Phase I study of samalizumab in chronic lymphocytic leukemia and multiple myeloma: blockade of the immune checkpoint CD200

First-in-Human Study of 23ME-00610, an Antagonistic Antibody for Genetically Validated CD200R1 Immune Checkpoint, in Participants with Advanced Solid Malignancies

PURPOSE

In this phase 1 portion of a first-in-human phase 1/2a study (NCT05199272), 23ME-00610 was evaluated in participants with advanced solid malignancies to determine its safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD). Exploratory biomarkers were evaluated to examine potential correlates of efficacy and safety.

PATIENTS AND METHODS

Eligible participants (≥18 years) were administered 23ME-00610 intravenously every 3 weeks (Q3W) using an accelerated titration design followed by a traditional 3 + 3 design, with an initial dose level of 2 mg.

RESULTS

Twenty-eight participants were enrolled across seven cohorts and received a median of four cycles of 23ME-00610. No treatment-related serious adverse events (AE) were observed, and the maximum tolerated dose was not reached. Overall, the PK of 23ME-00610 was linear and dose proportional for doses ≥60 mg, with a median terminal half-life of 13 days at 1,400 mg. Peripheral saturation of CD200R1 was observed for doses ≥60 mg. Immune-related AEs, including rash, pruritus, and hypothyroidism, were predicted by phenome-wide association studies and observed for doses ≥60 mg. A confirmed partial response was observed in a participant with well-differentiated pancreatic neuroendocrine cancer whose tumor was among those with the highest tumor CD200 expression.

CONCLUSIONS

23ME-00610 has mild-to-moderate on-target AEs and PK/PD consistent with tumor target saturation and dosing every 3 weeks. The trend for clinical benefit in participants with tumor CD200 expression suggests that 23ME-00610 inhibits CD200R1 signaling and may reverse CD200-mediated immune evasion. Based on PK/PD, safety, and preliminary antitumor activity, 1,400 mg Q3W was selected as the dose for further study.

SIGNIFICANCE

Genome-wide association studies (GWAS) of the 23andMe genetic database identified CD200R1 as a promising therapeutic target for cancer. This phase 1 study of 23ME-00610, a CD200R1 antagonist IgG1, showed acceptable safety and tolerability, PK supporting Q3W dosing, and PD and preliminary clinical activity supporting an initial recommended phase 2 dose of 1,400 mg.

A squalene oil emulsified MPL-A and anti-CD200/CD300a antibodies adjuvanted whole-killed Leishmania vaccine provides durable immunity against L. donovani parasites

Antigenic inefficacy to induce robust immune responses and durable memory are major causes of constantly failing prophylactic approaches in leishmaniasis. Here, we determine the potential of a standardized whole-killed Leishmania vaccine (Leishvacc) adjuvanted with anti-CD200 and anti-CD300a antibodies, either alone or with monophosphoryl lipid A (MPL-SE) emulsified in squalene oil, in restoring the compromised antigen presenting abilities of dendritic cells (DCs), effector properties of CD4+T cells and providing protection against Leishmania donovani parasites. In animals vaccinated with antibodies adjuvanted vaccines, either alone or with MPL-SE, the antigen presenting abilities of CD11c+ DCs against Leishmania antigens, measured in terms of CD80, CD86, MHC-I, and MHC-II surface receptors and intracellular IL-12 were found enhanced than non-adjuvanted vaccine. We observed more proliferative and pro-inflammatory cytokines i.e. IL-2, IFN-γ, IL-23, and IL-12 producing CD4+T cells in antibodies/MPL-SE adjuvanted vaccinated animals further suggesting that this approach helps antigen activated CD4+T cells to acquire pro-inflammatory cytokines producing abilities. In antibodies, either alone or with MPL-SE, vaccinated animals, the number of CD4+ central memory T cells and their longevity were found significantly enhanced that further evidenced the impact of this vaccination approach in inducing long term protective immunity. The animals, receiving antibodies adjuvanted vaccines, either alone or with MPL-SE, exhibited excellent protection against virulent parasites by restricting their growth, which correlated with the significantly reduced parasitemia, splenomegaly, and hepatomegaly, along with fewer numbers of liver granulomas. Our findings provide an insight to a new immunoprophylactic approach against visceral leishmaniasis, which not only satisfies the safety criteria, but also provides a robust immunogenic response with remarkable potential for parasites control. However, further in-depth investigations are needed to ascertain its ability in inducing long-lasting immunity.

The role of antibody therapies in treating relapsed chronic lymphocytic leukemia: a review

INTRODUCTION

Chronic lymphocytic leukemia (CLL) is one of the most common types of leukemia in adult patients. The landscape of CLL therapy has changed in the last decades with the introduction of antibody-based therapies and novel targeted agents resulting in improved outcomes.

AREAS COVERED

This article describes the use of monoclonal antibodies, bispecific antibodies and antibody-drug conjugates in the treatment of relapsed and refractory CLL. The mechanism of action and clinical applications and safety of antibody-based therapies, both as monotherapy and in combination with other drugs, are discussed. A literature search was performed using PubMed, Web of Science, and Google Scholar for articles published in English. Additional relevant publications were obtained by reviewing the references from the chosen articles.

EXPERT OPINION

Antibody-based therapeutic strategies have drastically changed the treatment of CLL, as they have introduced the concept of boosting immune responses against tumor cells. While immunotherapy is generally effective, some treatment failure can occur due to antigen loss, mutation, or down-regulation, and this remains the main obstacle to cure. The development of novel antibody therapies, including their combinations with targeted drugs and bispecific antibodies, might help to reduce toxicity and improve efficacy.

CD200 depletion in glioma enhances antitumor immunity and induces tumor rejection

High-grade gliomas are a major health challenge with poor prognosis and high morbidity. Immune-checkpoint inhibitors (ICI) have emerged as promising therapeutic options for several malignancies yet show little efficacy against central nervous system (CNS) tumors. CD200 is a newly recognized immune checkpoint that modulates immune homeostasis. CD200 protein is expressed by a variety of cells, including immune cells and stromal cells, and is overexpressed by many tumors. The shedding of CD200 from tumor cells can create an immunosuppressive environment that dampens anti-tumor immunity by modulating cytolytic activity and cytokine expression both within and outside the tumor microenvironment (TME). While it is well-accepted that CD200 induces a pro-tumorigenic environment through its ability to suppress the immune response, we sought to determine the role of glioma-specific expression of CD200. We show that CD200 is expressed across glioma types, is shed from tumor cells, and increases over time in the serum of patients undergoing immunotherapy. Using CD200 knockout (KO) glioma models, we demonstrated that glioma cell-derived CD200 promotes tumor growth in vivo and in vitro. Notably, CD200 KO gliomas are spontaneously rejected by their host, a process that required a fully functional immune system, including NK and T-cells. Moreover, we report that glioma-derived or brain-injected soluble CD200 contributes to the suppression of antigen-specific CD8 T-cells in the draining lymph nodes (dLNs). Our work provides new mechanistic insights regarding CD200-mediated immunosuppression by gliomas.

Statement of significance

We demonstrate mechanisms of the druggable glioma-derived CD200 checkpoint on tumor growth and immune suppression.

CD200 genotype is associated with clinical outcome of patients with multiple myeloma

Immune dysfunction in patients with MM affects both the innate and adaptive immune system. Molecules involved in the immune response pathways are essential to determine the ability of cancer cells to escape from the immune system surveillance. However, few data are available concerning the role of immune checkpoint molecules in predicting the myeloma control and immunological scape as mechanism of disease progression. We retrospectively analyzed the clinical impact of the CD200 genotype (rs1131199 and rs2272022) in 291 patients with newly diagnosed MM. Patients with a CD200 rs1131199 GG genotype showed a median overall survival (OS) significantly lower than those with CC+CG genotype (67.8 months versus 94.4 months respectively; p: 0.022) maintaining significance in the multivariate analysis. This effect was specially detected in patients not receiving an autologous stem cell transplant (auto-SCT) (p < 0.001). In these patients the rs1131199 GG genotype negatively influenced in the mortality not related with the progression of MM (p: 0.02) mainly due to infections events.

CD200/CD200R: Bidirectional Role in Cancer Progression and Immunotherapy

As an immune checkpoint molecule, CD200 serves a foundational role in regulating immune homeostasis and promoting self-tolerance. While CD200 expression occurs in various immune cell subsets and normal tissues, its aberrant expression patterns in hematologic malignancies and solid tumors have been linked to immune evasion and cancer progression under pathological conditions, particularly through interactions with its cognate receptor, CD200R. Through this CD200/CD200R signaling pathway, CD200 exerts its immunosuppressive effects by inhibiting natural killer (NK) cell activation, cytotoxic T cell functions, and M1-polarized macrophage activity, while also facilitating expansion of myeloid-derived suppressor cells (MDSCs) and Tregs. Moreover, CD200/CD200R expression has been linked to epithelial-to-mesenchymal transition and distant metastasis, further illustrating its role in cancer progression. Conversely, CD200 has also been shown to exert anti-tumor effects in certain cancer types, such as breast carcinoma and melanoma, indicating that CD200 may exert bidirectional effects on cancer progression depending on the specific tumor microenvironment (TME). Regardless, modulating the CD200/CD200R axis has garnered clinical interest as a potential immunotherapeutic strategy for cancer therapy, as demonstrated by early-phase clinical trials. However, further research is necessary to fully understand the complex interactions of CD200 in the tumor microenvironment and to optimize its therapeutic potential in cancer immunotherapy.

Novel targets for immune-checkpoint inhibition in cancer

Immune-checkpoint inhibitors have revolutionized cancer therapy, yet many patients either do not derive any benefit from treatment or develop a resistance to checkpoint inhibitors. Intrinsic resistance can result from neoantigen depletion, defective antigen presentation, PD-L1 downregulation, immune-checkpoint ligand upregulation, immunosuppression, and tumor cell phenotypic changes. On the other hand, extrinsic resistance involves acquired upregulation of inhibitory immune-checkpoints, leading to T-cell exhaustion. Current data suggest that PD-1, CTLA-4, and LAG-3 upregulation limits the efficacy of single-agent immune-checkpoint inhibitors. Ongoing clinical trials are investigating novel immune-checkpoint targets to avoid or overcome resistance. This review provides an in-depth analysis of the evolving landscape of potentially targetable immune-checkpoints in cancer. We highlight their biology, emphasizing the current understanding of resistance mechanisms and focusing on promising strategies that are under investigation. We also summarize current results and ongoing clinical trials in this crucial field that could once again revolutionize outcomes for cancer patients.

Emerging Immune Checkpoint Molecules on Cancer Cells: CD24 and CD200

Cancer immunotherapy strategies are based on the utilization of immune checkpoint inhibitors to instigate an antitumor immune response. The efficacy of immune checkpoint blockade, directed at adaptive immune checkpoints, has been demonstrated in select cancer types. However, only a limited subset of patients has exhibited definitive outcomes characterized by a sustained response after discontinuation of therapy. Recent investigations have highlighted the significance of immune checkpoint molecules that are overexpressed in cancer cells and inhibit myeloid lineage immune cells within a tumor microenvironment. These checkpoints are identified as potential targets for anticancer immune responses. Notably, the immune checkpoint molecules CD24 and CD200 have garnered attention owing to their involvement in tumor immune evasion. CD24 and CD200 are overexpressed across diverse cancer types and serve as signaling checkpoints by engaging their respective receptors, Siglec-10 and CD200 receptor, which are expressed on tumor-associated myeloid cells. In this review, we summarized and discussed the latest advancements and insights into CD24 and CD200 as emergent immune checkpoint moieties, further delving into their therapeutic potentials for cancer treatment.

Exploring the dual role of B cells in solid tumors: implications for head and neck squamous cell carcinoma

In the tumor milieu of head and neck squamous cell carcinoma (HNSCC), distinct B cell subpopulations are present, which exert either pro- or anti-tumor activities. Multiple factors, including hypoxia, cytokines, interactions with tumor cells, and other immune infiltrating lymphocytes (TILs), alter the equilibrium between the dual roles of B cells leading to cancerogenesis. Certain B cell subsets in the tumor microenvironment (TME) exhibit immunosuppressive function. These cells are known as regulatory B (Breg) cells. Breg cells suppress immune responses by secreting a series of immunosuppressive cytokines, including IL-10, IL-35, TGF-β, granzyme B, and adenosine or dampen effector TILs by intercellular contacts. Multiple Breg phenotypes have been discovered in human and mouse cancer models. However, when compartmentalized within a tertiary lymphoid structure (TLS), B cells predominantly play anti-tumor effects. A mature TLS contains a CD20+ B cell zone with several important types of B cells, including germinal-center like B cells, antibody-secreting plasma cells, and memory B cells. They kill tumor cells via antibody-dependent cytotoxicity and phagocytosis, and local complement activation effects. TLSs are also privileged sites for local T and B cell coordination and activation. Nonetheless, in some cases, TLSs may serve as a niche for hidden tumor cells and indicate a bad prognosis. Thus, TIL-B cells exhibit bidirectional immune-modulatory activity and are responsive to a variety of immunotherapies. In this review, we discuss the functional distinctions between immunosuppressive Breg cells and immunogenic effector B cells that mature within TLSs with the focus on tumors of HNSCC patients. Additionally, we review contemporary immunotherapies that aim to target TIL-B cells. For the development of innovative therapeutic approaches to complement T-cell-based immunotherapy, a full understanding of either effector B cells or Breg cells is necessary.

Current Approaches of Immune Checkpoint Therapy in Chronic Lymphocytic Leukemia

OPINION STATEMENT

Increasing understanding of the complex interaction between leukemic and immune cells, which is responsible for tumor progression and immune evasion, has paved the way for the development of novel immunotherapy approaches in chronic lymphocytic leukemia (CLL). One of the well-known immune escape mechanisms of tumor cells is the up-regulation of immune checkpoint molecules. In recent years, targeting immune checkpoint receptors is the most clinically effective immunotherapeutic strategy for cancer treatment. In this regard, various immune checkpoint blockade (ICB) drugs are currently been investigating for their potential effects on improving anti-tumor immune response and clinical efficacy in the hematological malignancies; however, their effectiveness in patients with CLL has shown less remarkable success, and ongoing research is focused on identifying strategies to enhance the efficacy of ICB in CLL.

Immune checkpoints represent a promising breakthrough in targeted therapy and prognosis of myelodysplastic syndrome

Myelodysplastic syndrome (MDS) is a hematological malignancy of undetermined etiology, possibly linked to chromosomal structural alterations, genetic mutations, presentation and carcinogenicity of variant antigens on cell surface, and the generation of pro-inflammatory microenvironment in the bone marrow. Current drugs are unable to cure this disease, and therefore, decreasing the survival and proliferation of malignant cells to delay disease progression and extend the survival time of patients becomes the primary approach to management. In recent years, the immune system has received increasing attention for its potential role in the occurrence and development of MDS, leading to the emergence of immunoregulation as a viable treatment option. The current review provides a brief overview of pathogenesis of MDS and current treatment principles. In the meantime, the significance of immune proteins in treatment and prognosis of MDS is also discussed.

Diagnostic Utility of CD200 Immunohistochemistry in Distinguishing EBV-Positive Large B-Cell Lymphoma From Classic Hodgkin Lymphoma

OBJECTIVES

Epstein-Barr virus-positive large B-cell lymphoma (EBV+ LBCL) is a heterogeneous group of diseases that may resemble classic Hodgkin lymphoma (CHL) both morphologically and immunophenotypically. However, these diseases are treated with different therapies and carry distinct prognoses. We examined CD200 expression by immunohistochemistry in EBV+ LBCL and evaluated its diagnostic utility in the differential diagnosis with CHL.

METHODS

CD200 immunohistochemistry was performed on archival material from 20 cases of CHL (11 EBV+, 9 EBV-), 11 cases of EBV+ LBCL, and 10 cases of diffuse large B-cell lymphoma, not otherwise specified (DLBCL NOS). Staining pattern and intensity (0-3+ scale) were recorded.

RESULTS

CD200 positivity was seen in Reed-Sternberg cells in 19 (95%) of 20 cases of CHL, predominantly in a strong (3+, 15/19) and diffuse (>50% of cells, 17/19) pattern. In contrast, CD200 was negative in 8 (73%) of 11 cases of EBV+ LBCL; the 3 positive cases showed 1 to 2+ staining in less than 50% of lesional cells. All cases of DLBCL NOS were negative for CD200.

CONCLUSIONS

CD200 may be a useful immunophenotypic marker in differentiating EBV+ LBCL from CHL, with negative to partial/weak staining favoring a diagnosis of EBV+ LBCL and strong diffuse staining favoring a diagnosis of CHL.

Twenty-four-color full spectrum flow cytometry panel for minimal residual disease detection in acute myeloid leukemia

Full spectrum flow cytometry brings a breakthrough for minimal residual disease (MRD) detection in acute myeloid leukemia (AML). We aimed to explore the role of a new panel in MRD detection. We established a 24-color full-spectrum flow cytometry panel. A tube of 24-color antibodies included CD45, CD117, CD34, HLA-DR, CD15, CD64, CD14, CD11c, CD11b, CD13, CD33, CD371, CD7, CD56, CD19, CD4, CD2, CD123, CD200, CD38, CD96, CD71, CD36, and CD9. We discovered that when a tube meets 26 parameters (24 colors), these markers were not only limited to the observation of MRD in AML, but also could be used for fine clustering of bone marrow cells. Mast cells, basophils, myeloid dendritic cells, and plasmacoid dendritic cells were more clearly observed. In addition, immune checkpoint CD96 had the higher expression in CD117+ myeloid naive cells and CD56dimNK cells, while had the lower expression in CD56briNK cells in AML-MRD samples than in normal bone marrow samples. CD200 expression was remarkably enhanced in CD117+ myeloid naive cells, CD4+ T cells, T cells, activated T cells, CD56dimNK cells, and CD56briNK cells in AML-MRD samples. Our results can be used as important basis for auxiliary diagnosis, prognosis judgment, treatment guidance, and immune regulation in AML.

CD200R signaling contributes to unfavorable tumor microenvironment through regulating production of chemokines by tumor-associated myeloid cells

CD200 is overexpressed in many solid tumors and considered as an immune checkpoint molecule dampening cancer immunity. In this study, we found that CD200R-/- mice were significantly more potent in rejecting these CD200+ tumors. scRNA sequencing demonstrated that tumors from CD200R-/- mice had more infiltration of CD4+ and CD8+ T cells, and NK cells but less infiltration of neutrophils. Antibody depletion experiments revealed that immune effector cells are crucial in inhibiting tumor growth in CD200R-/- mice. Mechanistically, we found that CD200R signaling regulates the expression of chemokines in tumor-associated myeloid cells (TAMCs). In the absence of CD200R, TAMCs increased expression of CCL24 and resulted in increased infiltration of eosinophils, which contributes to anti-tumor activity. Overall, we conclude that CD200R signaling contributes to unfavorable TME through chemokine-dependent recruitment of immune suppressive neutrophils and exclusion of anti-cancer immune effectors. Our study has implications in developing CD200-CD200R targeted immunotherapy of solid tumors.

Trap and ambush therapy using sequential primary and tumor escape-selective oncolytic viruses

In multiple models of oncolytic virotherapy, it is common to see an early anti-tumor response followed by recurrence. We have previously shown that frontline treatment with oncolytic VSV-IFN-β induces APOBEC proteins, promoting the selection of specific mutations that allow tumor escape. Of these mutations in B16 melanoma escape (ESC) cells, a C-T point mutation in the cold shock domain-containing E1 (CSDE1) gene was present at the highest frequency, which could be used to ambush ESC cells by vaccination with the mutant CSDE1 expressed within the virus. Here, we show that the evolution of viral ESC tumor cells harboring the escape-promoting CSDE1C-T mutation can also be exploited by a virological ambush. By sequential delivery of two oncolytic VSVs in vivo, tumors which would otherwise escape VSV-IFN-β oncolytic virotherapy could be cured. This also facilitated the priming of anti-tumor T cell responses, which could be further exploited using immune checkpoint blockade with the CD200 activation receptor ligand (CD200AR-L) peptide. Our findings here are significant in that they offer the possibility to develop oncolytic viruses as highly specific, escape-targeting viro-immunotherapeutic agents to be used in conjunction with recurrence of tumors following multiple different types of frontline cancer therapies.

23ME-00610, a genetically informed, first-in-class antibody targeting CD200R1 to enhance antitumor T cell function

Immune checkpoint inhibition (ICI) has revolutionized cancer treatment; however, only a subset of patients benefit long term. Therefore, methods for identification of novel checkpoint targets and development of therapeutic interventions against them remain a critical challenge. Analysis of human genetics has the potential to inform more successful drug target discovery. We used genome-wide association studies of the 23andMe genetic and health survey database to identify an immuno-oncology signature in which genetic variants are associated with opposing effects on risk for cancer and immune diseases. This signature identified multiple pathway genes mapping to the immune checkpoint comprising CD200, its receptor CD200R1, and the downstream adapter protein DOK2. We confirmed that CD200R1 is elevated on tumor-infiltrating immune cells isolated from cancer patients compared to the matching peripheral blood mononuclear cells. We developed a humanized, effectorless IgG1 antibody (23ME-00610) that bound human CD200R1 with high affinity (KD <0.1 nM), blocked CD200 binding, and inhibited recruitment of DOK2. 23ME-00610 induced T-cell cytokine production and enhanced T cell-mediated tumor cell killing in vitro. Blockade of the CD200:CD200R1 immune checkpoint inhibited tumor growth and engaged immune activation pathways in an S91 tumor cell model of melanoma in mice.

What is new in cancer-associated fibroblast biomarkers?

The tumor microenvironment is one of the important drivers of tumor development. Cancer-associated fibroblasts (CAFs) are a major component of the tumor stroma and actively participate in tumor development, invasion, metastasis, drug resistance, and other biological behaviors. CAFs are a highly heterogeneous group of cells, a reflection of the diversity of their origin, biomarkers, and functions. The diversity of CAF origin determines the complexity of CAF biomarkers, and CAF subpopulations expressing different biomarkers may play contrasting roles in tumor progression. In this review, we provide an overview of these emerging CAF biomarkers and the biological functions that they suggest, which may give a better understanding of the relationship between CAFs and tumor cells and be of great significance for breakthroughs in precision targeted therapy for tumors. Video Abstract.

Combination CD200R/PD-1 blockade in a humanised mouse model

There is an increasing number of immune-checkpoint inhibitors being developed and approved for cancer immunotherapy. Most of the new therapies aim to reactivate tumour-infiltrating T cells, which are responsible for tumour killing. However, in many tumours, the most abundant infiltrating immune cells are macrophages and myeloid cells, which can be tumour-promoting as well as tumouricidal. CD200R was initially identified as a myeloid-restricted, inhibitory immune receptor, but was subsequently also found to be expressed within the lymphoid lineage. Using a mouse model humanised for CD200R and PD-1, we investigated the potential of a combination therapy comprising nivolumab, a clinically approved PD-1 blocking antibody, and OX108, a CD200R antagonist. We produced nivolumab as a murine IgG1 antibody and validated its binding activity in vitro as well as ex vivo. We then tested the combination therapy in the immunogenic colorectal cancer model MC38 as well as the PD-1 blockade-resistant lung cancer model LLC1, which is characterised by a large number of infiltrating myeloid cells, making it an attractive target for CD200R blockade. No significant improvement of overall survival was found in either model, compared to nivolumab mIgG1 monotherapy. There was a trend for more complete responses in the MC38 model, but investigation of the infiltrating immune cells failed to account for this. Importantly, MC38 cells expressed low levels of CD200, whereas LLC1 cells were CD200-negative. Further investigation of CD200R-blocking antibodies in tumours expressing high levels of CD200 could be warranted.

The immunoregulatory protein CD200 as a potentially lucrative yet elusive target for cancer therapy

CD200 is an immunoregulatory cell surface ligand with proven pro-tumorigenic credentials via its ability to suppress CD200 receptor (CD200R)-expressing anti-tumor immune function. This definitive role for the CD200-CD200R axis in regulating an immunosuppressive tumor microenvironment has garnered increasing interest in CD200 as a candidate target for immune checkpoint inhibition therapy. However, while the CD200 blocking antibody samalizumab is still in the early stages of clinical testing, alternative mechanisms for the pro-tumorigenic role of CD200 have recently emerged that extend beyond direct suppression of anti-tumor T cell responses and, as such, may not be susceptible to CD200 antibody blockade. Herein, we will summarize the current understanding of CD200 expression and function in the tumor microenvironment as well as alternative strategies for potential neutralization of multiple CD200 mechanisms in human cancers.

Cancel cancer: The immunotherapeutic potential of CD200/CD200R blockade

Immune checkpoint molecules function to inhibit and regulate immune response pathways to prevent hyperactive immune activity from damaging healthy tissues. In cancer patients, targeting these key molecules may serve as a valuable therapeutic mechanism to bolster immune function and restore the body's natural defenses against tumors. CD200, an immune checkpoint molecule, is a surface glycoprotein that is widely but not ubiquitously expressed throughout the body. By interacting with its inhibitory receptor CD200R, CD200 suppresses immune cell activity within the tumor microenvironment, creating conditions that foster tumor growth. Targeting the CD200/CD200R pathway, either through the use of monoclonal antibodies or peptide inhibitors, has shown to be effective in boosting anti-tumor immune activity. This review will explore CD200 and the protein's expression and role within the tumor microenvironment, blood endothelial cells, and lymph nodes. This paper will also discuss the advantages and challenges of current strategies used to target CD200 and briefly summarize relevant preclinical/clinical studies investigating the immunotherapeutic efficacy of CD200/CD200R blockade.

CD200R1 promotes interleukin-17 production by group 3 innate lymphoid cells by enhancing signal transducer and activator of transcription 3 activation

Psoriasis is a common chronic inflammatory skin disease with no cure. It is driven by the interleukin (IL)-23/IL-17A axis and type 17 T helper cells; however, recently, group 3 innate lymphoid cells (ILC3s) have also been implicated. Despite being the focus of much research, factors regulating the activity of ILC3s remain incompletely understood. Immune regulatory pathways are particularly important at barrier sites, such as the skin, gut, and lungs, which are exposed to environmental substances and microbes. CD200R1 is an immune regulatory cell surface receptor that inhibits proinflammatory cytokine production in myeloid cells. CD200R1 is also highly expressed on ILCs, where its function remains largely unexplored. We previously observed reduced CD200R1 signaling in psoriasis-affected skin, suggesting that dysregulation may promote disease. Here, we show that contrary to this, psoriasis models are less severe in CD200R1-deficient mice due to reduced IL-17 production. Here, we uncover a key cell-intrinsic role for CD200R1 in promoting IL-23-driven IL-17A production by ILC3s by promoting signal transducer and activator of transcription 3 activation. Therefore, contrary to its inhibitory role in myeloid cells, CD200R1 is required on ILC3 to promote IL-23-stimulated signal transducer and activator of transcription 3 activation, triggering optimal IL-17 production.

Application of modified Matutes score containing CD200 in diagnosis of chronic lymphocytic leukemia

OBJECTIVES

Immunophenotyping technique is a powerful tool for the diagnosis and differential diagnosis of chronic lymphocytic leukemia (CLL) and other B-cell chronic lymphoproliferative diseases (B-CLPD). CD200 is strongly expressed in CLL. This study aims to analyze the clinical value of modified Matutes score (MMS) containing CD200 in the diagnosis of CLL.

METHODS

We retrospectively analyzed 103 B-CLPD patients diagnosed from January 2020 to July 2021, including 64 CLL patients, 11 follicular lymphoma (FL) patients, 14 mantle cell lymphoma (MCL) patients, 6 marginal zone lymphoma (MZL) patients, 1 hairy cell leukemia (HCL) patient, and 7 lymphoplasmic lymphoma/Waldenstrom macroglobulinemia (LPL/WM) patients. The expression of CD markers between the CLL group and the non-CLL group was compared, and the sensitivity, specificity, and clinical consistency of MMS and Royal Marsden Hospital (RMH) immunophenotyping score system were analyzed.

RESULTS

There were significant differences in the expressions of CD5, CD23, FMC7, CD22, CD79b, CD200, and sIg between the CLL group and the non-CLL group (χ2 values were 37.42, 54.98, 30.71, 11.67, 55.26, 68.48, and 17.88, respectively, all P<0.01). When the RMH immunophenotyping score≥4, the sensitivity was 79.7%, and the specificity was 100%. When the MMS≥3, the sensitivity was 95.3%, and the specificity was 100%. The Kappa coefficient of RMH immunophenotyping system was 0.677, and the Kappa coefficient of MMS system was 0.860.

CONCLUSIONS

The MMS system containing CD200 has better sensitivity and same specificity compared with RMH immunophenotyping system, and MMS system may be more useful in the diagnosis of CLL.

A short review on cancer therapeutics

Cancer as a disease has been a remarkable scourge and over the past years, advances have been made in understanding the molecular basis of carcinogenesis and combating this disease. The common traits exhibited by cancer have been individually studied to figure out its mode of action and its mechanism of survival even in the most austere conditions. The various hallmarks noted so far have been effectively studied and different therapies revolving around each hallmark are still being studied in order to find the most appropriate treatment for the different types of cancer in existence. Emerging therapies have been able to elucidate the mechanism of receptor blockage which facilitate the ability of cancer to proliferate as well as evade tumor suppressors, prevent cell death, support replicative immortality, escape immune destruction, stimulate angiogenesis, reduce cellular energetics as well as metabolism and prevent the destruction of the immune system. This life-threatening disease should be tackled aggressively with a combined therapy that involves two or more hallmarks of cancer and adverse effects of each therapy should also be considered.

Immunotherapeutic Strategies in Chronic Lymphocytic Leukemia: Advances and Challenges

Immune-based therapeutic strategies have drastically changed the landscape of hematological disorders, as they have introduced the concept of boosting immune responses against tumor cells. Anti-CD20 monoclonal antibodies have been the first form of immunotherapy successfully applied in the treatment of CLL, in the context of chemoimmunotherapy regimens. Since then, several immunotherapeutic approaches have been studied in CLL settings, with the aim of exploiting or eliciting anti-tumor immune responses against leukemia cells. Unfortunately, despite initial promising data, results from pilot clinical studies have not shown optimal results in terms of disease control - especially when immunotherapy was used individually - largely due to CLL-related immune dysfunctions hampering the achievement of effective anti-tumor responses. The growing understanding of the complex interactions between immune cells and the tumor cells has paved the way for the development of new combined approaches that rely on the synergism between novel agents and immunotherapy. In this review, we provide an overview of the most successful and promising immunotherapeutic modalities in CLL, including both antibody-based therapy (i.e. monoclonal antibodies, bispecific antibodies, bi- or tri- specific killer engagers) and adoptive cellular therapy (i.e. CAR T cells and NK cells). We also provide examples of successful new combination strategies and some insights on future perspectives.

Immunosuppression and outcomes in adult patients with de novo acute myeloid leukemia with normal karyotypes

Acute myeloid leukemia (AML) patients rarely have long first remissions (LFRs; >5 y) after standard-of-care chemotherapy, unless classified as favorable risk at presentation. Identification of the mechanisms responsible for long vs. more typical, standard remissions may help to define prognostic determinants for chemotherapy responses. Using exome sequencing, RNA-sequencing, and functional immunologic studies, we characterized 28 normal karyotype (NK)-AML patients with >5 y first remissions after chemotherapy (LFRs) and compared them to a well-matched group of 31 NK-AML patients who relapsed within 2 y (standard first remissions [SFRs]). Our combined analyses indicated that genetic-risk profiling at presentation (as defined by European LeukemiaNet [ELN] 2017 criteria) was not sufficient to explain the outcomes of many SFR cases. Single-cell RNA-sequencing studies of 15 AML samples showed that SFR AML cells differentially expressed many genes associated with immune suppression. The bone marrow of SFR cases had significantly fewer CD4⁺ Th1 cells; these T cells expressed an exhaustion signature and were resistant to activation by T cell receptor stimulation in the presence of autologous AML cells. T cell activation could be restored by removing the AML cells or blocking the inhibitory major histocompatibility complex class II receptor, LAG3. Most LFR cases did not display these features, suggesting that their AML cells were not as immunosuppressive. These findings were confirmed and extended in an independent set of 50 AML cases representing all ELN 2017 risk groups. AML cell-mediated suppression of CD4⁺ T cell activation at presentation is strongly associated with unfavorable outcomes in AML patients treated with standard chemotherapy.

Alveolar macrophages: novel therapeutic targets for respiratory diseases

Alveolar macrophages (AMs) are lung-resident myeloid cells that sit at the interface of the airway and lung tissue. Under homeostatic conditions, their primary function is to clear debris, dead cells and excess surfactant from the airways. They also serve as innate pulmonary sentinels for respiratory pathogens and environmental airborne particles and as regulators of pulmonary inflammation. However, they have not typically been viewed as primary therapeutic targets for respiratory diseases. Here, we discuss the role of AMs in various lung diseases, explore the potential therapeutic strategies to target these innate cells and weigh the potential risks and challenges of such therapies. Additionally, in the context of the COVID-19 pandemic, we examine the role AMs play in severe disease and the therapeutic strategies that have been harnessed to modulate their function and protect against severe lung damage. There are many novel approaches in development to target AMs, such as inhaled antibiotics, liposomal and microparticle delivery systems, and host-directed therapies, which have the potential to provide critical treatment to patients suffering from severe respiratory diseases, yet there is still much work to be done to fully understand the possible benefits and risks of such approaches.

BTK inhibitors, irrespective of ITK inhibition, increase efficacy of a CD19/CD3-bispecific antibody in CLL

Bruton tyrosine kinase inhibitors (BTKis) are a preferred treatment of patients with chronic lymphocytic leukemia (CLL). Indefinite therapy with BTKis, although effective, presents clinical challenges. Combination therapy can deepen responses, shorten treatment duration, and possibly prevent or overcome drug resistance. We previously reported on a CD19/CD3-bispecific antibody (bsAb) that recruits autologous T-cell cytotoxicity against CLL cells in vitro. Compared with observations with samples from treatment-naïve patients, T cells from patients being treated with ibrutinib expanded more rapidly and exerted superior cytotoxic activity in response to the bsAb. In addition to BTK, ibrutinib also inhibits interleukin-2 inducible T-cell kinase (ITK). In contrast, acalabrutinib, does not inhibit ITK. Whether ITK inhibition contributes to the observed immune effects is unknown. To better understand how BTKis modulate T-cell function and cytotoxic activity, we cultured peripheral blood mononuclear cells (PBMCs) from BTKi-naive and ibrutinib- or acalabrutinib-treated CLL patients with CD19/CD3 bsAb in vitro. T-cell expansion, activation, differentiation, and cytotoxicity were increased in PBMCs from patients on treatment with either BTKi compared with that observed for BKTi-naïve patients. BTKi therapy transcriptionally downregulated immunosuppressive effectors expressed by CLL cells, including cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) and CD200. CTLA-4 blockade with ipilimumab in vitro increased the cytotoxic activity of the bsAb in BTKi-naïve but not BTKi-treated PBMCS. Taken together, BTKis enhance bsAb-induced cytotoxicity by relieving T cells of immunosuppressive restraints imposed by CLL cells. The benefit of combining bsAb immunotherapy with BTKis needs to be confirmed in clinical trials.

Immunohistochemical Expression of CD200 in Renal Cell Carcinoma

Background and Objectives:

Renal cell carcinoma (RCC) is the most common malignant renal neoplasm in adults. CD200 is a transmembrane protein and is a promising target for cancer immunotherapy. The aim of this study is to assess the CD200 expression in RCC.

Materials and Methods:

Eighty paraffin-embedded radical nephrectomy specimens, diagnosed with RCC were evaluated immunohistochemically for CD200 expression.

Results:

Out of eighty cases studied, CD200 was expressed in n = 73 cases (91.25%) with high intensity in 27 cases (33.75%), moderate intensity in 22 cases (27.5%), and mild intensity in 24 cases (30%). No staining was observed in the adjacent apparently normal renal tissue in all examined sections. No significant relationship was found between CD200 expression and the gender, tumor size, tumor side, histologic type, nuclear grade, T stage, and tumor necrosis.

Conclusion:

CD200 expression in most of the studied cases of RCC may refer to the potential therapeutic of anti-CD200 antibody for this cancer.

Multiplex Quantitative Analysis of Tumor-Infiltrating Lymphocytes, Cancer-Associated Fibroblasts, and CD200 in Pancreatic Cancer

Pancreatic cancer is marked by a desmoplastic tumor microenvironment and low tumor immunogenicity, making it difficult for immunotherapy drugs to improve outcomes for patients. Tumor-infiltrating lymphocytes (TILs) and cancer-associated fibroblasts (CAFs) are seen in the tumor microenvironment of patients with pancreatic ductal adenocarcinoma (PDAC). In this work, we sought to characterize the expression levels and potential prognostic value of TILs (CD4, CD8, and CD20) and CAFs (Thy-1, FAP, and SMA) in a large retrospective cohort of PDAC patients. Additionally, we investigated the expression levels and prognostic significance of CD200, an immunoinhibitory protein that has shown interest as a potential target for immune checkpoint blockade. We measured the expression levels of these seven proteins with multiplexed immunofluorescence staining and quantitative immunofluorescence (QIF). We found CD8 and FAP to be independent predictors of progression-free survival and overall survival. CD200 was found to be heterogeneously expressed in both the tumor and stromal compartments of PDAC, with the majority of patients having positive stromal expression and negative tumor expression. This work demonstrates the potential clinical utility of CD8 and FAP in PDAC patients, and it sheds light on the expression patterns of CD200 in pancreatic cancer as the protein is being tested as a target for immune checkpoint blockade.

CD200 Blockade Modulates Tumor Immune Microenvironment but Fails to Show Efficacy in Inhibiting Tumor Growth in a Murine Model of Melanoma

CD200-CD200R pathway regulates immune responses and has been implicated in the pathogenesis of a number of cancer types. CD200 blockade is considered a strategy for immunotherapy of CD200-positive cancers such as melanoma. Thus, it is critical to understand the potential impacts of CD200 blockade in a more human relevant tumor model. In this study, we evaluated these issues using the CD200⁺ Yumm1.7 mouse melanoma model. Yumm1.7 cells bear Braf/Pten mutations resembling human melanoma. We found that Yumm1.7 tumors grow significantly faster in CD200R^–/– mice compared to wild type mice. Analysis of tumor immune microenvironment (TIME) revealed that tumors from CD200R^–/– or anti-CD200 treated mice had downregulated immune cell contents and reduced TCR clonality compared to tumors from untreated wild type mice. T cells also showed impaired effector functions, as reflected by reduced numbers of IFN-γ⁺ and TNF-α⁺ T cells. Mechanistically, we found upregulation of the CCL8 gene in CD200R^–/– tumors. In vitro co-culture experiments using Yumm1.7 tumor cells with bone marrow derived macrophages (BMDM) from WT and CD200R^–/– mice confirmed upregulation of macrophage CCL8 in the absence of CD200-CD200R interaction. Finally, we found that anti-CD200 therapy failed to show efficacy either alone or in combination with checkpoint inhibitors such as anti-PD-1 or anti-CTLA4 in inhibiting Yumm1.7 tumor growth. Given that CD200R-deficiency or anti-CD200 treatment leads to reduced T cell responses in TME, using blockade of CD200 as an immunotherapy for cancers such as melanoma should be practiced with caution.

CD200 expression in hematopoietic neoplasms: Beyond a marker for diagnosis of B-cell neoplasms

CD200 (OX-2) is expressed in myeloid cells, B cells, subsets of T cells and on other normal and neoplastic non-hematopoietic cells. It interacts with CD200R and has a suppressive effect on T cells immune mediated response. We aimed to review CD200 expression and its role in the immune evasion of non-B cell hematopoietic neoplasms. In acute myeloid leukemia, CD200 seems to be related to the worst outcome, even in diseases of good prognosis, possibly due to an immunosuppressive effect. In plasma cell myeloma studies, while some have associated CD200 expression with worst prognosis possibly due to its suppressive effect on monocyte and T cell-mediated immune response, in others CD200 appeared to be a marker of a better outcome, or even showed no impact in event-free survival (EFS). Few studies have evaluated CD200 expression in T cell neoplasms; however, it appears to be a good immunophenotypic marker for angioimmunoblastic T cell lymphoma. In conclusion, CD200 appears to be involved in the immune evasion of malignant cells, which could affect the survival of these patients.

Signaling by the inhibitory receptor CD200R is rewired by type I interferon

CD200 receptor 1 (CD200R) is an inhibitory immunoreceptor that suppresses Toll-like receptor (TLR)–induced cytokine production through the adaptor protein Dok2 and the GTPase activating protein (GAP) p120-RasGAP, which can be cleaved during mild cellular stress. We found that in the presence of cleaved p120-RasGAP, CD200R lost its capacity to inhibit phosphorylation of ribosomal S6 protein (rpS6), suggesting the reduced activity of mammalian target of rapamycin complex 1 (mTORC1). Furthermore, treatment of human peripheral blood mononuclear cells (PBMC) with interferon-α (IFN-α) resulted in increased amounts of cleaved p120-RasGAP. Upon pretreatment of cells with increasing concentrations of IFN-α, CD200R switched from inhibiting to potentiating the TLR7- and TLR8-induced expression of the gene encoding IFN-γ, a cytokine that is important for innate and adaptive immunity and is implicated in systemic lupus erythematosus (SLE) pathogenesis. PBMC from patients with SLE, a prototypic type I IFN disease, had an increased abundance of cleaved p120-RasGAP compared to that in cells from healthy controls. In a subset of SLE patients, CD200R stopped functioning as an inhibitory receptor or potentiated TLR-induced IFNG mRNA expression. Thus, our data suggest that type I IFN rewires CD200R signaling to be proinflammatory, which could contribute to the perpetuation of inflammation in patients with SLE.

Targeting pediatric leukemia-propagating cells with anti-CD200 antibody therapy

Treating refractory pediatric acute lymphoblastic leukemia (ALL) remains a challenge despite impressive remission rates (>90%) achieved in the last decade. The use of innovative immunotherapeutic approaches such as anti-CD19 chimeric antigen receptor T cells does not ensure durable remissions, because leukemia-propagating cells (LPCs) that lack expression of CD19 can cause relapse, which signifies the need to identify new markers of ALL. Here we investigated expression of CD58, CD97, and CD200, which were previously shown to be overexpressed in B-cell precursor ALL (BCP-ALL) in CD34+/CD19+, CD34+/CD19-, CD34-/CD19+, and CD34-/CD19- LPCs, to assess their potential as therapeutic targets. Whole-genome microarray and flow cytometric analyses showed significant overexpression of these molecules compared with normal controls. CD58 and CD97 were mainly co-expressed with CD19 and were not a prerequisite for leukemia engraftment in immune deficient mice. In contrast, expression of CD200 was essential for engraftment and serial transplantation of cells in measurable residual disease (MRD) low-risk patients. Moreover, these CD200+ LPCs could be targeted by using the monoclonal antibody TTI-CD200 in vitro and in vivo. Treating mice with established disease significantly reduced disease burden and extended survival. These findings demonstrate that CD200 could be an attractive target for treating low-risk ALL, with minimal off-tumor effects that beset current immunotherapeutic approaches.

Multiple myeloma: therapeutic delivery of antibodies and aptamers

Multiple myeloma is the second most common hematological malignancy in adults, accounting for 2% of all cancer-related deaths in the UK. Current chemotherapy-based regimes are insufficient, as most patients relapse and develop therapy resistance. This review focuses on current novel antibody- and aptamer-based therapies aiming to overcome current therapy limitations, as well as their respective limitations and areas of improvement. The use of computer modeling methods, as a tool to study and improve ligand-receptor alignments for the use of novel therapy development will also be discussed, as it has become a rapid, reliable and comparatively inexpensive method of investigation.

CD200 Baseline Serum Levels Predict Prognosis of Chronic Lymphocytic Leukemia

Simple Summary

This study aimed at investigating the prognostic significance of the soluble form of CD200 antigen evaluated at diagnosis in patients with chronic lymphocytic leukemia (CLL). In a large cohort of patients, we found that more aggressive features and a worse prognosis are correlated with higher baseline serum levels of CD200. These data support the relevant role of CD200 not only as a diagnostic tool but also as a prognostic indicator and a potential therapeutic target in CLL.

Abstract

Membrane-bound CD200 is overexpressed in chronic lymphocytic leukemia (CLL), and there is some evidence that its soluble ectodomain (sCD200) could also be involved in the pathophysiology and the disease. However, very little is known about sCD200’s prognostic significance. sCD200 was tested at diagnosis in 272 patients with CLL and in 78 age- and sex-matched healthy subjects using a specific human CD200 (OX-2 membrane glycoprotein) ELISA kit. A significantly higher concentration of sCD200 was found in CLL patients compared to controls. In our cohort, sCD200 was significantly higher in patients who were older than 66 years, with Binet stage C, unmutated IgVH and unfavorable (del11q or del17p) FISH. Time-to-first treatment and overall survival were significantly shorter in patients with higher sCD200 concentration, using as a cut-off 1281 pg/mL, the median value for sCD200 concentration in the whole CLL cohort. However, the prognostic impact of sCD200 was not confirmed in multivariate analysis. Baseline sCD200 values appeared to have an impact on the response to chemotherapy or chemo-immunotherapy, but not to targeted agents. Collectively, our data show that sCD200 serum levels correlate with more aggressive clinical and biological features and are able to predict a worse prognosis. This work supports the relevant role of CD200 not only as a diagnostic tool but also as a prognostic indicator and a potential therapeutic target in CLL.

Overexpression of CD200 is a Stem Cell-Specific Mechanism of Immune Evasion in AML

BACKGROUND

Acute myeloid leukemia (AML) stem cells (LSCs) are capable of surviving current standard chemotherapy and are the likely source of deadly, relapsed disease. While stem cell transplant serves as proof-of-principle that AML LSCs can be eliminated by the immune system, the translation of existing immunotherapies to AML has been met with limited success. Consequently, understanding and exploiting the unique immune-evasive mechanisms of AML LSCs is critical.

METHODS

Analysis of stem cell datasets and primary patient samples revealed CD200 as a putative stem cell-specific immune checkpoint overexpressed in AML LSCs. Isogenic cell line models of CD200 expression were employed to characterize the interaction of CD200+ AML with various immune cell subsets both in vitro and in peripheral blood mononuclear cell (PBMC)-humanized mouse models. CyTOF and RNA-sequencing were performed on humanized mice to identify novel mechanisms of CD200-mediated immunosuppression. To clinically translate these findings, we developed a fully humanized CD200 antibody (IgG1) that removed the immunosuppressive signal by blocking interaction with the CD200 receptor while also inducing a potent Fc-mediated response. Therapeutic efficacy of the CD200 antibody was evaluated using both humanized mice and patient-derived xenograft models.

RESULTS

Our results demonstrate that CD200 is selectively overexpressed in AML LSCs and is broadly immunosuppressive by impairing cytokine secretion in both innate and adaptive immune cell subsets. In a PBMC-humanized mouse model, CD200+ leukemia progressed rapidly, escaping elimination by T cells, compared with CD200- AML. T cells from mice with CD200+ AML were characterized by an abundance of metabolically quiescent CD8+ central and effector memory cells. Mechanistically, CD200 expression on AML cells significantly impaired OXPHOS metabolic activity in T cells from healthy donors. Importantly, CD200 antibody therapy could eliminate disease in the presence of graft-versus-leukemia in immune competent mice and could significantly improve the efficacy of low-intensity azacitidine/venetoclax chemotherapy in immunodeficient hosts.

CONCLUSIONS

Overexpression of CD200 is a stem cell-specific marker that contributes to immunosuppression in AML by impairing effector cell metabolism and function. CD200 antibody therapy is capable of simultaneously reducing CD200-mediated suppression while also engaging macrophage activity. This study lays the groundwork for CD200-targeted therapeutic strategies to eliminate LSCs and prevent AML relapse.

Optimizing NK Cell-Based Immunotherapy in Myeloid Leukemia: Abrogating an Immunosuppressive Microenvironment

Natural killer (NK) cells are prominent cytotoxic and cytokine-producing components of the innate immune system representing crucial effector cells in cancer immunotherapy. Presently, various NK cell-based immunotherapies have contributed to the substantial improvement in the reconstitution of NK cells against advanced-staged and high-risk AML. Various NK cell sources, including haploidentical NK cells, adaptive NK cells, umbilical cord blood NK cells, stem cell-derived NK cells, chimeric antigen receptor NK cells, cytokine-induced memory-like NK cells, and NK cell lines have been identified. Devising innovative approaches to improve the generation of therapeutic NK cells from the aforementioned sources is likely to enhance NK cell expansion and activation, stimulate ex vivo and in vivo persistence of NK cells and improve conventional treatment response of myeloid leukemia. The tumor-promoting properties of the tumor microenvironment and downmodulation of NK cellular metabolic activity in solid tumors and hematological malignancies constitute a significant impediment in enhancing the anti-tumor effects of NK cells. In this review, we discuss the current NK cell sources, highlight ongoing interventions in enhancing NK cell function, and outline novel strategies to circumvent immunosuppressive factors in the tumor microenvironment to improve the efficacy of NK cell-based immunotherapy and expand their future success in treating myeloid leukemia.

Intrinsic Resistance of Chronic Lymphocytic Leukemia Cells to NK Cell-Mediated Lysis Can Be Overcome In Vitro by Pharmacological Inhibition of Cdc42-Induced Actin Cytoskeleton Remodeling

Natural killer (NK) cells are innate effector lymphocytes with strong antitumor effects against hematologic malignancies such as chronic lymphocytic leukemia (CLL). However, NK cells fail to control CLL progression on the long term. For effective lysis of their targets, NK cells use a specific cell-cell interface, known as the immunological synapse (IS), whose assembly and effector function critically rely on dynamic cytoskeletal changes in NK cells. Here we explored the role of CLL cell actin cytoskeleton during NK cell attack. We found that CLL cells can undergo fast actin cytoskeleton remodeling which is characterized by a NK cell contact-induced accumulation of actin filaments at the IS. Such polarization of the actin cytoskeleton was strongly associated with resistance against NK cell-mediated cytotoxicity and reduced amounts of the cell-death inducing molecule granzyme B in target CLL cells. Selective pharmacological targeting of the key actin regulator Cdc42 abrogated the capacity of CLL cells to reorganize their actin cytoskeleton during NK cell attack, increased levels of transferred granzyme B and restored CLL cell susceptibility to NK cell cytotoxicity. This resistance mechanism was confirmed in primary CLL cells from patients. In addition, pharmacological inhibition of actin dynamics in combination with blocking antibodies increased conjugation frequency and improved CLL cell elimination by NK cells. Together our results highlight the critical role of CLL cell actin cytoskeleton in driving resistance against NK cell cytotoxicity and provide new potential therapeutic point of intervention to target CLL immune escape.

CD200 expression marks leukemia stem cells in human AML

The leukemia stem cell (LSC) populations of acute myeloid leukemia (AML) exhibit phenotypic, genetic, and functional heterogeneity that contribute to therapy failure and relapse. Progress toward understanding the mechanistic basis for therapy resistance in LSCs has been hampered by difficulties in isolating cell fractions that enrich for the entire heterogeneous population of LSCs within individual AML samples. We previously reported that CD200 gene expression is upregulated in LSC-containing AML fractions. Here, we show that CD200 is present on a greater proportion of CD45dim blasts compared with more differentiated CD45high cells in AML patient samples. In 75% (49 of 65) of AML cases we examined, CD200 was expressed on ≥10% of CD45dim blasts; of these, CD200 identified LSCs within the blast population in 9 of 10 (90%) samples tested in xenotransplantation assays. CD200+ LSCs could be isolated from CD200+ normal HSCs with the use of additional markers. Notably, CD200 expression captured both CD34- and CD34+ LSCs within individual AML samples. Analysis of highly purified CD200+ LSC-containing fractions from NPM1-mutated AMLs, which are commonly CD34-, exhibited an enrichment of primitive gene expression signatures compared with unfractionated cells. Overall, our findings support CD200 as a novel LSC marker that is able to capture the entire LSC compartment from AML patient samples, including those with NPM1 mutation.

BTLA/HVEM Axis Induces NK Cell Immunosuppression and Poor Outcome in Chronic Lymphocytic Leukemia

Simple Summary

Chronic lymphocytic leukemia (CLL) represents the most frequent B cell malignancy in Western countries and still remains as an incurable disease. Despite recent advances in targeted therapies including ibrutinib, idelalisib or venetoclax, resistance mechanisms have been described and patients develop a progressive immunosuppression. Since immune checkpoint blockade has demonstrated to reinvigorate T and NK cell-mediated anti-tumor responses, the aim of this work was to elucidate whether this immunosuppression relies, at least in part, in BTLA/HVEM axis in patients with CLL. Our results demonstrate that BTLA and HVEM expression is deeply dysregulated on leukemic and NK cells and correlates with poor outcome. Moreover, soluble BTLA levels correlated with adverse cytogenetics and shorter time to treatment. BTLA blockade restored, at least in part, NK cell-mediated responses in patients with CLL. Altogether, our results provide the rationale to further investigate the role of BTLA/HVEM axis in the pathogenesis of CLL.

Abstract

Chronic lymphocytic leukemia (CLL) is characterized by progressive immunosuppression and diminished cancer immunosurveillance. Immune checkpoint blockade (ICB)-based therapies, a major breakthrough against cancer, have emerged as a powerful tool to reinvigorate antitumor responses. Herein, we analyzed the role of the novel inhibitory checkpoint BTLA and its ligand, HVEM, in the regulation of leukemic and natural killer (NK) cells in CLL. Flow cytometry analyses showed that BTLA expression is upregulated on leukemic cells and NK cells from patients with CLL, whereas HVEM is downregulated only in leukemic cells, especially in patients with advanced Rai-Binet stage. In silico analysis revealed that increased HVEM, but not BTLA, mRNA expression in leukemic cells correlated with diminished overall survival. Further, soluble BTLA (sBTLA) was found to be increased in the sera of patients with CLL and highly correlated with poor prognostic markers and shorter time to treatment. BTLA blockade with an anti-BTLA monoclonal antibody depleted leukemic cells and boosted NK cell-mediated responses ex vivo by increasing their IFN-γ production, cytotoxic capability, and antibody-dependent cytotoxicity (ADCC). In agreement with an inhibitory role of BTLA in NK cells, surface BTLA expression on NK cells was associated with poor outcome in patients with CLL. Overall, this study is the first to bring to light a role of BTLA/HVEM in the suppression of NK cell-mediated immune responses in CLL and its impact on patient’s prognosis, suggesting that BTLA/HVEM axis may be a potential therapeutic target in this disease.

Quantitative Assessment of CD200 and CD200R Expression in Lung Cancer

CD200/CD200R is an immune checkpoint with broad expression patterns and a potential target for immune therapy. In this study, we assess both CD200 and CD200R expression in solid tumors, with a focus on lung cancer, and evaluate their association with clinicopathologic characteristics, mutation status, outcome, and programmed death-ligand 1 (PD-L1) expression. We used multiplexed quantitative immunofluorescence (QIF) to measure the expression of CD200 and CD200R in a total of 455 patients from three lung cancer cohorts. Using carefully validated antibodies, we performed target measurement with tyramide-based QIF panels and analyzed the data using the PM2000 microscope and AQUA software. CD200 tumor positivity was found in 29.7% of non-small cell lung cancer (NSCLC) patients and 33.3% of lung large cell neuroendocrine carcinoma (LCNEC) patients. CD200 demonstrated notable intratumoral heterogeneity. CD200R was expressed in immune cells in 25% of NSCLC and 41.3% of LCNEC patients. While CD200R is predominantly expressed in immune cells, rare tumor cell staining was seen in a highly heterogeneous pattern. CD200R expression in the stromal compartment was significantly higher in patients with squamous differentiation (p < 0.0001). Neither CD200 nor CD200R were associated with other clinicopathologic characteristics or mutation status. Both biomarkers were not prognostic for disease-free or overall survival in NSCLC. CD200 showed moderate correlation with PD-L1. CD200/CD200R pathway is frequently expressed in lung cancer patients. Differential expression patterns of CD200 and CD200R with PD-L1 suggest a potential role for targeting this pathway alone in patients with NSCLC.

CD200:CD200R Interactions and Their Importance in Immunoregulation

The molecule CD200, described many years ago as a naturally occurring immunomodulatory agent, capable of regulating inflammation and transplant rejection, has attracted additional interest over the past years with the realization that it may also serve as an important marker for progressive malignancy. A large body of evidence also supports the hypothesis that this molecule can contribute to immunoregulation of, among other diseases, infection, autoimmune disease and allergy. New data have also come to light to characterize the receptors for CD200 (CD200R) and their potential mechanism(s) of action at the biochemical level, as well as the description of a novel natural antagonist of CD200, lacking the NH₂-terminal region of the full-length molecule. Significant controversies exist concerning the relative importance of CD200 as a ligand for all reported CD200Rs. Nevertheless, some progress has been made in the identification of the structural constraints determining the interaction between CD200 and CD200R, and this information has in turn proved of use in developing novel small molecule agonists/antagonists of the interaction. The review below highlights many of these newer findings, and attempts to place them in the broad context of our understanding of the role of CD200-CD200R interactions in a variety of human diseases.

Clinical Importance of CD200 Expression in Colorectal Liver Metastasis

BACKGROUND

Approximately 30% of patients diagnosed with colorectal cancer (CRC) develop liver metastases. We evaluated the role of CD200, a potent immunosuppressive molecule, in colorectal liver metastases (CRLM).

METHODS

We examined 110 patients who underwent curative liver resection for CRLM at our institution between 2000 and 2016. Based on the results of immunohistochemical analysis, the patients were divided into high-CD200 (n = 47) and low-CD200 (n = 63) expression groups. The relationships between CD200 expression and various clinicopathological outcomes were investigated.

RESULTS

The overall survival (OS) of patients in the high-CD200 group was significantly worse than that in the low-CD200 group (p = 0.009). Multivariate analysis showed that the independent prognostic factors in CRLM were maximum tumor size > 30 mm (p = 0.002), preoperative carcinoembryonic antigen level > 20 ng/mL (p < 0.001), primary CRC N2-3 (p = 0.049), and high-CD200 expression (p = 0.004). Furthermore, CD4+, CD8+, and CD45RO+ tumor-infiltrating lymphocytes in CRLM were significantly higher in the low-CD200 group than in the high-CD200 group (p = 0.005, p = 0.001, and p < 0.001, respectively). In addition, patients who had received preoperative chemotherapy had higher CD200 expression than those who had not received preoperative chemotherapy, and OS was significantly worse in patients in the high-CD200 group who had received preoperative chemotherapy.

CONCLUSIONS

CD200 expression was an independent prognostic factor in CRLM. CD200 may play a critical role in tumor immunity in CRLM, and can therefore be used as a potential therapeutic target in CRLM.

CD200 and Chronic Lymphocytic Leukemia: Biological and Clinical Relevance

CD200, a transmembrane type Ia glycoprotein belonging to the immunoglobulin protein superfamily, is broadly expressed on a wide variety of cell types, such as B lymphocytes, a subset of T lymphocytes, dendritic cells, endothelial and neuronal cells. It delivers immunosuppressive signals through its receptor CD200R, which is expressed on monocytes/myeloid cells and T lymphocytes. Moreover, interaction of CD200 with CD200R has also been reported to play a role in the regulation of tumor immunity. Overexpression of CD200 has been reported in chronic lymphocytic leukemia (CLL) and hairy cell leukemia but not in mantle cell lymphoma, thus helping to better discriminate between these different B cell malignancies with different prognosis. In this review, we focus on the role of CD200 expression in the differential diagnosis of mature B-cell neoplasms and on the prognostic significance of CD200 expression in CLL, where conflicting results have been published so far. Of interest, increasing evidences indicate that anti-CD200 treatment might be therapeutically beneficial for treating CD200-expressing malignancies, such as CLL.

Tumor-Infiltrating T Cells Concurrently Overexpress CD200R with Immune Checkpoints PD-1, CTLA-4, and TIM-3 in Non-Small-Cell Lung Cancer

INTRODUCTION

CD200R has been reported to be the receptor for the immune checkpoint molecule CD200 and can transduce immune-suppressive signals. In this study, we mainly focused on the expression level of CD200R in T cells in pulmonary artery (PA) blood and non-small-cell lung cancer (NSCLC) tumor tissue.

METHODS

Immune cells were isolated from dissected tumor samples and PA blood of NSCLC patients and analyzed with multiparameter flow cytometry. The co-expression of CD200R with other immune checkpoints, including programmed cell death protein 1 (PD-1), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), and T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), was also investigated.

RESULTS

CD200R expression was observed on the surface of approximately 75% of T cells among tumor-infiltrating leukocytes (TILs). Compared to T cells extracted from TILs, only 55% of T cells extracted from PA blood exhibited CD200R expression. Moreover, with higher expression of CD200R, the expression of other immune checkpoints, including PD-1, CTLA-4, and TIM-3, was also increased in tumor-infiltrating T cells compared to T cells in PA blood.

CONCLUSIONS

Our results showed that those tumors were dominated by T cells expressing CD200R together with other checkpoints, which suggests a phenotypic change after T cell infiltration into the tumor, such as T cell exhaustion.

Immune Dysfunctions and Immune-Based Therapeutic Interventions in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy characterized by a wide range of tumor-induced alterations, which affect both the innate and adaptive arms of the immune response, and accumulate during disease progression. In recent years, the development of targeted therapies, such as the B-cell receptor signaling inhibitors and the Bcl-2 protein inhibitor venetoclax, has dramatically changed the treatment landscape of CLL. Despite their remarkable anti-tumor activity, targeted agents have some limitations, which include the development of drug resistance mechanisms and the inferior efficacy observed in high-risk patients. Therefore, additional treatments are necessary to obtain deeper responses and overcome drug resistance. Allogeneic hematopoietic stem cell transplantation (HSCT), which exploits immune-mediated graft-versus-leukemia effect to eradicate tumor cells, currently represents the only potentially curative therapeutic option for CLL patients. However, due to its potential toxicities, HSCT can be offered only to a restricted number of younger and fit patients. The growing understanding of the complex interplay between tumor cells and the immune system, which is responsible for immune escape mechanisms and tumor progression, has paved the way for the development of novel immune-based strategies. Despite promising preclinical observations, results from pilot clinical studies exploring the safety and efficacy of novel immune-based therapies have been sometimes suboptimal in terms of long-term tumor control. Therefore, further advances to improve their efficacy are needed. In this context, possible approaches include an earlier timing of immunotherapy within the treatment sequencing, as well as the possibility to improve the efficacy of immunotherapeutic agents by administering them in combination with other anti-tumor drugs. In this review, we will provide a comprehensive overview of main immune defects affecting patients with CLL, also describing the complex networks leading to immune evasion and tumor progression. From the therapeutic standpoint, we will go through the evolution of immune-based therapeutic approaches over time, including i) agents with broad immunomodulatory effects, such as immunomodulatory drugs, ii) currently approved and next-generation monoclonal antibodies, and iii) immunotherapeutic strategies aiming at activating or administering immune effector cells specifically targeting leukemic cells (e.g. bi-or tri-specific antibodies, tumor vaccines, chimeric antigen receptor T cells, and checkpoint inhibitors).

Clinical significance of CD200 expression in newly diagnosed multiple myeloma patients and dynamic changing during treatment

The aim of our study was to determine the impact of CD200 expression in newly diagnosed myltiple myeloma (MM) patients. CD200⁺ patients had significantly shorter median overall survival time (OS) than CD200^- patients (41.0 months vs. not reached, p = .009). The ratio of CD4⁺ to CD8⁺ T cells was lower in CD200⁺ patients and this reduction was significantly related to the increase of CD8⁺ T cells (p = .021). Moreover, we analyzed dynamic changes of CD200 expression in 47 CD200⁺ patients during treatment. Thirty-eight (80.9%) patients switched to CD200^- during treatment. Those patients had a favorable survival compared with the others (median OS, 65.0 vs. 32.0 months, p < .001; median PFS, 29.0 vs. 11.5 months, p = .027). We concluded that CD200 expression is an independent marker for MM prognostic estimation during treatment.

Prognostic Value of CD200R1 mRNA Expression in Head and Neck Squamous Cell Carcinoma

Immune system dysfunction is associated with head and neck squamous cell carcinoma (HNSCC) development and progression and immune checkpoint inhibitors have demonstrated substantial survival benefits in platinum-refractory HNSCC; therefore, we examined the prognostic value of immune-related gene (IRG) expression in HNSCC. We analyzed the expression of 82 IRGs in 71 patients with HNSCC enrolled in a feasibility study for a prospective HNSCC biomarker-driven umbrella trial (Korean Cancer Study Group TRIUMPH study, NCT03292250). CD200R1 was identified as an independent prognostic factor and validated in GEO and TCGA database. CD2000R1 mRNA expression was found to be an independent favorable prognostic factor in patients with HNSCC. Moreover, CD200R1 was found to affect genes and pathways associated with the immune response, while seven differentially expressed genes (CD8A, DOK2, CX3CR1, TYROBP, CXCL9, CD300LF, IFNG) were associated with CD200R1 expression. Samples with higher CD200R1 expression displayed higher tumor-infiltrating immune cell counts both in silico and in histological analysis. These findings will help in the development of more accurate prognostic tools and suggest CD200R1 modulation as a HNSCC immunotherapy.