1 expression was assessed by immunohistochemistry in 54 LSCCs and evaluate its correlation with clinical and histopathological features.

RESULTS

CEACAM subtype 1 (CEACAM1) expression was positive in 50% of the cases. No significant difference was observed in relation to age, gender, tumor size, and tumor stage. CEACAM1 expression correlated with tumor grade, development of local recurrence, node and distant metastasis. Kaplan-Meier survival curves showed that CEACAM1 staining was inversely correlated with both overall and disease-specific 5-year survival.

CONCLUSIONS

Our study is the first to demonstrate that CEACAM1 expression is associated with an adverse prognosis in LSCC. CEACAM1 is a valuable biomarker and a promising therapeutic target in LSCC.

Deep sequencing of primary human lung epithelial cells challenged with H5N1 influenza virus reveals a proviral role for CEACAM1

Current prophylactic and therapeutic strategies targeting human influenza viruses include vaccines and antivirals. Given variable rates of vaccine efficacy and antiviral resistance, alternative strategies are urgently required to improve disease outcomes. Here we describe the use of HiSeq deep sequencing to analyze host gene expression in primary human alveolar epithelial type II cells infected with highly pathogenic avian influenza H5N1 virus. At 24 hours post-infection, 623 host genes were significantly upregulated, including the cell adhesion molecule CEACAM1. H5N1 virus infection stimulated significantly higher CEACAM1 protein expression when compared to influenza A PR8 (H1N1) virus, suggesting a key role for CEACAM1 in influenza virus pathogenicity. Furthermore, silencing of endogenous CEACAM1 resulted in reduced levels of proinflammatory cytokine/chemokine production, as well as reduced levels of virus replication following H5N1 infection. Our study provides evidence for the involvement of CEACAM1 in a clinically relevant model of H5N1 infection and may assist in the development of host-oriented antiviral strategies.

On the Dual Role of Carcinoembryonic Antigen-Related Cell Adhesion Molecule 1 (CEACAM1) in Human Malignancies

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a glycoprotein belonging to the carcinoembryonic antigen (CEA) family that is expressed on a wide variety of cells and holds a complex role in inflammation through its alternate splicing and generation of various isoforms, mediating intricate mechanisms of modulation and dysregulation. Initially regarded as a tumor suppressor as its expression shows considerable downregulation within the epithelia in the early phases of many solid cancers, CEACAM1 has been linked lately to the progression of malignancy and metastatic spread as various papers point to its role in tumor progression, angiogenesis, and invasion. We reviewed the literature and discussed the various expression patterns of CEACAM1 in different types of tumors, describing its structure and general biologic functions and emphasizing the most significant findings that link this molecule to poor prognosis. The importance of understanding the role of CEACAM1 in cell transformation stands not only in this adhesion molecule's value as a prognostic factor but also in its promising premise as a potential new molecular target that could be exploited as a specific cancer therapy.

CEACAM1 in Liver Injury, Metabolic and Immune Regulation

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a transmembrane glycoprotein that is expressed on epithelial, endothelial and immune cells. CEACAM1 is a differentiation antigen involved in the maintenance of epithelial polarity that is induced during hepatocyte differentiation and liver regeneration. CEACAM1 regulates insulin sensitivity by promoting hepatic insulin clearance, and controls liver tolerance and mucosal immunity. Obese insulin-resistant humans with non-alcoholic fatty liver disease manifest loss of hepatic CEACAM1. In mice, deletion or functional inactivation of CEACAM1 impairs insulin clearance and compromises metabolic homeostasis which initiates the development of obesity and hepatic steatosis and fibrosis with other features of non-alcoholic steatohepatitis, and adipogenesis in white adipose depot. This is followed by inflammation and endothelial and cardiovascular dysfunctions. In obstructive and inflammatory liver diseases, soluble CEACAM1 is shed into human bile where it can serve as an indicator of liver disease. On immune cells, CEACAM1 acts as an immune checkpoint regulator, and deletion of Ceacam1 gene in mice causes exacerbation of inflammation and hyperactivation of myeloid cells and lymphocytes. Hence, hepatic CEACAM1 resides at the central hub of immune and metabolic homeostasis in both humans and mice. This review focuses on the regulatory role of CEACAM1 in liver and biliary tract architecture in health and disease, and on its metabolic role and function as an immune checkpoint regulator of hepatic inflammation.

The Paradoxical Role of NKG2D in Cancer Immunity

The activating receptor NKG2D and its ligands are recognized as a potent immune axis that controls tumor growth and microbial infections. With regards to cancer surveillance, various studies have demonstrated the antitumor function mediated by NKG2D on natural killer cells and on conventional and unconventional T cells. The use of NKG2D-deficient mice established the importance of NKG2D in delaying tumor development in transgenic mouse models of cancer. However, we recently demonstrated an unexpected, flip side to this coin, the ability for NKG2D to contribute to tumor growth in a model of inflammation-driven liver cancer. With a focus on the liver, here, we review current knowledge of NKG2D-mediated tumor surveillance and discuss evidence supporting a dual role for NKG2D in cancer immunity. We postulate that in certain advanced cancers, expression of ligands for NKG2D can drive cancer progression rather than rejection. We propose that the nature of the microenvironment within and surrounding tumors impacts the outcome of NKG2D activation. In a form of autoimmune attack, NKG2D promotes tissue damage, mostly in the inflamed tissue adjacent to the tumor, facilitating tumor progression while being ineffective at rejecting transformed cells in the tumor bed.

New Insights Into the Regulation of Natural-Killer Group 2 Member D (NKG2D) and NKG2D-Ligands: Endoplasmic Reticulum Stress and CEA-Related Cell Adhesion Molecule 1

Natural-killer group 2 member D (NKG2D) is a well-characterized activating receptor expressed by natural killer (NK) cells, NKT cells, activated CD8⁺ T cells, subsets of γδ⁺ T cells, and innate-like T cells. NKG2D recognizes multiple ligands (NKG2D-ligands) to mount an innate immune response against stressed, transformed, or infected cells. NKG2D-ligand surface expression is tightly restricted on healthy cells through transcriptional and post-transcriptional mechanisms, while transformed or infected cells express the ligands as a danger signal. Recent studies have revealed that unfolded protein response pathways during endoplasmic reticulum (ER) stress result in upregulation of ULBP-related protein via the protein kinase RNA-like ER kinase-activating factor 4-C/EBP homologous protein (PERK-ATF4-CHOP) pathway, which can be linked to the pathogenesis of autoimmune diseases. Transformed cells, however, possess mechanisms to escape NKG2D-mediated immune surveillance, such as upregulation of carcinoembryonic antigen (CEA)-related cell adhesion molecule 1 (CEACAM1), a negative regulator of NKG2D-ligands. In this review, we discuss mechanisms of NKG2D-ligand regulation, with a focus on newly discovered mechanisms that promote NKG2D-ligand expression on epithelial cells, including ER stress, and mechanisms that suppress NKG2D-ligand-mediated killing of cancer cells, namely by co-expression of CEACAM1.

Assessing the Impact of Targeting CEACAM1 in Head and Neck Squamous Cell Carcinoma

Objective In conjunction with advances made in cytotoxic chemotherapy, radiation, and surgery, immunotherapy has emerged as a fourth modality of treatment for head and neck squamous cell carcinoma (HNSCC). Understanding the mechanisms by which HNSCC evades immune-mediated control will aid in the development of new therapies to augment an antitumor immune response. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a cell surface receptor that is expressed on malignant cells and lymphocytes such as natural killer (NK) cells. We sought to determine whether tumor-derived CEACAM1 inhibits NK cell cytotoxicity and whether blockade of CEACAM1 restores antitumor immunity. Study Design In vitro HNSCC cell line study. Setting Research laboratory. Subject and Methods We utilized a real-time cell analyzer to assess NK cell cytotoxicity against an oral squamous cell carcinoma cell line after modulating CEACAM1 expression by cytokines and shRNA knockdown of CEACAM1 expression. Results NK cells and HNSCC cells both demonstrated cytokine-inducible expression of CEACAM1. Coincubation of NK cells and HNSCC cells resulted in the upregulation of CEACAM1 on the tumor cells. When compared with CEACAM1^- cells, CEACAM1⁺ tumor cells exhibited increased cell growth and increased size and number of organoids in 3-dimensional culture. Notably, CEACAM1⁺ HNSCC cells were more resistant to NK cell-mediated killing, but the inhibited expression of CEACAM1 by an shRNA construct restored NK cell cytotoxicity. Conclusion Together, these data indicate that CEACAM1 acts as an inducible checkpoint molecule, and they support the idea that targeting CEACAM1 could serve as a novel immunotherapy approach in HNSCC.

Abnormal expression of circulating and tumor-infiltrating carcinoembryonic antigen-related cell adhesion molecule 1 in patients with glioma

Glioma, the most prevalent primary tumor of the central nervous system, is known to evade immune surveillance and escape immune attacks by inducing immunosuppression. The homophilic interactions of the carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) serve a critical function in immunoregulation. In the present study, the expression levels of CEACAM1 in peripheral blood mononuclear cells and tumor-infiltrating lymphocytes (TILs) from patients with gliomas were assessed. Furthermore, associations between CEACAM1 expression and multiple clinicopathological characteristics in patients with gliomas were analyzed. The results of the present study suggested that the expression of CEACAM1 in circulating T cells was markedly increased in patients with gliomas compared with control subjects, and was further increased in TILs. Patients with high-grade gliomas [World Health Organization (WHO) grade III–IV] demonstrated a significantly increased expression of CEACAM1 on T cells compared with those with low-grade gliomas (WHO grade I–II). Furthermore, the expression of CEACAM1 on T cells was negatively correlated with the Karnofsky score and the plasma level of interferon-γ in patients with gliomas. Immunohistochemical analysis revealed that the expression levels of CEACAM1 in high-grade glioma tissues (WHO grade III–IV) were increased compared with the expression levels in the controls, and were associated with the expression of CEACAM1 in TILs. In summary, the results of the present study indicate that homophilic interactions of CEACAM1 may participate in the progression and development of gliomas through their negative regulatory effects on T cells. Thus, CEACAM1 may be a promising candidate for targeted glioma immunotherapy.

EphA2 signaling is impacted by carcinoembryonic antigen cell adhesion molecule 1-L expression in colorectal cancer liver metastasis in a cell context-dependent manner

We have shown that carcinoembryonic antigen cell adhesion molecule 1 long isoform (CEACAM1-L) expression in MC38 metastatic colorectal cancer (CRC) cells results in liver metastasis inhibition via CCL2 and STAT3 signaling. But other molecular mechanisms orchestrating CEACAM1-L-mediated metastasis inhibition remain to be defined. We screened a panel of mouse and human CRC cells and evaluated their metastatic outcome after CEACAM1 overexpression or downregulation. An unbiased transcript profiling and a phospho-receptor tyrosine kinase screen comparing MC38 CEACAM1-L-expressing and non-expressing (CT) CRC cells revealed reduced ephrin type-A receptor 2 (EPHA2) expression and activity. An EPHA2-specific inhibitor reduced EPHA2 downstream signaling in CT cells similar to that in CEACAM1-L cells with decreased proliferation and migration. Human CRC patients exhibiting high CEACAM1 in combination with low EPHA2 expression benefited from longer time to first recurrence/metastasis compared to those with high EPHA2 expression. With the added interaction of CEACAM6, we denoted that CEACAM1 high- and EPHA2 low-expressing patient samples with lower CEACAM6 expression also exhibited a longer time to first recurrence/metastasis. In HT29 human CRC cells, down-regulation of CEACAM1 along with CEA and CEACAM6 up-regulation led to higher metastatic burden. Overall, CEACAM1-L expression in poorly differentiated CRC can inhibit liver metastasis through cell context-dependent EPHA2-mediated signaling. However, CEACAM1’s role should be considered in the presence of other CEACAM family members.

Correlation between immunohistochemical staining of CEACAM1 and clinicopathological findings in oral pre-neoplastic lesions and squamous cell carcinoma

Squamous cell carcinoma of the oral cavity represents the sixth most common cancer worldwide and it is often preceded by pre-neoplastic lesions. Sometimes it is still difficult for pathologists to make objective differential diagnoses only on histological characteristics. Tumorigenesis is accompanied by altered expression of cell adhesion molecules, like carcinoembryonic antigen cell adhesion molecule (CEACAM)1. We wanted to investigative CEACAM1 in oral dysplastic lesions, carcinoma in situ (CIS) and oral squamous cell carcinoma (OSCC). We examined immunohistochemical CEACAM1 expression in 50 OSCC, 30 oral CIS and 40 pre-neoplastic lesions and assessed its correlation with clinical and pathological parameters. CEACAM1 was not expressed in normal mucosa, significantly expressed in CIS while it was negative in all the dysplastic lesions. In OSCC, high CEACAM1 expression was associated with tumor grade and inversely correlated with both overall and disease-specific 5-year survival. We showed that CEACAM1 expression is very dynamic: absent in dysplastic lesions, up-regulated in CIS and OSCC. We suggest that CEACAM1 could be a prognostic marker of OSCC and oral CIS. Our most important finding was that it could help pathologists diagnosing oral carcinoma in situ.

Intestinal epithelial cell endoplasmic reticulum stress promotes MULT1 up-regulation and NKG2D-mediated inflammation

Hosomi et al. show that intestinal epithelial cell–specific deletion of X-box–binding protein 1, an unfolded protein response–related transcription factor, results in CHOP-dependent increased expression of specific natural killer group 2 member D (NKG2D) ligands. This activates NKG2D-expressing intraepithelial group 1 ILCs and promotes small intestinal inflammation.

Endoplasmic reticulum (ER) stress is commonly observed in intestinal epithelial cells (IECs) and can, if excessive, cause spontaneous intestinal inflammation as shown by mice with IEC-specific deletion of X-box–binding protein 1 (Xbp1), an unfolded protein response–related transcription factor. In this study, Xbp1 deletion in the epithelium (Xbp1^ΔIEC) is shown to cause increased expression of natural killer group 2 member D (NKG2D) ligand (NKG2DL) mouse UL16-binding protein (ULBP)–like transcript 1 and its human orthologue cytomegalovirus ULBP via ER stress–related transcription factor C/EBP homology protein. Increased NKG2DL expression on mouse IECs is associated with increased numbers of intraepithelial NKG2D-expressing group 1 innate lymphoid cells (ILCs; NK cells or ILC1). Blockade of NKG2D suppresses cytolysis against ER-stressed epithelial cells in vitro and spontaneous enteritis in vivo. Pharmacological depletion of NK1.1⁺ cells also significantly improved enteritis, whereas enteritis was not ameliorated in Recombinase activating gene 1^−/−;Xbp1^ΔIEC mice. These experiments reveal innate immune sensing of ER stress in IECs as an important mechanism of intestinal inflammation.

CEACAM1 as a multi-purpose target for cancer immunotherapy

CEACAM1 is an extensively studied cell surface molecule with established functions in multiple cancer types, as well as in various compartments of the immune system. Due to its multi-faceted role as a recently appreciated immune checkpoint inhibitor and tumor marker, CEACAM1 is an attractive target for cancer immunotherapy. Herein, we highlight CEACAM1's function in various immune compartments and cancer types, including in the context of metastatic disease. This review outlines CEACAM1's role as a therapeutic target for cancer treatment in light of these properties.

CEACAM1 long isoform has opposite effects on the growth of human mastocytosis and medullary thyroid carcinoma cells

Carcinoembryonic antigen‐related cell adhesion molecule 1 (CEACAM1) is expressed in a number of tumor cell types. The immunoreceptor tyrosine‐based inhibitory motif (ITIM)‐containing isoforms of this molecule which possess a long cytoplasmic tail (CEACAM1‐L) generally play inhibitory roles in cell function by interacting with Src homology 2 domain‐containing tyrosine phosphatase (SHP)‐1 and/or SHP‐2. Src family kinases (SFKs) are also known to bind to and phosphorylate CEACAM1‐L isoforms. Here, we report that CEACAM1 was uniquely expressed at high levels in both human neoplastic mast cells (mastocytosis) and medullary thyroid carcinoma cell (MTC) lines, when compared with their expression in nonneoplastic mast cells or nonneoplastic C cells. This expression was mainly derived from CEACAM1‐L isoforms based upon assessment of CEACAM1 mRNA expression. CEACAM1 knockdown upregulated cell growth of HMC1.2 cells harboring KIT mutations detected in clinical mastocytosis, whereas downregulated the growth of TT cells harboring RET mutations detected in clinical MTCs. Immunoblotting, ELISA and immunoprecipitaion analysis showed that activated SHP‐1 is preferentially associated with CEACAM1 in HMC1.2 cells harboring KIT mutations, whereas Src family kinases (SFKs) are preferentially associated with CEACAM1 in TT cells harboring RET mutations. These studies suggest that the dominantly interacting proteins SHP1 or SFK determine whether CEACAM1‐L displays a positive or negative role in tumor cells.

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.

Glycosylation Alters Dimerization Properties of a Cell-surface Signaling Protein, Carcinoembryonic Antigen-related Cell Adhesion Molecule 1 (CEACAM1)

Human carcinoembryonic antigen-related cell adhesion molecule 1 (C?/Au: EACAM1) is a cell-surface signaling molecule involved in cell adhesion, proliferation, and immune response. It is also implicated in cancer angiogenesis, progression, and metastasis. This diverse set of effects likely arises as a result of the numerous homophilic and heterophilic interactions that CEACAM1 can have with itself and other molecules. Its N-terminal Ig variable (IgV) domain has been suggested to be a principal player in these interactions. Previous crystal structures of the β-sandwich-like IgV domain have been produced using Escherichia coli-expressed material, which lacks native glycosylation. These have led to distinctly different proposals for dimer interfaces, one involving interactions of ABED β-strands and the other involving GFCC'C″ β-strands, with the former burying one prominent glycosylation site. These structures raise questions as to which form may exist in solution and what the effect of glycosylation may have on this form. Here, we use NMR cross-correlation measurements to examine the effect of glycosylation on CEACAM1-IgV dimerization and use residual dipolar coupling (RDC) measurements to characterize the solution structure of the non-glycosylated form. Our findings demonstrate that even addition of a single N-linked GlcNAc at potential glycosylation sites inhibits dimer formation. Surprisingly, RDC data collected on E. coli expressed material in solution indicate that a dimer using the non-glycosylated GFCC'C″ interface is preferred even in the absence of glycosylation. The results open new questions about what other factors may facilitate dimerization of CEACAM1 in vivo, and what roles glycosylation may play in heterophylic interactions.

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.

Kaposi's Sarcoma-Associated Herpesvirus Interleukin-6 Modulates Endothelial Cell Movement by Upregulating Cellular Genes Involved in Migration

Kaposi’s sarcoma-associated herpesvirus (KSHV) is the causative agent of human Kaposi’s sarcoma, a tumor that arises from endothelial cells, as well as two B cell lymphoproliferative diseases, primary effusion lymphoma and multicentric Castleman’s disease. KSHV utilizes a variety of mechanisms to evade host immune responses and promote cellular transformation and growth in order to persist for the life of the host. A viral homolog of human interleukin-6 (hIL-6) named viral interleukin-6 (vIL-6) is encoded by KSHV and expressed in KSHV-associated cancers. Similar to hIL-6, vIL-6 is secreted, but the majority of vIL-6 is retained within the endoplasmic reticulum, where it can initiate functional signaling through part of the interleukin-6 receptor complex. We sought to determine how intracellular vIL-6 modulates the host endothelial cell environment by analyzing vIL-6’s impact on the endothelial cell transcriptome. vIL-6 significantly altered the expression of many cellular genes associated with cell migration. In particular, vIL-6 upregulated the host factor carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) at the protein and message levels. CEACAM1 has been implicated in tumor invasion and metastasis and promotes migration and vascular remodeling in endothelial cells. We report that vIL-6 upregulates CEACAM1 by a STAT3-dependent mechanism and that CEACAM1 promotes vIL-6-mediated migration. Furthermore, latent and de novo KSHV infections of endothelial cells also induce CEACAM1 expression. Collectively, our data suggest that vIL-6 modulates endothelial cell migration by upregulating the expression of cellular factors, including CEACAM1.

Kaposi’s sarcoma-associated herpesvirus (KSHV) is linked with the development of three human malignancies, Kaposi’s sarcoma, multicentric Castleman’s disease, and primary effusion lymphoma. KSHV expresses many factors that enable the virus to manipulate the host environment in order to persist and induce disease. The viral interleukin-6 (vIL-6) produced by KSHV is structurally and functionally homologous to the human cytokine interleukin-6, except that vIL-6 is secreted slowly and functions primarily from inside the host cell. To investigate the unique intracellular role of vIL-6, we analyzed the impact of vIL-6 on endothelial cell gene expression. We report that vIL-6 significantly alters the expression of genes associated with cell movement, including that for CEACAM1. The gene for CEACAM1 was upregulated by vIL-6 and by latent and primary KSHV infection and promotes vIL-6-mediated endothelial cell migration. This work advances the field’s understanding of vIL-6 function and its contribution to KSHV pathogenesis.

MITF is a critical regulator of the carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) in malignant melanoma

The multifunctional Ig-like carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is neo-expressed in the majority of malignant melanoma lesions. CEACAM1 acts as a driver of tumor cell invasion, and its expression correlates with poor patient prognosis. Despite its importance in melanoma progression, how CEACAM1 expression is regulated is largely unknown. Here, we show that CEACAM1 expression in melanoma cell lines and melanoma tissue strongly correlates with that of the microphthalmia-associated transcription factor (MITF), a key regulator of melanoma proliferation and invasiveness. MITF is revealed as a direct and positive regulator for CEACAM1 expression via binding to an M-box motif located in the CEACAM1 promoter. Taken together, our study provides novel insights into the regulation of CEACAM1 expression and suggests an MITF-CEACAM1 axis as a potential determinant of melanoma progression.

CEACAM1-3S Drives Melanoma Cells into NK Cell-Mediated Cytolysis and Enhances Patient Survival

CEACAM1 is a widely expressed multifunctional cell-cell adhesion protein reported to serve as a poor prognosis marker in melanoma patients. In this study, we examine the functional and clinical contributions of the four splice isoforms of CEACAM1. Specifically, we present in vitro and in vivo evidence that they affect melanoma progression and immune surveillance in a negative or positive manner that is isoform specific in action. In contrast with isoforms CEACAM1-4S and CEACAM1-4L, expression of isoforms CEACAM1-3S and CEACAM1-3L is induced during disease progression shown to correlate with clinical stage. Unexpectedly, overall survival was prolonged in patients with advanced melanomas expressing CEACAM1-3S. The favorable effects of CEACAM1-3S related to enhanced immunogenicity, which was mediated by cell surface upregulation of NKG2D receptor ligands, thereby sensitizing melanoma cells to lysis by natural killer cells. Conversely, CEACAM1-4L downregulated cell surface levels of the NKG2D ligands MICA and ULBP2 by enhanced shedding, thereby promoting malignant character. Overall, our results define the splice isoform-specific immunomodulatory and cell biologic functions of CEACAM1 in melanoma pathogenesis.

Carcinoembryonic antigen-related cell adhesion molecules (CEACAM) 1, 5 and 6 as biomarkers in pancreatic cancer

Background

Aim of this study was to assess the biological function in tumor progression and metastatic process carcinoembryonic antigen-related cell adhesion molecules (CEACAM) 1, 5 and 6 in pancreatic adenocarcinoma (PDAC).

Experimental Design

CEACAM knock down cells were established and assessed in vitro and in a subcutaneous and intraperitoneal mouse xenograft model. Tissue and serum expression of patients with PDAC were assessed by immunohistochemistry (IHC) and by enzyme linked immunosorbent assays.

Results

Presence of lymph node metastasis was correlated with CEACAM 5 and 6 expression (determined by IHC) and tumor recurrence exclusively with CEACAM 6. Patients with CEACAM 5 and 6 expression showed a significantly shortened OS in Kaplan-Meier survival analyses. Elevated CEACAM6 serum values showed a correlation with distant metastasis and. Survival analysis revealed a prolonged OS for patients with low serum CEACAM 1 values. In vitro proliferation and migration capacity was increased in CEACAM knock down PDAC cells, however, mice inoculated with CEACAM knock down cells showed a prolonged overall-survival (OS). The number of spontaneous pulmonary metastasis was increased in the CEACAM knock down group.

Conclusion

The effects mediated by CEACAM expression in PDAC are complex, though overexpression is correlated with loco-regional aggressive tumor growth. However, loss of CEACAM can be considered as a part of epithelial-mesenchymal transition and is therefore of rather importance in the process of distant metastasis.

Immunobiology and conflicting roles of the human NKG2D lymphocyte receptor and its ligands in cancer

Cancers adopt diverse strategies to safeguard their survival, which often involve blinding or incapacitating the immune response, thereby gaining battleground advantage against the host. In immune responses against cancer, an important stimulatory lymphocyte receptor is NKG2D because the tumor-associated expression of its ligands promotes destruction of malignant cells. However, with advanced human cancers profound changes unfold wherein NKG2D and its ligands are targeted or exploited for immune evasion and suppression. This negative imprinting on the immune system may be accompanied by another functional state wherein cancer cells coopt expression of NKG2D to complement the presence of its ligands for self-stimulation of tumor growth and presumably malignant progression. This review emphasizes these conflicting functional dynamics at the immunity-cancer biology interface in humans, within an overview of the immunobiology of NKG2D and mechanisms underlying the regulation of its ligands in cancer, with reference to instructive clinical observations and translational approaches.

Neutrophils infiltration in the tongue squamous cell carcinoma and its correlation with CEACAM1 expression on tumor cells

OBJECTIVE

The present study aimed to explore the clinical significance of neutrophils infiltration and carcinoembryonic antigen related cell adhesion molecule 1 (CEACAM1) expression in the tongue squamous cell carcinoma (TSCC), and to probe the possible relationship between them.

MATERIALS AND METHODS

Tissue microarray and immunohistochemistry were used to detect neutrophils density and CEACAM1 expression in 74 cases of primary TSCC specimens and 17 cases of corresponding peritumoral tissues. The relationship of CEACAM1 expression and neutrophils density with clinicopathologic parameters and cancer-related survival of TSCC patients were evaluated. The correlation between CEACAM1 expression and neutrophils density was also evaluated. Real-time quantitative transcription polymerase chain reaction (qRT-PCR) was used to explore the possible molecular mechanisms between CEACAM1 expression and neutrophils infiltration.

RESULTS

Immunohistochemistry evaluation revealed that there was more neutrophils infiltration in TSCC tissues than in peritumoral tissues. High neutrophil density was associated with LN metastasis (P=0.01), higher clinical stage (P=0.037) and tumor recurrence (P=0.024). CEACAM1 overexpression was also associated with lymph node metastasis (P=0.000) and higher clinical stage (P=0.001). Survival analysis revealed that both neutrophils infiltration and CEACAM1 overexpression were associated with poorer cancer-related survival of TSCC patients (P<0.05), and neutrophils infiltration was an independent prognostic factor for TSCC (P<0.05). Furthermore, overexpression of CEACAM1 was correlated with more neutrophils infiltration in TSCC tissues (P<0.01). qRT-PCR results showed that CEACAM1-4L can upregulate the mRNA expression of IL-8 and CXCL-6, which were strong chemotactic factors of neutrophils.

CONCLUSION

Our results demonstrated that more neutrophils infiltration and overexpression of CEACAM1 were associated with poor clinical outcomes in TSCC tissues. Overexpression of CEACAM1 on tumor cells correlated with more neutrophils infiltration to some extent through upregulating mRNA expression of IL-8 and CXCL-6.

Expression of stress ligands of the immunoreceptor NKG2D in melanoma: regulation and clinical significance

Tumor cells, in particular melanoma cells, can be detected as abnormal self by cytotoxic lymphocytes of the innate and adaptive immune system. Of major importance in this process is the activating lymphocyte receptor NKG2D that in humans binds to MIC and ULBP surface molecules on tumor cells. Expression of NKG2D ligands (NKG2DL) is an early event in malignant transformation, induced by stress-associated and oncogene-driven pathways. Thus NKG2DL expression is considered as an innate barrier against tumor development. However, tumor cells can overcome this barrier by shedding of NKG2DL. Ligand shedding leads to elevated levels of soluble ligands in sera of tumor patients that in case of melanoma are of strong prognostic relevance. Here we review important aspects of NKG2DL expression and regulation in tumor cells with a focus on melanoma, and discuss their clinical relevance and potential in immunotherapy.