Immune modulation by melanoma and ovarian tumor cells through expression of the immunosuppressive molecule CD200

Whole-genome resequencing reveals diversity and selective signals in the Wuxue goat

Animal genetic resources are crucial for ensuring global food security. However, in recent years, a noticeable decline in the genetic diversity of livestock has occurred worldwide. This decline is pronounced in developing countries, where the management of these resources is insufficient. In the current study, we performed whole genome sequencing for 20 Wuxue (WX) and five Guizhou White (GW) goats. Additionally, we utilized the published genomes of 131 samples representing five different goat breeds from various regions in China. We investigated and compared the genetic diversity and selection signatures of WX goats. Whole genome sequencing analysis of the WX and GW populations yielded 120 425 063 SNPs, which resided primarily in intergenic and intron regions. Population genetic structure revealed that WX exhibited genetic resemblance to GW, Chengdu Brown, and Jintang Black and significant differentiation from the other goat breeds. In addition, three methods (nucleotide diversity, linkage disequilibrium decay, and runs of homozygosity) showed moderate genetic diversity in WX goats. We used nucleotide diversity and composite likelihood ratio methods to identify within-breed signatures of positive selection in WX goats. A total of 369 genes were identified using both detection methods, including genes related to reproduction (GRID2, ZNF276, TCF25, and SPIRE2), growth (HMGA2 and GJA3), and immunity (IRF3 and SRSF3). Overall, this study explored the adaptability of WX goats, shedding light on their genetic richness and potential to thrive in challenges posed by climatic changes and diseases. Further investigations are warranted to harness these insights to enhance more efficient and sustainable goat breeding initiatives.

Leishmania antigens activated CD4+ T cells expressing CD200R receptors are the prime IL-10 producing phenotype and an important determinant of visceral leishmaniasis pathogenesis

The excessive production of IL-10, an anti-inflammatory cytokine, by Leishmania antigen-activated T cells is supposed to be a key player in the onset and progression of visceral leishmaniasis (VL). The IL-10-producing sources in VL remain unidentified and uncharacterized. In this study, we reveal that antigen-activated CD4+ T cells, i.e., CD44+CD4+ T cells expressing CD200R receptors, are the prime IL-10-producing phenotypes in Leishmania donovani infection-induced pathogenesis. These phenotypes are separate from CD25+Foxp3+CD4+ T regulatory cells, which are classical IL-10-producing phenotypes. In order to ascertain the role of CD200R and CD25 receptors in IL-10 overexpression-associated VL pathogenesis, we abrogated CD200R and CD25 receptor-mediated signaling in the infected mice. The splenic load of parasites and the size of the liver and spleen were significantly reduced in CD200-blocked mice as compared to CD25-blocked mice. Further, the CD200 blocking polarized CD4+ T cells to pro-inflammatory cytokines-producing phenotypes, as we observed a higher frequency of IFN-γ, TNF-α, and IL-12 positive cells as compared to controls including the CD25 blocking. Our findings suggest that in L. donovani infection-induced pathogenesis the expression of CD200R on antigen-activated T cells helps them to acquire IL-10-producing abilities as part of its one of the survival strategies. However, more studies would be warranted to better understand CD200R receptors role in VL pathogenesis and to develop the next generation of therapeutic and prophylactic control measures.

CAR NK Cell Therapy for the Treatment of Metastatic Melanoma: Potential & Prospects

Melanoma is among the most lethal forms of cancer, accounting for 80% of deaths despite comprising just 5% of skin cancer cases. Treatment options remain limited due to the genetic and epigenetic mechanisms associated with melanoma heterogeneity that underlie the rapid development of secondary drug resistance. For this reason, the development of novel treatments remains paramount to the improvement of patient outcomes. Although the advent of chimeric antigen receptor-expressing T (CAR-T) cell immunotherapies has led to many clinical successes for hematological malignancies, these treatments are limited in their utility by their immune-induced side effects and a high risk of systemic toxicities. CAR natural killer (CAR-NK) cell immunotherapies are a particularly promising alternative to CAR-T cell immunotherapies, as they offer a more favorable safety profile and have the capacity for fine-tuned cytotoxic activity. In this review, the discussion of the prospects and potential of CAR-NK cell immunotherapies touches upon the clinical contexts of melanoma, the immunobiology of NK cells, the immunosuppressive barriers preventing endogenous immune cells from eliminating tumors, and the structure and design of chimeric antigen receptors, then finishes with a series of proposed design innovations that could improve the efficacy CAR-NK cell immunotherapies in future studies.

The Use of CD200 in the Differential Diagnosis of B-Cell Lymphoproliferative Disorders

Background: B-Cell Lymphoproliferative Disorders (B-LPDs) are a group of heterogenous disorders characterised by the accumulation of B-cells in peripheral blood, bone marrow, lymph nodes and spleen. They have a variable disease course and outcome and many share similar features making differential diagnosis challenging. Therefore, accurate diagnosis is fundamental in particular for determining treatment options. Immunophenotyping by flow cytometry plays a crucial role in the diagnosis of B-LPDs. However, overlapping immunophenotyping patterns exist and the use of novel monoclonal antibodies has become increasingly important in immunophenotyping analysis. More recently differential expression of CD200 has been reported in various B-LPDs and that CD200 may improve the differentiation between chronic lymphocytic leukaemia (CLL) and mantle cell lymphoma (MCL). In this study CD200 expression is evaluated in different B-LPDs. Methods: A total of 100 samples were collected and analysed by immunophenotyping flow cytometry over a period of 1 year (2017-2018), by a panel of monoclonal antibodies including CD200. The percentage of CD200 and its expression intensity was evaluated and compared between different groups of B-LPDs. Results: All of the 50 cases of CLL expressed CD200 with moderate to bright intensity, 6 MCL cases lacked the expression of CD200. Furthermore, all 5 cases of hairy cell leukaemia (HCL) expressed CD200. Out of all B-LPDs evaluated, CD200 expression in HCL cases was noted to be the brightest. The other 39 cases were not found to be B-LPDs. Conclusion: CD200 has an important role in differentiating CLL from MCL, HCL has a consistent bright expression of CD200. By adding CD200 to the combinations of markers in routine testing panel, Immunophenotyping by flow cytometry can be an effective tool in the diagnosis of B-LPDs especially in cases with atypical immunophenotyping pattern. Our result support that CD200 can be added to routine testing panel as it is useful in differentiating them.

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.

The road of NSCLC stem cells toward bone metastases

Despite advancement in therapeutic options, Non-Small Cell lung cancer (NSCLC) remains a lethal disease mostly due to late diagnosis at metastatic phase and drug resistance. Bone is one of the more frequent sites for NSCLC metastatization. A defined subset of cancer stem cells (CSCs) that possess motile properties, mesenchymal features and tumor initiation potential are defined as metastasis initiating cells (MICs). A better understanding of the mechanisms supporting MIC dissemination and interaction with bone microenvironment is fundamental to design novel rational therapeutic option for long lasting efficient treatment of NSCLC. In this review we will summarize findings about bone metastatic process initiated by NSCLC MICs. We will review how MICs can reach bone and interact with its microenvironment that supports their extravasation, seeding, dormancy/proliferation. The role of different cell types inside the bone metastatic niche, such as endothelial cells, bone cells, hematopoietic stem cells and immune cells will be discussed in regards of their impact in dictating the success of metastasis establishment by MICs. Finally, novel therapeutic options to target NSCLC MIC-induced bone metastases, increasing the survival of patients, will be presented.

CD200 ectodomain shedding into the tumor microenvironment leads to NK cell dysfunction and apoptosis

The basis of immune evasion, a hallmark of cancer, can differ even when cancers arise from one cell type such as in the human skin keratinocyte carcinomas: basal and squamous cell carcinoma. Here we showed that the basal cell carcinoma tumor-initiating cell surface protein CD200, through ectodomain shedding, was responsible for the near absence of NK cells within the basal cell carcinoma tumor microenvironment. In situ, CD200 underwent ectodomain shedding by metalloproteinases MMP3 and MMP11, which released biologically active soluble CD200 into the basal cell carcinoma microenvironment. CD200 bound its cognate receptor on NK cells to suppress MAPK pathway signaling that in turn blocked indirect (IFN-γ release) and direct cell killing. In addition, reduced ERK phosphorylation relinquished negative regulation of PPARγ-regulated gene transcription and led to membrane accumulation of the Fas/FADD death receptor and its ligand, FasL, which resulted in activation-induced apoptosis. Blocking CD200 inhibition of MAPK or PPARγ signaling restored NK cell survival and tumor cell killing, with relevance to many cancer types. Our results thus uncover a paradigm for CD200 as a potentially novel and targetable NK cell-specific immune checkpoint, which is responsible for NK cell-associated poor outcomes in many cancers.

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.

The CD200-CD200R axis promotes squamous cell carcinoma metastasis via regulation of cathepsin K

The CD200-CD200R immunoregulatory signaling axis plays an etiological role in the survival and spread of numerous cancers primarily through suppression of anti-tumor immune surveillance. Our previous work outlined a pro-metastatic role for the CD200-CD200R axis in cutaneous squamous cell carcinoma (cSCC) that is independent of direct T cell suppression but modulates the function of infiltrating myeloid cells. To identify effectors of the CD200-CD200R axis important for cSCC metastasis, we conducted RNA-Seq profiling of infiltrating CD11B+Cd200R+ cells isolated from CD200+ versus CD200-null cSCCs and identified the cysteine protease cathepsin K (Ctsk) to be highly upregulated in CD200+ cSCCs. CD11B+Cd200R+ cells expressed phenotypic markers associated with myeloid-derived suppressor cell-like cells and tumor-associated macrophages and were the primary source of Ctsk expression in cSCC. A Cd200R+ myeloid cell-cSCC co-culture system showed that induction of Ctsk was dependent on engagement of the CD200-CD200R axis, indicating that Ctsk is a target gene of this pathway in the cSCC tumor microenvironment. Inhibition of Ctsk, but not matrix metalloproteinases (MMP), significantly blocked cSCC cell migration in vitro. Finally, targeted CD200 disruption in tumor cells and Ctsk pharmacological inhibition significantly reduced cSCC metastasis in vivo. Collectively, these findings support the conclusion that CD200 stimulates cSCC invasion and metastasis via induction of Ctsk in CD200R+ infiltrating myeloid cells.

Overexpression of Endogenous Retroviruses and Malignancy Markers in Neuroblastoma Cell Lines by Medium-Induced Microenvironmental Changes

Neuroblastoma (NB) is the commonest solid tumor outside the central nervous system in infancy and childhood with a unique biological heterogeneity. In patients with advanced, metastasizing neuroblastoma, treatment failure and poor prognosis is often marked by resistance to chemo- or immunotherapy. Thus, identification of robust biomarkers seems essential for understanding tumor progression and developing effective therapy. Here, we have studied the expression of human endogenous retroviruses (HERV) as potential targets in NB cell lines during stem-cell medium-induced microenvironmental change. Quantitative PCR revealed that relative expression of the HERV-K family and HERV-W1 ENV were increased in all three NB cell lines after incubation in stem-cell medium. Virus transcriptome analyses revealed the transcriptional activation of three endogenous retrovirus elements: HERV-R ENV (ERV3-1), HERV-E1 and HERV-Fc2 ENV (ERVFC1-1). Known malignancy markers in NB, e.g. proto-oncogenic MYC or MYCN were expressed highly heterogeneously in the three investigated NB cell lines with up-regulation of MYC and MYCN upon medium-induced microenvironmental change. In addition, SiMa cells exclusively showed a phenotype switching from loosely-adherent monolayers to low proliferating grape-like cellular aggregates, which was accompanied by an enhanced CD133 expression. Interestingly, the overexpression of HERV was associated with a significant elevation of immune checkpoint molecule CD200 in both quantitative PCR and RNA-seq analysis suggesting tumor escape mechanism in NB cell lines after incubation in serum-free stem cell medium.

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.

Whole-genome resequencing reveals diversity and selective signals in Longlin goat

The Longlin goat is one of the most valuable livestock species in Guangxi Autonomous Region of China, but its genomic diversity and selective signals are not clearly elucidated. Here we compared 20 genomes of Longlin goat to 66 genomes of other seven goat breeds worldwide to analyze patterns of Longlin goat genetic variation. We found the lowest linkage disequilibrium at the large distances between SNPs associated with the highest effective population size in the recent generations ago in Longlin goat. The eight goat breeds could be divided into Euro-African and East Asian goat population. Interestingly, like East Asian taurine, the same two migration phases might have occurred in the history of East Asian goat. More importantly, we identified selective signals implicated in immune resistance to disease, especially for skin disease, in Longlin goat. Our findings will not only help understand the evolutionary history and breed characteristic but can provide valuable resources for conservation of germplasm resources and implementation of crossbreeding programs.

Transcriptome analysis of desmoplastic small round cell tumors identifies actionable therapeutic targets: a report from the Children's Oncology Group

To further understand the molecular pathogenesis of desmoplastic small round cell tumor (DSRCT), a fatal malignancy occurring primarily in adolescent/young adult males, we used next-generation RNA sequencing to investigate the gene expression profiles intrinsic to this disease. RNA from DSRCT specimens obtained from the Children's Oncology Group was sequenced using the Illumina HiSeq 2000 system and subjected to bioinformatic analyses. Validation and functional studies included WT1 ChIP-seq, EWS-WT1 knockdown using JN-DSRCT-1 cells and immunohistochemistry. A panel of immune signature genes was also evaluated to identify possible immune therapeutic targets. Twelve of 14 tumor samples demonstrated presence of the diagnostic EWSR1-WT1 translocation and these 12 samples were used for the remainder of the analysis. RNA sequencing confirmed the lack of full-length WT1 in all fusion positive samples as well as the JN-DSRCT-1 cell line. ChIP-seq for WT1 showed significant overlap with genes found to be highly expressed, including IGF2 and FGFR4, which were both highly expressed and targets of the EWS-WT1 fusion protein. In addition, we identified CD200 and CD276 as potentially targetable immune checkpoints whose expression is independent of the EWS-WT1 fusion gene in cultured DSCRT cells. In conclusion, we identified IGF2, FGFR4, CD200, and CD276 as potential therapeutic targets with clinical relevance for patients with DSRCT.

PD-1 blockade inhibits osteoclast formation and murine bone cancer pain

Emerging immune therapy, such as with the anti-programmed cell death-1 (anti-PD-1) monoclonal antibody nivolumab, has shown efficacy in tumor suppression. Patients with terminal cancer suffer from cancer pain as a result of bone metastasis and bone destruction, but how PD-1 blockade affects bone cancer pain remains unknown. Here, we report that mice lacking Pdcd1 (Pd1-/-) demonstrated remarkable protection against bone destruction induced by femoral inoculation of Lewis lung cancer cells. Compared with WT mice, Pd1-/- mice exhibited increased baseline pain sensitivity, but the development of bone cancer pain was compromised in Pd1-/- mice. Consistently, these beneficial effects in Pd1-/- mice were recapitulated by repeated i.v. applications of nivolumab in WT mice, even though nivolumab initially increased mechanical and thermal pain. Notably, PD-1 deficiency or nivolumab treatment inhibited osteoclastogenesis without altering tumor burden. PD-L1 and CCL2 are upregulated within the local tumor microenvironment, and PD-L1 promoted RANKL-induced osteoclastogenesis through JNK activation and CCL2 secretion. Bone cancer upregulated CCR2 in primary sensory neurons, and CCR2 antagonism effectively reduced bone cancer pain. Our findings suggest that, despite a transient increase in pain sensitivity following each treatment, anti-PD-1 immunotherapy could produce long-term benefits in preventing bone destruction and alleviating bone cancer pain by suppressing osteoclastogenesis.

CD200 is overexpressed in neuroblastoma and regulates tumor immune microenvironment

Patients with pediatric cancers such as neuroblastoma (NB) are often unresponsive to checkpoint blockade immunotherapy. One major factor in pediatric tumor resistance to immunotherapy is considered to be the low mutation rate of pediatric tumors. Another factor may be the overexpression of additional inhibitory pathways. While analyzing the RNA-sequencing database TARGET, we found that human NB tumors overexpress immune checkpoint molecule CD200. To determine its significance and impact on tumor immune microenvironment, we analyzed 49 cases of previously untreated, surgically removed NB tumors using immunohistochemistry and multi-color flow cytometry (FACS). We found that CD200 is overexpressed in more than 90% of NB tumors. In the tumor microenvironment of NB, CD200 is mainly overexpressed in CD45^- NB tumor cells, while its cognate receptor (CD200R) is mainly expressed in HLA-DR⁺CD14⁺ myeloid cells and CD11c⁺ dendritic cells. Low-level expression of CD200R is also observed in tumor-infiltrating CD4⁺ and CD8⁺ T cells. In NB tumors with higher CD200 expression (CD200^high), we observed lower numbers of HLA-DR⁺CD14⁺ myeloid cells and less tumor-infiltrating CD4⁺ and CD8⁺ T cells. Moreover, we found that CD4⁺ and CD8⁺ T cells produced less IFN-γ and/or TNF-α in CD200^high NB tumors. Thus, CD200-CD200R pathway appears to downregulate anti-tumor immunity in the tumor microenvironment of NB tumors, and blockade of this pathway may be beneficial for NB patients.

CD200 promotes immunosuppression in the pancreatic tumor microenvironment

BACKGROUND

A significant challenge to overcome in pancreatic ductal adenocarcinoma (PDAC) is the profound systemic immunosuppression that renders this disease non-responsive to immunotherapy. Our supporting data provide evidence that CD200, a regulator of myeloid cell activity, is expressed in the PDAC microenvironment. Additionally, myeloid-derived suppressor cells (MDSC) isolated from patients with PDAC express elevated levels of the CD200 receptor (CD200R). Thus, we hypothesize that CD200 expression in the PDAC microenvironment limits responses to immunotherapy by promoting expansion and activity of MDSC.

METHODS

Immunofluorescent staining was used to determine expression of CD200 in murine and human PDAC tissue. Flow cytometry was utilized to test for CD200R expression by immune populations in patient blood samples. In vivo antibody blocking of CD200 was conducted in subcutaneous MT-5 tumor-bearing mice and in a genetically engineered PDAC model (KPC-Brca2 mice). Peripheral blood mononuclear cells (PBMC) from patients with PDAC were analyzed by single-cell RNA sequencing. MDSC expansion assays were completed using healthy donor PBMC stimulated with IL-6/GM-CSF in the presence of recombinant CD200 protein.

RESULTS

We found expression of CD200 by human pancreatic cell lines (BxPC3, MiaPaca2, and PANC-1) as well as on primary epithelial pancreatic tumor cells and smooth muscle actin+ stromal cells. CD200R expression was found to be elevated on CD11b+CD33+HLA-DRlo/- MDSC immune populations from patients with PDAC (p=0.0106). Higher expression levels of CD200R were observed in CD15+ MDSC compared with CD14+ MDSC (p<0.001). In vivo studies demonstrated that CD200 antibody blockade limited tumor progression in MT-5 subcutaneous tumor-bearing and in KPC-Brca2 mice (p<0.05). The percentage of intratumoral MDSC was significantly reduced in anti-CD200 treated mice compared with controls. Additionally, in vivo blockade of CD200 can also significantly enhance the efficacy of PD-1 checkpoint antibodies compared with single antibody therapies (p<0.05). Single-cell RNA sequencing of PBMC from patients revealed that CD200R+ MDSC expressed genes involved in cytokine signaling and MDSC expansion. Further, in vitro cytokine-driven expansion and the suppressive activity of human MDSC was enhanced when cocultured with recombinant CD200 protein.

CONCLUSIONS

These results indicate that CD200 expression in the PDAC microenvironment may regulate MDSC expansion and that targeting CD200 may enhance activity of checkpoint immunotherapy.

CD200 and CD200R1 are differentially expressed and have differential prognostic roles in non-small cell lung cancer

CD200, a member of the immunoglobulin superfamily, interacts with its receptor CD200R1 to modulate cancer immune microenvironments. Here, we explored the clinicopathological and prognostic implications of the CD200/CD200R1 axis in non-small-cell lung cancer (NSCLC) patients. We evaluated CD200/CD200R1 expression in the tumors and stroma of 632 NSCLC patients using immunohistochemistry. Associations between CD200/CD200R1 expression levels and clinicopathological data were analyzed. We also examined their expression in lung cancer cell lines. Changes in endogenous immune-related factors and cell proliferation were evaluated by CD200 and CD200R1 knockdown and CD200Fc fusion protein administration. CD200 expression was observed mainly in the tumor, and also in the stroma among a few cases, whereas CD200R1 expression was observed in both the tumor and stroma. High tumoral CD200 expression was significantly associated with female sex, never-smoking status, adenocarcinoma histology, EGFR mutation, and a low density of tumor-infiltrating lymphocytes. Meanwhile, high CD200R1 expression in the tumor and stroma was associated with ever smoking, non-adenocarcinoma histology, and increased tumor-infiltrating lymphocytes. High CD200R1 expression was associated with worse survival (log-rank, P <.001 for both tumor and stroma), whereas high CD200 expression was associated with better survival outcomes (log-rank, P <.001). The transient knockdown of CD200R1 in lung cancer cell lines impaired cell proliferation, and the in vitro modulation of CD200 and CD200R1 altered endogenous oncogenic and inflammation-related gene expression. CD200R1 expression was associated with poor prognosis, whereas CD200 expression was an independent favorable prognostic factor. Our results suggest the importance of CD200 and CD200R1 in lung cancer biology.

The CD200-CD200R cross-talk helps Leishmania donovani to down regulate macrophage and CD4+CD44+ T cells effector functions in an NFκB independent manner

The lacuna in the knowledge of immunobiology, especially in visceral infections that are fatal if left untreated, are a major hurdle in getting a vaccine candidate for leishmaniasis. Till date, only a few drugs are available to combat human leishmaniasis and a vaccine candidate either prophylactic or preventive is still awaited. Therefore, identification of host and parasitic factors involved in the regulation of specific immune mechanisms are essentially needed. In this study, we observed that CD200-CD200R immune inhibitory axis regulates host macrophages effectors properties and helps antigen experienced T cells (CD4⁺CD44⁺ T cells) to acquire anti-inflammatory cytokines (IL-4, IL-10, TGF-β, IL-27) producing abilities in an NFkB independent manner. After CD200 blocking the macrophages effectively inhibited proliferation of Leishmania amastigotes and also induced the production of IL-12, IFN-γ, TNF-α and nitric oxide (NOx). Further, the blocking of CD200 signaling also restored macrophages MHC-II expression and helped CD4⁺CD44⁺ T cells to produce pro-inflammatory cytokines like IL-2, IL-12 and IFN-γ. The finding of this study suggested the importance of immune inhibitory mechanisms in controlling Leishmania growth and survival and therefore, requires more studies to understand its role in vaccine induced immunity.

NK Cell-Based Immune Checkpoint Inhibition

Immunotherapy, with an increasing number of therapeutic dimensions, is becoming an important mode of treatment for cancer patients. The inhibition of immune checkpoints, which are the source of immune escape for various cancers, is one such immunotherapeutic dimension. It has mainly been aimed at T cells in the past, but NK cells are a newly emerging target. Simultaneously, the number of checkpoints identified has been increasing in recent times. In addition to the classical NK cell receptors KIRs, LIRs, and NKG2A, several other immune checkpoints have also been shown to cause dysfunction of NK cells in various cancers and chronic infections. These checkpoints include the revolutionized CTLA-4, PD-1, and recently identified B7-H3, as well as LAG-3, TIGIT & CD96, TIM-3, and the most recently acknowledged checkpoint-members of the Siglecs family (Siglec-7/9), CD200 and CD47. An interesting dimension of immune checkpoints is their candidacy for dual-checkpoint inhibition, resulting in therapeutic synergism. Furthermore, the combination of immune checkpoint inhibition with other NK cell cytotoxicity restoration strategies could also strengthen its efficacy as an antitumor therapy. Here, we have undertaken a comprehensive review of the literature to date regarding NK cell-based immune checkpoints.

CD200-CD200R Pathway in the Regulation of Tumor Immune Microenvironment and Immunotherapy

Tumor-associated inflammation and immune responses are key components in the tumor microenvironment (TME) which regulate tumor growth, progression, and metastasis. Tumor-associated myeloid cells (TAMCs) are a group of cells that play multiple key roles including induction of tumor-associated inflammation/angiogenesis and regulation of tumor-specific T-cell responses. Thus, identification and characterization of key pathways that can regulate TAMCs are of critical importance for developing cancer immunotherapy. Recent studies suggest that CD200-CD200 receptor (CD200R) interaction may be important in regulating the TME via affecting TAMCs. In this chapter, we will give a brief overview of the CD200-CD200R axis, including the biology behind CD200-CD200R interaction and the role(s) it plays in tumor microenvironment and tumor growth, and activation/effector functions of T cells. We will also discuss CD200-CD200R's role as potential checkpoint molecules for cancer immunotherapy. Further investigation of the CD200-CD200R pathway will not only advance our understanding of tumor pathogenesis and immunity but also provide the rationale for CD200-CD200R-targeted immunotherapy of human cancer.

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

PURPOSE

Samalizumab is a novel recombinant humanized monoclonal antibody that targets CD200, an immunoregulatory cell surface member of the immunoglobulin superfamily that dampens excessive immune responses and maintains self-tolerance. This first-in-human study investigated the therapeutic use of samalizumab as a CD200 immune checkpoint inhibitor in chronic lymphocytic leukemia (CLL) and multiple myeloma (MM).

EXPERIMENTAL DESIGN

Twenty-three patients with advanced CLL and 3 patients with MM were enrolled in an open-label phase 1 study (NCT00648739). Patients were assigned sequentially to one of 7 dose level cohorts (50 to 600 mg/m²) in a 3 + 3 study design, receiving a single dose of samalizumab intravenously once every 28 days. Primary endpoints were safety, identification of the maximum tolerated dose (MTD), and pharmacokinetics. Secondary endpoints were samalizumab binding to CD200, pharmacodynamic effects on circulating tumor cells and leukocyte subsets, and clinical responses.

RESULTS

Twenty-one patients received > 1 treatment cycle. Adverse events (AEs) were generally mild to moderate in severity. Samalizumab produced dose-dependent decreases in CD200 expression on CLL cells and decreased frequencies of circulating CD200 + CD4+ T cells that were sustained at higher doses. The MTD was not reached. Decreased tumor burden was observed in 14 CLL patients. One CLL patient achieved a durable partial response and 16 patients had stable disease. All MM patients had disease progression.

CONCLUSIONS

Samalizumab had a good safety profile and treatment was associated with reduced tumor burden in a majority of patients with advanced CLL. These preliminary positive results support further development of samalizumab as an immune checkpoint inhibitor.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT00648739 registered April 1, 2008.

Single nucleotide polymorphism rs3746444 in miR‑499a affects susceptibility to non‑small cell lung carcinoma by regulating the expression of CD200

The present study evaluated the association between single nucleotide polymorphism (SNP) rs3746444 and the risk of non‑small cell lung carcinoma (NSCLC) in a Chinese population. Computational analyses and luciferase assays were performed to investigate the regulatory relationship between miR‑499a and CD200. In addition, reverse transcription‑quantitative polymerase chain reaction and western blot assays were performed to examine the effect of rs3746444 on the expression of miR‑499a and CD200. The results demonstrated a significant difference in the smoking history of patients carrying malignant pulmonary nodules and those carrying benign pulmonary nodules. Furthermore, CD200 was demonstrated to be a direct target of miR‑499a, and a miR‑499a binding site was located in the 3'UTR of CD200. Notably, the levels of miR‑499a in malignant pulmonary nodules were higher compared with benign pulmonary nodules, while the levels of CD200 were higher in benign pulmonary nodules compared with malignant pulmonary nodules. In addition, the subjects carrying the AA genotype of SNP rs3746444 exhibited upregulated miR‑499a expression and reduced CD200 expression, compared with the subjects carrying AG and GG genotypes. These findings indicate that the SNP rs3746444 in miR‑499a could affect the prognosis of NSCLC patients by regulating the expression of CD200.

Treatment Combining CD200 Immune Checkpoint Inhibitor and Tumor-Lysate Vaccination after Surgery for Pet Dogs with High-Grade Glioma

Recent advances in immunotherapy have included inhibition of immune checkpoint proteins in the tumor microenvironment and tumor lysate-based vaccination strategies. We combined these approaches in pet dogs with high-grade glioma. Administration of a synthetic peptide targeting the immune checkpoint protein, CD200, enhanced the capacity of antigen-presenting cells to prime T-cells to mediate an anti-glioma response. We found that in canine spontaneous gliomas, local injection of a canine-specific, CD200-directed peptide before subcutaneous delivery of an autologous tumor lysate vaccine prolonged survival relative to a historical control treated with autologous tumor lysate alone (median survivals of 12.7 months and 6.36 months, respectively). Antigen-presenting cells and T-lymphocytes primed with this peptide suppressed their expression of the inhibitory CD200 receptor, thereby enhancing their ability to initiate immune reactions in a glioblastoma microenvironment replete with the immunosuppressive CD200 protein. These results support consideration of a CD200 ligand as a novel glioblastoma immunotherapeutic agent.

CD200 expression is a feature of solid pseudopapillary neoplasms of the pancreas

CD200 has been recently indicated as a robust marker of well-differentiated neuroendocrine neoplasms. Here, we evaluate its role in differential diagnosis of solid pancreatic neoplasms. We immunostained for CD200 22 solid pseudopapillary neoplasms (SPNs), 8 acinar carcinomas (ACs), 2 pancreatoblastomas (PBs), 138 neuroendocrine tumors (PanNETs), and 48 ductal adenocarcinomas. All SPNs showed strong cytoplasmic and membranous staining for CD200, while only one case of AC had focal positivity. The two PBs showed focal CD200 positivity, mainly located in squamoid nests. The vast majority of PanNETs (96%) showed strong cytoplasmic and membranous staining for CD200, whereas all PDACs were negative. As both PanNETs and SPNs express CD200, it has no role in the differential diagnosis between these two entities.

Merkel cell carcinoma expresses the immunoregulatory ligand CD200 and induces immunosuppressive macrophages and regulatory T cells

Merkel cell carcinoma (MCC) is a rare and aggressive skin cancer that responds to PD-1/PD-L1 immune checkpoint inhibitors. CD200 is another checkpoint modulator whose receptor is found on tumor-promoting myeloid cells, including M2 macrophages. We found high CD200 mRNA expression in MCC tumors, and CD200 immunostaining was demonstrated on 95.5% of MCC tumors. CD200R-expressing myeloid cells were present in the MCC tumor microenvironment. MCC-associated macrophages had a higher average CD163:CD68 staining ratio (2.67) than controls (1.13), indicating an immunosuppressive M2 phenotype. Accordingly, MCC tumors contained increased densities of FOXP3⁺ regulatory T-cells. Intravenous administration of blocking anti-CD200 antibody to MCC xenograft mice revealed specific targeting of drug to tumor. In conclusion, MCC are highly CD200 positive and associated with immunosuppressive M2 macrophages and regulatory T-cells. As anti-CD200 antibody effectively targets CD200 on MCC tumor cells in vivo, this treatment may provide a novel immunotherapy for MCC independent of PD-1/PD-L1 blockade.

A CD200R-CD28 fusion protein appropriates an inhibitory signal to enhance T-cell function and therapy of murine leukemia

Acute myeloid leukemia (AML), the most common adult acute leukemia in the United States, has the poorest survival rate, with 26% of patients surviving 5 years. Adoptive immunotherapy with T cells genetically modified to recognize tumors is a promising and evolving treatment option. However, antitumor activity, particularly in the context of progressive leukemia, can be dampened both by limited costimulation and triggering of immunoregulatory checkpoints that attenuate T-cell responses. Expression of CD200 (OX2), a negative regulator of T-cell function that binds CD200 receptor (CD200R), is commonly increased in leukemia and other malignancies and is associated with poor prognosis in leukemia patients. To appropriate and redirect the inhibitory effects of CD200R signaling on transferred CD8+ T cells, we engineered CD200R immunomodulatory fusion proteins (IFPs) with the cytoplasmic tail replaced by the signaling domain of the costimulatory receptor, CD28. An analysis of a panel of CD200R-CD28 IFP constructs revealed that the most effective costimulation was achieved in IFPs containing a dimerizing motif and a predicted tumor-T-cell distance that facilitates localization to the immunological synapse. T cells transduced with the optimized CD200R-CD28 IFPs exhibited enhanced proliferation and effector function in response to CD200+ leukemic cells in vitro. In adoptive therapy of disseminated leukemia, CD200R-CD28-transduced leukemia-specific CD8 T cells eradicated otherwise lethal disease more efficiently than wild-type cells and bypassed the requirement for interleukin-2 administration to sustain in vivo activity. The transduction of human primary T cells with the equivalent human IFPs increased proliferation and cytokine production in response to CD200+ leukemia cells, supporting clinical translation. This trial was registered at www.clinicaltrials.gov as #NCT01640301.

Checkpoint blockade in solid tumors and B-cell malignancies, with special consideration of the role of CD200

In the ontogeny of a normal immune response, a series of checkpoints must be overcome to ensure that unwanted and/or harmful self-directed activation responses are avoided. Many of the molecules now known to be active in this overseeing of the evolving immune activation cascade, contributing inhibitory signals to dampen an overexuberant response, belong to the immunoglobulin supergene family. These include members of the CD28/CTLA-4:B7.1/B7.2 receptor/ligand family, PD-1 and PDL-1, CD200 and CD200R, and the more recently described V-domain immunoglobulin suppressor of T-cell activation and its ligand (VSIG-3/IGSF11). Unfortunately, from the point of view of improving immunotargeting of cancer cells, triggering these checkpoint inhibitory signaling pathways, so necessary to maintain self-tolerance, simultaneously acts to prevent effective tumor immunity. The recent development of reagents, predominantly antibodies, to act as checkpoint blockade agents, has had a dramatic effect on human cancer treatment, with a marked reported success for anti-CTLA-4 and PD-1 in particular in clinical trials. This review provides a general overview of the data now available showing the promise of such treatments to our cancer armamentarium and elaborates in depth on the potential promise of what can be regarded as an underappreciated target molecule for checkpoint blockade in chronic lymphocytic leukemia and solid tumors, CD200.

CD200 Expression in Neuroendocrine Neoplasms

Objectives

CD200 expression has been well studied in hematopoietic malignancies; however, CD200 expression has not been well-characterized in neuroendocrine neoplasms. We examined CD200 expression in 391 neuroendocrine neoplasms from various anatomic sites.

Methods

Tissue blocks containing pulmonary small cell carcinoma, pulmonary carcinoid, large cell neuroendocrine carcinoma, pancreatic neuroendocrine tumor, gastrointestinal carcinoid, and Merkel cell carcinoma were evaluated for CD200 expression by immunohistochemistry. A set of nonneuroendocrine carcinomas was stained for comparison.

Results

CD200 was expressed in 87% of the neuroendocrine neoplasms studied, including 60 of 72 (83%) pulmonary small cell carcinomas, 15 of 22 (68%) pulmonary carcinoids, three of four (75%) pulmonary large cell neuroendocrine carcinomas, 125 of 146 (86%) Merkel cell carcinomas, 79 of 83 (95%) gastrointestinal luminal carcinoids, and 56 of 60 (93%) pancreatic neuroendocrine tumors. Thirty-two of 157 (20%) nonneuroendocrine carcinomas expressed CD200. In gastrointestinal carcinoid and pancreatic neuroendocrine neoplasms, CD200 negativity correlated with higher grade.

Conclusions

CD200 is a relatively sensitive marker of neuroendocrine neoplasms and represents a potential therapeutic target in these difficult-to-treat malignancies.

Tumor-derived vaccines containing CD200 inhibit immune activation: implications for immunotherapy

There are over 400 ongoing clinical trials using tumor-derived vaccines. This approach is especially attractive for many types of brain tumors, including glioblastoma, yet so far the clinical response is highly variable. One contributor to poor response is CD200, which acts as a checkpoint blockade, inducing immune tolerance. We demonstrate that, in response to vaccination, glioma-derived CD200 suppresses the anti-tumor immune response. In contrast, a CD200 peptide inhibitor that activates antigen-presenting cells overcomes immune tolerance. The addition of the CD200 inhibitor significantly increased leukocyte infiltration into the vaccine site, cytokine and chemokine production, and cytolytic activity. Our data therefore suggest that CD200 suppresses the immune system's response to vaccines, and that blocking CD200 could improve the efficacy of cancer immunotherapy.

A Truncated form of CD200 (CD200S) Expressed on Glioma Cells Prolonged Survival in a Rat Glioma Model by Induction of a Dendritic Cell-Like Phenotype in Tumor-Associated Macrophages

CD200 induces immunosuppression in myeloid cells expressing its receptor CD200R, which may have consequences for tumor immunity. We found that human carcinoma tissues express not only full-length CD200 (CD200L) but also its truncated form, CD200S. Although CD200S is reported to antagonize the immunosuppressive actions of CD200L, the role of CD200S in tumor immunity has never been investigated. We established rat C6 glioma cell lines that expressed either CD200L or CD200S; the original C6 cell line did not express CD200 molecules. The cell lines showed no significant differences in growth. Upon transplantation into the neonatal Wistar rat forebrain parenchyma, rats transplanted with C6-CD200S cells survived for a significantly longer period than those transplanted with the original C6 and C6-CD200L cells. The C6-CD200S tumors were smaller than the C6-CD200L or C6-original tumors, and many apoptotic cells were found in the tumor cell aggregates. Tumor-associated macrophages (TAMs) in C6-CD200S tumors displayed dendritic cell (DC)-like morphology with multiple processes and CD86 expression. Furthermore, CD3⁺, CD4⁺ or CD8⁺ cells were more frequently found in C6-CD200S tumors, and the expression of DC markers, granzyme, and perforin was increased in C6-CD200S tumors. Isolated TAMs from original C6 tumors were co-cultured with C6-CD200S cells and showed increased expression of DC markers. These results suggest that CD200S activates TAMs to become DC-like antigen presenting cells, leading to the activation of CD8⁺ cytotoxic T lymphocytes, which induce apoptotic elimination of tumor cells. The findings on CD200S action may provide a novel therapeutic modality for the treatment of carcinomas.

Checkpoint Proteins in Pediatric Brain and Extracranial Solid Tumors: Opportunities for Immunotherapy

Pediatric brain and extracranial solid tumors are a diverse group of malignancies that represent almost half of all pediatric cancers. Standard therapy includes various combinations of surgery, cytotoxic chemotherapy, and radiation, which can be very harmful to a developing child, and survivors carry a substantial burden of long-term morbidities. Although these therapies have improved survival rates for children with solid tumors, outcomes still remain extremely poor for subsets of patients. Recently, immunosuppressive checkpoint molecules that negatively regulate immune cell function have been described. When found on malignant cells or in the tumor microenvironment, they contribute to immune evasion and tumor escape. Agents designed to inhibit these proteins have demonstrated significant efficacy in human adult solid tumor studies. However, there is limited research focusing on immune checkpoint molecules and inhibitors in pediatric solid tumors. In this review, we examine the current knowledge on immune checkpoint proteins with an emphasis on cytotoxic T lymphocyte antigen-4 (CTLA-4); programmed cell death protein-1 (PD-1) and programmed death-ligand 1 (PD-L1); OX-2 membrane glycoprotein (CD200); and indoleamine 2,3-dioxygenase (IDO). We review T-cell signaling, the mechanisms of action of these checkpoint molecules, pediatric preclinical studies on checkpoint proteins and checkpoint blockade, pediatric checkpoint inhibitor clinical trials conducted to date, and future immunotherapy opportunities for childhood cancers. Clin Cancer Res; 23(2); 342-50. ©2016 AACR.

Over-Expression of CD200 Predicts Poor Prognosis in Cutaneous Squamous Cell Carcinoma

BACKGROUND

CD200 is reported to be involved in tumor progression and can serve as a prognostic marker in several cancers. The purpose of this study was to evaluate the prognostic significance of CD200 in cutaneous squamous cell carcinoma (CSCC).

MATERIAL/METHODS

The relative mRNA and protein expression of CD200 in the tumor tissues and corresponding normal tissues of 102 CSCC patients were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot analysis, respectively. The chi-square test was used to analyze the association between CD200 expression and clinical features of CSCC patients. In addition, the overall survival of the patients according to the expression level of CD200 was estimated by Kaplan-Meier analysis and the prognostic significance of the gene was analyzed by Cox regression analysis.

RESULTS

Increased expression of CD200 was detected in the tumor tissues compared with the corresponding normal tissues both at mRNA and protein level. And CD200 expression level was associated with tumor differentiation grade (P=0.041) and clinical stage (P=0.004). Patients with high expression level of CD200 had a shorter overall survival than those with low expression (31.3 months vs. 41.9 months) and there was a significant difference between them (log-rank test, P<0.001). Cox regression analysis indicated that CD200 could be an independent marker for the prognosis of CSCC.

CONCLUSIONS

CD200 is up-regulated and may be a novel biomarker for the prognosis in CSCC, and it may be a potential therapeutic target for CSCC.

Targeting of heme oxygenase-1 as a novel immune regulator of neuroblastoma

Heme oxygenase (HO)-1 catalyzes the degradation of cytotoxic heme into biliverdin and blocks antitumor immune responses, thus protecting cancer against host defense. Whether this scenario also applies to neuroblastoma (NB), the most common extracranial solid childhood tumor, is not known. Here, we demonstrate for the first time a prognostic relevance of HO-1 expression in samples from NB patients and show that targeting of HO-1 prevents both cancer resistance against cellular stress and immune escape in the syngeneic NXS2 A/J mouse model of NB. High HO-1 RNA expression in NB tissues emerged as unfavorable prognostic marker, in particular for patients older than 18 months as indicated by univariate as well as multivariate survival probability analyses including disease stage and MYCN status. On the basis of this observation we aimed to target HO-1 by systemic as well as tumor-specific zinc protoporphyrin-mediated HO-1 suppression in a syngeneic immunocompetent NB mouse model. This resulted in 50% reduction of primary tumor growth and a suppression of spontaneous liver metastases. Importantly, HO-1 inhibition abrogated immune cell paralysis affecting CD4 and CD8 T-effector cells. This in turn reverted HO-1-dependent immune escape mechanisms in NB by increasing NB apoptosis and improved DC maturation. In summary, HO-1 emerges as a novel immune regulator in NB and emerges as a promising target for the development of therapeutic approaches.

Flow cytometric analysis of CD200 expression by pulmonary small cell carcinoma

BACKGROUND

CD200 is a membrane bound glycoprotein that is expressed by a variety of normal tissues and hematopoietic malignancies. Flow cytometric analysis of CD200 expression has utility in the evaluation of mature B-cell neoplasms, myeloma, and acute leukemia; however, CD200 expression in nonhematopoietic malignancies has not been extensively studied.

METHODS

We studied 14 cases of biopsy proven pulmonary small cell carcinoma in which a discrete CD45 negative, CD56 positive abnormal cell population was identified by flow cytometry. We retrospectively evaluated these cases for flow cytometric and immunohistochemical evidence of CD200 expression.

RESULTS

Twelve of the 14 cases of pulmonary small cell carcinoma showed convincing expression of CD200 by both immunohistochemistry and flow cytometry.

CONCLUSIONS

Pulmonary small cell carcinoma frequently expresses CD200 at a level that can be detected by flow cytometry and immunohistochemistry. CD200 expression therefore may be used to help identify pulmonary small cell carcinoma in flow cytometry specimens and tissue sections. CD200 may also play a role in the biology of pulmonary small cell carcinoma and is a potential target of future therapies. © 2015 International Clinical Cytometry Society.

Negative immune checkpoints on T lymphocytes and their relevance to cancer immunotherapy

The term 'inhibitory checkpoint' refers to the broad spectrum of co-receptors expressed by T cells that negatively regulate T cell activation thus playing a crucial role in maintaining peripheral self-tolerance. Co-inhibitory receptor ligands are highly expressed by a variety of malignancies allowing evasion of anti-tumour immunity. Recent studies demonstrate that manipulation of these co-inhibitory pathways can remove the immunological brakes that impede endogenous immune responses against tumours. Antibodies that block the interactions between co-inhibitory receptors and their ligands have delivered very promising clinical responses, as has been shown by recent successful trials targeting the CTLA-4 and PD-1 pathways. In this review, we discuss the mechanisms of action and expression pattern of co-inhibitory receptors on different T cells subsets, emphasising differences between CD4(+) and CD8(+) T cells. We also summarise recent clinical findings utilising immune checkpoint blockade.

The evolution of checkpoint blockade as a cancer therapy: what's here, what's next?

Unleashing the immune system to fight cancer has become one of the main treatment modalities since the anti-CTLA-4 antibody, ipilimumab was approved for patients with advanced melanoma in 2011. Pembrolizumab and nivolumab, two anti-PD-1 antibodies recently approved for the treatment of patients with metastatic melanoma, are being actively investigated for the treatment of multiple caners including lung, breast, bladder and renal cancers along with other anti-PD-1/L1 antibodies. Early results of combining of anti-CTLA-4 antibody and anti-PD-1 antibody treatment for advanced melanoma patients are showing impressive response rates with manageable toxicity profiles. There are several other checkpoint molecules that are likely potential inhibitory targets. The outcome of blocking some of these negative immune regulators, such as LAG-3 or TIM-3, is being pursued in the clinic or about to enter clinical development. Blockade of these molecules is demonstrating promising preclinical activity alone or when combined with anti-PD-1/L1. Future studies will define bio-markers of these therapies and how to target them alone or in combination with other immunotherapies, chemotherapy, radiotherapy and small molecule inhibitors.

Granulin-epithelin precursor renders hepatocellular carcinoma cells resistant to natural killer cytotoxicity

Immunoevasion is an emerging hallmark of cancer. Impairment of natural killer (NK) cytotoxicity is a mechanism to evade host immunosurveillance. Granulin-epithelin precursor (GEP) is a hepatic oncofetal protein regulating growth, invasion, and chemoresistance in hepatocellular carcinoma (HCC). We examined the role of GEP in conferring HCC cells the ability to evade NK cytotoxicity. In HCC cell lines, GEP overexpression reduced, whereas GEP suppression enhanced sensitivity to NK cytotoxicity. GEP downregulated surface expression of MHC class I chain-related molecule A (MICA), ligand for NK stimulatory receptor NK group 2 member D (NKG2D), and upregulated human leukocyte antigen-E (HLA-E), ligand for NK inhibitory receptor CD94/NKG2A. Functionally, GEP augmented production of soluble MICA, which suppressed NK activation. Matrix metalloproteinase (MMP)2 and MMP9 activity was involved partly in the GEP-regulated MICA shedding from HCC cells. In primary HCCs (n = 80), elevated GEP (P < 0.001), MICA (P < 0.001), and HLA-E (P = 0.089) expression was observed when compared with those in nontumor (n = 80) and normal livers (n = 10). Serum GEP (P = 0.010) and MICA (P < 0.001) levels were higher in patients with HCC (n = 80) than in healthy individuals (n = 30). High serum GEP and/or MICA levels were associated with poor recurrence-free survival (log-rank test, P = 0.042). Importantly, GEP blockade by mAbs sensitized HCC cells to NK cytotoxicity through MICA. In summary, GEP rendered HCC cells resistant to NK cytotoxicity by modulating MICA expression, which could be reversed by GEP blockade using antibody. Serum GEP and MICA levels are prognostic factors and can be used to stratify patients for targeted therapy.

Spiradenoma and cylindroma originate from the hair follicle bulge and not from the eccrine sweat gland: an immunohistochemical study with CD200 and other stem cell markers

BACKGROUND

Spiradenoma and cylindroma have historically been described as sweat gland tumors and have often been considered to be of eccrine lineage. However, (a) associations with trichoepitheliomas in Brooke-Spiegler syndrome or with trichoepitheliomas and milia in Rasmussen syndrome, (b) neoplastic combinations with hair follicle tumors in solitary cases, and (c) anatomical considerations support a folliculosebaceous-apocrine lineage. Follicular stem cell markers may allow for further characterization of these neoplasms.

METHODS

A total of 97 tumors were examined for the expression pattern of follicular stem cell markers cytokeratin 15 (CK15), cytokeratin 19 (CK19), pleckstrin homology-like domain, family A, member 1 (PHLDA1), and CD200. The tumors were comprised of 27 spiradenomas, 30 cylindromas, 16 hidradenomas, 19 poromas, 4 dermal duct tumors and 1 hidroacanthoma simplex.

RESULTS

All spiradenomas and cylindromas were CD200-positive whereas the other tumors classified as eccrine in lineage were all CD200-negative. CK15 also discriminated between spiradenomas and cylindromas and the remaining neoplasms but not to the degree of CD200. PHLDA1 and CK19 were noncontributory.

CONCLUSIONS

It is concluded that both spiradenoma and cylindroma are not eccrine but follicular tumors. More specifically, it is proposed that both adnexal neoplasms are derived from the hair follicle bulge and as such represent one of the least differentiated follicular tumors.

Comparison of immunity in mice cured of primary/metastatic growth of EMT6 or 4THM breast cancer by chemotherapy or immunotherapy

PURPOSE

We have compared cure from local/metastatic tumor growth in BALB/c mice receiving EMT6 or the poorly immunogenic, highly metastatic 4THM, breast cancer cells following manipulation of immunosuppressive CD200:CD200R interactions or conventional chemotherapy.

METHODS

We reported previously that EMT6 tumors are cured in CD200R1KO mice following surgical resection and immunization with irradiated EMT6 cells and CpG oligodeoxynucleotide (CpG), while wild-type (WT) animals developed pulmonary and liver metastases within 30 days of surgery. We report growth and metastasis of both EMT6 and a highly metastatic 4THM tumor in WT mice receiving iv infusions of Fab anti-CD200R1 along with CpG/tumor cell immunization. Metastasis was followed both macroscopically (lung/liver nodules) and microscopically by cloning tumor cells at limiting dilution in vitro from draining lymph nodes (DLN) harvested at surgery. We compared these results with local/metastatic tumor growth in mice receiving 4 courses of combination treatment with anti-VEGF and paclitaxel.

RESULTS

In WT mice receiving Fab anti-CD200R, no tumor cells are detectable following immunotherapy, and CD4+ cells produced increased TNFα/IL-2/IFNγ on stimulation with EMT6 in vitro. No long-term cure was seen following surgery/immunotherapy of 4THM, with both microscopic (tumors in DLN at limiting dilution) and macroscopic metastases present within 14 d of surgery. Chemotherapy attenuated growth/metastases in 4THM tumor-bearers and produced a decline in lung/liver metastases, with no detectable DLN metastases in EMT6 tumor-bearing mice-these latter mice nevertheless showed no significantly increased cytokine production after restimulation with EMT6 in vitro. EMT6 mice receiving immunotherapy were resistant to subsequent re-challenge with EMT6 tumor cells, but not those receiving curative chemotherapy. Anti-CD4 treatment caused tumor recurrence after immunotherapy, but produced no apparent effect in either EMT6 or 4THM tumor bearers after chemotherapy treatment.

CONCLUSION

Immunotherapy, but not chemotherapy, enhances CD4+ immunity and affords long-term control of breast cancer growth and resistance to new tumor foci.

Diagnostic and prognostic significance of CD200 expression and its stability in plasma cell myeloma

Aim

Previous studies showed that CD200 expression is a prognostic factor for plasma cell myeloma (PCM), but the prognostic effect is conflicting between studies. We studied CD200 protein expression and the stability of expression in PCM to clarify its potential utility in diagnosis, prognosis and monitoring of disease.

Method

CD200 expression was studied in 77 cases of PCM by immunohistochemistry on paraffin sections from decalcified bone marrow biopsies.

Result

There were 16 newly diagnosed cases and 61 post-treatment cases from 54 patients: 37 men and 17 women, with a median age of 62 years (range, 41–88 years). CD200 demonstrated moderate to strong membrane expression in positive cases. Fifty-six of 77 cases (73%) showed CD200 expression. Twenty of the 22 (91%) patients with serial specimens demonstrated stable CD200 expression (n=15) or lack of CD200 expression (n=5). One patient lost CD200 expression, while another one gained CD200 expression during treatment. The clinical, pathologic and cytogenetic features between the CD200+ group and the CD200− group were similar in most instances. However, CD200 expression was associated with lower serum β2-microglobulin (p=0.03). There was no significant difference in overall survival and progression-free survival between the CD200+ and CD200− patients (p>0.05).

Conclusions

CD200 is expressed in a majority of PCM cases, and the expression is stable during the treatment process. Therefore, immunohistochemical expression of CD200 is a useful marker for the diagnosis and follow-up of PCM.

Cure of metastatic growth of EMT6 tumor cells in mice following manipulation of CD200:CD200R signaling

In previous studies, we observed that regulation of expression of CD200, both on cells of a transplantable breast cancer, EMT6, and of the host, as well as of the receptor, CD200R in host mice, regulated local tumor growth and metastasis in immunocompetent animals. This in turn led to an improved ability to document immunity to EMT6 in CD200R1KO mice. In the current study, we have explored the ability to cure BALB/c CD200KO or CD200R1KO mice of tumors ≤1 cm³ in size by surgical resection of localized tumor, followed by immunization with irradiated EMT6 cells along with CpG as adjuvant. While control animals treated in this fashion developed significant pulmonary and liver metastases within 30 days of surgery, significant protection was seen in both CD200KO or CD200R1KO mice, with no macroscopic lung/liver metastases observed in CD200R1KO mice on sacrifice at day 300. Following surgical resection and immunization, draining lymph nodes from control mice contained tumor cells cloned at limiting dilution in vitro even before pulmonary and hepatic metastasis was seen. In contrast, within the limits of detection of the assay used (sensitivity ~1 in 10⁷ cells), no tumor cells were detected at limiting dilution in similarly treated CD200R1KO mice, and significant reductions were seen in CD200KO mice. Infusion of anti-CD4, but less so anti-CD8, mAb into surgically treated and immunized CD200R1KO mice attenuated protection from both macroscopic (liver/lung) and microscopic (assayed by limiting dilution of DLN) metastasis. Adoptive transfer of lymphocytes from treated CD200R1KO mice to surgically treated control mice also attenuated metastatic growth of tumor, which was abolished by pretreatment of transferred cells with anti-CD4 mAb. Our data suggest that CD200:CD200R attenuates a potentially tumor-protective CD4 host response to breast cancer.

Combination immunotherapy approaches

Combination immunotherapy approaches involving radiation, chemotherapy, androgen manipulation and T-cell modulation have been studied extensively in animal models, setting the stage for clinical trials. Radiation therapy, in particular, is an interesting modality in this regard, leading to synergistic efficacy when used in combination with immunotherapies in several models. Chemotherapy, the foundation of treatment of metastatic disease, may also augment the immune response to cancer; however, the potential immunosuppressive effects of chemotherapy render issues of dosing and timing critical. Perhaps, the most exciting combinatorial approach may be the co-administration of multiple immunological treatments. For example, in preclinical investigations, combined blockade of programmed death-1 (PD1) and cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), which have key roles in the negative regulation of T-cell activation, has been shown to enhance antitumour immune responses compared with either agent alone. Taken together, the available data provide a strong rationale for initiating combination clinical trials, but lend a note of caution in that issues of dosing and timing likely require careful exploration in a phase II setting.

Coinhibitory molecules in cancer biology and therapy

The adaptive immune response is controlled by checkpoints represented by coinhibitory molecules, which are crucial for maintaining self-tolerance and minimizing collateral tissue damage under physiological conditions. A growing body of preclinical evidence supports the hypothesis that unleashing this immunological break might be therapeutically beneficial in the fight against cancer, as it would elicit an effective antitumor immune response. Remarkably, recent clinical trials have demonstrated that this novel strategy can be highly effective in the treatment of patients with cancer, as shown by the paradigmatic case of ipilimumab (a monoclonal antibody blocking the coinhibitory molecule cytotoxic T lymphocyte associated antigen-4 [CTLA4]) that is opening a new era in the therapeutic approach to a chemoresistant tumor such as cutaneous melanoma. In this review we summarize the biology of coinhibitory molecules, overview the experimental and clinical attempts to interfere with these immune checkpoints to treat cancer and critically discuss the challenges posed by such a promising antitumor modality.