Molecular mechanisms of HLA class I-mediated immune evasion of human tumors and their role in resistance to immunotherapies

Tumor mutational burden for the prediction of PD-(L)1 blockade efficacy in cancer: challenges and opportunities

Tumor mutational burden (TMB) is a biomarker that measures the number of somatic mutations in a tumor's genome. TMB has emerged as a predictor of response to immune checkpoint inhibitors (ICIs) in various cancer types, and several studies have shown that patients with high TMB have better outcomes when treated with programmed death-ligand 1-based therapies. Recently, the Food and Drug Administration has approved TMB as a companion diagnostic for the use of pembrolizumab in solid tumors. However, despite its potential, the use of TMB as a biomarker for immunotherapy efficacy is limited by several factors. Here we review the limitations of TMB in predicting immunotherapy outcomes in patients with cancer and discuss potential strategies to optimize its use in the clinic.

A diversity of novel type-2 innate lymphoid cell subpopulations revealed during tumour expansion

Type 2 innate lymphoid cells (ILC2s) perform vital functions in orchestrating humoral immune responses, facilitating tissue remodelling, and ensuring tissue homeostasis. Additionally, in a role that has garnered considerably less attention, ILC2s can also enhance Th1-related cytolytic T lymphocyte immune responses against tumours. Studies have thus far generally failed to address the mystery of how one ILC2 cell-type can participate in a multiplicity of functions. Here we utilized single cell RNA sequencing analysis to create the first comprehensive atlas of naïve and tumour-associated lung ILC2s and discover multiple unique subtypes of ILC2s equipped with developmental gene programs that become skewed during tumour expansion favouring inflammation, antigen processing, immunological memory and Th1-related anti-tumour CTL responses. The discovery of these new subtypes of ILC2s challenges current paradigms of ILC2 biology and provides an explanation for their diversity of function.

Immune Evasion Through Human Leukocyte Antigen Implications and Its Impact on Targeted Therapy

The malfunctioning of human leukocyte antigen (HLA) class I antigens has a substantial negative impact on the effectiveness of leukemia treatment, particularly in the development of immunotherapies that rely on T-cell activation. HLA-G, a molecule that suppresses the immune response, plays a role in repressing the activation and proliferation of T cells, natural killer cells, and antigen-presenting cells. The expression of HLA-G is associated with various pathological conditions. Tumor cells exploit the immune evasion capabilities of HLA, allowing them to evade detection and elimination by the immune system. Understanding and modifying the HLA molecules is crucial for the advancement of innovative immunotherapies targeting chronic lymphocytic leukemia. Numerous mechanisms have been investigated to elucidate how HLA facilitates tumor evasion in patients with chronic lymphocytic leukemia and other malignancies. These mechanisms include inhibiting immune cell cytolysis, altering cytokine production levels, promoting immune cell programmed cell death, and impairing chemotaxis. This review provides a comprehensive overview of immune evasion mediated by HLA and its implications for targeted therapy.

EMT-induced immune evasion: connecting the dots from mechanisms to therapy

Epithelial-mesenchymal transition (EMT) is a dynamic program crucial for organismal development and tissue regeneration. Unfortunately, this program is often hijacked by epithelial tumors to facilitate metastasis. Beyond its role in cancer spread, EMT increases cancer cell survival by activating stem cell programs and bypassing apoptotic programs. Importantly, the capacity of EMT to enforce tumor progression by altering the tumor cell phenotype without triggering immune responses opens the intriguing possibility of a mechanistic link between EMT-driven cancers and immune evasion. Indeed, EMT has been acknowledged as a of driver immune evasion, but the mechanisms are still evolving. Here, we review recent insights into the influence of EMT on tumor immune evasion. Specifically, we focus on the mechanistic roles of EMT in immune escape as the basis that may provide a platform for innovative therapeutic approaches in advanced tumors. We summarize promising therapeutic approaches currently in clinical trials and trending preclinical studies aimed at reinvigorating the tumor microenvironment to create immune-permissive conditions that facilitates immune-mediated tumor clearance. We anticipate that this will assist researchers and pharmaceutical companies in understanding how EMT compromises the immune response, potentially paving the way for effective cancer therapies.

Frequency changes in HLA-I alleles: A marker to guide immunotherapy in lung adenocarcinoma patients and its relationship with tumor mutational burden and PD-L1 expression

BACKGROUND

The aim of the study was to investigate differences in HLA-I alleles between lung adenocarcinoma patients and healthy controls and determine their association with PD-L1 expression and tumor mutational burden (TMB) to understand the mechanism underlying lung adenocarcinoma susceptibility.

METHODS

Differences in HLA allele frequencies between the two groups were analyzed in a case-control study. PD-L1 expression and TMB in lung adenocarcinoma patients were determined and their relationships with HLA-I were analyzed.

RESULTS

The lung adenocarcinoma group showed significantly higher HLA-A*30:01 (p = 0.0067, odds ratio [OR], 1.834; 95% confidence interval [CI]: 1.176-2.860), B*13:02 (p = 0.0050, OR, 1.855; 95% CI: 1.217-2.829), and C*06:02 (p = 0.0260, OR, 1.478; 95% CI: 1.060-2.060) and significantly lower B*51:01 (p = 0.0290, OR, 0.6019; 95% CI: 0.3827-0.9467), and C*14:02 (p = 0.0255, OR, 0.5089; 95% CI: 0.2781-0.9312) than the control group. Haplotype analysis results showed that HLA-A*30:01-B*13:02 (p = 0.0100, OR, 1.909; 95% CI: 1.182-3.085), A*11:01-C*01:02 (p = 0.0056, OR, 1.909; 95% CI: 1.182-3.085), A*30:01-C*06:02 (p = 0.0111, OR, 1.846; 95% CI: 1.147-2.969), and B*13:02-C*06:02 (p = 0.0067, OR, 1.846; 95% CI: 1.147-2.969) frequencies significantly increased and B*51:01-C*14:02 (p = 0.0219, OR, 0.490; 95% CI: 0.263-0.914) frequency significantly decreased in lung adenocarcinoma patients. Three-locus haplotype analysis showed that HLA-A*30:01-B*13:02-C*06:02 frequency (p = 0.0100, OR, 1.909; 95% CI: 1.182-3.085) significantly increased in patients.

CONCLUSION

HLA-A*30:01, B*13:02, and C*06:02 may be the susceptibility genes and HLA-B*51:01 and C*14:01 act as the resistance genes of lung adenocarcinoma. The changes in HLA-I allele frequencies had no association with PD-L1 expression and TMB among these patients.

Adaptive and Innate Cytotoxic Effectors in Chronic Lymphocytic Leukaemia (CLL) Subjects with Stable Disease

Chronic lymphocytic leukaemia (CLL) is characterised by the expansion of a neoplastic mature B cell clone. CLL clinical outcome is very heterogeneous, with some subjects never requiring therapy and some showing an aggressive disease. Genetic and epigenetic alterations and pro-inflammatory microenvironment influence CLL progression and prognosis. The involvement of immune-mediated mechanisms in CLL control needs to be investigated. We analyse the activation profile of innate and adaptive cytotoxic immune effectors in a cohort of 26 CLL patients with stable disease, as key elements for immune-mediated control of cancer progression. We observed an increase in CD54 expression and interferon (IFN)-γ production by cytotoxic T cells (CTL). CTL ability to recognise tumour-targets depends on human leukocyte antigens (HLA)-class I expression. We observed a decreased expression of HLA-A and HLA-BC on B cells of CLL subjects, associated with a significant reduction in intracellular calnexin that is relevant for HLA surface expression. Natural killer (NK) cells and CTL from CLL subjects show an increased expression of the activating receptor KIR2DS2 and a reduction of 3DL1 and NKG2A inhibiting molecules. Therefore, an activation profile characterises CTL and NK cells of CLL subjects with stable disease. This profile is conceivable with the functional involvement of cytotoxic effectors in CLL control.

A novel cell-based screen identifies chemical entities that reverse the immune-escape phenotype of metastatic tumours

Genetic and epigenetic events have been implicated in the downregulation of the cellular antigen processing and presentation machinery (APM), which in turn, has been associated with cancer evasion of the immune system. When these essential components are lacking, cancers develop the ability to subvert host immune surveillance allowing cancer cells to become invisible to the immune system and, in turn, promote cancer metastasis. Here we describe and validate the first high-throughput cell-based screening assay to identify chemical extracts and unique chemical entities that reverse the downregulation of APM components in cell lines derived from metastatic tumours. Through the screening of a library of 480 marine invertebrate extracts followed by bioassay-guided fractionation, curcuphenol, a common sesquiterpene phenol derived from turmeric, was identified as the active compound of one of the extracts. We demonstrate that curcuphenol induces the expression of the APM components, TAP-1 and MHC-I molecules, in cell lines derived from both metastatic prostate and lung carcinomas. Turmeric and curcumins that contain curcuphenol have long been utilized not only as a spice in the preparation of food, but also in traditional medicines for treating cancers. The remarkable discovery that a common component of spices can increase the expression of APM components in metastatic tumour cells and, therefore reverse immune-escape mechanisms, provides a rationale for the development of foods and advanced nutraceuticals as therapeutic candidates for harnessing the power of the immune system to recognize and destroy metastatic cancers.

Roles of tumor-associated macrophages in anti-PD-1/PD-L1 immunotherapy for solid cancers

In recent years, tumor immunotherapy has made significant progress. However, tumor immunotherapy, particularly immune checkpoint inhibitors (e.g., PD-1/PD-L1 inhibitors), benefits only a tiny proportion of patients in solid cancers. The tumor microenvironment (TME) acts a significant role in tumor immunotherapy. Studies reported that tumor-associated macrophages (TAMs), as one of the main components of TME, seriously affected the therapeutic effect of PD-1/PD-L1 inhibitors. In this review, we analyzed TAMs from epigenetic and single-cell perspectives and introduced the role and mechanisms of TAMs in anti-programmed death protein 1(anti-PD-1) therapy. In addition, we summarized combination regimens that enhance the efficacy of tumor PD-1/PD-L1 inhibitors and elaborated on the role of the TAMs in different solid cancers. Eventually, the clinical value of TAMs by influencing the therapeutic effect of tumor PD-1/PD-L1 inhibitors was discussed. These above are beneficial to elucidate poor therapeutic effect of PD-1/PD-L1 inhibitors in solid tumors from the point of view of TAMs and explore the strategies to improve its objective remission rate of solid cancers.

Pervasiveness of HLA allele-specific expression loss across tumor types

BACKGROUND

Efficient presentation of mutant peptide fragments by the human leukocyte antigen class I (HLA-I) genes is necessary for immune-mediated killing of cancer cells. According to recent reports, patient HLA-I genotypes can impact the efficacy of cancer immunotherapy, and the somatic loss of HLA-I heterozygosity has been established as a factor in immune evasion. While global deregulated expression of HLA-I has also been reported in different tumor types, the role of HLA-I allele-specific expression loss - that is, the preferential RNA expression loss of specific HLA-I alleles - has not been fully characterized in cancer.

METHODS

Here, we use RNA and whole-exome sequencing data to quantify HLA-I allele-specific expression (ASE) in cancer using our novel method arcasHLA-quant.

RESULTS

We show that HLA-I ASE loss in at least one of the three HLA-I genes is a pervasive phenomenon across TCGA tumor types. In pancreatic adenocarcinoma, tumor-specific HLA-I ASE loss is associated with decreased overall survival specifically in the basal-like subtype, a finding that we validated in an independent cohort through laser-capture microdissection. Additionally, we show that HLA-I ASE loss is associated with poor immunotherapy outcomes in metastatic melanoma through retrospective analyses.

CONCLUSIONS

Together, our results highlight the prevalence of HLA-I ASE loss and provide initial evidence of its clinical significance in cancer prognosis and immunotherapy treatment.

lncRNA HCG11 suppresses cell proliferation in hormone receptor-positive breast cancer via SRSF1/β-catenin

Hormone receptor positive (HR-positive) breast cancer (BC) is the most common subtype of breast cancer. Despite adjuvant endocrine therapy and chemotherapy-based treatment, the therapeutic response is often not satisfactory in HR-positive BC patients. Therefore, elucidating the mechanisms that regulate the progression of HR-positive BC is urgently required to identify new therapeutic targets. Previously, HLA Complex Group 11 (HCG11), located on the major histocompatibility complex (MHC) region, was found to be abnormally expressed in a variety of tumor cells. However, the role of HCG11 in HR-positive BC cells has not been explored to date. In the current study, we found that HCG11 is downregulated in HR-positive BC tissues and cell lines. Both in vitro and in vivo, HCG11 acts as a tumor suppressor in HR-positive BC cells. Furthermore, the mechanistic details unraveled that HCG11 recruits Serine/arginine-rich splicing factor 1 (SRSF1) to target β-catenin mRNA for promoting the translation of β-catenin. Our study emphasizes the potential of HCG11 as a novel intervention target for HR-positive BC treatment.

Immunogenic cell death triggered by impaired deubiquitination in multiple myeloma relies on dysregulated type I interferon signaling

Introduction

Proteasome inhibition is first line therapy in multiple myeloma (MM). The immunological potential of cell death triggered by defects of the ubiquitin-proteasome system (UPS) and subsequent perturbations of protein homeostasis is, however, less well defined.

Methods

In this paper, we applied the protein homeostasis disruptors bortezomib (BTZ), ONX0914, RA190 and PR619 to various MM cell lines and primary patient samples to investigate their ability to induce immunogenic cell death (ICD).

Results

Our data show that while BTZ treatment triggers sterile type I interferon (IFN) responses, exposure of the cells to ONX0914 or RA190 was mostly immunologically silent. Interestingly, inhibition of protein de-ubiquitination by PR619 was associated with the acquisition of a strong type I IFN gene signature which relied on key components of the unfolded protein and integrated stress responses including inositol-requiring enzyme 1 (IRE1), protein kinase R (PKR) and general control nonderepressible 2 (GCN2). The immunological relevance of blocking de-ubiquitination in MM was further reflected by the ability of PR619-induced apoptotic cells to facilitate dendritic cell (DC) maturation via type I IFN-dependent mechanisms.

Conclusion

Altogether, our findings identify de-ubiquitination inhibition as a promising strategy for inducing ICD of MM to expand current available treatments.

Construction of Prognostic Risk Model for Small Cell Lung Cancer Based on Immune-Related Genes

Small cell lung cancer (SCLC) is a highly invasive and fatal malignancy. Research at the present stage implied that the expression of immune-related genes is associated with the prognosis in SCLC. Accordingly, it is essential to explore effective immune-related molecular markers to judge prognosis and treat SCLC. Our research obtained SCLC dataset from Gene Expression Omnibus (GEO) and subjected mRNAs in it to differential expression analysis. Differentially expressed mRNAs (DEmRNAs) were intersected with immune-related genes to yield immune-related differentially expressed genes (DEGs). The functions of these DEGs were revealed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. Thereafter, we categorized 3 subtypes of immune-related DEGs via K-means clustering. Kaplan-Meier curves analyzed the effects of 3 subtypes on SCLC patients' survival. Single-sample gene set enrichment analysis (ssGSEA) and ESTIMATE validated that the activation of different immune gene subtypes differed significantly. Finally, an immune-related-7-gene assessment model was constructed by univariate-Lasso-multiple Cox regression analyses. Riskscores, Kaplan-Meier curves, receiver operating characteristic (ROC) curves, and independent prognostic analyses validated the prognostic value of the immune-related-7-gene assessment model. As suggested by GSEA, there was a prominent difference in cytokine-related pathways between high- and low-risk groups. As the analysis went further, we discovered a statistically significant difference in the expression of human leukocyte antigen (HLA) proteins and costimulatory molecules expressed on the surface of CD274, CD152, and T lymphocytes in different groups. In a word, we started with immune-related genes to construct the prognostic model for SCLC, which could effectively evaluate the clinical outcomes and offer guidance for the treatment and prognosis of SCLC patients.

Reversible epigenetic alterations regulate class I HLA loss in prostate cancer

Downregulation of HLA class I (HLA-I) impairs immune recognition and surveillance in prostate cancer and may underlie the ineffectiveness of checkpoint blockade. However, the molecular mechanisms regulating HLA-I loss in prostate cancer have not been fully explored. Here, we conducted a comprehensive analysis of HLA-I genomic, epigenomic and gene expression alterations in primary and metastatic human prostate cancer. Loss of HLA-I gene expression was associated with repressive chromatin states including DNA methylation, histone H3 tri-methylation at lysine 27, and reduced chromatin accessibility. Pharmacological DNA methyltransferase (DNMT) and histone deacetylase (HDAC) inhibition decreased DNA methylation and increased H3 lysine 27 acetylation and resulted in re-expression of HLA-I on the surface of tumor cells. Re-expression of HLA-I on LNCaP cells by DNMT and HDAC inhibition increased activation of co-cultured prostate specific membrane antigen (PSMA)_27-38-specific CD8⁺ T-cells. HLA-I expression is epigenetically regulated by functionally reversible DNA methylation and chromatin modifications in human prostate cancer. Methylated HLA-I was detected in HLA-I^low circulating tumor cells (CTCs), which may serve as a minimally invasive biomarker for identifying patients who would benefit from epigenetic targeted therapies.

Hypoxia-inducible factors: master regulators of hypoxic tumor immune escape

Hypoxia, a common feature of the tumor microenvironment in various types of cancers, weakens cytotoxic T cell function and causes recruitment of regulatory T cells, thereby reducing tumoral immunogenicity. Studies have demonstrated that hypoxia and hypoxia-inducible factors (HIFs) 1 and 2 alpha (HIF1A and HIF2A) are involved in tumor immune escape. Under hypoxia, activation of HIF1A induces a series of signaling events, including through programmed death receptor-1/programmed death ligand-1. Moreover, hypoxia triggers shedding of complex class I chain-associated molecules through nitric oxide signaling impairment to disrupt immune surveillance by natural killer cells. The HIF-1-galactose-3-O-sulfotransferase 1-sulfatide axis enhances tumor immune escape via increased tumor cell-platelet binding. HIF2A upregulates stem cell factor expression to recruit tumor-infiltrating mast cells and increase levels of cytokines interleukin-10 and transforming growth factor-β, resulting in an immunosuppressive tumor microenvironment. Additionally, HIF1A upregulates expression of tumor-associated long noncoding RNAs and suppresses immune cell function, enabling tumor immune escape. Overall, elucidating the underlying mechanisms by which HIFs promote evasion of tumor immune surveillance will allow for targeting HIF in tumor treatment. This review discusses the current knowledge of how hypoxia and HIFs facilitate tumor immune escape, with evidence to date implicating HIF1A as a molecular target in such immune escape. This review provides further insight into the mechanism of tumor immune escape, and strategies for tumor immunotherapy are suggested.

Human Leukocyte Antigen Class I Deficiency in Gastric Carcinoma: An Adaptive Immune Evasion Strategy Most Common in Microsatellite Instable Tumors

Immune checkpoint inhibitor therapy is effective only for a subset of patients with gastric cancer. Impaired neoantigen presentation caused by deficiency of human leukocyte antigen class I (HLA-I) has been reported as a common mechanism of immune evasion which is associated with resistance to immune checkpoint blockade. To elucidate the significance of HLA-I deficiency in gastric cancer with special focus on microsatellite instable (MSI) and Epstein-Barr virus (EBV)-positive tumors, we examined HLA-I expression on tumor cells and correlated the results with clinicopathologic features, programmed death-ligand 1 (PD-L1) expression, and degree of tumor-infiltrating immune cells. This study included 58 MSI, 44 EBV-positive, and 107 non-EBV non-MSI tumors for comparison. The frequency of HLA-I deficiency (≥1% tumor cells) was significantly higher in MSI tumors (52%) compared with EBV-positive tumors (23%) and the other tumors (28%). In contrast, PD-L1 expression levels were highest in EBV-positive tumors, followed by MSI tumors, with the lowest prevalence in the other tumors in both Tumor Proportion Score and Combined Positive Score. HLA-I deficiency was significantly more frequent in advanced tumors (pT2-4) than in early tumors (pT1) in MSI and non-EBV non-MSI subtypes. In addition, the degree of CD8-positive cells infiltration was significantly reduced in HLA-I deficient tumor areas compared with HLA-I preserved tumor area within a tumor. Based on our observations, HLA-I, as well as PD-L1, should be considered as a common mechanism of immune escape especially in the MSI subtype, and therefore could be a biomarker predicting response to immune checkpoint inhibitor therapy in gastric cancer.

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.

Clinical and immunological characteristics of sarcomas patients with clonogenic tumors

Tumorigenesis is related to the generation of heterogeneous tumor cell population, which is the result of genetic and epigenetic alterations followed by clonal selections and subsequent expansion. In basic studies genetic, histological and morphological diversity of different clones within a patient's neoplasm and specifics of their interrelation with patient's immune system are investigated mostly on the models of tumors of epithelial origin. Mesenchymal tumors such as soft tissue and bone-derived sarcomas (STBS) have been poorly studied in this regard. The molecular genetic methods used to examine intratumoral heterogeneity do not currently provide insight into which portion of the identified subclones are able to grow autonomously. Limiting dilution cloning demonstrates the existence of self-regulating tumor cells in the population and can serve as an independent prognostic predictor of poor prognosis. Intratumoral heterogeneity results not only in differences in growth dynamics, gene expression, and phenotypic markers, but also in the resistance to treatment, especially immunotherapy, thus causing tumor eluding immune escape. The changes that accompany this process can be affected by the cellular immune system, resulting in an imbalance between populations. The variations in the population composition of immune system cells are now widely debated as a predictor of response to immunotherapy, which is of obvious interest for sarcomas, where the effectiveness of chemotherapy is low and the prognosis is unfavorable, especially in case of metastatic disease development. The search for new predictive markers of disease prognosis and treatment efficacy is an important task, to which this study is focused. Our results demonstrate that clonogenic tumor characteristics such as clonogenic potential is independent predictor of unfavorable prognosis in cases of cancer and correlate with the clinical characteristics of the tumor such as overall survival (OS) and progression free survival (PFS). It was found that patients with clonogenic sarcomas had a lower content of activated cytotoxic T-lymphocytes (CTL) with the CD3⁺CD8⁺HLA^-DR⁺ phenotype and an increased number of natural NK killers (p < 0.05) compared to nonclonogenic tumors. In addition, according to our data, a high neutrophil to lymphocyte ratio (NLR), a low value of major T-lymphocyte populations, and a higher number of natural killer cells (NK) in the blood can be negative prognostic factors for the immunotherapy of this disease.

Targeting NK Cells to Enhance Melanoma Response to Immunotherapies

Natural killer (NK) cells are a key component of an innate immune system. They are important not only in initiating, but also in augmenting adaptive immune responses. NK cell activation is mediated by a carefully orchestrated balance between the signals from inhibitory and activating NK cell receptors. NK cells are potent producers of proinflammatory cytokines and are also able to elicit strong antitumor responses through secretion of perforin and granzyme B. Tumors can develop many mechanisms to evade NK cell antitumor responses, such as upregulating ligands for inhibitory receptors, secreting anti-inflammatory cytokines and recruiting immunosuppressive cells. Enhancing NK cell responses will likely augment the effectiveness of immunotherapies, and strategies to accomplish this are currently being evaluated in clinical trials. A comprehensive understanding of NK cell biology will likely provide additional opportunities to further leverage the antitumor effects of NK cells. In this review, we therefore sought to highlight NK cell biology, tumor evasion of NK cells and clinical trials that target NK cells.

Tumor Microenvironment, HLA Class I and APM Expression in HPV-Negative Oral Squamous Cell Carcinoma

Simple Summary

Oral squamous cell carcinoma has developed different strategies to escape from T-cell-mediated immune surveillance, which is mediated by changes in the composition of cellular and soluble components of the tumor microenvironment as well as an impaired expression of molecules of the antigen processing machinery leading to a downregulation of HLA class I surface antigens. In depth characterization of these escape mechanisms might help to develop strategies to overcome this tolerance. In this study, human papilloma virus negative oral squamous cell carcinoma lesions were analyzed regarding the protein expression of major components of the HLA class I antigen processing/presentation pathway in correlation to the intra-tumoral immune cell composition, IFN-γ signaling and clinical parameters, which was further confirmed by bioinformatics analyses of datasets obtained from The Cancer Genome Atlas. This novel knowledge could be used for optimizing the design of immunotherapeutic approaches of this disease.

Abstract

Progression of oral squamous cell carcinoma (OSCC) has been associated with an escape of tumor cells from the host immune surveillance due to an increased knowledge of its underlying molecular mechanisms and its modulation by the tumor microenvironment and immune cell repertoire. In this study, the expression of HLA class I (HLA-I) antigens and of components of the antigen processing machinery (APM) was analyzed in 160 pathologically classified human papilloma virus (HPV)-negative OSCC lesions and correlated to the intra-tumoral immune cell response, IFN-γ signaling and to the patient’s outcome. A heterogeneous but predominantly lower constitutive protein expression of HLA-I APM components was found in OSCC sections when compared to non-neoplastic cells. Tumoral HLA-I APM component expression was further categorized into the three major phenotypes HLA-I^high/APM^high, HLA-I^low/APM^low and HLA-I^{discordant high/low}/APM^high. In the HLA-I^high/APM^high group, the highest frequency of intra-tumoral CD8⁺ T cells and lowest number of CD8⁺ T cells close to FoxP3⁺ cells were found. Patients within this group presented the most unfavorable survival, which was significantly evident in stage T2 tumors. Despite a correlation with the number of intra-tumoral CD8⁺ T cells, tumoral JAK1 expression as a surrogate marker for IFN-γ signaling was not associated with HLA-I/APM expression. Thus, the presented findings strongly indicate the presence of additional factors involved in the immunomodulatory process of HPV-negative OSCC with a possible tumor-burden-dependent complex network of immune escape mechanisms beyond HLA-I/APM components and T cell infiltration in this tumor entity.

Immune Cluster and PPI Network Analyses Identified CXCR3 as a Key Node of Immunoregulation in Head and Neck Cancer

The tumor microenvironment (TME) is significantly associated with clinical outcomes and therapeutic efficacy. However, the landscape of the head and neck cancer (HNC) microenvironment is not fully understood. Therefore, we divided HNCs into three classes according to differences in the TME to determine effective personalized treatments. We explored the immune landscape of head and neck cancer by analysing the gene expression profile of 501 cases from the Cancer Genome Atlas (TCGA) data portal and validated our findings in 270 cases from the Gene Expression Omnibus (GEO) database. The levels of immune components in the tumor microenvironment were evaluated via single-sample gene set enrichment (ssGSEA) analysis. The HNCs were clustered into an Immunity-H group, Immunity-M group and Immunity-L group according to 40 immune components in the tumor microenvironment. DNA damage and HLA genes play an important role in immune regulation. The patients in the Immunity-H group had a favourable survival compared with patients in the Immunity-M group and the Immunity-L group. The patients in the Immunity-H group and Immunity-M group could benefit from radiotherapy. In addition, the Immunity-L group showed the lowest immunophenoscore and had poor response to anti-PD-1 treatment. CXCR3 was demonstrated to be downregulated in the Immunity-L group, which was related to shorter OS in the TCGA and GEO databases, suggesting CXCR3 as a potential therapeutic target. Taken together, our findings proposed three new microenvironment-related phenotypes of HNCs and suggested that CXCR3 played a major role in immune regulation and could be a novel therapeutic target, providing a reference for clinical decisions and research directions in the future.

The role of HLA in Balkan endemic nephropathy

Balkan endemic nephropathy (BEN), a progressive chronic tubulointerstitial disease, occurs in the endemic focus of Croatia in a population of about 10,000 inhabitants. One of its most peculiar characteristics is a strong association with upper tract urothelial carcinoma (UTUC). Despite a high number of studies, currently there are insufficient data about the association of BEN and HLA genes. The aim of this study was to investigate the polymorphism of HLA-A, -B, and -DRB1 alleles and haplotypes among BEN patients and to determine whether an association between HLA and BEN exists. In this study, we investigated HLA-A, -B, and -DRB1 alleles and haplotypes in a population of patients with BEN (N = 111) and matched healthy controls (N = 190). All individuals were tested by PCR-SSO and PCR-SSP methods to assess the possible contribution of HLA alleles and haplotypes to the development of/protection from BEN. Our results showed a positive association between the presence of HLA-B*35:02 and DRB1*04:02 alleles and BEN (P = 0.0179 and P = 0.0151, respectively) in contrast to the protective effect of HLA-A*01:01, B*27:05 and B*57:01 alleles (P = 0.0111, P = 0.0330 and P = 0.0318, respectively). Moreover, when BEN patients' HLA haplotypes were compared to controls, two haplotypes were associated with BEN susceptibility among Croatians (HLA-A*02:01~B*08:01~DRB1*03:01 and HLA-A*02:01~B*27:02~DRB1*16:01, P = 0.0064 and P = 0.0023, respectively), while haplotypes HLA-A*02:01~B*27:05~DRB1*01:01 and HLA-A*02:01~B*38:01~DRB1*13:01 each showed a possible protective effect (P = 0.0495). Our results point toward genetic susceptibility to BEN and observed differences in both susceptible/protective HLA profiles indicate the necessity of further studies in order to elucidate the pathogenesis of this disease.

Identification of microRNAs Targeting the Transporter Associated with Antigen Processing TAP1 in Melanoma

The underlying molecular mechanisms of the aberrant expression of components of the HLA class I antigen processing and presentation machinery (APM) in tumors leading to evasion from T cell-mediated immune surveillance could be due to posttranscriptional regulation mediated by microRNAs (miRs). So far, some miRs controlling the expression of different APM components have been identified. Using in silico analysis and an miR enrichment protocol in combination with small RNA sequencing, miR-26b-5p and miR-21-3p were postulated to target the 3′ untranslated region (UTR) of the peptide transporter TAP1, which was confirmed by high free binding energy and dual luciferase reporter assays. Overexpression of miR-26b-5p and miR-21-3p in melanoma cells downregulated the TAP1 protein and reduced expression of HLA class I cell surface antigens, which could be reverted by miR inhibitors. Moreover, miR-26b-5p overexpression induced a decreased T cell recognition. Furthermore, an inverse expression of miR-26b-5p and miR-21-3p with TAP1 was found in primary melanoma lesions, which was linked with the frequency of CD8⁺ T cell infiltration. Thus, miR-26-5p and miR-21-3p are involved in the HLA class I-mediated immune escape and might be used as biomarkers or therapeutic targets for HLA class I^low melanoma cells.

Natural killer cell impairment in ovarian clear cell carcinoma

In the present study, we report the analysis of NK cells derived from patients suffering from a rare ovarian cancer histotype of clear cell carcinoma (OCCC) resistant to conventional chemotherapies. We analyzed the phenotype of NK cells derived from peripheral blood (PB) and peritoneal fluid (PF) and evaluated cytotoxic interactions between NK cells and autologous tumor cells (ATC) derived from patients. We provided evidence of impaired degranulation capacity of NK cells derived from patients' PF in the presence of ATC. Analyzing tumor cell ligands recognized by NK cell receptors, we found that ATC are characterized by an HLA class I⁺ phenotype (although the level of HLA-I expression varies among all patients) and by a heterogeneous expression of ligands for activating NK receptors (from normal to decreased expression of some markers). Furthermore, we observed a down-regulation of crucial NK cell activating receptors, primarily DNAX Accessory Molecule-1 (DNAM-1), on tumor-associated NK cells. Based on these results, we propose that this severe lysis defect may be due to both negative interactions between HLA-I-specific inhibitory NK cell receptors/HLA-I molecules and to defective interactions between activating NK receptors and cognate ligands. In conclusion, for the first time, the phenotypic and functional properties of tumor-associated NK cells and their ATC derived from PF of patients with advanced stage of OCCC were characterized. Taken together results indicate altered interactions between NK cells and ATC and shed light on the aggressive mechanisms of this cancer histotype. Further studies on this rare tumor will be helpful to improve and define more effective therapies.

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.

Rationale of combination of anti-PD-1/PD-L1 antibody therapy and radiotherapy for cancer treatment

Significant technological advances in radiotherapy have been made in the past few decades. High-precision radiotherapy has recently become popular and is contributing to improvements in the local control of the irradiated target lesions and the reduction of adverse effects. Accordingly, for long-term survival, the importance of systemic cancer control, including at non-irradiated sites, is growing. Toward this challenge, the treatment methods in which anti-PD-1/PD-L1 antibodies that exert systemic effects by restoring anti-tumour immunity are combined with radiotherapy has attracted attention in recent years. Previous studies have reported the activation of anti-tumour immunity by radiotherapy, which simultaneously elevates PD-L1 expression, suggesting a potential for combination therapy. Radiotherapy induces so-called ‘immunogenic cell death’, which involves cell surface translocation of calreticulin and extracellular release of high-mobility group protein box 1 (HMGB-1) and adenosine-5′-triphosphate (ATP). Furthermore, radiotherapy causes immune activation via MHC class I upregulation and cGAS–STING pathway. In contrast, induction of immunosuppressive lymphocytes and the release of immunosuppressive cytokines and chemokines by radiotherapy contribute to immunosuppressive reactions. In this article, we review immune responses induced by radiotherapy as well as previous reports to support the rationale of combination of radiotherapy and anti-PD-1/PD-L1 antibodies. A number of preclinical and clinical studies have shown the efficacy of radiotherapy combined with immune checkpoint inhibition, hence combination therapy is considered to be an important future strategy for cancer treatment.

The characteristic of tumor immune microenvironment in pulmonary carcinosarcoma

Pulmonary carcinosarcoma (PCS) is a rare but aggressive neoplasm, due to late diagnosis and early metastasis. Surgery combined with radiotherapy is a standard treatment. However, PCS features an easy relapse after surgery resection and resistance to chemotherapy and radiotherapy. Tumor immune microenvironment reflects tumor immunophenotyping and affects immunotherapy efficiency. This review summarized current studies on the characteristic of tumor immune microenvironment in PCS and discussed the potential of immunotherapy combined with other regimes strategy as a candidate for treatments in PCS.

Differential prognostic impact of CD8+ T cells based on human leucocyte antigen I and PD-L1 expression in microsatellite-unstable gastric cancer

BACKGROUND

The aim of the study was to determine the human leucocyte antigen class-I (HLA-I), programmed death-ligand 1 (PD-L1) expression and tumour-infiltrating lymphocytes (TILs) of microsatellite instability-high gastric cancer.

METHODS

The HLA-I expression type was determined by immunohistochemistry of HLA-A, HLA-B, HLA-C and β2-microglobulin in the centre of the tumour (CT) and in the invasive margin (IM) of samples from 293 patients (total loss vs. preserved type). PD-L1 expression and TIL density was examined immunohistochemically. HLA-I genotyping was also performed.

RESULTS

The expression loss of the HLA-I molecules was significantly associated with low TIL density. According to survival analyses, the HLA-I expression type and PD-L1 positivity were not independent prognostic factors. The TIL density had no prognostic implication when survival analysis was performed for the whole patient group; however, high CD8⁺ TIL infiltration was significantly associated with good prognosis in only HLA-I-preserved-type/PD-L1-positive group (p = 0.034). The homozygosity of the HLA-I allele was more frequently observed in the total loss type group.

CONCLUSIONS

We confirmed differential prognostic implication of CD8⁺ TILs according to the HLA-I and PD-L1 expression. Determination of the HLA-I expression could be helpful to select patients who would benefit from anti-PD-1/PD-L1 therapy.

Basis of PD1/PD-L1 Therapies

It is obvious that tumor cells have developed a number of strategies to escape immune surveillance including an altered expression of various immune checkpoints, such as the programmed death-1 receptor (PD-1) and its ligands PD-L1 and PD-L2. The interaction between PD-1 and PD-L1 results in an activation of self-tolerance pathways in both immune cells as well as tumor cells. Thus, these molecules represent excellent targets for T cell-based immunotherapies. However, the efficacy of therapies using checkpoint inhibitors is variable and only a limited number of patients receive a long-term response, while others develop resistances. Therefore, a better insight into the constitutive expression levels and their control as well as the predictive and prognostic value of PD-1/PD-L1, which are controversially discussed due to the methodological assessment, the dynamic and time-related variable expression of these molecules, is urgently required. In this review, the current knowledge of the PD-L1 and PD-1 genes, their expression in immune and tumor cells, the underlying molecular mechanisms of their regulation and their association with clinical parameters and therapy responses are summarized.

The Role of the Lymphocyte Functional Crosstalk and Regulation in the Context of Checkpoint Inhibitor Treatment-Review

During the last decade, the dynamics of the cellular crosstalk have highlighted the significance of the host vs. tumor interaction. This resulted in the development of novel immunotherapeutic strategies in order to modulate/inhibit the mechanisms leading to escape of tumor cells from immune surveillance. Different monoclonal antibodies directed against immune checkpoints, e.g., the T lymphocyte antigen 4 and the programmed cell death protein 1/ programmed cell death ligand 1 have been successfully implemented for the treatment of cancer. Despite their broad activity in many solid and hematologic tumor types, only 20–40% of patients demonstrated a durable treatment response. This might be due to an impaired T cell tumor interaction mediated by immune escape mechanisms of tumor and immune cells as well as alterations in the composition of the tumor microenvironment, peripheral blood, and microbiome. These different factors dynamically regulate different steps of the cancer immune process thereby negatively interfering with the T cell –mediated anti-tumoral immune responses. Therefore, this review will summarize the current knowledge of the different players involved in inhibiting tumor immunogenicity and mounting resistance to checkpoint inhibitors with focus on the role of tumor T cell interaction. A better insight of this process might lead to the development of strategies to revert these inhibitory processes and represent the rational for the design of novel immunotherapies and combinations in order to improve their efficacy.

Human leukocyte antigen class II expression is a good prognostic factor in adult T-cell leukemia/lymphoma

Attenuated human leukocyte antigen (HLA) class I expression is implicated as a major immune escape mechanism in several types of tumor. We previously reported that HLA class I/β2 microglobulin and programmed death ligand-1 expression are prognostic factors in adult T-cell leukemia/lymphoma. A recent report suggested that HLA class II expression is also an important prognostic factor for the clinical outcome of programmed death-1 blockade therapy in recurrent/refractory Hodgkin lymphoma. This prompted us to evaluate HLA class II expression in adult T-cell leukemia/lymphoma and to compare the findings with the patients’ clinicopathological features. Of the 132 biopsy specimens examined from newly diagnosed patients, lymphoma cells were positive for HLA class II expression in 44 patients (33.3%), whereas programmed death ligand-1 expression was observed on neoplastic cells from nine patients (6.9%) and on stromal cells in the tumor microenvironment in 83 cases (62.9%). HLA class II-positive cases showed a significantly better overall survival compared to the HLA class II-negative cases (P<0.0001). Patients positive for HLA class II and programmed death ligand-1 microenvironmental expression had significantly better prognosis than the other groups (P<0.0001). HLA class II-positive and HLA class II-negative groups also showed a significant difference in complete remission rate (P=0.0421), HLA class I/β2 microglobulin expression (P=0.0165), and the number of programmed death-1-positive tumor infiltrating cells (P=0.0020). HLA class II expression was a prognostic factor for overall survival both in univariate and multivariate analyses (P<0.0001 and P=0.0007, respectively). Our study reveals that HLA class II is a novel prognostic factor in adult T-cell leukemia/lymphoma.

Influence of tumor-associated macrophages and HLA class I expression according to HPV status in head and neck cancer patients receiving chemo/bioradiotherapy

BACKGROUND AND PURPOSE

To investigate the prognostic value of tumor-associated macrophages (TAM) and HLA class I expression according to HPV status in patients with head and neck squamous cell carcinoma treated with definitive radiotherapy combining cisplatin (CRT) or cetuximab (BRT).

MATERIAL AND METHODS

Ninety-five patients were enrolled. The density of CD68+ cells and CD68+ CD163+ cells (further referred as M2) in the intraepithelial and the stromal compartments, respectively, as well as HLA class I expression in tumor cells, were evaluated semi-quantitatively. Correlations between biomarker expression and treatment outcomes were analyzed.

RESULTS

Multivariate analysis showed that the intraepithelial macrophage density (IEMD) was prognostic for favorable progression-free survival (PFS) and there was a non-significant trend for improved overall survival (OS). HLA class I down-regulation was not an independent prognostic factor. Subgroup analysis showed that in p16+ population, patients with high IEMD had improved 5-year PFS vs. patients with low IEMD (81.2% vs. 25.0%, p < 0.001), while in p16- population, no difference was observed. Similarly, when stratified by primary tumor site, IEMD showed prognostic value in oropharyngeal cancer patients (OPC) but not non-OPC patients. Five-year PFS of patients with low stromal M2 macrophage density treated with CRT was significantly improved vs. those with BRT (54.5% vs. 36.1%, p = 0.03), while in tumors with high M2, there was no significant difference (50.3% vs. 42.9%, p = 0.67).

CONCLUSIONS

The prognostic role of TAM phenotype and distribution depends on HPV status and might predict treatment response. They prompt further validation in prospective studies.

The good, the (not so) bad and the ugly of immune homeostasis in melanoma

Within the immune system multiple mechanisms balance the need for efficient pathogen recognition and destruction with the prevention of tissue damage by excessive, inappropriate or even self-targeting (auto)immune reactions. This immune homeostasis is a tightly regulated system which fails during tumor development, often due to the hijacking of its essential self-regulatory mechanisms by cancer cells. It is facilitated not only by tumor intrinsic properties, but also by the microbiome, host genetics and other factors. In certain ways many cancers can therefore be considered a rare failure of immune control rather than an uncommon or rare disease of the tissue of origin, as the acquisition of potentially oncogenic traits through mutation occurs constantly in most tissues during proliferation. Normally, aberrant cells are well-controlled by cell intrinsic (repair or apoptosis) and extrinsic (immune) mechanisms. However, occasionally oncogenic cells survive and escape control. Melanoma is one of the first cancer types where treatments aimed at restoring and enhancing an immune response to regain control over the tumor have been used with various success rates. With the advent of "modern" immunotherapeutics such as anti-CTLA-4 or anti-PD-1 antibodies that both target negative immune-regulatory pathways on immune cells resulting in durable responses in a proportion of patients, the importance of the interplay between the immune system and cancer has been established beyond doubt.

Predicting response and toxicity to immune checkpoint inhibitors using routinely available blood and clinical markers

Immune checkpoint inhibitors (ICI) are an important development in the treatment of advanced cancer. A substantial proportion of patients treated with ICI do not respond, and additionally patients discontinue treatment due to adverse effects. While many novel biological markers related to the specific mechanisms of ICI actions have been investigated, there has also been considerable research to identify routinely available blood and clinical markers that may predict response to ICI therapy. If validated, these markers have the advantage of being easily integrated into clinical use for nominal expense. Several markers have shown promise, including baseline and post-treatment changes in leucocyte counts, lactate dehydrogenase and C-reactive protein. While promising, the results between studies have been inconsistent due to small sample sizes, follow-up time and variability in the assessed markers. To date, research on routinely available blood and clinical markers has focussed primarily on ICI use in melanoma, the use of ipilimumab and on univariate associations, but preliminary evidence is emerging for other cancer types, other ICIs and for combining markers in multivariable clinical prediction models.

Acquired IFNγ resistance impairs anti-tumor immunity and gives rise to T-cell-resistant melanoma lesions

Melanoma treatment has been revolutionized by antibody-based immunotherapies. IFNγ secretion by CD8⁺ T cells is critical for therapy efficacy having anti-proliferative and pro-apoptotic effects on tumour cells. Our study demonstrates a genetic evolution of IFNγ resistance in different melanoma patient models. Chromosomal alterations and subsequent inactivating mutations in genes of the IFNγ signalling cascade, most often JAK1 or JAK2, protect melanoma cells from anti-tumour IFNγ activity. JAK1/2 mutants further evolve into T-cell-resistant HLA class I-negative lesions with genes involved in antigen presentation silenced and no longer inducible by IFNγ. Allelic JAK1/2 losses predisposing to IFNγ resistance development are frequent in melanoma. Subclones harbouring inactivating mutations emerge under various immunotherapies but are also detectable in pre-treatment biopsies. Our data demonstrate that JAK1/2 deficiency protects melanoma from anti-tumour IFNγ activity and results in T-cell-resistant HLA class I-negative lesions. Screening for mechanisms of IFNγ resistance should be considered in therapeutic decision-making.