Role of HLA-G in tumor escape through expansion of myeloid-derived suppressor cells and cytokinic balance in favor of Th2 versus Th1/Th17. Blood. 2011;117:7021-7031. [PMID: 21482709 DOI: 10.1182/blood-2010-07-294389]

Plasmodium yoelii Infection Enhances the Expansion of Myeloid-Derived Suppressor Cells via JAK/STAT3 Pathway

Myeloid-derived suppressor cells (MDSCs), the negative immune regulators, have been demonstrated to be involved in immune responses to a variety of pathological conditions, such as tumors, chronic inflammation, and infectious diseases. However, the roles and mechanisms underlying the expansion of MDSCs in malaria remain unclear. In this study, the phenotypic and functional characteristics of splenic MDSCs during Plasmodium yoelii NSM infection are described. Furthermore, we provide compelling evidence that the sera from P. yoelii-infected C57BL/6 mice containing excess IL-6 and granulocyte-macrophage colony-stimulating factor promote the accumulation of MDSCs by inducing Bcl2 expression. Serum-induced MDSCs exert more potent suppressive effects on T cell responses than control MDSCs within both in vivo P. yoelii infection and in vitro serum-treated bone marrow cells experiments. Serum treatment increases the MDSC inhibitory effect, which is dependent on Arg1 expression. Moreover, mechanistic studies reveal that the serum effects are mediated by JAK/STAT3 signaling. By inhibiting STAT3 phosphorylation with the JAK inhibitor JSI-124, effects of serum on MDSCs are almost eliminated. In vivo depletion of MDSCs with anti-Gr-1 or 5-fluorouracil significantly reduces the parasitemia and promotes Th1 immune response in P. yoelii-infected C57BL/6 mice by upregulating IFN-γ expression. In summary, this study indicates that P. yoelii infection facilitates the accumulation and function of MDSCs by upregulating the expression of Bcl2 and Arg1 via JAK/STAT3 signaling pathway in vivo and in vitro. Manipulating the JAK/STAT3 signaling pathway or depleting MDSCs could be promising therapeutic interventions to treat malaria.

Harnessing the potential of HLA-G in cancer therapy: advances, challenges, and prospects

Immune checkpoint blockades have been prized in circumventing and ablating the impediments posed by immunosuppressive receptors, reaching an exciting juncture to be an innovator in anticancer therapy beyond traditional therapeutics. Thus far, approved immune checkpoint blockades have principally targeted PD-1/PD-L1 and CTLA-4 with exciting success in a plethora of tumors and yet are still trapped in dilemmas of limited response rates and adverse effects. Hence, unveiling new immunotherapeutic targets has aroused immense scientific interest in the hope of expanding the clinical application of immune checkpoint blockades to scale new heights. Human leukocyte antigen-G (HLA-G), a non-classical major histocompatibility complex (MHC) class I molecule, is enriched on various malignant cells and is involved in the hindrance of immune effector cells and the facilitation of immunosuppressive cells. HLA-G stands out as a crucial next-generation immune checkpoint showing great promise for the benefit of cancer patients. Here, we provide an overview of the current understanding of the expression pattern and immunological functions of HLA-G, as well as its interaction with well-characterized immune checkpoints. Since HLA-G can be shed from the cell surface or released by various cells as free soluble HLA-G (sHLA-G) or as part of extracellular vesicles (EVs), namely HLA-G-bearing EVs (HLA-GEV), we discuss the potential of sHLA-G and HLA-GEV as predictive biomarkers. This review also addresses the advancement of HLA-G-based therapies in preclinical and clinical settings, with a focus on their clinical application in cancer.

[Profile and immune environment of upper tract urothelial carcinoma]

INTRODUCTION AND OBJECTIVES

Upper Tract Urothelial Carcinoma (UTUC) are tumors that share similarities with bladder tumors. Immunotherapy is already used for bladder locations and appears to have interest for UTUC. In order to rationalize the immunotherapy development pipeline it seemed necessary to describe the immune infiltrate of a cohort of UTUC treated with nephroureterectomy and to determine the expression of a panel of immune checkpoints and co-stimulatory molecules on tumor cells as well as on infiltrating and circulating lymphocytes.

MATERIALS AND METHODS

This is a monocentric, prospective and exploratory work. Patients treated with total nephroureterectomy or segmental ureterectomy for presumably infiltrative (≥ T1) UTUC managed at the Saint-Louis Hospital were included from January 2019 to July 2020. A set of markers and immune checkpoints were studied by flow fluorocytometry on circulating lymphocytes (PBMCs) and tumor-infiltrating lymphocytes (TILs). Some markers were also studied by immunohistochemistry on tumor sample.

RESULTS

In total, 14 patients were included and 13 patients could be analyzed. 1 patient had no residual tumor. 5 tumors out of the 12 (41.7%) showed a lymphocytic inflammatory infiltrate. PD1 was the most represented checkpoint with a median expression rate of 41.4% on CD4+ TILs and 3.89% on circulating CD4+ T cells. This rate was 62.4% and 7.45% respectively on CD8+ T cells. TIGIT was the second most represented marker with a median expression rate on tumor-infiltrating CD4+ T cells of 25% and 2.9% on circulating CD4+ T cells. The median expression level of TIGIT on tumor-infiltrating CD8+ T cells was 23.3% and 3.2% on circulating CD8+ T cells. ICOS was highly expressed on CD4+ TILS with a median of 33.9% in contrast to CD8+ TILS (median: 6.67%). Variable expression of other checkpoints (ILT2, TIM3, LAG3 and OX40) was found without clear trend.

CONCLUSION

This exploratory work highlighted that PD1 was the most represented checkpoint. TIGIT was the second most represented checkpoint while ICOS, TIM3 and LAG3 were 3 other checkpoints whose expression was found to be less important. ILT2 and OX40 appeared to be weakly expressed.

LEVEL OF EVIDENCE

II.

Human leukocyte immunoglobulin-like receptors in health and disease

Human leukocyte immunoglobulin (Ig)-like receptors (LILR) are a family of 11 innate immunomodulatory receptors, primarily expressed on lymphoid and myeloid cells. LILRs are either activating (LILRA) or inhibitory (LILRB) depending on their associated signalling domains (D). With the exception of the soluble LILRA3, LILRAs mediate immune activation, while LILRB1-5 primarily inhibit immune responses and mediate tolerance. Abnormal expression and function of LILRs is associated with a range of pathologies, including immune insufficiency (infection and malignancy) and overt immune responses (autoimmunity and alloresponses), suggesting LILRs may be excellent candidates for targeted immunotherapies. This review will discuss the biology and clinical relevance of this extensive family of immune receptors and will summarise the recent developments in targeting LILRs in disease settings, such as cancer, with an update on the clinical trials investigating the therapeutic targeting of these receptors.

Prognostic significance of HLA-G in patients with colorectal cancer: a meta-analysis and bioinformatics analysis

PURPOSE

Human leukocyte antigen-G (HLA-G) has been reported to be aberrantly expressed in colorectal cancer (CRC); however, its prognostic value remains controversial. Hence, our meta-analysis aims to assess the prognostic value of HLA-G in CRC patients based on published literature and The Cancer Genome Atlas (TCGA) datasets.

METHODS

A systematic search was conducted on relevant studies retrieved from four electronic databases including PubMed, Embase, Web of Science and Cochrane Library. Hazard ratios (HRs) with 95% confidence intervals (CIs) were recorded to be applied as effective values. Fixed-effects models or random-effects models were applied on the basis of the value of heterogeneity (I 2). Publication bias was analyzed by Begg's and Egger's tests. In addition, the results were validated by using TCGA datasets.

RESULTS

Thirteen studies comprising 3896 patients were incorporated into this meta-analysis. The pooled results showed that HLA-G expression was significantly associated with poor overall survival (OS) in both the univariate analysis (HR = 1.44, 95% CI: 1.14-1.83, P = 0.002) and the multivariate analysis (HR = 1.55, 95% CI: 1.23-1.95, P < 0.001). Nevertheless, the expression of HLA-G is not related to age, sex, tumor type, tumor differentiation, TNM stage, or distant metastasis but lymph node metastasis. Notably, the prognosis of colorectal cancer was not consistent with the analysis result from TCGA data.

CONCLUSION

HLA-G expression was significantly related to poor OS in CRC according to the results of our meta-analysis. However, we found that the prognostic significance was inconsistent with our results according to the TCGA data in CRC. Hence, more research is still needed to further illustrate the prognostic role of HLA-G in CRC.

Identification of the prognostic value of Th1/Th2 ratio and a novel prognostic signature in basal-like breast cancer

BACKGROUND

Breast cancer is a heterogeneous group of diseases. The polarization of CD4+ T helper (Th) lymphocytes (mainly Th1 and Th2) may differ in breast cancers with different outcomes, but this has not been fully validated.

METHODS

This study is a bioinformatic analysis, in which differentially expressed genes (DEGs) were identified in patients with low and high Th1/Th2 ratios. And then, DEG functions, hub genes and independent predictors were determined.

RESULTS

Low Th1/Th2 ratio was associated with poor outcome in Luminal A and basal-like breast cancer (p < 0.05). GSEA and KEGG analysis of DEGs obtained from comparing low and high Th1/Th2 ratios illuminated downregulation of immune-related gene sets and pathways affecting Th1/Th2 balance toward Th2 polarization (p < 0.05). Survival and Cox analyses of all the DEGs confirmed CCL1 and MYH6 were independent protective factors and IFNK and SOAT2 were independent risk factors for basal-like breast cancer (95%CI: 1.06-2.5, p = 0.026). Then a four-gene signature was constructed and achieved a promising prognostic value (C-index = 0.82; AUC = 0.826).

CONCLUSIONS

Low Th1/Th2 ratio predicts poor outcome in Luminal A and Basal-like breast cancer, and downregulation of immune-related gene sets and pathways contribute to Th1/Th2 balance toward Th2 polarization. CCL1, MYH6, IFNK, and SOAT2 have an independent prognostic value of survival outcome and might be novel markers in basal-like breast cancer.

BND-22, a first-in-class humanized ILT2-blocking antibody, promotes antitumor immunity and tumor regression

BACKGROUND

Cancer immunotherapy has revolutionized cancer treatment. However, considering the limited success of immunotherapy to only some cancer types and patient cohorts, there is an unmet need for developing new treatments that will result in higher response rates in patients with cancer. Immunoglobulin-like transcript 2 (ILT2), a LILRB family member, is an inhibitory receptor expressed on a variety of immune cells including T cells, natural killer (NK) cells and different myeloid cells. In the tumor microenvironment, binding of class I MHC (in particular HLA-G) to ILT2 on immune cells mediates a strong inhibitory effect, which manifests in inhibition of antitumor cytotoxicity of T and NK cells, and prevention of phagocytosis of the tumor cells by macrophages.

METHODS

We describe here the development and characteristics of BND-22, a novel, humanized monoclonal antibody that selectively binds to ILT2 and blocks its interaction with classical MHC I and HLA-G. BND-22 was evaluated for its binding and blocking characteristics as well as its ability to increase the antitumor activity of macrophages, T cells and NK cells in various in vitro, ex vivo and in vivo systems.

RESULTS

Collectively, our data suggest that BND-22 enhances activity of both innate and adaptive immune cells, thus generating robust and comprehensive antitumor immunity. In humanized mice models, blocking ILT2 with BND-22 decreased the growth of human tumors, hindered metastatic spread to the lungs, and prolonged survival of the tumor-bearing mice. In addition, BND-22 improved the antitumor immune response of approved therapies such as anti-PD-1 or anti-EGFR antibodies.

CONCLUSIONS

BND-22 is a first-in-human ILT2 blocking antibody which has demonstrated efficient antitumor activity in various preclinical models as well as a favorable safety profile. Clinical evaluation of BND-22 as a monotherapy or in combination with other therapeutics is under way in patients with cancer.

TRIAL REGISTRATION NUMBER

NCT04717375.

Differentially Expressed Bone Marrow microRNAs Are Associated With Soluble HLA-G Bone Marrow Levels in Childhood Leukemia

HLA-G is a nonclassical histocompatibility class I molecule that plays a role in immune vigilance in cancer and infectious diseases. We previously reported that highly soluble HLA-G (sHLA-G) levels in the bone marrow were associated with a high blood cell count in T-acute lymphoblastic leukemia, a marker associated with a poor prognosis. To understand the posttranscriptional HLA-G gene regulation in leukemia, we evaluated the bone marrow microRNA profile associated with the HLA-G bone marrow mRNA expression and sHLA-G bone marrow levels in children exhibiting acute leukemia (B-ALL, T-ALL, and AML) using massively parallel sequencing. Ten differentially expressed miRNAs were associated with high sHLA-G bone marrow levels, and four of them (hsa-miR-4516, hsa-miR-486-5p, hsa-miR-4488, and hsa-miR-5096) targeted HLA-G, acting at distinct HLA-G gene segments. For qPCR validation, these miRNA expression levels (ΔCt) were correlated with HLA-G5 and RREB1 mRNA expressions and sHLA-G bone marrow levels according to the leukemia subtype. The hsa-miR-4488 and hsa-miR-5096 expression levels were lower in B-ALL than in AML, while that of hsa-miR-486-5p was lower in T-ALL than in AML. In T-ALL, hsa-miR-5096 correlated positively with HLA-G5 and negatively with sHLA-G. In addition, hsa-miR-4516 correlated negatively with sHLA-G levels. In AML, hsa-miR-4516 and hsa-miR-4488 correlated positively with HLA-G5 mRNA, but the HLA-G5 negatively correlated with sHLA-G. Our findings highlight the need to validate the findings of massively parallel sequencing since the experiment generally uses few individuals, and the same type of leukemia can be molecularly quite variable. We showed that miRNA's milieu in leukemia's bone marrow environment varies according to the type of leukemia and that the regulation of sHLA-G expression exerted by the same miRNA may act by a distinct mechanism in different types of leukemia.

Suppressor CD4+ T cells expressing HLA-G are expanded in the peripheral blood from patients with acute decompensation of cirrhosis

OBJECTIVE

Identifying components of immuneparesis, a hallmark of chronic liver failure, is crucial for our understanding of complications in cirrhosis. Various suppressor CD4⁺ T cells have been established as potent inhibitors of systemic immune activation. Here, we establish the presence, regulation and mechanism of action of a suppressive CD4⁺ T cell subset expressing human leucocyte antigen G (HLA-G) in patients with acute decompensation of cirrhosis (AD).

DESIGN

Flow cytometry was used to determine the proportion and immunophenotype of CD4⁺HLA-G⁺ T cells from peripheral blood of 20 healthy controls (HCs) and 98 patients with cirrhosis (28 with stable cirrhosis (SC), 20 with chronic decompensated cirrhosis (CD) and 50 with AD). Transcriptional and functional signatures of cell-sorted CD4⁺HLA-G⁺ cells were delineated by NanoString technology and suppression assays, respectively. The role of immunosuppressive cytokine interleukin (IL)-35 in inducing this population was investigated through in vitro blockade experiments. Immunohistochemistry (IHC) and cultures of primary human Kupffer cells (KCs) were performed to assess cellular sources of IL-35. HLA-G-mediated T cell suppression was explored using neutralising antibodies targeting co-inhibitory pathways.

RESULTS

Patients with AD were distinguished by an expansion of a CD4⁺HLA-G⁺CTLA-4⁺IL-35⁺ immunosuppressive population associated with disease severity, clinical course of AD, infectious complications and poor outcome. Transcriptomic analyses excluded the possibility that these were thymic-derived regulatory T cells. IHC analyses and in vitro cultures demonstrate that KCs represent a potent source of IL-35 which can induce the observed HLA-G⁺ phenotype. These exert cytotoxic T lymphocyte antigen-4-mediated impaired responses in T cells paralleled by an HLA-G-driven downregulation of T helper 17-related cytokines.

CONCLUSION

We have identified a cytokine-driven peripherally derived suppressive population that may contribute to immuneparesis in AD.

Mesenchymal Stem Cell Mechanisms of Action and Clinical Effects in Osteoarthritis: A Narrative Review

With the insufficient satisfaction rates and high cost of operative treatment for osteoarthritis (OA), alternatives have been sought. Furthermore, the inability of current medications to arrest disease progression has led to rapidly growing clinical research relating to mesenchymal stem cells (MSCs). The availability and function of MSCs vary according to tissue source. The three primary sources include the placenta, bone marrow, and adipose tissue, all of which offer excellent safety profiles. The primary mechanisms of action are trophic and immunomodulatory effects, which prevent the further degradation of joints. However, the function and degree to which benefits are observed vary significantly based on the exosomes secreted by MSCs. Paracrine and autocrine mechanisms prevent cell apoptosis and tissue fibrosis, initiate angiogenesis, and stimulate mitosis via growth factors. MSCs have even been shown to exhibit antimicrobial effects. Clinical results incorporating clinical scores and objective radiological imaging have been promising, but a lack of standardization in isolating MSCs prevents their incorporation in current guidelines.

Human Leucocyte Antigen G and Murine Qa-2 Are Critical for Myeloid Derived Suppressor Cell Expansion and Activation and for Successful Pregnancy Outcome

During pregnancy, maternal immune system has to balance tightly between protection against pathogens and tolerance towards a semi-allogeneic organism. Dysfunction of this immune adaptation can lead to severe complications such as pregnancy loss, preeclampsia or fetal growth restriction. In the present study we analyzed the impact of the murine MHC class Ib molecule Qa-2 on pregnancy outcome in vivo. We demonstrate that lack of Qa-2 led to intrauterine growth restriction and increased abortion rates especially in late pregnancy accompanied by a disturbed trophoblast invasion and altered spiral artery remodeling as well as protein aggregation in trophoblast cells indicating a preeclampsia-like phenotype. Furthermore, lack of Qa-2 caused imbalanced immunological adaptation to pregnancy with altered immune cell and especially T-cell homeostasis, reduced T_reg numbers and decreased accumulation and functional activation of myeloid-derived suppressor cells. Lastly, we show that application of sHLA-G reduced abortion rates in Qa-2 deficient mice by inducing MDSC. Our results highlight the importance of an interaction between HLA-G and MDSC for pregnancy success and the therapeutic potential of HLA-G for treatment of immunological pregnancy complications.

Role of HLA-G in Viral Infections

The human leukocyte antigen (HLA)-G is a non-classical HLA class I molecule, which has distinct features to classical HLA-A, -B, -C antigens, such as a low polymorphism, different splice variants, highly restricted, tightly regulated expression and immune modulatory properties. HLA-G expression in tumor cells and virus-infected cells, as well as the release of soluble HLA-G leads to escape from host immune surveillance. Increased knowledge of the link between HLA-G expression, viral infection and disease progression is urgently required, which highlights the possible use of HLA-G as novel diagnostic and prognostic biomarker for viral infections, but also as therapeutic target. Therefore, this review aims to summarize the expression, regulation, function and impact of HLA-G in the context of different viral infections including virus-associated cancers. The characterization of HLA-G-driven immune escape mechanisms involved in the interactions between host cells and viruses might result in the design of novel immunotherapeutic strategies targeting HLA-G and/or its interaction with its receptors on immune effector cells.

Engineered cells as glioblastoma therapeutics

In spite of significant recent advances in our understanding of the genetics and cell biology of glioblastoma, to date, this has not led to improved treatments for this cancer. In addition to small molecule, antibody, and engineered virus approaches, engineered cells are also being explored as glioblastoma therapeutics. This includes CAR-T cells, CAR-NK cells, as well as engineered neural stem cells and mesenchymal stem cells. Here we review the state of this field, starting with clinical trial studies. These have established the feasibility and safety of engineered cell therapies for glioblastoma and show some evidence for activity. Next, we review the preclinical literature and compare the strengths and weaknesses of various starting cell types for engineered cell therapies. Finally, we discuss future directions for this nascent but promising modality for glioblastoma therapy.

Perspective of HLA-G Induced Immunosuppression in SARS-CoV-2 Infection

COVID-19, the disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has threatened public health worldwide. Host antiviral immune responses are essential for viral clearance and disease control, however, remarkably decreased immune cell numbers and exhaustion of host cellular immune responses are commonly observed in patients with COVID-19. This is of concern as it is closely associated with disease severity and poor outcomes. Human leukocyte antigen-G (HLA-G) is a ligand for multiple immune inhibitory receptors, whose expression can be upregulated by viral infections. HLA-G/receptor signalling, such as engagement with immunoglobulin-like transcript 2 (ILT-2) or ILT-4, not only inhibit T and natural killer (NK) cell immune responses, dendritic cell (DC) maturation, and B cell antibody production. It also induces regulatory cells such as myeloid-derived suppressive cells (MDSCs), or M2 type macrophages. Moreover, HLA-G interaction with CD8 and killer inhibitory receptor (KIR) 2DL4 can provoke T cell apoptosis and NK cell senescence. In this context, HLA-G can induce profound immune suppression, which favours the escape of SARS-CoV-2 from immune attack. Although detailed knowledge on the clinical relevance of HLA-G in SARS-CoV-2 infection is limited, we herein review the immunopathological aspects of HLA-G/receptor signalling in SARS-CoV-2 infection, which could provide a better understanding of COVID-19 disease progression and identify potential immunointerventions to counteract SARS-CoV-2 infection.

Harnessing the immune system against cancer: current immunotherapy approaches and therapeutic targets

Cancer immunotherapy is a rapidly evolving concept that has been given the tag "fifth pillar" of cancer therapy while radiation therapy, chemotherapy, surgery and targeted therapy remain the other four pillars. This involves the stimulation of the immune system to control tumor growth and it specifically targets the neoplastic cells rather than the normal cells. Conventional chemotherapy has many limitations which include drug resistance, recurrence of cancer and severe adverse effects. Immunology has made major treatment breakthroughs for several cancers such as colorectal cancer, prostate cancer, breast cancer, lung cancer, liver cancer, kidney cancer, stomach cancer, acute lymphoblastic leukaemia etc. Currently, therapeutic strategies harnessing the immune system involve Checkpoint inhibitors, Chimeric antigen receptor T cells (CAR T cells), Monoclonal antibodies, Cancer vaccines, Cytokines, Radio-immunotherapy and Oncolytic virus therapy. The molecular characterization of several tumor antigens (TA) indicates that these TA can be utilized as promising candidates in cancer immunotherapy strategies. Here in this review, we highlight and summarize the different categories of emerging cancer immunotherapies along with the immunologically recognized tumor antigens involved in the tumor microenvironment.

Comparative analysis of the tumor immune-microenvironment of primary and brain metastases of non-small-cell lung cancer reveals organ-specific and EGFR mutation-dependent unique immune landscape

BACKGROUND

To evaluate the characteristics of the tumor immune-microenvironment in brain metastases of non-small-cell lung cancer (NSCLC), we investigated the immunophenotype of primary NSCLC and its brain metastasis.

METHODS

Expression profiling of 770 immune-related genes in 28 tissues from primary and brain metastases of NSCLC was performed using the NanoString nCounter PanCancer Immune Profiling Panel. The immune cell profiles were validated by immunohistochemistry of 42 matched samples.

RESULTS

Based on unsupervised clustering and principal component analysis of the immune-related gene expression profile, tumors were primarily clustered according to the involved organ and further grouped according to the EGFR mutation status. Fifty-four genes were significantly differentially expressed between primary and brain metastatic tumors. Clustering using these genes showed that tumors harboring mutated EGFR tended to be grouped together in the brain. Pathway analysis revealed that various immune-related functions involving immune regulation, T cell activity, and chemokines were enriched in primary tumors compared to brain metastases. Diverse immune-related pathways were upregulated in brain metastases of EGFR-mutated compared to EGFR-wild-type adenocarcinoma, but not in primary tumors. The interferon-γ-related gene signature was significantly decreased in brain metastases. The anti-inflammatory markers TOLLIP and HLA-G were upregulated in brain metastases. The proportions of most immune cell subsets were decreased in brain metastases, but those of macrophages and CD56dim-NK-cells were increased, as was the ratios of CD163+M2- to iNOS+M1-macrophages and NCR1+NK-cells to CD3+T cells.

CONCLUSIONS

Our findings illustrate the immune landscape of brain metastases from NSCLC and reveal potential therapeutic strategies targeting cellular and non-cellular components of the tumor immune-microenvironment.

Tumor infiltrating and peripheral CD4+ILT2+ T cells are a cytotoxic subset selectively inhibited by HLA-G in clear cell renal cell carcinoma patients

HLA-G

ILT2 has recently been positioned as a major immune checkpoint in urologic cancers. In clear cell renal cell carcinoma (ccRCC), tumor-infiltrating CD8⁺ T cells expressing ILT2 are a highly cytotoxic cell population, distinct from PD1⁺ T cells, and whose function is inhibited by HLA-G⁺ targets. Here we report that ILT2 receptor can also be expressed by CD4⁺ T cells in urologic cancer patients. In the course of deciphering the role of these ILT2⁺CD4⁺ T cells, we found a statistical association between the tumor context and these T cells, and a positive correlation between the levels of peripheral and intra-tumoral CD4⁺ILT2⁺ T cells. Phenotypic analyses revealed that CD4⁺ILT2⁺ T cells express memory T cell (CD27^-CD28^-CD57⁺) and cytotoxicity (Tbet⁺Perforin⁺KLRG1⁺NKp80⁺GPR56⁺) markers, consistent with a CD4⁺CTL phenotype. Functional assays showed that ccRCC-infiltrating CD4⁺ILT2⁺ T cells indeed have high cytolytic properties and therefore function as proper CD4⁺CTLs, but are selectively inhibited by HLA-G⁺ targets. Clinical relevance was provided by immunohistochemical analyses on ccRCC tumor lesions with HLA-G⁺ HLA class II⁺ tumor cells next to CD4⁺ T cell infiltrates. Our findings provide evidence supporting that ILT2⁺ T cells constitute a reservoir of intratumor cytotoxic T cells that is not targeted by the current checkpoint inhibitors, but could be by anti-HLA-G/anti-ILT2 antibodies as novel immunotherapy in HLA-G⁺ tumors.

HLA-G and HLA-E Immune Checkpoints Are Widely Expressed in Ewing Sarcoma but Have Limited Functional Impact on the Effector Functions of Antigen-Specific CAR T Cells

Simple Summary

Solid cancers can effectively counteract immune attack by inhibitory checkpoints in the tumor microenvironment. Blockade of relevant immune checkpoints could be a useful tool for enhancing the efficacy of antitumor T cell therapies. Here, we studied the capacity of two nonclassical HLA molecules with known immunosuppressive function, HLA-G and HLA-E, to prevent antigen-specific immune effector functions of gene-engineered T cells against Ewing sarcoma. Inflammatory conditions and interactions of Ewing sarcoma cells with antitumor T cells reliably induced upregulation of the two molecules on the tumor cells. Moreover, as previously shown for HLA-G, HLA-E was detected in a high proportion of human Ewing sarcoma biopsies. However, artificial expression of either of the two molecules on Ewing sarcoma cells failed to reduce cytolytic and activation responses of antigen-specific T cells. We conclude that blockade of HLA-G and HLA-E immune checkpoints is not a promising strategy for enhancing T cell therapies in Ewing sarcoma.

Abstract

Immune-inhibitory barriers in the tumor microenvironment of solid cancers counteract effective T cell therapies. Based on our finding that Ewing sarcomas (EwS) respond to chimeric antigen receptor (CAR) gene-modified effector cells through upregulation of human leukocyte antigen G (HLA-G), we hypothesized that nonclassical HLA molecules, HLA-G and HLA-E, contribute to immune escape of EwS. Here, we demonstrate that HLA-G isotype G1 expression on EwS cells does not directly impair cytolysis by G_D2-specific CAR T cells (CART), whereas HLA-G1 on myeloid bystander cells reduces CART degranulation responses against EwS cells. HLA-E was induced in EwS cells by IFN-γ stimulation in vitro and by G_D2-specific CART treatment in vivo and was detected on tumor cells or infiltrating myeloid cells in a majority of human EwS biopsies. Interaction of HLA-E-positive EwS cells with G_D2-specific CART induced upregulation of HLA-E receptor NKG2A. However, HLA-E expressed by EwS tumor cells or by myeloid bystander cells both failed to reduce antitumor effector functions of CART. We conclude that non-classical HLA molecules are expressed in EwS under inflammatory conditions, but have limited functional impact on antigen-specific T cells, arguing against a relevant therapeutic benefit from combining CART therapy with HLA-G or HLA-E checkpoint blockade in this cancer.

HLA-G and single nucleotide polymorphism (SNP) associations with cancer in African populations: Implications in personal medicine

The immune system plays an important role in protecting the body against malignancy. During cancer immunoediting, the immune system can recognize and keep checking the tumor cells by down-expression of some self-molecules or by increasing expression of some novel molecules. However, the microenvironment created in the course of cancer development hampers the immune ability to recognize and destroy the transforming cells. Human Leukocyte Antigen G (HLA-G) is emerging as immune checkpoint molecule produced more by cancer cells to weaken the immune response against them. HLA-G is a non-classical HLA class I molecule which is normally expressed in immune privileged tissues as a soluble or membrane-bound protein. HLA-G locus is highly polymorphic in the non-coding 3′ untranslated region (UTR) and in the 5′ upstream regulatory region (5′ URR). HLA-G expression is controlled by polymorphisms located in these regions, and several association studies between these polymorphic sites and disease predisposition, response to therapy, and/or HLA-G protein expression have been reported. Various polymorphisms are demonstrated to modulate its expression and this is increasingly finding more significance in cancer biology. This review focuses on the relevance of the HLA-G gene and its polymorphisms in cancer development. We highlight population genetics of HLA-G as evidence to espouse the need and importance of exploring potential utility of HLA-G in cancer diagnosis, prognosis and immunotherapy in the currently understudied African population.

Human leukocyte antigen-G upregulates immunoglobulin-like transcripts and corrects dysfunction of immune cells in immune thrombocytopenia

Human leukocyte antigen-G (HLA-G) is a non-classical major histocompatibility complex class I antigen with potent immune-inhibitory function. HLA-G benefit patients in allotransplantation and autoimmune diseases by interacting with its receptors, immunoglobulinlike transcripts. Here we observed significantly less HLA-G in plasma from immune thrombocytopenia (ITP) patients positive for anti-platelet autoantibodies compared with autoantibodies-negative patients or healthy controls, while we found that HLA-G is positively correlated with platelet counts in both patients and healthy controls. We also found less membranebound HLA-G and immunoglobulin-like transcripts on CD4⁺ and CD14⁺ cells in patients. Recombinant HLA-G upregulated immunoglobulin-like transcript 2 expression on CD4⁺ and immunoglobulin-like transcript 4 on CD14⁺ cells. HLA-G upregulated IL-4 and IL-10, and downregulated tumor necrosis factor-a, IL-12 and IL-17 secreted by patient peripheral blood mononuclear cells, suggesting a stimulation of Th2 differentiation and downregulation of Th1 and Th17 immune response. HLA-G-modulated dendritic cells from ITP patients showed decreased expression of CD80 and CD86, and suppressed CD4⁺ T-cell proliferation compared to unmodulated cells. Moreover, HLA-G-modulated cells from patients induced less platelet apoptosis. HLA-G administration also significantly alleviated thrombocytopenia in a murine model of ITP. In conclusion, our data demonstrated that impaired expression of HLA-G and immunoglobulin-like transcripts is involved in the pathogenesis of ITP; recombinant HLA-G can correct this abnormality via upregulation of immunoglobulin-like transcripts, indicating that HLA-G can be a diagnostic marker and a therapeutic option for ITP.

First immunotherapeutic CAR-T cells against the immune checkpoint protein HLA-G

BACKGROUND

CAR-T cells immunotherapy is a breakthrough in the treatment of hematological malignancies such as acute lymphoblastic leukemia (ALL) and B-cell malignancies. However, CAR-T therapies face major hurdles such as the lack of tumor-specific antigen (TSA), and immunosuppressive tumor microenvironment sometimes caused by the tumorous expression of immune checkpoints (ICPs) such as HLA-G. Indeed, HLA-G is remarkable because it is both a potent ICP and a TSA. HLA-G tumor expression causes immune escape by impairing innate and adaptive immune responses and by inducing a suppressive microenvironment. Yet, to date, no immunotherapy targets it.

METHODS

We have developed two anti-HLA-G third-generation CARs based on new anti-HLA-G monoclonal antibodies.

RESULTS

Anti-HLA-G CAR-T cells were specific for immunosuppressive HLA-G isoforms. HLA-G-activated CAR-T cells polarized toward T helper 1, and became cytotoxic against HLA-G+ tumor cells. In vivo, anti-HLA-G CAR-T cells were able to control and eliminate HLA-G+ tumor cells. The interaction of tumor-HLA-G with interleukin (IL)T2-expressing T cells is known to result in effector T cell functional inhibition, but anti-HLA-G CAR-T cells were insensitive to this inhibition and still exerted their function even when expressing ILT2. Lastly, we show that anti-HLA-G CAR-T cells differentiated into long-term memory effector cells, and seemed not to lose function even after repeated stimulation by HLA-G-expressing tumor cells.

CONCLUSION

We report for the first time that HLA-G, which is both a TSA and an ICP, constitutes a valid target for CAR-T cell therapy to specifically target and eliminate both tumor cells and HLA-G+ suppressive cells.

The Role of HLA-G in Tumor Escape: Manipulating the Phenotype and Function of Immune Cells

Human leukocyte antigen-G (HLA-G) is a non-classical major histocompatibility complex class I (MHC I) molecule, and under physiological conditions, its expression is strictly restricted to the maternal–fetal interface and immune-privileged organs where HLA-G is expected to contribute to establishment and maintenance of immune tolerance. However, the expression of HLA-G has been found in various types of tumors, and the level of its expression frequently correlates with high-grade histology and poor prognosis, raising the possibility that it may play a negative role in tumor immunity. ILT2 and ILT4, present on a broad of immune cells, have been identified as the main receptors engaging HLA-G, and their interactions have been found to allow the conversion of effectors like NK cells and T cells to anergic or unresponsive state, activated DCs to tolerogenic state, and to drive the differentiation of T cells toward suppressive phenotype. Therefore, tumors can employ HLA-G to modulate the phenotype and function of immune cells, allowing them to escape immune attack. In this review, we discuss the mechanism underlying HLA-G expression and function, its role played in each step of the tumor-immunity cycle, as well as the potential to target it for therapeutic benefit.

Intratumor Heterogeneity of HLA-G Expression in Cancer Lesions

Signaling pathway between human leukocyte antigen (HLA)-G and immune inhibitory receptors immunoglobulin-like transcript (ILT)-2/4 has been acknowledged as one of immune checkpoints, and as a potential target for cancer immunotherapy. Like other immune checkpoints, inter- and even intratumor heterogeneity of HLA-G could render a rather complexity for HLA-G-target immunotherapy. However, little information for intratumor heterogeneity of HLA-G is available. In this study, HLA-G expression in a serial section of colorectal cancer (CRC) lesions from three CRC patients (each sample with serial section of 50 slides, 10 randomized slides for each antibody), three different locations within a same sample (five CRC), and three case-matched blocks that each includes 36 esophageal cancer samples, were evaluated with immunohistochemistry using anti-HLA-G antibodies (mAbs 4H84, MEM-G/1 and MEM-G/2 probing for all denatured HLA-G isoforms, 5A6G7, and 2A12 probing for denatured HLA-G5 and HLA-G6 isoforms). Our results revealed that, in addition to the frequently observed inter-tumor heterogeneity, intratumor heterogeneous expression of HLA-G is common in different areas within a tumor in CRC and esophageal cancer samples included in this study. Moreover, percentage of HLA-G expression probed with different anti-HLA-G antibodies also varies dramatically within a tumor. Given HLA-G has been considered as an important immune checkpoint, intratumor heterogeneity of HLA-G expression, and different specificity of anti-HLA-G antibodies being used among studies, interpretation and clinical significance of HLA-G expression in cancers should be with caution.

HLA-G Neo-Expression on Tumors

HLA-G is known to modulate the immune system activity in tissues where physiological immune-tolerance is necessary (i.e., maternal-fetal interface, thymus, and cornea). However, the frequent neo-expression of HLA-G in many cancer types has been previously and extensively described and is correlated with a bad prognosis. Despite being an MHC class I molecule, HLA-G is highly present in tumor context and shows unique characteristics of tissue restriction of a Tumor Associated Antigen (TAA), and potent immunosuppressive activity of an Immune CheckPoint (ICP). Consequently, HLA-G appears to be an excellent molecular target for immunotherapy. Although the relevance of HLA-G in cancer incidence and development has been proven in numerous tumors, its neo-expression pattern is still difficult to determine. Indeed, the estimation of HLA-G's actual expression in tumor tissue is limited, particularly concerning the presence and percentage of the new non-canonical isoforms, for which detection antibodies are scarce or inexistent. Here, we summarize the current knowledge about HLA-G neo-expression and implication in various tumor types, pointing out the need for the development of new tools to analyze in-depth the HLA-G neo-expression patterns, opening the way for the generation of new monoclonal antibodies and cell-based immunotherapies.

Expression of classical human leukocyte antigen class I antigens, HLA-E and HLA-G, is adversely prognostic in pancreatic cancer patients

The expression of classical human leukocyte antigen class I antigens (HLA-I) on the surfaces of cancer cells allows cytotoxic T cells to recognize and eliminate these cells. Reduction or loss of HLA-I is a mechanism of escape from antitumor immunity. The present study aimed to investigate the clinicopathological impacts of HLA-I and non-classical HLA-I antigens expressed on pancreatic ductal adenocarcinoma (PDAC) cells. We performed immunohistochemistry to detect expression of HLA-I antigens in PDAC using 243 PDAC cases and examined their clinicopathological influences. We also investigated the expression of immune-related genes to characterize PDAC tumor microenvironments. Lower expression of HLA-I, found in 33% of PDAC cases, was significantly associated with longer overall survival. Higher expression of both HLA-E and HLA-G was significantly associated with shorter survival. Multivariate analyses revealed that higher expression of these three HLA-I antigens was significantly correlated with shorter survival. Higher HLA-I expression on PDAC cells was significantly correlated with higher expression of IFNG, which also correlated with PD1, PD-L1 and PD-L2 expression. In vitro assay revealed that interferon gamma (IFNγ) stimulation increased surface expression of HLA-I in three PDAC cell lines. It also upregulated surface expression of HLA-E, HLA-G and immune checkpoint molecules, including PD-L1 and PD-L2. These results suggest that the higher expression of HLA-I, HLA-E and HLA-G on PDAC cells is an unfavorable prognosticator. It is possible that IFNγ promotes a tolerant microenvironment by inducing immune checkpoint molecules in PDAC tissues with higher HLA-I expression on PDAC cells.

The immune-checkpoint HLA-G/ILT4 is involved in the regulation of VEGF expression in clear cell renal cell carcinoma

Background

Clear cell renal cell carcinoma (ccRCC), the most aggressive renal cancer, is characterized by early lymph node metastases and bad prognosis. Most therapies targeting advanced or metastatic ccRCC are based, as first-line treatment, on the administration of the vascular endothelial growth factor (VEGF) neutralizing antibody termed Bevacizumab. Despite proven benefits, the expected results were not obtained for the majority of patients. The possibility that an intricate interplay between angiogenesis and immune-checkpoints might exist lead us to evaluate tumor angiogenesis, by means of VEGF expression together with the immune checkpoint HLA-G/ILT4.

Methods

Tumor specimens were obtained from patients from two separate cohorts: One from “Evita Pueblo” Hospital from Berazategui, (Buenos Aires, Argentina) and the second includes patients surgically operated at the Urology Department of Saint-Louis Hospital (Paris, France) with a confirmed ccRCC diagnosis. Immunohistochemistry was performed with specific antibodies directed against HLA-G, VEGF-A, VEGF-C, D240, CD34, ILT4 and Ca-IX. In addition, gene expression levels were measured in a cell line derived from a ccRCC patient by semi-quantitative RT-PCR.

Results

Our results show that the highly vascularized tumors of ccRCC patients express high levels of VEGF and the immune-checkpoint HLA-G. In addition, ILT4, one of the HLA-G receptors, was detected on macrophages surrounding tumor cells, suggesting the generation of an immune-tolerant microenvironment that might favor tumorigenesis. Notably, RT-qPCR analysis provided the first evidence on the transcriptional relationship between HLA-G/ILT4 and the VEGF family. Namely, in the presence of HLA-G or ILT4, the levels of VEGF-A are diminished whereas those of VEGF-C are increased.

Conclusions

In an effort to find new therapeutic molecules and fight against metastasis dissemination associated with the poor survival rates of ccRCC patients, these findings provide the rationale for co-targeting angiogenesis and the immune checkpoint HLA-G.

The Role of HLA-G in Human Papillomavirus Infections and Cervical Carcinogenesis

Human leukocyte antigen (HLA)-G, a non-classical HLA-class I molecule, has a low polymorphism frequency, restricted tissue distribution and immunoinhibitory property. HLA-G expression in tumor cells and cells chronically infected with virus may enable them to escape from host immune surveillance. It is well-known that the HLA-G molecule is a novel biomarker and potential therapeutic target that is relevant in various types of cancers, but its role in cervical cancer has not been fully explored. In this review, we aim to summarize and discuss the immunologic role of the HLA-G molecule in the context of HPV infections and the process of cervical cancer carcinogenesis. A better understanding of the potential impact of HLA-G on the clinical course of persistent HPV infections, cervical epithelial cell transformation, tumor growth, recurrence and metastasis is needed to identify a novel diagnostic/prognostic biomarker for cervical cancer, which is critical for cervical cancer risk screening. In addition, it is also necessary to identify HLA-G-driven immune mechanisms involved in the interactions between host and virus to explore novel immunotherapy strategies that target HLA-G/immunoglobulin-like transcript (ILT) immune checkpoints.

HLA-G: A New Immune Checkpoint in Cancer?

Human leukocyte antigen G (HLA-G), known as a central protein in providing immune tolerance to the fetus in pregnant women, is also studied for a possible role in tumor development. Many studies have claimed HLA-G as a new immune checkpoint in cancer. Therefore, HLA-G and its receptors might be targets for immune checkpoint blockade in cancer immunotherapy. In order to substantiate that HLA-G is indeed an immune checkpoint in cancer, two important questions need to be answered: (1) To what extent is HLA-G expressed in the tumor by cancer cells? and (2) What is the function of HLA-G in cancer immune evasion? In this review, we discuss these questions. We agree that HLA-G is a potentially new immune checkpoint in cancer, but additional evidence is required to show the extent of intra-tumor and inter-tumor expression. These studies should focus on tumor expression patterns of the seven different HLA-G isoforms and of the receptors for HLA-G. Furthermore, specific roles for the different HLA-G isoforms should be established.

Comprehensive landscape of immune-checkpoints uncovered in clear cell renal cell carcinoma reveals new and emerging therapeutic targets

Clear cell renal cell carcinoma (ccRCC) constitutes the most common renal cell carcinoma subtype and has long been recognized as an immunogenic cancer. As such, significant attention has been directed toward optimizing immune-checkpoints (IC)-based therapies. Despite proven benefits, a substantial number of patients remain unresponsive to treatment, suggesting that yet unreported, immunosuppressive mechanisms coexist within tumors and their microenvironment. Here, we comprehensively analyzed and ranked forty-four immune-checkpoints expressed in ccRCC on the basis of in-depth analysis of RNAseq data collected from the TCGA database and advanced statistical methods designed to obtain the group of checkpoints that best discriminates tumor from healthy tissues. Immunohistochemistry and flow cytometry confirmed and enlarged the bioinformatics results. In particular, by using the recursive feature elimination method, we show that HLA-G, B7H3, PDL-1 and ILT2 are the most relevant genes that characterize ccRCC. Notably, ILT2 expression was detected for the first time on tumor cells. The levels of other ligand-receptor pairs such as CD70:CD27; 4-1BB:4-1BBL; CD40:CD40L; CD86:CTLA4; MHC-II:Lag3; CD200:CD200R; CD244:CD48 were also found highly expressed in tumors compared to adjacent non-tumor tissues. Collectively, our approach provides a comprehensible classification of forty-four IC expressed in ccRCC, some of which were never reported before to be co-expressed in ccRCC. In addition, the algorithms used allowed identifying the most relevant group that best discriminates tumor from healthy tissues. The data can potentially assist on the choice of valuable immune-therapy targets which hold potential for the development of more effective anti-tumor treatments.

Comprehensive analysis of the association between tumor glycolysis and immune/inflammation function in breast cancer

Background

Metabolic reprogramming, immune evasion and tumor-promoting inflammation are three hallmarks of cancer that provide new perspectives for understanding the biology of cancer. We aimed to figure out the relationship of tumor glycolysis and immune/inflammation function in the context of breast cancer, which is significant for deeper understanding of the biology, treatment and prognosis of breast cancer.

Methods

Using mRNA transcriptome data, tumor-infiltrating lymphocytes (TILs) maps based on digitized H&E-stained images and clinical information of breast cancer from The Cancer Genome Atlas projects (TCGA), we explored the expression and prognostic implications of glycolysis-related genes, as well as the enrichment scores and dual role of different immune/inflammation cells in the tumor microenvironment. The relationship between glycolysis activity and immune/inflammation function was studied by using the differential genes expression analysis, gene ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, gene set enrichment analyses (GSEA) and correlation analysis.

Results

Most glycolysis-related genes had higher expression in breast cancer compared to normal tissue. Higher phosphoglycerate kinase 1 (PGK1) expression was associated with poor prognosis. High glycolysis group had upregulated immune/inflammation-related genes expression, upregulated immune/inflammation pathways especially IL-17 signaling pathway, higher enrichment of multiple immune/inflammation cells such as Th2 cells and macrophages. However, high glycolysis group was associated with lower infiltration of tumor-killing immune cells such as NKT cells and higher immune checkpoints expression such as PD-L1, CTLA4, FOXP3 and IDO1.

Conclusions

In conclusion, the enhanced glycolysis activity of breast cancer was associated with pro-tumor immunity. The interaction between tumor glycolysis and immune/inflammation function may be mediated through IL-17 signaling pathway.

Evaluation of the Reactivity and Receptor Competition of HLA-G Isoforms toward Available Antibodies: Implications of Structural Characteristics of HLA-G Isoforms

The human leucocyte antigen (HLA)-G, which consists of seven splice variants, is a tolerogenic immune checkpoint molecule. It plays an important role in the protection of the fetus from the maternal immune response by binding to inhibitory receptors, including leukocyte Ig-like receptors (LILRs). Recent studies have also revealed that HLA-G is involved in the progression of cancer cells and the protection from autoimmune diseases. In contrast to its well characterized isoform, HLA-G1, the binding activities of other major HLA-G isoforms, such as HLA-G2, toward available anti-HLA-G antibodies are only partially understood. Here, we investigate the binding specificities of anti-HLA-G antibodies by using surface plasmon resonance. MEM-G9 and G233 showed strong affinities to HLA-G1, with a nM range for their dissociation constants, but did not show affinities to HLA-G2. The disulfide-linker HLA-G1 dimer further exhibited significant avidity effects. On the other hand, 4H84 and MEM-G1, which can be used for the Western blotting of HLA-G isoforms, can bind to native HLA-G2, while MEM-G9 and G233 cannot. These results reveal that HLA-G2 has a partially intrinsically disordered structure. Furthermore, MEM-G1, but not 4H84, competes with the LILRB2 binding of HLA-G2. These results provide novel insight into the functional characterization of HLA-G isoforms and their detection systems.

Immune modulation by mesenchymal stem cells

Mesenchymal stem cells (MSCs) can be derived from various adult tissues with multipotent and self‐renewal abilities. The characteristics of presenting no major ethical concerns, having low immunogenicity and possessing immune modulation functions make MSCs promising candidates for stem cell therapies. MSCs could promote inflammation when the immune system is underactivated and restrain inflammation when the immune system is overactivated to avoid self‐overattack. These cells express many immune suppressors to switch them from a pro‐inflammatory phenotype to an anti‐inflammatory phenotype, resulting in immune effector cell suppression and immune suppressor cell activation. We would discuss the mechanisms governing the immune modulation function of these cells in this review, especially the immune‐suppressive effects of MSCs.

CD8+PD-1-ILT2+ T Cells Are an Intratumoral Cytotoxic Population Selectively Inhibited by the Immune-Checkpoint HLA-G

Only some cancer patients respond to the immune-checkpoint inhibitors being used in the clinic, and other therapeutic targets are sought. Here, we investigated the HLA-G/ILT2 checkpoint in clear-cell renal-cell carcinoma (ccRCC) patients and focused on tumor-infiltrating CD8⁺ T lymphocytes (TIL) expressing the HLA-G receptor ILT2. Using transcriptomics and flow cytometry, we characterized both peripheral blood and tumor-infiltrating CD8⁺ILT2⁺ T cells from cancer patients as late-differentiated CD27^-CD28^-CD57⁺ cytotoxic effectors. We observed a clear dichotomy between CD8⁺ILT2⁺ and CD8⁺PD-1⁺ TIL subsets. These subsets, which were sometimes present at comparable frequencies in TIL populations, barely overlapped phenotypically and were distinguished by expression of exclusive sets of surface molecules that included checkpoint molecules and activating and inhibitory receptors. CD8⁺ILT2⁺ TILs displayed a more mature phenotype and higher expression of cytotoxic molecules. In ex vivo functional experiments with both peripheral blood T cells and TILs, CD8⁺ILT2⁺ T cells displayed significantly higher cytotoxicity and IFNγ production than their ILT2^- (peripheral blood mononuclear cells, PBMC) and PD-1⁺ (TILs) counterparts. HLA-G expression by target cells specifically inhibited CD8⁺ILT2⁺ T-cell cytotoxicity, but not that of their CD8⁺ILT2^- (PBMC) or CD8⁺PD-1⁺ (TIL) counterparts, an effect counteracted by blocking the HLA-G/ILT2 interaction. CD8⁺ILT2⁺ TILs may therefore constitute an untapped reservoir of fully differentiated cytotoxic T cells within the tumor microenvironment, independent of the PD1⁺ TILs targeted by immune therapies, and specifically inhibited by HLA-G. These results emphasize the potential of therapeutically targeting the HLA-G/ILT2 checkpoint in HLA-G⁺ tumors, either concomitantly with anti-PD-1/PD-L1 or in cases of nonresponsiveness to anti-PD-1/PD-L1.

Tumor-induced escape mechanisms and their association with resistance to checkpoint inhibitor therapy

Immunotherapy aims to activate the immune system to fight cancer in a very specific and targeted manner. Despite the success of different immunotherapeutic strategies, in particular antibodies directed against checkpoints as well as adoptive T-cell therapy, the response of patients is limited in different types of cancers. This attributes to escape of the tumor from immune surveillance and development of acquired resistances during therapy. In this review, the different evasion and resistance mechanisms that limit the efficacy of immunotherapies targeting tumor-associated antigens presented by major histocompatibility complex molecules on the surface of the malignant cells are summarized. Overcoming these escape mechanisms is a great challenge, but might lead to a better clinical outcome of patients and is therefore currently a major focus of research.

Next-generation sequencing of HLA-G based on long-range polymerase chain reaction

Clarifying the functional roles of HLA-G and the variation in the HLA-G gene that affects the expression are increasingly important in reproduction, cancer, organ transplantation, and autoimmune diseases. The homology between HLA genes and the genetic variability within each gene complicates the design of HLA gene-specific genotyping assays. We have designed a high-throughput, cost-efficient, robust, and specific assay for sequencing the full HLA-G gene including the 5'-upstream regulatory region, introns, and the 3'-untranslated region, using the next-generation sequencing (NGS) platform Ion Torrent PGM (Thermo Fisher Scientific, Waltham, Massachusetts). Conventional sequencing methods require the design of multiple primer pairs in order to cover the entire HLA-G gene. Designing multiple primer pairs specific for the HLA-G gene that also target all known alleles is difficult. Here, we present a setup that by the use of long-range polymerase chain reaction amplifies the whole HLA-G gene in a single reaction, which only requires a single HLA-G-specific primer pair. Enzymatic DNA shearing is used to break the long-range PCR product into shorter fragments ranging from 75 to 200 bp in length that are sequenced by NGS.

The immunology of the macaque placenta: A detailed analysis and critical comparison with the human placenta

The cynomolgus monkey is increasingly considered in toxicological research as the most appropriate model for humans due to the species' close physiological contiguity, including reproductive physiology. Here, literature on the cynomolgus monkey placenta is reviewed in regards to its similarity to the human placenta and particularly for its immunological role, which is not entirely mirrored in humans. Pertinent original data are included in this article. The cynomolgus monkey placenta is evaluated based on three aspects: first, morphological development; second, the spatial and temporal appearance of maternal and fetal immune cells and certain immune cell products of the innate and adaptive immune systems; and third, the expression of relevant immune tolerance-related molecules including the homologs of anti-human leucocyte antigen, indoleamine 2,3-dioxygenase, FAS/FAS-L, annexin II, and progesterone. Parameters relevant to the immunological role of the placenta are evaluated from the immunologically immature stage of gestational day (GD) 50 until more mature stages close to birth. Selected comparisons are drawn with human and other laboratory animal placentas. In conclusion, the cynomolgus monkey placenta has a high degree of morphological and physiological similarity to the human placenta. However, there are differences in the topographical distribution of cell types and immune tolerance-related molecules. Three basic features are recognized: (1) the immunological capacity of the placenta changes throughout the lifetime of the organ; (2) these immunological changes include multiple parameters such as morphological adaptations, cell type involvement, and changes in immune-relevant molecule expression; and (3) the immune systems of two genetically disparate individuals (mother and child) are functionally intertwined at the maternal-fetal interface.

Heterogeneity of HLA-G Expression in Cancers: Facing the Challenges

Phenotypic heterogeneity has been observed in most malignancies, which represents a considerable challenge for tumor therapy. In recent decades, the biological function and clinical significance of the human leukocyte antigen (HLA)-G have been intensively explored. It is now widely accepted that HLA-G is a critical marker of immunotolerance in cancer cell immune evasion and is strongly associated with disease progress and prognosis for cancer patients. Moreover, it has recently been emphasized that the signaling pathway linking HLA-G and immunoglobulin-like transcripts (ILTs) is considered an immune checkpoint. In addition, HLA-G itself can generate at least seven distinct isoforms, and intertumor and intratumor heterogeneity of HLA-G expression is common across different tumor types. Furthermore, HLA-G heterogeneity in cancers has been related to disease stage and outcomes, metastatic status and response to different therapies. This review focuses on the heterogeneity of HLA-G expression in malignant lesions, and clinical implications of this heterogeneity that might be relevant to personalized treatments are also discussed.

Clinical Significance of Potential Unidentified HLA-G Isoforms Without α1 Domain but Containing Intron 4 in Colorectal Cancer Patients

The ectopic HLA-G expression in malignancies has been extensively explored and clinical significance of the molecule was widely acknowledged. Besides previously well-documented seven isoforms (HLA-G1~-G7), other novel isoforms of HLA-G have been reported but their clinical relavenace remians evaluated. In this study, lesion HLA-G expression in 379 case-matched serial section primary colorectal cancers (CRC) were evaluated with mAb 4H84 (recognizing an epitope in HLA-G α1 domain), and mAb 5A6G7 (recognizing an epitope encoded by intron 4), respectively. Data showed that HLA-G positive staining with mAbs 4H84 and 5A6G7 was 70.7 and 60.4%, respectively. When percentage of HLA-G expression detected with mAb 4H84 subtracted that with mAb 5A6G7, the difference (_ΔHLA-G) with negative (_ΔHLA-G_neg), comparable (_ΔHLA-G_com) and positive (_ΔHLA-G_pos) were observed in 64 (16.9%), 159 (42.0%), and 156 (41.2%) cases, respectively. Noteworthy, unexpected immunostaining was observed in 44 (11.6%) lesions that no staining was detected with mAb 4H84 but positive with mAb 5A6G7 (4H84^neg5A6G7^pos). This staining pattern was unpredictable because all seven known HLA-G isoforms containing the α 1 domain could be recognized by the mAb 4H84. Moreover, patients with _ΔHLA-G_neg had obviously better survival than those with _ΔHLA-G_com and _ΔHLA-G_pos (p = 0.017), and _ΔHLA-G could be an independent prognostic factor for CRC patients (p = 0.008). Our findings provides the first report that potential unidentified HLA-G isoforms is of distinct clinical significance in CRC patients.

HLA-G and anti-HCV in patients on the waiting list for kidney transplantation

PURPOSE

Human leukocyte antigen (HLA)-G is a non-classic major histocompatibility complex HLA class I molecule. HLA-G may have tolerogenic properties which are linked to epigenetic-sensitive pathways. There is a correlation of sHLA-G levels and graft acceptance in transplantation studies. There are previous data on correlation of sHLA-G with graft rejection as well as with viral infections such as hepatitis C virus (HCV) in kidney transplanted patients. Here, we report the sHLA-G expression in patients on the waiting list for kidney transplantation, with and without anti-HCV compared to a control group.

METHODS

Serum of 67 patients on the waiting list for kidney transplantation (n = 43 with anti-HCV and n = 24 without anti-HCV) was analyzed. Among these patients, n = 39 were on the waiting list for the first transplantation, while n = 28 were patients who returned in the list. The control group included n = 23 blood donors with anti-HCV (n = 13) and without anti-HCV (n = 10).

RESULTS

The expression of sHLA-G was significantly lower in the control group (39.6 ± 34.1 U/ml) compared to both - patients on the waiting list for the first transplantation (62.5 ± 42.4 U/ml, p=0.031) and patients who returned in the list (76.7 ± 53.9 U/ml, p=0.006). No significant differences were observed in all anti-HCV positive groups. A positive linear correlation between sHLA-G and TNF-α, and patient age was observed.

CONCLUSIONS

Serum sHLA-G values were significantly increased in both - patients on the waiting list for the first transplantation and patients who returned in the list, as compared to control group. Our findings confirm the key tolerogenic role of sHLA-G levels as epigenetic-related marker for measuring the state of kidney allograft acceptance.

Sonodynamic therapy-assisted immunotherapy: A novel modality for cancer treatment

Sonodynamic therapy (SDT), which is based on photodynamic therapy (PDT), is a new cancer treatment modality. Unlike PDT, which has poor tissue penetration, ultrasound can penetrate deeply into tissues and largely target tumor tissue to mediate the cytotoxicity of sonosensitizers. We hypothesize that, similar to PDT, SDT may perform effectively as a cancer vaccine. Thus, we developed a therapeutic strategy to explore whether SDT can eliminate primary tumors, inhibit metastases, and prevent tumor relapse. In the present study, we found that HiPorfin (HPD)‐induced SDT killed tumor cells, promoted calreticulin expression on the cell surface and elicited immune responses. Meanwhile, we observed that SDT induced functional antitumor vaccination and abscopal effects in H22 tumor‐bearing mice. Furthermore, this strategy conferred an immunological memory, which could protect against tumor recurrence after the elimination of the initial tumor. These results showed important effects of SDT on immune responses.

Importance of the plasma soluble HLA-G levels for prognostic stratification with traditional prognosticators in colorectal cancer

An increased peripheral soluble HLA-G (sHLA-G) expression has been observed in various malignancies while its prognostic significance was rather limited. In this study, the prognostic value of plasma sHLA-G in 178 colorectal cancer (CRC) patients was investigated. sHLA-G levels were analyzed by specific enzyme-linked immunosorbent assay. Data showed sHLA-G levels were significantly increased in CRC patients compared with normal controls (36.8 U/ml vs 25.4 U/ml, p = 0.009). sHLA-G in the died were obviously higher than that of alive CRC patients (46.8 U/ml vs 27.4 U/ml, p = 0.012). Patients with sHLA-G above median levels (≥ 36.8 U/ml, sHLA-Ghigh) had a significantly shorter survival time than those with sHLA-Glow (< 36.8 U/ml, p < 0.001), and sHLA-G could be an independent prognostic factor for CRC patients. With stratification of clinical parameters in survival by sHLA-Glow and sHLA-Ghigh, sHLA-G exhibited a significant predictive value for CRC patients of the female (p = 0.036), the elder (p = 0.009), advanced tumor burden (T3 + 4, p = 0.038), regional lymph node status (N0, p = 0.041), both metastasis status (M0, p = 0.014) and (M1, p=0.018), and clinical stage (I + II, p = 0.018), respectively. Summary, our data demonstrated for the first time that sHLA-G levels is an independent prognosis factor and improves the prognostic stratification offered by traditional prognosticators in CRC patients.

The genetic diversity within the 1.4 kb HLA-G 5' upstream regulatory region moderately impacts on cellular microenvironment responses

The HLA-G 5'URR extending 1.4 kb from the ATG presents a unique set of regulatory elements among HLA genes. Several variable sites have been described that coincide with or are close to these elements, thus HLA-G 5'URR polymorphism might influence the HLA-G expression level. We cloned the ten most frequent HLA-G 5'URR haplotypes to evaluate their activity on a luciferase reporter gene in HLA-G⁺ cell lines (JEG-3/choriocarcinoma and FON⁺/melanoma). We also investigated associations between the plasma HLA-G (sHLA-G) levels and the HLA-G 5'URR variability in 157 healthy individuals. Cell lines were transfected with pGL3-Basic vector constructions containing HLA-G 5'URR sequences. The G010101a (in JEG-3) and G010101b (in FON⁺) haplotypes exhibited higher promoter activity, whereas the G010101d (in JEG-3) and G010102a (in FON⁺) haplotypes exhibited lower promoter activity. In the presence of HLA-G inducers (interferon-β and progesterone) or repressors (cyclopamine) HLA-G promoter activity was modulated, but certain haplotypes exhibited differential responses. No strict association was observed between plasma sHLA-G levels and the 5'URR haplotypes or genotypes; however, the G010101b haplotype was underrepresented among HLA-G-negative plasmas. Therefore, the HLA-G 5'URR polymorphism may have an impact on the modulation of HLA-G gene expression, but alone provides a limited predictive value for sHLA-G levels in vivo.

Interplay between myeloid-derived suppressor cells (MDSCs) and Th17 cells: foe or friend?

Myeloid-derived suppressor cells (MDSCs) and Th17 cells were first discovered in the fields of cancer and autoimmunity, respectively. In recent years, their activities have been explored in other biological and pathological conditions, such as infective diseases and solid organ transplantation. However, the interplay between MDSCs and Th17 cells and the mechanism of their interaction remain obscure. This review summarized and analyzed the relationship between MDSCs and Th17 cells, both of which participate in tumor, autoimmune disease, infection and other conditions. In tumors, the increase in MDSCs at the tumor site is usually accompanied by the accumulation of Th17 cells. However, their relationship is inconsistent in different tumors. In arthritic mice or rheumatoid arthritis (RA) patients, an increase in MDSCs, which could ameliorate disease symptoms, causes decreased IL-17A gene expression and Th17 cells accumulation. Furthermore, we concluded that the interaction between MDSCs and Th17 cells is mainly mediated by cytokines. However, the mechanisms require further investigation. Determining the details of their interplay will provide a better understanding of immune networks and could lead to the development of immunotherapeutic strategies in the future.

T cell infiltration into Ewing sarcomas is associated with local expression of immune-inhibitory HLA-G

Ewing sarcoma (EwS) is an aggressive mesenchymal cancer of bones or soft tissues. The mechanisms by which this cancer interacts with the host immune system to induce tolerance are not well understood. We hypothesized that the non-classical, immune-inhibitory HLA-molecule HLA-G contributes to immune escape of EwS. While HLA-G^pos suppressor T cells were not increased in the peripheral blood of EwS patients, HLA-G was locally expressed on the tumor cells and/or on infiltrating lymphocytes in 16 of 47 pretherapeutic tumor biopsies and in 4 of 12 relapse tumors. HLA-G expression was not associated with risk-related patient variables or response to standard chemotherapy, but with significantly increased numbers of tumor-infiltrating CD3+ T cells compared to HLA-G^neg EwS biopsies. In a mouse model, EwS xenografts after adoptive therapy with tumor antigen-specific CAR T cells strongly expressed HLA-G whereas untreated control tumors were HLA-G^neg. IFN-γ stimulation of EwS cell lines in vitro induced expression of HLA-G protein. We conclude that EwS cells respond to tumor-infiltrating T cells by upregulation of HLA-G, a candidate mediator of local immune escape. Strategies that modulate HLA-G expression in the tumor microenvironment may enhance the efficacy of cellular immunotherapeutics in this cancer.

The choriocarcinoma cell line JEG-3 upregulates regulatory T cell phenotypes and modulates pro-inflammatory cytokines through HLA-G

An understanding of the interactions between immune cells and trophoblast cells, as well as choriocarcinoma cells, are of extreme importance in reproductive immunology and cancer immunology. In this study, we found that the human HLA-G-positive choriocarcinoma cell line JEG-3 upregulates CD4⁺CD25^hiCD127^lo T cells, increases the expression of HLA-G⁺CD4⁺ and CD8⁺ T cells, and decreases the expression of ILT2⁺ on CD4⁺ T cells in resting PBMCs after six days of co-culture. Expression of HLA-G on JEG-3 cells did not affect regulatory T cell phenotypes, but promoted modulation of pro-inflammatory cytokines IFN-γ, TNF-α and IL-17A. When JEG-3 cells were stimulated with rhIFN-γ prior to co-culture, CD4⁺HLA-G⁺ T cells were significantly increased, and IFN-γ and TNF-α elevated. Taken together, the results indicate that JEG-3 cells upregulate regulatory T cell phenotypes and modulate the level of pro-inflammatory cytokines, which might be important mechanisms in the tumor microenvironment and at the feto-maternal interface during pregnancy.