HLA-G: A New Immune Checkpoint in Cancer?

Immune cells and checkpoints in pancreatic adenocarcinoma: Association with clinical and pathological characteristics

INTRODUCTION

Pancreatic adenocarcinoma is an extremely aggressive neoplasm, with many challenges to be overcome in order to achieve a truly effective treatment. It is characterized by a mostly immunosuppressed environment, with dysfunctional immune cells and active immunoinhibitory pathways that favor tumor evasion and progression. Thus, the study and understanding of the tumor microenvironment and the various cells subtypes and their functional capacities are essential to achieve more effective treatments, especially with the use of new immunotherapeutics.

METHODS

Seventy cases of pancreatic adenocarcinoma divided into two groups 43 with resectable disease and 27 with unresectable disease were analyzed using immunohistochemical methods regarding the expression of programmed cell death ligand 1 (PD-L1), programmed cell death ligand 2 (PD-L2), and human leukocyte antigen G (HLA-G) molecules as well as the populations of CD4+ and CD8+ T lymphocytes, regulatory T cells (Tregs), and M2 macrophages (MM2). Several statistical tests, including multivariate analyses, were performed to examine how those immune cells and immunoinhibitory molecules impact the evolution and prognosis of pancreatic adenocarcinoma.

RESULTS

CD8+ T lymphocytes and M2 macrophages predominated in the group operated on, and PD-L2 expression predominated in the unresectable group. PD-L2 was associated with T stage, lymph node metastasis, and clinical staging, while in survival analysis, PD-L2 and HLA-G were associated with a shorter survival. In the inoperable cases, Tregs cells, MM2, PD-L1, PD-L2, and HLA-G were positively correlated.

CONCLUSIONS

PD-L2 and HLA-G expression correlated with worse survival in the cases studied. Tumor microenvironment was characterized by a tolerant and immunosuppressed pattern, mainly in unresectable lesions, where a broad positive influence was observed between immunoinhibitory cells and immune checkpoint proteins expressed by tumor cells.

The implication of serum HLA-G in angiogenesis of multiple myeloma

BACKGROUND

Despite the advances of therapies, multiple myeloma (MM) remains an incurable hematological cancer that most patients experience relapse. Tumor angiogenesis is strongly correlated with cancer relapse. Human leukocyte antigen G (HLA-G) has been known as a molecule to suppress angiogenesis. We aimed to investigate whether soluble HLA-G (sHLA-G) was involved in the relapse of MM.

METHODS

We first investigated the dynamics of serum sHLA-G, vascular endothelial growth factor (VEGF) and interleukin 6 (IL-6) in 57 successfully treated MM patients undergoing remission and relapse. The interactions among these angiogenesis-related targets (sHLA-G, VEGF and IL-6) were examined in vitro. Their expression at different oxygen concentrations was investigated using a xenograft animal model by intra-bone marrow and skin grafts with myeloma cells.

RESULTS

We found that HLA-G protein degradation augmented angiogenesis. Soluble HLA-G directly inhibited vasculature formation in vitro. Mechanistically, HLA-G expression was regulated by hypoxia-inducible factor-1α (HIF-1α) in MM cells under hypoxia. We thus developed two mouse models of myeloma xenografts in intra-bone marrow (BM) and underneath the skin, and found a strong correlation between HLA-G and HIF-1α expressions in hypoxic BM, but not in oxygenated tissues. Yet when stimulated with IL-6, both HLA-G and HIF-1α could be targeted to ubiquitin-mediated degradation via PARKIN.

CONCLUSION

These results highlight the importance of sHLA-G in angiogenesis at different phases of multiple myeloma. The experimental evidence that sHLA-G as an angiogenesis suppressor in MM may be useful for future development of novel therapies to prevent relapse.

CRISPR-Cas9 immune-evasive hESCs are rejected following transplantation into immunocompetent mice

Although current stem cell therapies exhibit promising potential, the extended process of employing autologous cells and the necessity for donor-host matching to avert the rejection of transplanted cells significantly limit the widespread applicability of these treatments. It would be highly advantageous to generate a pluripotent universal donor stem cell line that is immune-evasive and, therefore, not restricted by the individual's immune system, enabling unlimited application within cell replacement therapies. Before such immune-evasive stem cells can be moved forward to clinical trials, in vivo testing via transplantation experiments in immune-competent animals would be a favorable approach preceding preclinical testing. By using human stem cells in immune competent animals, results will be more translatable to a clinical setting, as no parts of the immune system have been altered, although in a xenogeneic setting. In this way, immune evasiveness, cell survival, and unwanted proliferative effects can be assessed before clinical trials in humans. The current study presents the generation and characterization of three human embryonic stem cell lines (hESCs) for xenogeneic transplantation in immune-competent mice. The major histocompatibility complexes I- and II-encoding genes, B2M and CIITA, have been deleted from the hESCs using CRISPR-Cas9-targeted gene replacement strategies and knockout. B2M was knocked out by the insertion of murine CD47. Human-secreted embryonic alkaline phosphatase (hSEAP) was inserted in a safe harbor site to track cells in vivo. The edited hESCs maintained their pluripotency, karyotypic normality, and stable expression of murine CD47 and hSEAP in vitro. In vivo transplantation of hESCs into immune-competent BALB/c mice was successfully monitored by measuring hSEAP in blood samples. Nevertheless, transplantation of immune-evasive hESCs resulted in complete rejection within 11 days, with clear immune infiltration of T-cells on day 8. Our results reveal that knockout of B2M and CIITA together with species-specific expression of CD47 are insufficient to prevent rejection in an immune-competent and xenogeneic context.

Role of HLA-G in tumors and upon COVID-19 infection

HLA-G expression of tumors and upon viral infections is involved in their immune escape leading to the evasion from both T and NK cell recognition. The underlying mechanisms of HLA-G expression in both pathophysiologic conditions are broad and range from genetic abnormalities to epigenetic, transcriptional and posttranscriptional regulation. This review summarizes the current knowledge of the frequency, regulation and clinical relevance of HLA-G expression upon neoplastic and viral transformation, its interaction with components of the microenvironment as well as its potential as diagnostic marker and/or therapeutic target. In addition, it discusses urgent topics, which have to be addressed in HLA-G research.

Adoptive cell therapy for solid tumors beyond CAR-T: Current challenges and emerging therapeutic advances

Adoptive cellular immunotherapy using immune cells expressing chimeric antigen receptors (CARs) is a highly specific anti-tumor immunotherapy that has shown promise in the treatment of hematological malignancies. However, there has been a slow progress toward the treatment of solid tumors owing to the complex tumor microenvironment that affects the localization and killing ability of the CAR cells. Solid tumors with a strong immunosuppressive microenvironment and complex vascular system are unaffected by CAR cell infiltration and attack. To improve their efficacy toward solid tumors, CAR cells have been modified and upgraded by "decorating" and "pruning". This review focuses on the structure and function of CARs, the immune cells that can be engineered by CARs and the transformation strategies to overcome solid tumors, with a view to broadening ideas for the better application of CAR cell therapy for the treatment of solid tumors.

Comprehensive analysis of DNA methylation gene expression profiles in GEO dataset reveals biomarkers related to malignant transformation of sinonasal inverted papilloma

BACKGROUND

DNA methylation may be involved in the regulation of malignant transformation from sinonasal inverted papilloma (SNIP) to squamous cell carcinoma (SCC). The study of gene methylation changes and screening of differentially methylated loci (DMLs) are helpful to predict the possible key genes in the malignant transformation of SNIP-SCC.

MATERIALS AND METHODS

Microarray dataset GSE125399 was downloaded from the Gene Expression Omnibus (GEO) database and differentially methylated loci (DMLs) were analyzed using R language (Limma package). ClusterProfiler R package was used to perform Gene Ontology (GO) analysis on up-methylated genes and draw bubble maps. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and its visualization analysis were analyzed to speculate the possible key Genes in SNIP-SCC malignant transformation. Subsequently, SNIP cases archived in our department were collected, tissue microarray was made, and immunohistochemical staining was performed to analyze the expression levels of UCKL1, GSTT1, HLA-G, MAML2 and NRGN in different grades of sinonasal papilloma tissues.

RESULTS

Analysis of dataset GSE125399 identified 56 DMLs, including 49 upregulated DMLs and 7 downregulated DMLs. Thirty-one genes containing upregulated DNA methylation loci and three genes containing downregulated DNA methylation loci were obtained by methylation microarray annotation analysis. In addition, KEGG pathway visualization analysis of 31 up-methylated genes showed that there were four significantly up-methylated genes including UCKL1, GSTT1, HLA-G and MAML2, and one significantly down-methylated gene NRGN. Subsequently, compared with non-neoplasia nasal epithelial tissues, the expression of HLA-G and NRGN was upregulated in grade I, II, III and IV tissues, while the expression of MAML2 was lost. The protein expression changes of MAML2 and NRGN were significantly negatively correlated with their gene methylation levels.

CONCLUSIONS

By analyzing the methylation dataset, we obtained four up-regulated methylation genes UCKL1, GSTT1, HLA-G and MAML2 and one down-regulated gene NRGN. MAML2, a tumor suppressor gene with high methylation modification but loss of protein expression, and NRGN, a tumor gene with low methylation modification but upregulated protein expression, can be used as biological indicators to judge the malignant transformation of SNIP-SCC.

From glioma gloom to immune bloom: unveiling novel immunotherapeutic paradigms-a review

In tumor therapeutics, the transition from conventional cytotoxic drugs to targeted molecular therapies, such as those targeting receptor tyrosine kinases, has been pivotal. Despite this progress, the clinical outcomes have remained modest, with glioblastoma patients' median survival stagnating at less than 15 months. This underscores the urgent need for more specialized treatment strategies. Our review delves into the progression toward immunomodulation in glioma treatment. We dissect critical discoveries in immunotherapy, such as spotlighting the instrumental role of tumor-associated macrophages, which account for approximately half of the immune cells in the glioma microenvironment, and myeloid-derived suppressor cells. The complex interplay between tumor cells and the immune microenvironment has been explored, revealing novel therapeutic targets. The uniqueness of our review is its exhaustive approach, synthesizing current research to elucidate the intricate roles of various molecules and receptors within the glioma microenvironment. This comprehensive synthesis not only maps the current landscape but also provides a blueprint for refining immunotherapy for glioma, signifying a paradigm shift toward leveraging immune mechanisms for improved patient prognosis.

Analysis of HLA-G 14 bp Insertion/Deletion Polymorphism and HLA-G, ILT2 and ILT4 Expression in Head and Neck Squamous Cell Carcinoma Patients

HLA-G is the checkpoint molecule involved in the suppression of the immune response. Increased expression of HLA-G and its ILTs receptors have been correlated with tumor progression in various cancer types. In head and neck squamous cell carcinoma (HNSCC) tumors, the effect of HLA-G, ILT2 and ILT4 expression on cancer development has to be explained. The 34 HNSCC patients and 98 controls were genotyped for the HLA-G 14 bp ins/del polymorphism. In HNSCC lesions, HLA-G, ILT2 and ILT4 mRNA expression was analysed using real-time PCR. The association between HLA-G, ILT2 and ILT4 mRNA expression and clinical variables (age at onset, TNM staging system and p16 positivity) was also evaluated. No genetic association between the HLA-G 14 bp ins/del and HNSCC risk was detected (p > 0.05). However, in the non-metastatic HNSCC group, a significantly higher HLA-G mRNA expression was noted in tumors in the T4 stage compared to those in the T1 and T2 stages (p = 0.0289). ILT2 mRNA expression was significantly increased in non-metastatic vs. metastatic tumors (p = 0.0269). Furthermore, a significantly higher ILT4 mRNA expression was noted in tumors in the T1+T2 stage compared to those in the T3 stage (p = 0.0495). Our results suggest that the HLA-G molecule creates an immunological microenvironment involved in HNSCC development.

RNA m6A modifications regulate crosstalk between tumor metabolism and immunity

In recent years, m6A modifications in RNA transcripts have arisen as a hot topic in cancer research. Indeed, a number of independent studies have elaborated that the m6A modification impacts the behavior of tumor cells and tumor-infiltrating immune cells, altering tumor cell metabolism along with the differentiation and functional activity of immune cells. This review elaborates on the links between RNA m6A modifications, tumor cell metabolism, and immune cell behavior, discussing this topic from the viewpoint of reciprocal regulation through "RNA m6A-tumor cell metabolism-immune cell behavior" and "RNA m6A-immune cell behavior-tumor cell metabolism" axes. In addition, we discuss the various factors affecting RNA m6A modifications in the tumor microenvironment, particularly the effects of hypoxia associated with cancer cell metabolism along with immune cell-secreted cytokines. Our analysis proposes the conclusion that RNA m6A modifications support widespread interactions between tumor metabolism and tumor immunity. With the current viewpoint that long-term cancer control must tackle cancer cell malignant behavior while strengthening anti-tumor immunity, the recognition of RNA m6A modifications as a key factor provides a new direction for the targeted therapy of tumors. This article is categorized under: RNA Processing > RNA Editing and Modification RNA in Disease and Development > RNA in Disease RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.

Targeting MHC-I molecules for cancer: function, mechanism, and therapeutic prospects

The molecules of Major histocompatibility class I (MHC-I) load peptides and present them on the cell surface, which provided the immune system with the signal to detect and eliminate the infected or cancerous cells. In the context of cancer, owing to the crucial immune-regulatory roles played by MHC-I molecules, the abnormal modulation of MHC-I expression and function could be hijacked by tumor cells to escape the immune surveillance and attack, thereby promoting tumoral progression and impairing the efficacy of cancer immunotherapy. Here we reviewed and discussed the recent studies and discoveries related to the MHC-I molecules and their multidirectional functions in the development of cancer, mainly focusing on the interactions between MHC-I and the multiple participators in the tumor microenvironment and highlighting the significance of targeting MHC-I for optimizing the efficacy of cancer immunotherapy and a deeper understanding of the dynamic nature and functioning mechanism of MHC-I in cancer.

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.

HLA-G 14 bp Ins/Del (rs66554220) Variant Is Not Associated with Breast Cancer in Women from Western Mexico

HLA-G is a physiology and pathologic immunomodulator detrimentally related to cancer. Its gene is heavily transcriptionally and post-transcriptionally regulated by variants located in regulator regions like 3'UTR, being the most studied Ins/Del of 14-bp (rs66554220), which is known to influence the effects of endogen cell factors; nevertheless, the reports are discrepant and controversial. Herein, the relationship of the 14-bp Ins/Del variant (rs66554220) with breast cancer (BC) and its clinical characteristics were analyzed in 182 women with non-familial BC and 221 disease-free women as a reference group. Both groups from western Mexico and sex-age-matched (sm-RG). The rs66554220 variant was amplified by SSP-PCR and the fragments were visualized in polyacrylamide gel electrophoresis. The variant rs66554220 was not associated with BC in our population. However, we suggest the Ins allele as a possible risk factor for developing BC at clinical stage IV (OR = 3.05, 95% CI = 1.16-7.96, p = 0.01); nevertheless, given the small stratified sample size (n = 11, statistical power = 41%), this is inconclusive. In conclusion, the 14-bp Ins/Del (rs66554220) variant of HLA-G is not associated with BC in the Mexican population, but might be related to advanced breast tumors. Further studies are required.

Non-Classical HLA Class 1b and Hepatocellular Carcinoma

A number of studies are underway to gain a better understanding of the role of immunity in the pathogenesis of hepatocellular carcinoma and to identify subgroups of individuals who may benefit the most from systemic therapy according to the etiology of their tumor. Human leukocyte antigens play a key role in antigen presentation to T cells. This is fundamental to the host's defense against pathogens and tumor cells. In addition, HLA-specific interactions with innate lymphoid cell receptors, such those present on natural killer cells and innate lymphoid cell type 2, have been shown to be important activators of immune function in the context of several liver diseases. More recent studies have highlighted the key role of members of the non-classical HLA-Ib and the transcript adjacent to the HLA-F locus, FAT10, in hepatocarcinoma. The present review analyzes the major contribution of these molecules to hepatic viral infection and hepatocellular prognosis. Particular attention has been paid to the association of natural killer and Vδ2 T-cell activation, mediated by specific HLA class Ib molecules, with risk assessment and novel treatment strategies to improve immunotherapy in HCC.

A review of the main genetic factors influencing the course of COVID-19 in Sardinia: the role of human leukocyte antigen-G

Introduction

A large number of risk and protective factors have been identified during the SARS-CoV-2 pandemic which may influence the outcome of COVID-19. Among these, recent studies have explored the role of HLA-G molecules and their immunomodulatory effects in COVID-19, but there are very few reports exploring the genetic basis of these manifestations. The present study aims to investigate how host genetic factors, including HLA-G gene polymorphisms and sHLA-G, can affect SARS-CoV-2 infection.

Materials and Methods

We compared the immune-genetic and phenotypic characteristics between COVID-19 patients (n = 381) with varying degrees of severity of the disease and 420 healthy controls from Sardinia (Italy).

Results

HLA-G locus analysis showed that the extended haplotype HLA-G*01:01:01:01/UTR-1 was more prevalent in both COVID-19 patients and controls. In particular, this extended haplotype was more common among patients with mild symptoms than those with severe symptoms [22.7% vs 15.7%, OR = 0.634 (95% CI 0.440 - 0.913); P = 0.016]. Furthermore, the most significant HLA-G 3'UTR polymorphism (rs371194629) shows that the HLA-G 3'UTR Del/Del genotype frequency decreases gradually from 27.6% in paucisymptomatic patients to 15.9% in patients with severe symptoms (X² = 7.095, P = 0.029), reaching the lowest frequency (7.0%) in ICU patients (X² = 11.257, P = 0.004). However, no significant differences were observed for the soluble HLA-G levels in patients and controls. Finally, we showed that SARS-CoV-2 infection in the Sardinian population is also influenced by other genetic factors such as β-thalassemia trait (rs11549407C>T in the HBB gene), KIR2DS2/HLA-C C1+ group combination and the HLA-B*58:01, C*07:01, DRB1*03:01 haplotype which exert a protective effect [P = 0.005, P = 0.001 and P = 0.026 respectively]. Conversely, the Neanderthal LZTFL1 gene variant (rs35044562A>G) shows a detrimental consequence on the disease course [P = 0.001]. However, by using a logistic regression model, HLA-G 3'UTR Del/Del genotype was independent from the other significant variables [OR_M = 0.4 (95% CI 0.2 - 0.7), P_M = 6.5 x 10^-4].

Conclusion

Our results reveal novel genetic variants which could potentially serve as biomarkers for disease prognosis and treatment, highlighting the importance of considering genetic factors in the management of COVID-19 patients.

Association of HLA-G 3' untranslated region indel polymorphism and its serum expression with susceptibility to colorectal cancer

Background: Colorectal cancer (CRC) is a significant global health challenge with increasing incidence and mortality rates in developing countries. Genome-wide association studies have identified new low-penetrance genetic variants linked to CRC. This study aimed to explore the relationship between HLA-G polymorphism and serum expression with CRC. Methodology: In a case-control configuration, standard PCR was used for genotyping HLA-G 3' indel polymorphism and ELISA for quantifying soluble HLA-G in plasma. Results: The study revealed a significant association between the rs371194629 deletion allele and CRC, as well as higher soluble HLA-G levels in CRC patients. Conclusion: These findings suggest that HLA-G could be a promising biomarker for CRC, and further research could lead to improved screening and treatment for more personalized care.

Assessment of Impact of Human Leukocyte Antigen-Type and Cytokine-Type Responses on Outcomes after Targeted Therapy Currently Used to Treat Chronic Lymphocytic Leukemia

Tumor growth and metastasis are reliant on intricate interactions between the host immune system and various counter-regulatory immune escape mechanisms employed by the tumor. Tumors can resist immune surveillance by modifying the expression of human leukocyte antigen (HLA) molecules, which results in the impaired presentation of tumor-associated antigens, subsequently evading detection and destruction by the immune system. The management of chronic lymphocytic leukemia (CLL) is based on symptom severity and includes various types of targeted therapies, including rituximab, obinutuzumab, ibrutinib, acalabrutinib, zanubrutinib, idelalisib, and venetoclax. These therapies rely on the recognition of specific peptides presented by HLAs on the surface of tumor cells by T cells, leading to an immune response. HLA class I molecules are found in most human cell types and interact with T-cell receptors (TCRs) to activate T cells, which play a vital role in inducing adaptive immune responses. However, tumor cells may evade T-cell attack by downregulating HLA expression, limiting the efficacy of HLA-dependent immunotherapy. The prognosis of CLL largely depends on the presence or absence of genetic abnormalities, such as del(17p), TP53 point mutations, and IGHV somatic hypermutation status. These oral targeted therapies alone or in combination with anti-CD20 antibodies have replaced chemoimmunotherapy as the primary treatment for CLL. In this review, we summarize the current clinical evidence on the impact of HLA- and cytokine-type responses on outcomes after targeted therapies currently used to treat CLL.

Dimerization of Transmembrane Proteins in Cancer Immunotherapy

Transmembrane proteins (TMEMs) are integrated membrane proteins that span the entire lipid bilayer and are permanently anchored to it. TMEMs participate in various cellular processes. Some TMEMs usually exist and perform their physiological functions as dimers rather than monomers. TMEM dimerization is associated with various physiological functions, such as the regulation of enzyme activity, signal transduction, and cancer immunotherapy. In this review, we focus on the dimerization of transmembrane proteins in cancer immunotherapy. This review is divided into three parts. First, the structures and functions of several TMEMs related to tumor immunity are introduced. Second, the characteristics and functions of several typical TMEM dimerization processes are analyzed. Finally, the application of the regulation of TMEM dimerization in cancer immunotherapy is introduced.

Immunological and biological dissection of normal and tumoral salivary glands

Salivary glands naturally play central roles in oral immunity. The salivary glands microenvironment inevitable may be exposed to exogenous factors consequently triggering the initiation and formation of various malignant and benign tumors. Mesenchymal stem cells are recruited into salivary gland microenvironment, interact with tumor cells, and induce inhibitory cytokines as well as cells with immunosuppressive phenotypes such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs). The immune components and tumor immune responses in malignant and benign SGTs are still under investigation. Immune responses may directly play a limiting role in tumor growth and expansion, or may participate in formation of a rich milieu for tumor growth in cooperation with other cellular and regulatory molecules. Immune checkpoint molecules (e.g. PDLs, HLA-G and LAG3) are frequently expressed on tumor cells and/or tumor-infiltrating lymphocytes (TILs) in salivary gland microenvironment, and an increase in their expression is associated with T cell exhaustion, immune tolerance and tumor immune escape. Chemokines and chemokine receptors have influential roles on aggressive behaviors of SGTs, and thereby they could be candidate targets for cancer immunotherapy. To present a broad knowledge on salivary glands, this review first provides a brief description on immunological functions of normal salivary glands, and then describe the SGT's tumor microenvironment, by focusing on mesenchymal stem cells, immune cell subsets, immune checkpoint molecules, chemokines and chemokine receptors, and finally introduces immune checkpoint inhibitors as well as potential targets for cancer therapy.

Genetic Influences in Cancer-Associated Myositis

Idiopathic inflammatory myopathies (IIMs) comprise a heterogeneous group of rare immune-mediated disorders that primarily affect muscles but also lead to dysfunction in other organs. Five different clinical subphenotypes of IIM have been distinguished: dermatomyositis, polymyositis, inclusion body myositis, antisynthetase syndrome, and immune-mediated necrotizing myopathy. Excess mortality and morbidity associated with IIM are largely attributed to comorbidities, particularly cancer. The risk of malignancy is not equally distributed among IIM groups and is particularly high among patients with dermatomyositis. The cancer risk peaks around 3 years on either side of the IIM diagnosis and remains elevated even 10 years after the onset of the disease. Lung, colorectal, and ovarian neoplasms typically arise before the onset of IIM, whereas melanoma, cervical, oropharyngeal, and nonmelanoma skin cancers usually develop after IIM diagnosis. Given the close temporal proximity between IIM diagnosis and the emergence of malignancy, it has been proposed that IIM could be a consequence rather than a cause of cancer, a process known as a paramalignant phenomenon. Thus, a separate group of IIMs related to paramalignant phenomenon has been distinguished, known as cancer-associated myositis (CAM). Although the relationship between IIM and cancer is widely recognized, the pathophysiology of CAM remains elusive. Given that genetic factors play a role in the development of IIM, dissection of the molecular mechanisms shared between IIM and cancer presents an opportunity to examine the role of autoimmunity in cancer development and progression. In this review, the evidence supporting the contribution of genetics to CAM will be discussed.

HLA and tumour immunology: immune escape, immunotherapy and immune-related adverse events

PURPOSE

As molecules responsible for presenting antigens to T lymphocytes, leukocytes antigens (HLAs) play a vital role in cancer immunology. This review aims to provide current understanding of HLAs in tumour immunology.

METHODS

Perspectives on how HLA alterations may contribute to the immune escape of cancer cells and resistance to immunotherapy, and potential methods to overcome HLA defects were summarized. In addition, we discussed the potential association between HLA and immune-related adverse events (irAEs), which has not been reviewed elsewhere.

RESULTS

Downregulation, loss of heterogeneity and entire loss of HLAs are responsible for the immune escape of tumour cells. The strategies to overcome the HLA defects can be effective therapies of cancer. Compared with classical HLA-I, non-classical HLA-I molecules, such as HLA-E and HLA-G, appear to be more reliable predictors of prognosis, as they tend to play immunosuppressive roles in antitumor response. Relative diversified or high expression of classical HLA-I are potential predictors of favourable response of immunotherapy. Certain HLA types may be associated to enhanced affinity to self-antigen-mimicked tumour-antigens, thus may positively correlated to irAEs triggered by checkpoint inhibitors.

CONCLUSIONS

Further studies exploring the relationship between HLAs and cancer may not only lead to the development of novel therapies but also bring about better management of irAEs.

The association between genetic variants at 3'-UTR and 5'-URR of HLA-G gene and the clinical outcomes of patients with leukemia receiving hematopoietic stem cell transplantation

In addition to the classical human leukocyte antigen (HLA) genes, the outcomes of post-hematopoietic stem cell transplantation (HSCT) are associated with human leukocyte antigen (HLA)-related genes and non-HLA genes involved in immune regulation. HLA-G gene plays an important role in immune tolerance, assisting immune escape of tumor cells, and decrease of transplant rejection. In this study, we explored the association of genetic variants at the 3'-untranslated region (3'-UTR) and 5'-upstream regulatory region (5'-URR) of HLA-G gene with the adverse outcomes of patients with leukemia receiving HSCT. The genomic DNAs of 164 patients who had acute leukemia and received HSCT were collected for analysis. Nine single nucleotide polymorphisms (SNPs) and six haplotypes in the 3'-UTR and 27 SNPs and 6 haplotypes in the 5'-URR were selected to investigate their relationship with the development of adverse outcomes for patients receiving HSCT, including mortality, relapse, and graft-versus-host disease. Our results revealed that two SNPs (rs371194629 and rs9380142) and one haplotype (UTR-3) located in the 3'-UTR and two SNPs (rs3823321 and rs1736934) and one haplotype (G0104a) located in the 5'-URR of HLA-G were associated with the occurrence of chronic GVHD or development of any forms of GVHD. No SNP was found to associate with the occurrence of mortality and relapse for patients receiving HSCT. These SNPs and haplotypes may play important roles in regulating immune tolerance of allografts post-HSCT that can be used to predict the risk of poor outcomes after receiving HSCT and giving preventive treatment to patients on time.

Cancer Cell De-Differentiation: Plasticity-Driven Stratagem For Tumor Metastasis and Recurrence

Tumor recurrence is a colossal challenge in clinical oncology. This multifactorial problem is attributed to the emergence of additional genetic mutations and the presence of dormant cancer cells. However, the plasticity of non-stem cancer cells and the acquisition of cancer stem cell (CSC) functionality is another contributing factor to tumor recurrence. Herein, I focus attention on the mechanisms that fuel cancer cell de-differentiation and the interplay between intra-cellular regulators and tumor microenvironment (TME) landscape that promotes cancer cell stemness. Our understanding of the mechanisms underlying tumor cell de-differentiation is crucial for developing innovative therapeutic strategies that prevent cancer from ever recurring.

TMPRSS4 is a novel biomarker and correlated with immune infiltration in thyroid carcinoma

Transmembrane protease serine 4 (TMPRSS4) is a cancer-associated protease associated with prognosis in various types of cancer. Mechanistically, TMPRSS4 mainly regulates malignant phenotypes, such as tumor invasion and metastasis, by either the epithelial to mesenchymal transition (EMT) program or promoting the proliferation of cancer cells. To date, TMPRSS4 and immune infiltration in thyroid carcinoma (TC) are largely unknown. Thus, this paper evaluated the expression of TMPRSS4 in tumor tissue through the Tumor Immune Estimation Resource (TIMER) database, and Oncomine, and its correlation with clinical parameters by UALCAN databases. Furthermore, we analyzed its prognostic value from Kaplan-Meier Plotter database, and the relationship between TMPRSS4 and the abundance of tumor-infiltrating lymphocytes (TILs) in TC in TISIDB, screening potential immune targets to explore novel mechanisms for the clinical management of TC. Finally, we assessed the correlation between TMPRSS4 and some immune markers to uncover a potential immune-related biomarker in TC patients by TIMER2.0. The results revealed that TMPRSS4 was highly expressed in TC and was also associated with lymphatic metastasis, advanced stage, histological subtype, and favorable clinical outcome. The stratified analysis based on immune cell content showed that decreased TMPRSS4 had worse prognosis in CD8⁺ T cell-enriched TC patients. TMPRSS4 was positively correlated with tumor immune infiltration and the expression of gene markers of immune cells. Notably, its expression was lower in the lymphocyte-depleted subtype than in other immunosubtypes in TC. Moreover, TMPRSS4 was closely related to chemokines as well as their receptors and the immunosuppressive checkpoints CTLA-4, PD-1, and HLA-G. In conclusion, TMPRSS4 may act as a novel biomarker predicting prognosis and immune infiltration in TC.

A novel chromatin regulator-related immune checkpoint related gene prognostic signature and potential candidate drugs for endometrial cancer patients

Background

Endometrial cancer (EC) is the most common gynecologic malignancy in developed countries and its prevalence is increasing. As an emerging therapy with a promising efficacy, immunotherapy has been extensively applied in the treatment of solid tumors. In addition, chromatin regulators (CRs), as essential upstream regulators of epigenetics, play a significant role in tumorigenesis and cancer development.

Methods

CRs and immune checkpoint-related genes (ICRGs) were obtained from the previous top research. The Genome Cancer Atlas (TCGA) was utilized to acquire the mRNA expression and clinical information of patients with EC. Correlation analysis was utilized for screen CRs-related ICRGs (CRRICRGs). By Cox regression and least absolute shrinkage and selection operator (LASSO) analysis, prognosis related CRRICRGs were screened out and risk model was constructed. The Kaplan–Meier curve was used to estimate the prognosis between high- and low-risk group. By comparing the IC50 value, the drugs sensitivity difference was explored. We obtained small molecule drugs for the treatment of UCEC patients based on CAMP dataset.

Results

We successfully constructed a 9 CRRICRs-based prognostic signature for patients with UCEC and found the riskscore was an independent prognostic factor. The results of functional analysis suggested that CRRICRGs may be involved in immune processes associated with cancer. Immune characteristics analysis provided further evidence that the CRRICRGs-based model was correlated with immune cells infiltration and immune checkpoint. Eight small molecule drugs that may be effective for the treatment of UCEC patients were screened. Effective drugs identified by drug sensitivity profiling in high- and low-risk groups.

Conclusion

In summary, our study provided novel insights into the function of CRRICRGs in UCEC. We also developed a reliable prognostic panel for the survival of patients with UCEC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41065-022-00253-w.

Dynamic changes of soluble HLA-G and cytokine plasma levels in cervical cancer patients: potential role in cancer progression and immunotherapy

PURPOSE

Chronic inflammation has been proven to be an important factor in carcinogenesis. Cytokines are the central mediators in the inflammatory microenvironment, and their release may be influenced by soluble HLA-G (sHLA-G). The aim of this study was to monitor the dynamic process of these soluble factors in patients with cervical cancer at Taizhou Hospital of Zhejiang Province, trying to understand their relationship with diagnosis, treatment, and prognosis.

METHODS

We quantified plasma levels of sHLA-G and 12 cytokines using ELISA and flow cytometry, respectively, in the peripheral blood of patients with cervical cancer divided into three groups: preoperation, postoperation and clinical relapse. Healthy women were used as the control group. Data were analysed by non-parametric tests, receiver-operating characteristic (ROC) curves, and Kaplan-Meier plotter (log-rank test).

RESULTS

In this study, our findings showed that preoperation plasma levels of sHLA-G and the cytokines IL-6, IL-10, and IFN-γ in cervical cancer patients had a good discriminatory effect between cervical cancer patients and healthy women. It should be noted that plasma levels of sHLA-G, IL-6, and IL-10 were significantly decreased within 30 days after radical hysterectomy (P < 0.05). A positive correlation was observed between IL-6 and IL-10, IL-8 and IL-17 levels preoperatively. In contrast, sHLA-G levels were negatively correlated with IL-10 but not with other cytokines. An increased survival rate in patients with cervical cancer was associated with IL-5 < 1.70 pg/mL, IL-17 < 2.30 pg/mL, and IFN-α < 2.26 pg/mL preoperatively. In addition, our findings showed that the levels of cytokines IL-6, IL-8, IL-12p70, IL-17, and IFN-γ may be related to 5-year relapse rates and/or the metastasis of cervical cancer.

CONCLUSION

The current findings enhance our understanding of the dynamic process (preoperation, postoperation and clinical relapse) of sHLA-G and these cytokines in the plasma of patients with cervical cancer from diagnosis to prognosis. These biomarkers may play a potential therapeutic target role of such dynamic changes in the immunotherapy for cervical cancer.

NKG2A-checkpoint inhibition and its blockade critically depends on peptides presented by its ligand HLA-E

NKG2A has emerged as a new immunotherapy target and its blockade with the novel immune checkpoint inhibitor (ICI) monalizumab can boost both NK cell and CD8+ T cell responses. NKG2A forms heterodimers with CD94 and binds to the human non-classical MHC class I molecule HLA-E. HLA-E forms complexes with a limited set of peptides mainly derived from the leader sequences of the classical MHC class I molecules (HLA-A, HLA-B and HLA-C) and the non-classical class I paralogue HLA-G, and it is well established that the interaction between CD94/NKG2x receptors and its ligand HLA-E is peptide-sensitive. Here, we have evaluated peptide dependence of NKG2A-mediated inhibition and the efficiency of interference by monalizumab in a transcriptional T cell reporter system. NKG2A inhibition was mediated by cell-expressed HLA-E molecules stably presenting disulfate-trapped peptide ligands. We show that different HLA-class I leader peptides mediate varying levels of inhibition. We have used NKG2A/NKG2C chimeric receptors to map the binding site of NKG2A and NKG2C blocking antibodies. Furthermore, we determined the functional EC50 values of blocking NKG2A antibodies and show that they greatly depend on the HLA-leader peptide presented by HLA-E. Monalizumab was less effective in augmenting NK cell-mediated killing of target cells displaying HLA-G peptide on HLA-E, than cells expressing HLA-E complexed with HLA-A, HLA-B and HLA-C peptides. Our results indicate that peptides displayed by HLA-E molecules on tumour cells might influence the effectivity of NKG2A-ICI therapy and potentially suggest novel approaches for patient stratification, for example, based on tumoral HLA-G levels.

Maintenance of Hypoimmunogenic Features via Regulation of Endogenous Antigen Processing and Presentation Machinery

Universally acceptable donor cells have been developed to address the unmet need for immunotypically matched materials for regenerative medicine. Since forced expression of hypoimmunogenic genes represses the immune response, we established universal pluripotent stem cells (PSCs) by replacing endogenous β2-microglobulin (β2m) with β2m directly conjugated to human leukocyte antigen (HLA)-G, thereby simultaneously suppressing HLA-I expression and the natural killer (NK) cell-mediated immune response. These modified human PSCs retained their pluripotency and differentiation capacity; however, surface presentation of HLA-G was absent from subsequently differentiated cells, particularly cells of neural lineages, due to the downregulation of antigen processing and presentation machinery (APM) genes. Induction of APM genes by overexpression of NLR-family CARD domain-containing 5 (NLRC5) or activator subunit of nuclear factor kappa B (NF-κB) heterodimer (RelA) recovered the surface expression of HLA-G and the hypoimmunogenicity of neural cells. Our findings enhance the utility of hypoimmunogenic cells as universal donors and will contribute to the development of off-the-shelf stem-cell therapeutics.

A Novel Prognostic Risk Model for Cervical Cancer Based on Immune Checkpoint HLA-G-Driven Differentially Expressed Genes

Human leukocyte antigen G (HLA-G) is a potential checkpoint molecule that plays a key role in cervical carcinogenesis. The purpose of this study was to construct and validate a prognostic risk model to predict the overall survival (OS) of cervical cancer patients, providing a reference for individualized clinical treatment that may lead to better clinical outcomes. HLA-G-driven differentially expressed genes (DEGs) were obtained from two cervical carcinoma cell lines, namely, SiHa and HeLa, with stable overexpression of HLA-G by RNA sequencing (RNA-seq). The biological functions of these HLA-G-driven DEGs were analysed by GO enrichment and KEGG pathway using the “clusterProfiler” package. The protein-protein interactions (PPIs) were assessed using the STRING database. The prognostic relevance of each DEG was evaluated by univariate Cox regression using the TCGA-CESC dataset. After the TCGA-CESC cohort was randomly divided into training set and testing set, and a prognostic risk model was constructed by LASSO and stepwise multivariate Cox regression analysis in training set and validated in testing set or in different types of cervical cancer set. The predictive ability of the prognostic risk model or nomogram was evaluated by a series of bioinformatics methods. A total of 1108 candidate HLA-G-driven DEGs, including 391 upregulated and 717 downregulated genes, were obtained and were enriched mostly in the ErbB pathway, steroid biosynthesis, and MAPK pathway. Then, an HLA-G-driven DEG signature consisting of the eight most important prognostic genes CD46, LGALS9, PGM1, SPRY4, CACNB3, PLIN2, MSMO1, and DAGLB was identified as a key predictor of cervical cancer. Multivariate Cox regression analysis showed that this signature is an independent risk factor for the overall survival of CESC patients. Kaplan-Meier survival analysis showed that the 5-year overall survival rate is 23.0% and 84.6% for the high-risk and low-risk patients, respectively (P<0.001). The receiver operating characteristic (ROC) curve of this prognostic model with an area under the curve (AUC) was 0.896 for 5 years, which was better than that of other clinical traits. This prognostic risk model was also successfully validated in different subtypes of cervical cancer, including the keratinizing squamous cell carcinoma, non-keratinizing squamous cell carcinoma, squamous cell neoplasms, non-squamous cell neoplasms set. Single-sample gene set enrichment (ssGSEA) algorithm and Tumor Immune Dysfunction and Exclusion (TIDE) analysis confirmed that this signature influence tumour microenvironment and immune checkpoint blockade. A nomogram that integrated risk score, age, clinical stage, histological grade, and pathological type was then built to predict the overall survival of CESC patients and evaluated by calibration curves, AUC, concordance index (C-index) and decision curve analysis (DCA). To summarize, we developed and validated a novel prognostic risk model for cervical cancer based on HLA-G-driven DEGs, and the prognostic signature showed great ability in predicting the overall survival of patients with cervical cancer.

The Novel Immune Checkpoint GPR56 Is Expressed on Tumor-Infiltrating Lymphocytes and Selectively Upregulated upon TCR Signaling

High levels of tumor-infiltrating lymphocytes (TILs) in the tumor microenvironment (TME) are associated with a survival benefit in various cancer types and the targeted (re)activation of TILs is an attractive therapeutic anti-cancer approach that yields curative responses. However, current T cell targeting strategies directed at known immune checkpoints have not increased objective response rates for all cancer types, including for epithelial ovarian cancer (EOC). For this reason, the identification of new immune checkpoints that regulate T cell immunity remains of great interest. One yet largely uninvestigated checkpoint of potential interest is the G protein-coupled receptor 56 (GPR56), which belongs to the adhesion GPCR family. GPR56 was originally reported to function in cerebral cortical development and in anti-depressant response, but also in cancer. Recently, GPR56 was identified as an inhibitory receptor expressed on human NK cells that by cis-interaction with the tetraspanin CD81 attenuated the cytotoxic activity of NK cells. This NK cell checkpoint could be blocked by an GPR56 antibody, leading to increased cytotoxicity. Interestingly, GPR56 expression has also been reported on cytokine producing memory CD8 T lymphocytes and may thus represent a T cell checkpoint as well. Here, GPR56 mRNA expression was characterized in the context of TILs, with GPR56 expression being detected predominantly in tumor infiltrating CD8 T cells with a cytotoxic and (pre-)exhausted phenotype. In accordance with this mRNA profile, TILs from ovarian cancer patients expressed GPR56 primarily within the effector memory and central memory T cell subsets. On T cells from healthy donors the expression was limited to effector memory and terminally differentiated T cells. Notably, GPR56 expression further increased on TILs upon T cell receptor (TCR)-mediated stimulation in co-cultures with cancer cells, whereas GPR56 expression on healthy primary human T cells did not. Further, the ectopic expression of GPR56 significantly reduced the migration of GPR56-positive T cells. Taken together, GPR56 is a potential immune-checkpoint in EOC found on (pre-)exhausted CD8 TILs that may regulate migratory behavior.

HLA-G 14bp Ins/Del Polymorphism, Plasma Level of Soluble HLA-G, and Association with IL-6/IL-10 Ratio and Survival of Glioma Patients

HLA-G is an immune checkpoint molecule with immunosuppressive and anti-inflammatory activities, and its expression and level of its soluble form (sHLA-G) may play an important role in tumor prognosis. The HLA-G 14bp ins/del polymorphism and the plasma level of soluble HLA-G (sHLA-G) were investigated by a polymerase chain reaction and ELISA, respectively, in 59 glioma patients. A significantly higher proportion of glioma patients had the 14 nt insert in both homozygous and heterozygous states compared to the control group. Glioma patients also had higher plasma levels of sHLA-G. Patients with methylated MGMT promoters had lower levels of sHLA-G than those with unmethylated MGMT promoters. The level of sHLA-G negatively correlated with the overall survival of patients. Glioblastoma patients who survived more than one year after diagnosis had lower levels of sHLA-G than those surviving less than one year. Patients with sHLA-G levels below the cut-off value of 40 U/mL survived significantly longer than patients with sHLA-G levels above 40 U/mL. The levels of sHLA-G were also negatively correlated with the level of IL-6 (p = 0.0004) and positively with IL-10/IL-6 (p = 0.046). Conclusion: The presence of the 14 nt insert in both homozygous and heterozygous states of the HLA-G 14bp ins/del polymorphism is more frequent in glioma patients and the elevated plasma levels of sHLA-G are negatively associated with their survival.

The role of cellular proteostasis in anti-tumor immunity

Immune checkpoint blockade therapy is perhaps the most important development in cancer treatment in recent memory. It is based on decades of investigation into the biology of immune cells and the role of the immune system in controlling cancer growth. While the molecular circuitry that governs the immune system in general - and anti-tumor immunity in particular - is intensely studied, far less attention has been paid to the role of cellular stress in this process. Proteostasis, intimately linked to cell stress responses, refers to the dynamic regulation of the cellular proteome and is maintained through a complex network of systems that govern the synthesis, folding, and degradation of proteins in the cell. Disruption of these systems can result in the loss of protein function, altered protein function, the formation of toxic aggregates, or pathologies associated with cell stress. However, the importance of proteostasis extends beyond its role in maintaining proper protein function; proteostasis governs how tolerant cells may be to mutations in protein coding genes and the overall half-life of proteins. Such gene expression changes may be associated with human diseases including neurodegenerative diseases, metabolic disease, and cancer and manifest at the protein level against the backdrop of the proteostasis network in any given cellular environment. In this review, we focus on the role of proteostasis in regulating immune responses against cancer as well the role of proteostasis in determining immunogenicity of cancer cells.

The Human Leukocyte Antigen G as an Immune Escape Mechanism and Novel Therapeutic Target in Urological Tumors

The non-classical human leukocyte antigen G (HLA-G) is a potent regulatory protein involved in the induction of immunological tolerance. This is based on the binding of membrane-bound as well as soluble HLA-G to inhibitory receptors expressed on various immune effector cells, in particular NK cells and T cells, leading to their attenuated functions. Despite its restricted expression on immune-privileged tissues under physiological conditions, HLA-G expression has been frequently detected in solid and hematopoietic malignancies including urological cancers, such as renal cell and urothelial bladder carcinoma and has been associated with progression of urological cancers and poor outcome of patients: HLA-G expression protects tumor cells from anti-tumor immunity upon interaction with its inhibitory receptors by modulating both the phenotype and function of immune cells leading to immune evasion. This review will discuss the expression, regulation, functional and clinical relevance of HLA-G expression in urological tumors as well as its use as a putative biomarker and/or potential therapeutic target for the treatment of renal cell carcinoma as well as urothelial bladder cancer.

HLA-G and Other Immune Checkpoint Molecules as Targets for Novel Combined Immunotherapies

HLA-G is an HLA-class Ib molecule that is involved in the establishment of tolerance at the maternal/fetal interface during pregnancy. The expression of HLA-G is highly restricted in adults, but the de novo expression of this molecule may be observed in different hematological and solid tumors and is related to cancer progression. Indeed, tumor cells expressing high levels of HLA-G are able to suppress anti-tumor responses, thus escaping from the control of the immune system. HLA-G has been proposed as an immune checkpoint (IC) molecule due to its crucial role in tumor progression, immune escape, and metastatic spread. We here review data available in the literature in which the interaction between HLA-G and other IC molecules is reported, in particular PD-1, CTLA-4, and TIM-3, but also IDO and TIGIT. Clinical trials using monoclonal antibodies against HLA-G and other IC are currently ongoing with cancer patients where antibodies and inhibitors of PD-1 and CTLA-4 showed encouraging results. With this background, we may envisage that combined therapies using antibodies targeting HLA-G and another IC may be successful for clinical purposes. Indeed, such immunotherapeutic protocols may achieve a better rescue of effective anti-tumor immune response, thus improving the clinical outcome of patients.

NK cells in the brain: implications for brain tumor development and therapy

Natural killer (NK) cells are innate lymphoid cells with robust antitumor functions rendering them promising therapeutic tools against malignancies. Despite constituting a minor fraction of the immune cells infiltrating tumors in the brain, insights into their role in central nervous system (CNS) pathophysiology are emerging. The challenges posed by a profoundly immunosuppressive microenvironment as well as by tumor resistance mechanisms necessitate exploring avenues to enhance the therapeutic potential of NK cells in both primary and metastatic brain malignancies. In this review, we summarize the role of NK cells in the pathogenesis of tumors in the brain and discuss the avenues investigated to harness their anticancer effects against primary and metastatic CNS tumors, including sources of therapeutic NK cells, combinations with other treatments, and novel engineering approaches for augmenting their cytotoxicity. We also highlight relevant preclinical evidence and clinical trials of NK cell-based therapies.

Nobel Prize for immune checkpoint inhibitors, understanding the immunological switching between immunosuppression and autoimmunity

INTRODUCTION

Immune checkpoint inhibitors (ICIs) are a revolutionary form of immunotherapy in cancer. However, the percentage of patients responding to therapy is relatively low, while adverse effects occur in a large number of patients. In addition, the therapeutic mechanisms of ICIs are not yet completely described.

AREAS COVERED

The initial view (articles published in PubMed, Scopus, Web of Science, etc.) was that ICIs increase tumor-specific immunity. Recent data (collected from the same databases) suggest that the ICIs pharmacotherapy actually extends beyond the topic of immune reactivity, including additional immune pathways, such as disrupting immunosuppression and increasing tumor-specific autoimmunity. Unfortunately, there is no clear delimitation between these specific autoimmune reactions that are therapeutically beneficial, and nonspecific autoimmune reactions/toxicity that can be extremely severe side effects.

EXPERT OPINION

Immune checkpoint mechanisms perform a non-selective immune regulation, maintaining a dynamic balance between immunosuppression and autoimmunity. By blocking these mechanisms, ICIs actually perform an immunological reset, decreasing immunosuppression and increasing tumor-specific immunity and predisposition to autoimmunity. The predisposition to autoimmunity induces both side effects and beneficial autoimmunity. Consequently, further studies are necessary to maximize the beneficial tumor-specific autoimmunity, while reducing the counterproductive effect of associated autoimmune toxicity.

Identification of CCL4 as an Immune-Related Prognostic Biomarker Associated With Tumor Proliferation and the Tumor Microenvironment in Clear Cell Renal Cell Carcinoma

The last decade has witnessed revolutionary advances taken in immunotherapy for various malignant tumors. However, immune-related molecules and their characteristics in the prediction of clinical outcomes and immunotherapy response in clear cell renal cell carcinoma (ccRCC) remain largely unclear. C-C Motif Chemokine Ligand 4 (CCL4) was extracted from the intersection analysis of common differentially expressed genes (DEGs) of four microarray datasets from the Gene Expression Omnibus database and immune-related gene lists in the ImmPort database using Cytoscape plug-ins and univariate Cox regression analysis. Subsequential analysis revealed that CCL4 was highly expressed in ccRCC patients, and positively correlated with multiple clinicopathological characteristics, such as grade, stage and metastasis, while negatively with overall survival (OS). We performed gene set enrichment analysis (GSEA) and gene set variant analysis (GSVA) with gene sets coexpressed with CCL4, and observed that gene sets positively related to CCL4 were enriched in tumor proliferation and immune-related pathways while metabolic activities in the negatively one. To further explore the correlation between CCL4 and immune-related biological process, the CIBERSORT algorithm, ESTIMATE method, and tumor mutational burden (TMB) score were employed to evaluate the tumor microenvironment (TME) characteristics of each sample and confirmed that high CCL4 expression might give rise to high immune cell infiltration. Moreover, correlation analysis revealed that CCL4 was positively correlated with common immune checkpoint genes, such as programmed cell death protein 1 (PD-1), cytotoxic T-lymphocyte-associated protein 4 (CTLA4), and lymphocyte activating 3 (LAG3). Overall, this study demonstrated that CCL4 might serve as a potential immune-related prognostic biomarker to predict clinical outcomes and immunotherapy response in ccRCC. Moreover, CCL4 might contribute to TME modulation, indicating the mechanism CCL4 involved in tumor proliferation and metastasis, which could provide novel therapeutic perceptions for ccRCC patients.

Old and New Players of Inflammation and Their Relationship With Cancer Development

Pathogens or genotoxic agents continuously affect the human body. Acute inflammatory reaction induced by a non-sterile or sterile environment is triggered for the efficient elimination of insults that caused the damage. According to the insult, pathogen-associated molecular patterns, damage-associated molecular patterns, and homeostasis-altering molecular processes are released to facilitate the arrival of tissue resident and circulating cells to the injured zone to promote harmful agent elimination and tissue regeneration. However, when inflammation is maintained, a chronic phenomenon is induced, in which phagocytic cells release toxic molecules damaging the harmful agent and the surrounding healthy tissues, thereby inducing DNA lesions. In this regard, chronic inflammation has been recognized as a risk factor of cancer development by increasing the genomic instability of transformed cells and by creating an environment containing proliferation signals. Based on the cancer immunoediting concept, a rigorous and regulated inflammation process triggers participation of innate and adaptive immune responses for efficient elimination of transformed cells. When immune response does not eliminate all transformed cells, an equilibrium phase is induced. Therefore, excessive inflammation amplifies local damage caused by the continuous arrival of inflammatory/immune cells. To regulate the overstimulation of inflammatory/immune cells, a network of mechanisms that inhibit or block the cell overactivity must be activated. Transformed cells may take advantage of this process to proliferate and gradually grow until they become preponderant over the immune cells, preserving, increasing, or creating a microenvironment to evade the host immune response. In this microenvironment, tumor cells resist the attack of the effector immune cells or instruct them to sustain tumor growth and development until its clinical consequences. With tumor development, evolving, complex, and overlapping microenvironments are arising. Therefore, a deeper knowledge of cytokine, immune, and tumor cell interactions and their role in the intricated process will impact the combination of current or forthcoming therapies.

Immune Regulatory Processes of the Tumor Microenvironment under Malignant Conditions

The tumor microenvironment (TME) is a critical regulator of tumor growth, progression, and metastasis. Since immune cells represent a large fraction of the TME, they play a key role in mediating pro- and anti-tumor immune responses. Immune escape, which suppresses anti-tumor immunity, enables tumor cells to maintain their proliferation and growth. Numerous mechanisms, which have been intensively studied in recent years, are involved in this process and based on these findings, novel immunotherapies have been successfully developed. Here, we review the composition of the TME and the mechanisms by which immune evasive processes are regulated. In detail, we describe membrane-bound and soluble factors, their regulation, and their impact on immune cell activation in the TME. Furthermore, we give an overview of the tumor/antigen presentation and how it is influenced under malignant conditions. Finally, we summarize novel TME-targeting agents, which are already in clinical trials for different tumor entities.

HLA-G: An Important Mediator of Maternal-Fetal Immune-Tolerance

Maternal-fetal immune-tolerance occurs throughout the whole gestational trimester, thus a mother can accept a genetically distinct fetus without immunological aggressive behavior. HLA-G, one of the non-classical HLA class I molecules, is restricted-expression at extravillous trophoblast. It can concordantly interact with various kinds of receptors mounted on maternally immune cells residing in the uterus (e.g. CD4+ T cells, CD8+ T cells, natural killer cells, macrophages, and dendritic cells) for maintaining immune homeostasis of the maternal-fetus interface. HLA-G is widely regarded as the pivotal protective factor for successful pregnancies. In the past 20 years, researches associated with HLA-G have been continually published. Indeed, HLA-G plays a mysterious role in the mechanism of maternal-fetal immune-tolerance. It can also be ectopically expressed on tumor cells, infected sites and other pathologic microenvironments to confer a significant local tolerance. Understanding the characteristics of HLA-G in immunologic tolerance is not only beneficial for pathological pregnancy, but also helpful to the therapy of other immune-related diseases, such as organ transplant rejection, tumor migration, and autoimmune disease. In this review, we describe the biological properties of HLA-G, then summarize our understanding of the mechanisms of fetomaternal immunologic tolerance and the difference from transplant tolerance. Furthermore, we will discuss how HLA-G contributes to the tolerogenic microenvironment during pregnancy. Finally, we hope to find some new aspects of HLA-G in fundamental research or clinical application for the future.

Effect of MHC Linked 7-Gene Signature on Delayed Hepatocellular Carcinoma Recurrence

Dysregulated immune response significantly affects hepatocellular carcinoma's (HCC) prognosis. Human Leukocyte Antigens are key in devising immune responses against HCC. Here, we investigated how HLAs modulate HCC development at the transcriptomic level. RNA-seq data of 576 patients from two independent cohorts was retrieved. The clinicopathological relevance of all HLA genes was investigated using Fisher-Exact, correlation, and Kaplan-Meier and cox regression survival tests. Clustering of ~800 immune-related genes against HLAs was completed using a ward-agglomerative method. Networks were generated using 40 HLA associated unique genes and hub genes were investigated. HLAs including HLA-DMA, HLA-DMB, HLA-DOA and HLA-DRB6 were associated with delayed recurrence in both discovery (204 HCC cases) and validation (372 HCC cases) cohorts. Clustering analyses revealed 40 genes associated with these four HLAs in both cohorts. A set of seven genes (NCF4, TYROBP, LCP2, ZAP70, PTPRC, FYN and WAS) was found co-expressed at gene-gene interaction level in both cohorts. Furthermore, survival analysis revealed seven HLA-linked genes as predictors of delayed recurrence. Multivariate analysis also predicted that mean expression of 7-gene is an independent predictor of delayed recurrence in both cohorts. We conclude that the expression of 7-gene signature may lead to improved patient prognosis. Further studies are required for consideration in clinical practice.

Immune checkpoint blockade in the treatment of malignant tumor: current statue and future strategies

After being stagnant for decades, there has finally been a paradigm shift in the treatment of cancer with the emergence and application of immune checkpoint inhibitors (ICIs). The most extensively utilized ICIs are targeting the pathways involving programmed death-1 (PD-1) and cytotoxic T-lymphocyte associated protein 4 (CTLA-4). PD-1, as an crucial immune inhibitory molecule, by and large reasons the immune checkpoint response of T cells, making tumor cells get away from immune surveillance. Programmed cell death ligand-1 (PD-L1) is exceptionally expressed in most cancers cells and approves non-stop activation of the PD-1 pathway in the tumor microenvironment. PD-1/PD-L1 inhibitors can block the combination of PD-1 and PD-L1, inhibit hostile to regulatory signals, and restore the activity of T cells, thereby bettering immune response. The current researchers assume that the efficacy of these drugs is related to PD-L1 expression in tumor tissue, tumor mutation burden (TMB), and other emerging biomarkers. Although malignant tumors can benefit from the immunotherapy of PD-1/PD-L1 inhibitors, formulating a customized medication model and discovering biomarkers that can predict efficacy are the new trend in the new era of malignant tumor immunotherapy. This review summarizes the mechanism of action of PD-1/PD-L1 inhibitors, their clinical outcomes on various malignant tumors, their efficacy biomarkers, as well as predictive markers of irAEs.

Deregulation of HLA-I in cancer and its central importance for immunotherapy

It is now well accepted that many tumors undergo a process of clonal selection which means that tumor antigens arising at various stages of tumor progression are likely to be represented in just a subset of tumor cells. This process is thought to be driven by constant immunosurveillance which applies selective pressure by eliminating tumor cells expressing antigens that are recognized by T cells. It is becoming increasingly clear that the same selective pressure may also select for tumor cells that evade immune detection by acquiring deficiencies in their human leucocyte antigen (HLA) presentation pathways, allowing important tumor antigens to persist within cells undetected by the immune system. Deficiencies in antigen presentation pathway can arise by a variety of mechanisms, including genetic and epigenetic changes, and functional antigen presentation is a hard phenomenon to assess using our standard analytical techniques. Nevertheless, it is likely to have profound clinical significance and could well define whether an individual patient will respond to a particular type of therapy or not. In this review we consider the mechanisms by which HLA function may be lost in clinical disease, we assess the implications for current immunotherapy approaches using checkpoint inhibitors and examine the prognostic impact of HLA loss demonstrated in clinical trials so far. Finally, we propose strategies that might be explored for possible patient stratification.

A Critical Assessment of the Association between HLA-G Expression by Carcinomas and Clinical Outcome

Human leukocyte antigen-G (HLA-G) conveys immunological tolerance at the maternal-foetal interface. HLA-G expression by tumour cells may also play such a role, resulting in tumour immune evasion, making HLA-G a potential target for immunotherapies. The aim of this review was to determine to what extent it is justified that HLA-G expression is considered as a target for immune checkpoint inhibiting therapy by critically assessing the association between HLA-G expression by carcinomas and clinical outcome of patients. The used HLA-G-detecting mAb, HLA-G quantification methods and statistically significant HLA-G-associated clinicopathological parameters are discussed. Tumour HLA-G expression correlated with poor clinical outcome in breast, esophageal, gastric and hepatocellular carcinoma patients. Tumour HLA-G expression was not associated with clinical outcome in ovarian and oral carcinoma patients. Cervical, colorectal, lung, and pancreatic carcinoma patients presented discrepant and therefore inconclusive results regarding the association between tumour HLA-G expression and clinical outcome. These disparities might partly be the result of differences in the methodological approach to quantify HLA-G expression between studies. Therefore, implementation of universal methodological procedures is strongly advised. Overall, HLA-G expression did not univocally result in poor clinical outcome of carcinoma patients. This implies that tumour HLA-G expression is not necessarily part of an inhibited tumour-immune response and tumour progression. Consequently, it remains elusive whether HLA-G expression by carcinomas functions as an immune checkpoint molecule affecting a tumour-immune response. It may also reflect derailed control of gene expression in tumours, with no real functional consequences.

Comprehensive Transcriptomic Analysis Reveals the Role of the Immune Checkpoint HLA-G Molecule in Cancers

Human leukocyte antigen G (HLA-G) is known as a novel immune checkpoint molecule in cancer; thus, HLA-G and its receptors might be targets for immune checkpoint blockade in cancer immunotherapy. The aim of this study was to systematically identify the roles of checkpoint HLA-G molecules across various types of cancer. ONCOMINE, GEPIA, CCLE, TRRUST, HAP, PrognoScan, Kaplan-Meier Plotter, cBioPortal, LinkedOmics, STRING, GeneMANIA, DAVID, TIMER, and CIBERSORT were utilized. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed. In this study, we comprehensively analysed the heterogeneous expression of HLA-G molecules in various types of cancer and focused on genetic alterations, coexpression patterns, gene interaction networks, HLA-G interactors, and the relationships between HLA-G and pathological stage, prognosis, and tumor-infiltrating immune cells. We first identified that the mRNA expression levels of HLA-G were significantly upregulated in both most tumor tissues and tumor cell lines on the basis of in-depth analysis of RNAseq data. The expression levels of HLA-G were positively associated with those of the other immune checkpoints PD-1 and CTLA-4. Abnormal expression of HLA-G was significantly correlated with the pathological stage of some but not all tumor types. There was a significant difference between the high and low HLA-G expression groups in terms of overall survival (OS) or disease-free survival (DFS). The results showed that HLA-G highly expressed have positive associations with tumor-infiltrating immune cells in the microenvironment in most types of tumors (P<0.05). Additionally, we identified the key transcription factor (TF) targets in the regulation of HLA-G expression, including HIVEP2, MYCN, CIITA, MYC, and IRF1. Multiple mutations (missense, truncating, etc.) and the methylation status of the HLA-G gene may explain the differential expression of HLA-G across different tumors. Functional enrichment analysis showed that HLA-G was primarily related to T cell activation, T cell regulation, and lymphocyte-mediated immunity. The data may provide novel insights for blockade of the HLA-G/ILT axis, which holds potential for the development of more effective antitumour treatments.

HLA-G/ILTs Targeted Solid Cancer Immunotherapy: Opportunities and Challenges

Immune checkpoint inhibitors (ICIs) have become a promising immunotherapy for cancers. Human leukocyte antigen-G (HLA-G), a neoantigen, its biological functions and clinical relevance have been extensively investigated in malignancies, and early clinical trials with “anti-HLA-G strategy” are being launched for advance solid cancer immunotherapy. The mechanism of HLA-G as a new ICI is that HLA-G can bind immune cell bearing inhibitory receptors, the immunoglobulin-like transcript (ILT)-2 and ILT-4. HLA-G/ILT-2/-4 (HLA-G/ILTs) signaling can drive comprehensive immune suppression, promote tumor growth and disease progression. Though clinical benefits could be expected with application of HLA-G antibodies to blockade the HLA-G/ILTs signaling in solid cancer immunotherapy, major challenges with the diversity of HLA-G isoforms, HLA-G/ILTs binding specificity, intra- and inter-tumor heterogeneity of HLA-G, lack of isoform-specific antibodies and validated assay protocols, which could dramatically affect the clinical efficacy. Clinical benefits of HLA-G-targeted solid cancer immunotherapy may be fluctuated or even premature unless major challenges are addressed.

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.

Antigen presentation in cancer: insights into tumour immunogenicity and immune evasion

Immune checkpoint blockade, which blocks inhibitory signals of T cell activation, has shown tremendous success in treating cancer, although success still remains limited to a fraction of patients. To date, clinically effective CD8⁺ T cell responses appear to target predominantly antigens derived from tumour-specific mutations that accumulate in cancer, also called neoantigens. Tumour antigens are displayed on the surface of cells by class I human leukocyte antigens (HLA-I). To elicit an effective antitumour response, antigen presentation has to be successful at two distinct events: first, cancer antigens have to be taken up by dendritic cells (DCs) and cross-presented for CD8⁺ T cell priming. Second, the antigens have to be directly presented by the tumour for recognition by primed CD8⁺ T cells and killing. Tumours exploit multiple escape mechanisms to evade immune recognition at both of these steps. Here, we review the tumour-derived factors modulating DC function, and we summarize evidence of immune evasion by means of quantitative modulation or qualitative alteration of the antigen repertoire presented on tumours. These mechanisms include modulation of antigen expression, HLA-I surface levels, alterations in the antigen processing and presentation machinery in tumour cells. Lastly, as complete abrogation of antigen presentation can lead to natural killer (NK) cell-mediated tumour killing, we also discuss how tumours can harbour antigen presentation defects and still evade NK cell recognition.

Certain haplotypes of the 3'-UTR region of the HLA-G gene are linked to breast cancer

Background: Human leukocyte antigen G belongs to the family of non-classical HLA class I genes, its expression considered an important immune escape mechanism of cancer cells. The polymorphisms in the 3'-untranslated region (UTR) region of HLA-G influence the magnitude of the protein by modulating HLA-G mRNA stability. We hypothesised links between any of eight (UTR) single nucleotide polymorphisms (SNPs) and their haplotype of the HLA-G gene with breast cancer. Materials and Methods: Peripheral blood DNA from 100 patients affected by breast cancer and 100 controls was PCR sequenced for genotyping of 25 HLA-G 3'-UTR regions, including rs371194629 (+2960), rs1707 (+3003), rs1710 (+3010), rs17179101 (+3027), rs1063320 (+3142), rs9380142 (+3187), rs1610696 (+3196), and rs1233331 (+3227). Results: The 14-bp deletion (p = 0.01), and the +3010 (p = 0.021), +3142 (p = 0.006) and +3187 (p = 0.046) variants were significantly more prevalent in patients than in controls. In combining these data, two haplotypes of all eight SNPs and deletion/insertion (UTR-1 and UTR-4) are associated with breast cancer. Conclusion: Certain variants in the 3-UTR, and their combination as a haplotype, of the HLA-G gene are linked to breast cancer.