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

Indoxyl sulfate in atherosclerosis

Atherosclerosis (AS), a chronic vascular inflammatory disease, has become a main focus of attention worldwide for its chronic progressing disease course and serious complications in the later period. Nevertheless, explanations for the exact molecular mechanisms of AS initiation and development remain to be an unsolved problem. The classic pathogenesis theories, such as lipid percolation and deposition, endothelium injury, inflammation and immune damage, provide the foundation for discovering the new key molecules or signaling mechanisms. Recently, indoxyl sulfate (IS), one of non-free uremia toxins, has been noticeable for its multiple atherogenic effects. IS exists at high concentration in plasma for its great albumin binding rate. Patients with uremia have markedly elevated serum levels of IS due both to the deterioration of renal function and to the high binding affinity of IS to albumin. Nowadays, elevated incidence of circulatory disease among patients with renal dysfunction indicates correlation of uremic toxins with cardiovascular damage. In this review, the atherogenic effects of IS and the underlying mechanisms are summarized with emphasis on several key pathological events associated with AS developments, such as vascular endothelium dysfunction, arterial medial lesions, vascular oxidative stress, excessive inflammatory responses, calcification, thrombosis and foam cell formation. Although recent studies have proved the great correlation between IS and AS, deciphering cellular and pathophysiological signaling by confirming key factors involved in IS-mediated atherosclerosis development may enable identification of novel therapeutic targets.

IGSF11 and VISTA: a pair of promising immune checkpoints in tumor immunotherapy

Immunotherapy has become the major treatment for tumors in clinical practice, but some intractable problems such as the low response rate and high rates of immune-related adverse events still hinder the progress of tumor immunotherapy. Hence, it is essential to explore additional immunotherapy treatment targets. In this review, we focus on the structure, expression and expression-related mechanisms, interactions, biological functions and the progress in preclinical/clinical research of IGSF11 and VISTA in tumors. We cover the progress in recent research with this pair of immune checkpoints in tumor immune regulation, proliferation, immune resistance and predictive prognosis. Both IGSF11 and VISTA are highly expressed in tumors and are modulated by various factors. They co-participate in the functional regulation of immune cells and the inhibition of cytokine production. Besides, in the downregulation of IGSF11 and VISTA, both inhibit the growth of some tumors. Preclinical and clinical trials all emphasize the predictive role of IGSF11 and VISTA in the prognosis of tumors, and that the predictive role of the same gene varies from tumor to tumor. At present, further research is proving the enormous potential of IGSF11 and VISTA in tumors, and especially the role of VISTA in tumor immune resistance. This may prove to be a breakthrough to solve the current clinical immune resistance, and most importantly, since research has focused on VISTA but less on IGSF11, IGSF11 may be the next candidate for tumor immunotherapy.

Preparation of an anti-NEK2 monoclonal antibody and its application in liver cancer

Background

Never in mitosis gene-A (NIMA)-related expressed kinase 2 (NEK2) is a serine/threonine protein kinase regulated by the cell cycle. The purpose of this study was to obtain NEK2 protein to prepare an anti-NEK2 monoclonal antibody (mAb) and explore the application of the anti-NEK2 mAb of therapeutic and diagnostic in hepatocellular carcinoma (HCC).

Results

The NEK2 gene sequence was cloned from the normal liver cell line HL7702, and the full-length NEK2 gene sequence was cloned into the prokaryotic expression vector pET30a and transformed into Escherichia coli BL21 (DE3) cells. The recombinant fusion protein was obtained under optimized conditions and injected in BALB/c mice to prepare an anti-NEK2 mAb. By screening, we obtained a stable hybridoma cell line named 3A3 that could stably secrete anti-NEK2 mAb. Anti-NEK2 3A3 mAb was purified from ascites fluid. The isotype was IgG1, and the affinity constant (K_aff) was 6.0 × 10⁸ L/mol. Western blot, indirect enzyme-linked immunosorbent assay (iELISA), immunofluorescence and immunocytochemical analyses showed that the mAb could specifically recognize the NEK2 protein. MTT assays showed that the mAb 3A3 could inhibit the proliferation of HCC cells. KEGG pathway analysis showed that NEK2 might affected pathways of the cell cycle. Moreover, NEK2-related genes were mainly enriched in the S and G2 phases and might act as tumor-promoting genes by regulating the S/G2 phase transition of HCC cells.

Conclusions

An anti-NEK2 mAb with high potency, high affinity and high specificity was prepared by prokaryotic expression system in this study and may be used in the establishment of ELISA detection kits and targeted treatment of liver cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12896-021-00717-3.

Unraveling the Role of Immune Checkpoints in Leishmaniasis

Leishmaniasis are Neglected Tropical Diseases affecting millions of people every year in at least 98 countries and is one of the major unsolved world health issues. Leishmania is a parasitic protozoa which are transmitted by infected sandflies and in the host they mainly infect macrophages. Immunity elicited against those parasites is complex and immune checkpoints play a key role regulating its function. T cell receptors and their respective ligands, such as PD-1, CTLA-4, CD200, CD40, OX40, HVEM, LIGHT, 2B4 and TIM-3 have been characterized for their role in regulating adaptive immunity against different pathogens. However, the exact role those receptors perform during Leishmania infections remains to be better determined. This article addresses the key role immune checkpoints play during Leishmania infections, the limiting factors and translational implications.

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 CD200 Expression and Soluble CTLA-4 Concentrations in Intermediate and High-Risk Myelodysplastic Syndrome Patients

OBJECTIVE

This study was designed in order to identify the prognostic relevance of CD200 expression and soluble Cytotoxic T-lymphocyte antigen-4 (CTLA-4) levels in myelodysplastic syndrome (MDS) patients.

METHODS

The study included 57 MDS (37 intermediate and 20 high risk) patients and 10 controls. For all of included patients; CD200 expression was identified by flowcytometry on CD33 positive cells and soluble CTLA-4 (CD152) concentration was determined by ELISA.

RESULTS

CD200 positive expression was detected in 32/57 (56.1%) of MDS cases, the mean serum CTLA-4 concentrations were significantly higher in MDS patients as compared to controls (P<0.01). Significant association between high CD200 positive expression; high CTLA-4   concentration levels and   MDS risk stages being higher in high risk MDS group as compared to intermediate risk one (P < 0.01).  After 36-month follow-up; the subgroup of MDS patients with high expression of CD200; and high serum CTLA-4 concentrations showed high death rate and high frequency of acute myeloid leukemia transformation.

CONCLUSIONS

CD200 positive expression could be considered as a new prognostic marker for risk stratification of MDS patients. CD200 expression may exert its effect through upregulation of CTLA-4.<br />.

Pediatric patients with acute lymphoblastic leukemia generate abundant and functional neoantigen-specific CD8+ T cell responses

Cancer arises from the accumulation of genetic alterations, which can lead to the production of mutant proteins not expressed by normal cells. These mutant proteins can be processed and presented on the cell surface by major histocompatibility complex molecules as neoepitopes, allowing CD8⁺ T cells to mount responses against them. For solid tumors, only an average 2% of neoepitopes predicted by algorithms have detectable endogenous antitumor T cell responses. This suggests that low mutation burden tumors, which include many pediatric tumors, are poorly immunogenic. Here, we report that pediatric patients with acute lymphoblastic leukemia (ALL) have tumor-associated neoepitope-specific CD8⁺ T cells, responding to 86% of tested neoantigens and recognizing 68% of the tested neoepitopes. These responses include a public neoantigen from the ETV6-RUNX1 fusion that is targeted in seven of nine tested patients. We characterized phenotypic and transcriptional profiles of CD8⁺ tumor-infiltrating lymphocytes (TILs) at the single-cell level and found a heterogeneous population that included highly functional effectors. Moreover, we observed immunodominance hierarchies among the CD8⁺ TILs restricted to one or two putative neoepitopes. Our results indicate that robust antitumor immune responses are induced in pediatric ALL despite their low mutation burdens and emphasize the importance of immunodominance in shaping cellular immune responses. Furthermore, these data suggest that pediatric cancers may be amenable to immunotherapies aimed at enhancing immune recognition of tumor-specific neoantigens.

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.

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.

Transcriptome Profiling Reveals Indoxyl Sulfate Should Be Culpable of Impaired T Cell Function in Chronic Kidney Disease

Introduction: Chronic inflammation and immune system dysfunction have been evaluated as major factors in the pathogenesis of chronic kidney disease (CKD), contributing to the high mortality rates observed in these populations. Uremic toxins seem to be the potential “missing link.” Indoxyl sulfate (IS) is one of the protein-bound renal toxins. It participates in multiple pathologies of CKD complications, yet its effect on immune cell has not been studied. This study aimed to explore the genome-wide expression profile in human peripheral blood T cells under stimulation by IS.

Methods: In this study, we employed RNA-sequencing transcriptome profiling to identify differentially expressed genes (DEGs) responding to IS stimulation in human peripheral T cells in vitro. Flow cytometry and western blot were used to verify the discovery in RNA-sequencing analysis.

Results: Our results yielded a total of 5129 DEGs that were at least twofold up-regulated or down-regulated significantly by IS stimulation and half of them were concentration-specific. Analysis of T cell functional markers revealed a quite different transcription profile under various IS concentration. Transcription factors analysis showed the similar pattern. Aryl hydrocarbon receptor (AhR) target genes CYP1A1, CYP1B1, NQO1, and AhRR were up-regulated by IS stimulation. Pro-inflammatory genes TNF-α and IFN-γ were up-regulated as verified by flow cytometry analysis. DNA damage was induced by IS stimulation as confirmed by elevated protein level of p-ATM, p-ATR, p-BRCA1, and p-p53 in T cells.

Conclusion: The toxicity of IS to T cells could be an important source of chronic inflammation in CKD patients. As an endogenous ligand of AhR, IS may influence multiple biological functions of T cells including inflammatory response and cell cycle regulation. Further researches are required to promulgate the underling mechanism and explore effective method of reserving T cell function in CKD.

Co-signaling receptors regulate T-cell plasticity and immune tolerance

We took an experimental database mining analysis to determine the expression of 28 co-signaling receptors in 32 human tissues in physiological/pathological conditions. We made the following significant findings: 1) co-signaling receptors are differentially expressed in tissues; 2) heart, trachea, kidney, mammary gland and muscle express co-signaling receptors that mediate CD4⁺T cell functions such as priming, differentiation, effector, and memory; 3) urinary tumor, germ cell tumor, leukemia and chondrosarcoma express high levels of co-signaling receptors for T cell activation; 4) expression of inflammasome components are correlated with the expression of co-signaling receptors; 5) CD40, SLAM, CD80 are differentially expressed in leukocytes from patients with trauma, bacterial infections, polarized macrophages and in activated endothelial cells; 6) forward and reverse signaling of 50% co-inhibition receptors are upregulated in endothelial cells during inflammation; and 7) STAT1 deficiency in T cells upregulates MHC class II and co-stimulation receptors. Our results have provided novel insights into co-signaling receptors as physiological regulators and potentiate identification of new therapeutic targets for the treatment of sterile inflammatory disorders.

Inflammation and transcriptional responses of peripheral blood mononuclear cells in classic ataxia telangiectasia

INTRODUCTION

Classic ataxia telangiectasia (A-T) is an autosomal recessive disease characterized by early onset ataxia, immune deficiency, sino-pulmonary disease, lymphoid/solid malignancies and telangiectasias. Prior studies have suggested that chronic inflammation and premature aging may contribute to the development of malignancy and pulmonary disease in people with A-T. To further examine the link between A-T and inflammation, we hypothesized that subjects with classic A-T would have greater enrichment of inflammatory pathways in peripheral blood mononuclear cells (PBMCs) compared to non A-T age-matched controls. To test this hypothesis we used RNAseq as an unsupervised approach to identify biological processes altered in people with classic A-T.

METHODS

PBMCs were isolated from subjects with classic A-T and compared to non-A-T age-matched healthy controls. RNAseq with differential gene expression analyses was then performed. Selected genes were validated by RT-qPCR using cohorts of subjects consisting of classic A-T, mild A-T or non-A-T controls. Subjects with mild A-T were characterized by later onset/mild neurologic features and normal/near normal immune status.

RESULTS

RNAseq revealed 310 differentially expressed genes (DEGs) including genes involved in inflammation, immune regulation, and cancer. Using gene set enrichment analysis, A-T subjects were found to have biological processes enriched for inflammatory and malignancy pathways. In examining a cohort of A-T subjects in which baseline serum IL8 and IL6 levels were measured previously, an association was found between higher serum IL8 levels and higher likelihood of developing malignancy and/or death in a subsequent 4-6 year period.

CONCLUSION

RNAseq using PBMCs from subjects with classic A-T uncovered differential expression of immune response genes and biological processes associated with inflammation, immune regulation, and cancer. Follow-up of A-T subjects over a 4-6 year period revealed an association between higher baseline serum IL8 levels and malignancy/death. These findings support a role for inflammation as a contributing factor in A-T phenotypes.

An autologous tumor vaccine for CLL

Chronic Lymphocytic Leukemia B cells (CLL) are malignant cells which retain at least some functions of normal B cells. Paramount amongst the latter is that when such cells are appropriately stimulated, they are able to present antigens, including any potential tumor antigens, making them excellent choices as a candidate tumor vaccine. We show that following stimulation of CLL cells with Phorbol myristic acetate, IL-2, the TLR7 agonist imiquimod (P2I) and ionomycin (P2Iio), markedly increased expression of CD54 and CD83 was seen, indicative of B cell activation and a transition to antigen-presenting cells. However, this occurred in the context of augmented expression of the known immunoregulatory molecule, CD200. Accordingly we explored the effect of stimulation of CLL cells with P2Iio, followed by coating of cells with a non-depleting anti-CD200mAb, on the ability of those cells to immunize PBL in vitro to become cytotoxic to CLL cells, or to protect NOD-SCIDγc^null (NSG) mice from subsequent CLL tumor challenge. Our data indicate that this protocol is effective in inducing CD8⁺ CTL able to lyse CLL cells in vitro, and decrease tumor burden in vivo in spleen and marrow of mice injected with CLL cells. Pre-treatment of mice with a CD8 depleting antibody before vaccination with P2Iio/anti-CD200 coated cells abolished any protection seen. These data suggest a potential role for blockade of CD200 expression on CLL cells as a component of a tumor vaccination strategy.