Tumor escape mechanisms: potential role of soluble HLA antigens and NK cells activating ligands

Glioblastoma vaccines: past, present, and opportunities

Glioblastoma (GBM) is one of the most lethal central nervous systems (CNS) tumours in adults. As supplements to standard of care (SOC), various immunotherapies improve the therapeutic effect in other cancers. Among them, tumour vaccines can serve as complementary monotherapy or boost the clinical efficacy with other immunotherapies, such as immune checkpoint blockade (ICB) and chimeric antigen receptor T cells (CAR-T) therapy. Previous studies in GBM therapeutic vaccines have suggested that few neoantigens could be targeted in GBM due to low mutation burden, and single-peptide therapeutic vaccination had limited efficacy in tumour control as monotherapy. Combining diverse antigens, including neoantigens, tumour-associated antigens (TAAs), and pathogen-derived antigens, and optimizing vaccine design or vaccination strategy may help with clinical efficacy improvement. In this review, we discussed current GBM therapeutic vaccine platforms, evaluated and potential antigenic targets, current challenges, and perspective opportunities for efficacy improvement.

Chondroitin sulfate proteoglycan 4: An attractive target for antibody-based immunotherapy

Multifunctional molecules involved in tumor progression and metastasis have been identified as valuable targets for immunotherapy. Among these, chondroitin sulfate proteoglycan 4 (CSPG4), a significant tumor cell membrane-bound proteoglycan, has emerged as a promising target, especially in light of advances in chimeric antigen receptor (CAR) T-cell therapy. The profound bioactivity of CSPG4 and its role in pivotal processes such as tumor proliferation, migration, and neoangiogenesis underline its therapeutic potential. We reviewed the molecular intricacies of CSPG4, its functional attributes within tumor cells, and the latest clinical-translational advances targeting it. Strategies such as blocking monoclonal antibodies, conjugate therapies, bispecific antibodies, small-molecule inhibitors, CAR T-cell therapies, trispecific killer engagers, and ribonucleic acid vaccines against CSPG4 were assessed. CSPG4 overexpression in diverse tumors and its correlation with adverse prognostic outcomes emphasize its significance in cancer biology. These findings suggest that targeting CSPG4 offers a promising avenue for future cancer therapy, with potential synergistic effects when combined with existing treatments.

Soluble HLA peptidome: A new resource for cancer biomarkers

Using circulating molecular biomarkers to screen for cancer and other debilitating disorders in a high-throughput and low-cost fashion is becoming increasingly attractive in medicine. One major limitation of investigating protein biomarkers in body fluids is that only one-fourth of the entire proteome can be routinely detected in these fluids. In contrast, Human Leukocyte Antigen (HLA) presents peptides from the entire proteome on the cell surface. While peptide-HLA complexes are predominantly membrane-bound, a fraction of HLA molecules is released into body fluids which is referred to as soluble HLAs (sHLAs). As such peptides bound by sHLA molecules represent the entire proteome of their cells/tissues of origin and more importantly, recent advances in mass spectrometry-based technologies have allowed for accurate determination of these peptides. In this perspective, we discuss the current understanding of sHLA-peptide complexes in the context of cancer, and their potential as a novel, relatively untapped repertoire for cancer biomarkers. We also review the currently available tools to detect and quantify these circulating biomarkers, and we discuss the challenges and future perspectives of implementing sHLA biomarkers in a clinical setting.

Soluble HLA peptidome of pleural effusions is a valuable source for tumor antigens

Background

Soluble human leucocyte antigen (sHLA) molecules, released into the plasma, carry their original peptide cargo and provide insight into the protein synthesis and degradation schemes of their source cells and tissues. Other body fluids, such as pleural effusions, may also contain sHLA-peptide complexes, and can potentially serve as a source of tumor antigens since these fluids are drained from the tumor microenvironment. We explored this possibility by developing a methodology for purifying and analyzing large pleural effusion sHLA class I peptidomes of patients with malignancies or benign diseases.

Methods

Cleared pleural fluids, cell pellets present in the pleural effusions, and the primary tumor cells cultured from cancer patients’ effusions, were used for immunoaffinity purification of the HLA molecules. The recovered HLA peptides were analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) and the resulting LC-MS/MS data were analyzed with the MaxQuant software tool. Selected tumor antigen peptides were tested for their immunogenicity potential with donor peripheral blood mononuclear cells (PBMCs) in an in vitro assay.

Results

Mass spectrometry analysis of the pleural effusions revealed 39,669 peptides attributable to 11,305 source proteins. The majority of peptides identified from the pleural effusions were defined as HLA ligands that fit the patients’ HLA consensus sequence motifs. The membranal and soluble HLA peptidomes of each individual patient correlated to each other. Additionally, soluble HLA peptidomes from the same patient, obtained at different visits to the clinic, were highly similar. Compared with benign effusions, the soluble HLA peptidomes of malignant pleural effusions were larger and included HLA peptides derived from known tumor-associated antigens, including cancer/testis antigens, lung-related proteins, and vascular endothelial growth factor pathway proteins. Selected tumor-associated antigens that were identified by the immunopeptidomics were able to successfully prime CD8⁺ T cells.

Conclusions

Pleural effusions contain sHLA-peptide complexes, and the pleural effusion HLA peptidome of patients with malignant tumors can serve as a rich source of biomarkers for tumor diagnosis and potential candidates for personalized immunotherapy.

Cancer Immunoediting: Elimination, Equilibrium, and Immune Escape in Solid Tumors

Emphasizing the dynamic processes between cancer and host immune system, the initially discovered concept of cancer immunosurveillance has been replaced by the current concept of cancer immunoediting consisting of three phases: elimination, equilibrium, and escape. Solid tumors composed of both cancer and host stromal cells are an example how the three phases of cancer immunoediting functionally evolve and how tumor shaped by the host immune system gets finally resistant phenotype. The elimination, equilibrium, and escape have been described in this chapter in details, including the role of immune surveillance, cancer dormancy, disruption of the antigen-presenting machinery, tumor-infiltrating immune cells, resistance to apoptosis, as well as the function of tumor stroma, microvesicles, exosomes, and inflammation.

Open MHC Class I Conformers: A Look through the Looking Glass

Studies carried out during the last few decades have consistently shown that cell surface MHC class I (MHC-I) molecules are endowed with functions unrelated with antigen presentation. These include cis–trans-interactions with inhibitory and activating KIR and LILR, and cis-interactions with receptors for hormones, growth factors, cytokines, and neurotransmitters. The mounting body of evidence indicates that these non-immunological MHC-I functions impact clinical and biomedical settings, including autoimmune responses, tumor escape, transplantation, and neuronal development. Notably, most of these functions appear to rely on the presence in hematopoietic and non-hematopoietic cells of heavy chains not associated with β2m and the peptide at the plasma membrane; these are known as open MHC-I conformers. Nowadays, open conformers are viewed as functional cis-trans structures capable of establishing physical associations with themselves, with other surface receptors, and being shed into the extracellular milieu. We review past and recent developments, strengthening the view that open conformers are multifunctional structures capable of fine-tuning cell signaling, growth, differentiation, and cell communication.

Defective HLA Class I Expression and Patterns of Lymphocyte Infiltration in Chordoma Tumors

BACKGROUND

There are no effective systemic therapies for chordoma. The recent successes of immunotherapeutic strategies in other cancers have resulted in a resurgence of interest in using immunotherapy in chordoma. These approaches rely on a functional interaction between the host's immune system and the expression of tumor peptides via the human leukocyte antigen (HLA) Class I antigen. It is not known whether chordoma cells express the HLA Class I antigen.

QUESTIONS/PURPOSES

(1) Do chordoma tumors exhibit defects in HLA Class I antigen expression? (2) What is the pattern of lymphocyte infiltration in chordoma tumors?

METHODS

Patients with chordoma treated at Massachusetts General Hospital between 1989 and 2009 were identified with permission from the institutional review board. Of the 75 patients who were identified, 24 human chordoma tumors were selected from 24 distinct patients based on tissue availability. Histology slides from these 24 formalin-fixed paraffin-embedded chordoma tissue samples were deparaffinized using xylene and ethanol and underwent heat-induced antigen retrieval in a citrate buffer. Samples were incubated with monoclonal antibodies directed against HLA Class I antigen processing machinery components. Antibody binding was detected via immunohistochemical staining. Staining intensity (negative, weakly positive, strongly positive) was assessed semiquantitatively and the percentage of chordoma cells stained for HLA Class I antigen subunits was assessed quantitatively. Hematoxylin and eosin-stained histology slides from the same 24 chordoma samples were assessed qualitatively for the presence of tumor-infiltrating lymphocytes and histologic location of these lymphocytes. Immunohistochemical staining with monoclonal antibodies directed against CD4 and CD8 was performed in a quantitative manner to identify the lymphocyte subtype present in chordoma tumors. All results were scored independently by two investigators and were confirmed by a senior bone and soft tissue pathologist.

RESULTS

Seven of 24 chordoma samples exhibited no staining by the anti-HLA-A heavy chain monoclonal antibody HC-A2, two had weak staining intensity, and eight had a heterogeneous staining pattern, with fewer than 60% of chordoma cells exhibiting positive staining results. Four of 24 samples tested were not stained by the anti-HLA-B/C heavy chain monoclonal antibody HC-10, five had weak staining intensity, and 11 displayed a heterogeneous staining pattern. For the anti-β-2-microglobulin monoclonal antibody NAMB-1, staining was detected in all samples, but 11 had weak staining intensity and four displayed a heterogeneous staining pattern. Twenty-one of 24 samples tested had decreased expression in at least one subunit of HLA Class I antigens. No tumors were negative for all three subunits. Lymphocytic infiltration was found in 21 of 24 samples. Lymphocytes were primarily found in the fibrous septae between chordoma lobules but also within the tumor lobules and within the fibrous septae and tumor lobules. Twenty-one of 24 tumors had CD4+ T cells and 11 had CD8+ T cells.

CONCLUSION

In chordoma tissue samples, HLA Class I antigen defects commonly were present, suggesting a mechanism for escape from host immunosurveillance. Additionally, nearly half of the tested samples had cytotoxic CD8+ T cells present in chordoma tumors, suggesting that the host may be capable of mounting an immune response against chordoma tumors. The resulting selective pressure imposed on chordoma tumors may lead to the outgrowth of chordoma cell subpopulations that can evade the host's immune system.

CLINICAL RELEVANCE

These findings have implications in the design of immunotherapeutic strategies for chordoma treatment. T cell recognition of tumor cells requires HLA Class I antigen expression on the targeted tumor cells. Defects in HLA Class I expression may play a role in the clinical course of chordoma and may account for the limited or lack of efficacy of T cell-based immunity triggered by vaccines and/or checkpoint inhibitors.

NK cells sense tumors, course of disease and treatments: Consequences for NK-based therapies

The recent findings on NK activation indicate that these cells are important antitumor effectors. NK cells participate in the graft-vs.-leukemia effect to control the relapse in leukemic patients transplanted with allogeneic hematopoietic stem cells. In various tumors, correlation between NK cell infiltrates and prognosis were reported. However, tumor-infiltrating NK cells are yet poorly characterized. We here summarize our results and the recent studies of the literature on tumor-infiltrating NK cells, and discuss the impact of these novel insights into NK cell responses against tumors for the design of NK cell-based therapies.

The Potential of Soluble Human Leukocyte Antigen Molecules for Early Cancer Detection and Therapeutic Vaccine Design

Human leukocyte antigen (HLA) molecules are essential for anti-tumor immunity, as they display tumor-derived peptides to drive tumor eradication by cytotoxic T lymphocytes. HLA molecules are primarily studied as peptide-loaded complexes on cell membranes (mHLA) and much less attention is given to their secretion as soluble HLA–peptide complexes (sHLA) into bodily fluids. Yet sHLA levels are altered in various pathologies including cancer, and are thus of high interest as biomarkers. Disconcordance in results across studies, however, hampers interpretation and generalization of the relationship between sHLA levels and cancer presence, thereby impairing its use as a biomarker. Furthermore, the question remains to what extent sHLA complexes exert immunomodulatory effects and whether shifts in sHLA levels contribute to disease or are only a consequence of disease. sHLA complexes can also bear tumor-derived peptides and recent advancements in mass spectrometry now permit closer sHLA peptide cargo analysis. sHLA peptide cargo may represent a “liquid biopsy” that could facilitate the use of sHLA for cancer diagnosis and target identification for therapeutic vaccination. This review aims to outline the contradictory and unexplored aspects of sHLA and to provide direction on how the full potential of sHLA as a quantitative and qualitative biomarker can be exploited.

Designing precision medicine panels for drug refractory cancers targeting cancer stemness traits

Cancer is one amongst the major causes of death today and cancer biology is one of the most well researched fields in medicine. The driving force behind cancer is considered to be a minor subpopulation of cells, the cancer stem cells (CSCs). Similar to other stem cells, these cells are self-renewing and proliferating but CSCs are also difficult to target by chemo- or radio-therapies. Cancer stem cells are known to be present in most of the cancer subgroups such as carcinoma, sarcoma, myeloma, leukemia, lymphomas and mixed cancer types. There is a wide gamut of factors attributed to the stemness of cancers, ranging from dysregulated signaling pathways, and activation of enzymes aiding immune evasion, to conducive tumor microenvironment, to name a few. The defining outcome of the increased presence of CSCs is tumor metastasis and relapse. Predictive medicine approach based on the plethora of CSC markers would be a move towards precision medicine to specifically identify CSC-rich tumors. In this review, we discuss the cancer subtypes and the role of different CSC specific markers in these varying subtypes. We also categorize the CSC markers based their defining trait contributing to stemness. This review thus provides a comprehensive approach to catalogue a predictive set of markers to identify the resistant and refractory cancer stem cell population within different tumor subtypes, so as to facilitate better prognosis and targeted therapeutic strategies.

Therapeutic applications of the selective high affinity ligand drug SH7139 extend beyond non-Hodgkin's lymphoma to many other types of solid cancers

SH7139, the first of a series of selective high affinity ligand (SHAL) oncology drug candidates designed to target and bind to the HLA-DR proteins overexpressed by B-cell lymphomas, has demonstrated exceptional efficacy in the treatment of Burkitt lymphoma xenografts in mice and a safety profile that may prove to be unprecedented for an oncology drug. The aim of this study was to determine how frequently the HLA-DRs targeted by SH7139 are expressed by different subtypes of non-Hodgkin’s lymphoma and by other solid cancers that have been reported to express HLA-DR. Binding studies conducted with SH7129, a biotinylated analog of SH7139, reveal that more than half of the biopsy sections obtained from patients with different types of non-Hodgkin’s lymphoma express the HLA-DRs targeted by SH7139. Similar analyses of tumor biopsy tissue obtained from patients diagnosed with eighteen other solid cancers show the majority of these tumors also express the HLA-DRs targeted by SH7139. Cervical, ovarian, colorectal and prostate cancers expressed the most HLA-DR. Only a few esophageal and head and neck tumors bound the diagnostic. Within an individual’s tumor, cell to cell differences in HLA-DR target expression varied by only 2 to 3-fold while the expression levels in tumors obtained from different patients varied as much as 10 to 100-fold. The high frequency with which SH7129 was observed to bind to these cancers suggests that many patients diagnosed with B-cell lymphomas, myelomas, and other non-hematological cancers should be considered potential candidates for new therapies such as SH7139 that target HLA-DR-expressing tumors.

Harnessing NK Cell Checkpoint-Modulating Immunotherapies

During the host immune response, the precise balance of the immune system, regulated by immune checkpoint, is required to avoid infection and cancer. These immune checkpoints are the mainstream regulator of the immune response and are crucial for self-tolerance. During the last decade, various new immune checkpoint molecules have been studied, providing an attractive path to evaluate their potential role as targets for effective therapeutic interventions. Checkpoint inhibitors have mainly been explored in T cells until now, but natural killer (NK) cells are a newly emerging target for the determination of checkpoint molecules. Simultaneously, an increasing number of therapeutic dimensions have been explored, including modulatory and inhibitory checkpoint molecules, either causing dysfunction or promoting effector functions. Furthermore, the combination of the immune checkpoint with other NK cell-based therapeutic strategies could also strengthen its efficacy as an antitumor therapy. In this review, we have undertaken a comprehensive review of the literature to date regarding underlying mechanisms of modulatory and inhibitory checkpoint molecules.

Genetic and Epigenetic Biomarkers of Immune Checkpoint Blockade Response

Checkpoint inhibitor therapy constitutes a promising cancer treatment strategy that targets the immune checkpoints to re-activate silenced T cell cytotoxicity. In recent pivotal trials, immune checkpoint blockade (ICB) demonstrated durable responses and acceptable toxicity, resulting in the regulatory approval of 8 checkpoint inhibitors to date for 15 cancer indications. However, up to ~85% of patients present with innate or acquired resistance to ICB, limiting its clinical utility. Current response biomarker candidates, including DNA mutation and neoantigen load, immune profiles, as well as programmed death-ligand 1 (PD-L1) expression, are only weak predictors of ICB response. Thus, identification of novel, more predictive biomarkers that could identify patients who would benefit from ICB constitutes one of the most important areas of immunotherapy research. Aberrant DNA methylation (5mC) and hydroxymethylation (5hmC) were discovered in multiple cancers, and dynamic changes of the epigenomic landscape have been identified during T cell differentiation and activation. While their role in cancer immunosuppression remains to be elucidated, recent evidence suggests that 5mC and 5hmC may serve as prognostic and predictive biomarkers of ICB-sensitive cancers. In this review, we describe the role of epigenetic phenomena in tumor immunoediting and other immune evasion related processes, provide a comprehensive update of the current status of ICB-response biomarkers, and highlight promising epigenomic biomarker candidates.

Ex Vivo-expanded Natural Killer Cells Derived From Long-term Cryopreserved Cord Blood are Cytotoxic Against Primary Breast Cancer Cells

With over 600,000 units of umbilical cord blood (CB) stored on a global scale, it is important to elucidate the therapeutic abilities of this cryopreserved reservoir. In the advancing field of natural killer (NK) cell cancer immunotherapy, CB has proven to be a promising and noninvasive source of therapeutic NK cells. Although studies have proven the clinical efficacy of using long-term cryopreserved CB in the context of hematopoietic stem cell transplantations, little is known about its use for the ex vivo expansion of effector immune cells. Therefore, our group sought to derive ex vivo-expanded NK cells from long-term cryopreserved CB, using an artificial antigen presenting cell-mediated expansion technique. We compared the expansion potential and antitumor effector function of CB-derived NK (CB-NK) cells expanded from fresh (n=4), short-term cryopreserved (<1-year old, n=5), and long-term cryopreserved (1-10-year old, n=5) CB. Here, we demonstrated it is possible to obtain an exponential amount of expanded CB-NK cells from long-term cryopreserved CB. Ex vivo-expanded CB-NK cells had an increased surface expression of activating markers and showed potent antitumor function by producing robust levels of proinflammatory cytokines, interferon-γ, and tumor necrosis factor-α. Moreover, expanded CB-NK cells (n=3-5) demonstrated cytotoxicity towards primary breast cancer cells (n=2) derived from a triple-negative breast cancer and an estrogen receptor-positive/progesterone receptor-positive breast cancer patient. Long-term cryopreservation had no effect on the expansion potential or effector function of expanded CB-NK cells. Therefore, we propose that long-term cryopreserved CB remains clinically useful for the ex vivo expansion of therapeutic NK cells.

Soluble HLA in the Aqueous Humour of Uveal Melanoma Is Associated with Unfavourable Tumour Characteristics

A high HLA expression in uveal melanoma (UM) is part of the prognostically unfavorable inflammatory phenotype. We wondered whether the presence of soluble HLA (sHLA) in the aqueous humour is associated with clinical, histopathological or genetic tumour characteristics, and represents tumour HLA expression and intratumoural inflammation. Aqueous humour from 108 UM patients was analysed for the presence of sHLA, using a Luminex assay specific for HLA Class I. Clinical and genetic parameters were compared between sHLA-positive and negative eyes. A qPCR analysis was performed on tumour tissue using a Fluidigm assay. In 19/108 UM-containing eyes, the sHLA level in the aqueous was above the detection limit. Tumours in sHLA-positive eyes were significantly larger, more frequently involved the ciliary body, and more often showed monosomy 3, gain of chromosome 8q and loss of BAP1 staining. Melanoma-related survival was worse in patients with sHLA-positive aqueous humour. sHLA in the aqueous did not represent the tumour's HLA expression and did not relate to immune cell infiltration in the tumour. We conclude that UM-containing eyes may contain sHLA in the aqueous humour, where it is a prognostically-unfavourable sign and may influence local immune responses.

Upregulation of Myc promotes the evasion of NK cell‑mediated immunity through suppression of NKG2D ligands in K562 cells

c-Myc is a characteristic oncogene with dual functions in cell proliferation and apoptosis. Since the overexpression of the c-Myc proto-oncogene is a common event in the development and growth of various human types of cancer, the present study investigated whether oncogenic c-Myc can alter natural killer (NK) cell-mediated immunity through the expression of associated genes, using PCR, western blotting and flow cytometry assays. Furthermore, whether c-Myc could influence the expression levels of natural killer group 2 member D (NKG2D) ligands, which are well known NK activation molecules, as well as NK cell-mediated immunity, was investigated. c-Myc was inhibited by 10058-F4 treatment and small interfering RNA transfection. Upregulation of c-Myc was achieved by transfection with a pCMV6-myc vector. The inhibition of c-Myc increased MHC class I polyeptide-related sequence B and UL16 binding protein 1 expressions among NKG2D ligands, and the overexpression of c-Myc suppressed the expression of all NKG2D ligands, except MHC class I polyeptide-related sequence A. Furthermore, the alteration of c-Myc activity altered the susceptibility of K562 cells to NK cells. These results suggested that the overexpression of c-Myc may contribute to the immune escape of cancer cells and cell proliferation. Combined treatment with NK-based cancer immunotherapy and inhibition of c-Myc may achieve improved therapeutic results.

Identification of Tumor Antigens Among the HLA Peptidomes of Glioblastoma Tumors and Plasma

Glioblastoma multiforme (GBM) is the most aggressive brain tumor with poor prognosis to most patients. Immunotherapy of GBM is a potentially beneficial treatment option, whose optimal implementation may depend on familiarity with tumor specific antigens, presented as HLA peptides by the GBM cells. Further, early detection of GBM, such as by a routine blood test, may improve survival, even with the current treatment modalities. This study includes large-scale analyses of the HLA peptidome (immunopeptidome) of the plasma-soluble HLA molecules (sHLA) of 142 plasma samples, and the membranal HLA of GBM tumors of 10 of these patients' tumor samples. Tumor samples were fresh-frozen immediately after surgery and the plasma samples were collected before, and at multiple visits after surgery. In total, this HLA peptidome analysis involved 52 different HLA allotypes and resulted in the identification of more than 35,000 different HLA peptides. Strong correlations were observed in the signal intensities and in the repertoires of identified peptides between the tumors and plasma-soluble HLA peptidomes of the individual patients, whereas low correlations were observed between these HLA peptidomes and the tumors' proteomes. HLA peptides derived from Cancer/Testis Antigens (CTAs) were selected based on their presence among the HLA peptidomes of the patients and absence of expression of their source genes from any healthy and essential human tissues, except from immune-privileged sites. Additionally, peptides were selected as potential biomarkers if their levels in the plasma-sHLA peptidome were significantly reduced after the removal of tumor mass. The CTAs identified among the analyzed HLA peptidomes provide new opportunities for personalized immunotherapy and for early diagnosis of GBM.

Addressing barriers to effective cancer immunotherapy with nanotechnology: achievements, challenges, and roadmap to the next generation of nanoimmunotherapeutics

Cancer is a complex systemic disorder that affects many organs and tissues and arises from the altered function of multiple cellular and molecular mechanisms. One of the systems malfunctioning in cancer is the immune system. Restoring and improving the ability of the immune system to effectively recognize and eradicate cancer is the main focus of immunotherapy, a topic which has garnered recent and significant interest. The initial excitement about immunotherapy, however, has been challenged by its limited efficacy in certain patient populations and the development of adverse effects such as therapeutic resistance and autoimmunity. At the same time, a number of advances in the field of nanotechnology have sought to address the challenges faced by modern immunotherapeutics and allow these therapeutic strategies to realize their full potential. This endeavour requires an understanding of not only the immunological barriers in cancer but also the mechanisms by which modern technologies and immunotherapeutics modulate the function of the immune system. Herein, we summarize the major barriers relevant to cancer immunotherapy and review current progress in addressing these obstacles using various approaches and clinically approved therapies. We then discuss the remaining challenges and how they can be addressed by nanotechnology. We lay out translational considerations relevant to the therapies described and propose a framework for the development of next-generation nanotechnology-enabled immunotherapies.

Identification of Tumor Antigens Among the HLA Peptidomes of Glioblastoma Tumors and Plasma

Glioblastoma multiforme (GBM) is the most aggressive brain tumor with poor prognosis to most patients. Immunotherapy of GBM is a potentially beneficial treatment option, whose optimal implementation may depend on familiarity with tumor specific antigens, presented as HLA peptides by the GBM cells. Furthermore, early detection of GBM, such as by a routine blood test, may improve survival, even with the current treatment modalities. This study includes large-scale analyses of the HLA peptidome (immunopeptidome) of the plasma-soluble HLA molecules (sHLA) of 142 plasma samples, and the membranal HLA of GBM tumors of 10 of these patients' tumor samples. Tumor samples were fresh-frozen immediately after surgery and the plasma samples were collected before, and at multiple visits after surgery. In total, this HLA peptidome analysis involved 52 different HLA allotypes and resulted in the identification of more than 35,000 different HLA peptides. Strong correlations were observed in the signal intensities and in the repertoires of identified peptides between the tumors and plasma-soluble HLA peptidomes of the individual patients, whereas low correlations were observed between these HLA peptidomes and the tumors' proteomes. HLA peptides derived from Cancer/Testis Antigens (CTAs) were selected based on their presence among the HLA peptidomes of the patients and absence of expression of their source genes from any healthy and essential human tissues, except from immune-privileged sites. Additionally, peptides were selected as potential biomarkers if their levels in the plasma-sHLA peptidome were significantly reduced after the removal of tumor mass. The CTAs identified among the analyzed HLA peptidomes provide new opportunities for personalized immunotherapy and for early diagnosis of GBM.

Mapping the tumour human leukocyte antigen (HLA) ligandome by mass spectrometry

The entirety of human leukocyte antigen (HLA)-presented peptides is referred to as the HLA ligandome of a cell or tissue, in tumours often termed immunopeptidome. Mapping the tumour immunopeptidome by mass spectrometry (MS) comprehensively views the pathophysiologically relevant antigenic signature of human malignancies. MS is an unbiased approach stringently filtering the candidates to be tested as opposed to epitope prediction algorithms. In the setting of peptide-specific immunotherapies, MS-based strategies significantly diminish the risk of lacking clinical benefit, as they yield highly enriched amounts of truly presented peptides. Early immunopeptidomic efforts were severely limited by technical sensitivity and manual spectra interpretation. The technological progress with development of orbitrap mass analysers and enhanced chromatographic performance led to vast improvements in mass accuracy, sensitivity, resolution, and speed. Concomitantly, bioinformatic tools were developed to process MS data, integrate sequencing results, and deconvolute multi-allelic datasets. This enabled the immense advancement of tumour immunopeptidomics. Studying the HLA-presented peptide repertoire bears high potential for both answering basic scientific questions and translational application. Mapping the tumour HLA ligandome has started to significantly contribute to target identification for the design of peptide-specific cancer immunotherapies in clinical trials and compassionate need treatments. In contrast to prediction algorithms, rare HLA allotypes and HLA class II can be adequately addressed when choosing MS-guided target identification platforms. Herein, we review the identification of tumour HLA ligands focusing on sources, methods, bioinformatic data analysis, translational application, and provide an outlook on future developments.

Circulating histocompatibility antigen (HLA) gene products may help differentiate benign from malignant indeterminate pulmonary lesions

BACKGROUND

This study explores the potential diagnostic utility of soluble Human Leukocyte Antigen (sHLA) molecules differentially released by lung adenocarcinoma and benign lung lesions.

METHODS

Conditioned media from the NSCLC cell lines H358 and H1703 were immunoblotted for soluble isoforms of major histocompatibility complex (MHC) class I (ABC) and II (DRB1, DMB, and DQ) antigens. Sera from 25 patients with benign and 25 patients with malignant lesions were similarly evaluated to appraise the potential diagnostic value.

RESULTS

Higher concentrations of soluble HLA class I molecules were observed in conditioned medium for the highly-invasive H1703 cell line, relative to the more indolent H358 cells. Evaluation of these markers against a cohort of 50 cases demonstrated that patients with malignant lesions possess higher levels of HLA class I and II molecules relative to those with benign lesions (p < 0.05), with exception to the primary isoform, DQA1, which was suppressed in malignancies. An analysis of biomarker performance via ROC analysis revealed promising performance (AUC > 0.75) for DMB and the 26 kDa isoform of DQ in distinguishing lesion pathology.

CONCLUSIONS

Soluble HLA molecules may have diagnostic value for early-stage NSCLC. Validation studies are currently underway using sera from a lung cancer screening cohort.

Tumor immunotherapy: New aspects of natural killer cells

A group of impressive immunotherapies for cancer treatment, including immune checkpoint-blocking antibodies, gene therapy and immune cell adoptive cellular immunotherapy, have been established, providing new weapons to fight cancer. Natural killer (NK) cells are a component of the first line of defense against tumors and virus infections. Studies have shown dysfunctional NK cells in patients with cancer. Thus, restoring NK cell antitumor functionality could be a promising therapeutic strategy. NK cells that are activated and expanded ex vivo can supplement malfunctional NK cells in tumor patients. Therapeutic antibodies, chimeric antigen receptor (CAR), or bispecific proteins can all retarget NK cells precisely to tumor cells. Therapeutic antibody blockade of the immune checkpoints of NK cells has been suggested to overcome the immunosuppressive signals delivered to NK cells. Oncolytic virotherapy provokes antitumor activity of NK cells by triggering antiviral immune responses. Herein, we review the current immunotherapeutic approaches employed to restore NK cell antitumor functionality for the treatment of cancer.

Immunotherapy as a Potential Treatment for Chordoma: a Review

Chordoma is a locally aggressive primary malignancy of the axial skeleton. The gold standard for treatment is en bloc resection, with some centers now advocating for the use of radiation to help mitigate the risk of recurrence. Local recurrence is common, and salvaging local failures is quite difficult. Chemotherapy has been ineffective and small molecule targeted therapy has had only marginal benefits in small subsets of patients with rare tumor phenotypes or refractory disease. Recent successes utilizing immunotherapy in a variety of cancers has led to a resurgence of interest in modifying the host immune system to develop new ways to treat tumors. This review will discuss these studies and will highlight the early studies employing immune strategies for the treatment of chordoma.

Mechanism of immune evasion in breast cancer

Breast cancer (BC) is the most common malignant tumor among women, with high morbidity and mortality. Its onset, development, metastasis, and prognosis vary among individuals due to the interactions between tumors and host immunity. Many diverse mechanisms have been associated with BC, with immune evasion being the most widely studied to date. Tumor cells can escape from the body’s immune response, which targets abnormal components and foreign bodies, using different approaches including modification of surface antigens and modulation of the surrounding environment. In this review, we summarize the mechanisms and factors that impact the immunoediting process and analyze their functions in detail.

Cutaneous squamous cell cancer (cSCC) risk and the human leukocyte antigen (HLA) system

Cutaneous squamous cell carcinoma (cSCC) is the second most common cancer among Caucasians in the United States, with rising incidence over the past decade. Treatment for non-melanoma skin cancer, including cSCC, in the United States was estimated to cost $4.8 billion in 2014. Thus, an understanding of cSCC pathogenesis could have important public health implications. Immune function impacts cSCC risk, given that cSCC incidence rates are substantially higher in patients with compromised immune systems. We report a systematic review of published associations between cSCC risk and the human leukocyte antigen (HLA) system. This review includes studies that analyze germline class I and class II HLA allelic variation as well as HLA cell-surface protein expression levels associated with cSCC risk. We propose biological mechanisms for these HLA-cSCC associations based on known mechanisms of HLA involvement in other diseases. The review suggests that immunity regulates the development of cSCC and that HLA-cSCC associations differ between immunocompetent and immunosuppressed patients. This difference may reflect the presence of viral co-factors that affect tumorigenesis in immunosuppressed patients. Finally, we highlight limitations in the literature on HLA-cSCC associations, and suggest directions for future research aimed at understanding, preventing and treating cSCC.

Treating Hepatobiliary Cancer: The Immunologic Approach

Hepatobiliary cancer comprises a heterogeneous group of malignancies in which the standard treatments for advanced disease are minimally effective and evolve slowly over time. Like the majority of gastrointestinal cancers, with some notable exceptions, the impact of immune-based approaches is yet to be experienced. Notwithstanding this, the etiological background of hepatobiliary cancer - overlapping in almost every known causative or associated factor with inflammation - provides a strong clue that these approaches may have an impact on this group of diseases. This review seeks to put the management of hepatobiliary cancers in the context of its inflammation-based etiology, with the aim of pointing to the therapeutic opportunities in immune-based approaches currently entering the clinic or those that are about to do so.

Purification of soluble HLA class I complexes from human serum or plasma deliver high quality immuno peptidomes required for biomarker discovery

Soluble human leukocyte antigen class I (sHLA)-peptide complexes have been suggested to play a role in the modulation of immune responses and in immune evasion of cancer cells. The set of peptides eluted from sHLA molecules could serve as biomarker for the monitoring of patients with cancer or other conditions. Here, we describe an improved sHLA peptidomics methodology resulting in the identification of 1816 to 2761 unique peptide sequences from triplicate analyses of serum or plasma taken from three healthy donors. More than 90% of the identified peptides were 8-11mers and 74% of these sequences were predicted to bind to cognate HLA alleles, confirming the quality of the resulting immunopeptidomes. In comparison to the HLA peptidome of cultured cells, the plasma-derived peptides were predicted to have a higher stability in complex with the cognate HLA molecules and mainly derived from proteins of the plasma membrane or from the extracellular space. The sHLA peptidomes can efficiently be characterized by using the new methodology, thus serving as potential source of biomarkers in various pathological conditions.

The case for immune-based approaches in biliary tract carcinoma

Biliary tract cancers (BTC) comprise a group of uncommon malignancies in which the standard therapies are minimally effective and evolve slowly. Like the majority of gastrointestinal cancers, with some notable exceptions, the impact of immune-based approaches has yet to be seen. However, the etiological background of BTC-overlapping in almost every known causative or associated factor with inflammation-provides a strong clue that these approaches may have an impact in this group of diseases. This review covers what we currently know about the role of the immune system in the etiology of BTC, highlighting differences by subtype, and pointing to the therapeutic opportunities currently entering the clinic or about to do so. (Hepatology 2016;64:1785-1791).

Synergistic Effect and Molecular Mechanisms of Traditional Chinese Medicine on Regulating Tumor Microenvironment and Cancer Cells

The interaction of tumor cells with the microenvironment is like a relationship between the “seeds” and “soil,” which is a hotspot in recent cancer research. Targeting at tumor microenvironment as well as tumor cells has become a new strategy for cancer treatment. Conventional cancer treatments mostly focused on single targets or single mechanism (the seeds or part of the soil); few researches intervened in the whole tumor microenvironment and achieved ideal therapeutic effect as expected. Traditional Chinese medicine displays a broad range of biological effects, and increasing evidence has shown that it may relate with synergistic effect on regulating tumor microenvironment and cancer cells. Based on literature review and our previous studies, we summarize the synergistic effect and the molecular mechanisms of traditional Chinese medicine on regulating tumor microenvironment and cancer cells.

Serum antibodies to human leucocyte antigen (HLA)-E, HLA-F and HLA-G in patients with systemic lupus erythematosus (SLE) during disease flares: Clinical relevance of HLA-F autoantibodies

T lymphocyte hyperactivity and progressive inflammation in systemic lupus erythematosus (SLE) patients results in over-expression of human leucocyte antigen (HLA)-Ib on the surface of lymphocytes. These are shed into the circulation upon inflammation, and may augment production of antibodies promoting pathogenicity of the disease. The objective was to evaluate the association of HLA-Ib (HLA-E, HLA-F and HLA-G) antibodies to the disease activity of SLE. The immunoglobulin (Ig)G/IgM reactivity to HLA-Ib and β2m in the sera of 69 German, 29 Mexican female SLE patients and 17 German female controls was measured by multiplex Luminex(®)-based flow cytometry. The values were expressed as mean flourescence intensity (MFI). Only the German SLE cohort was analysed in relation to the clinical disease activity. In the controls, anti-HLA-G IgG predominated over other HLA-Ib antibodies, whereas SLE patients had a preponderance of anti-HLA-F IgG over the other HLA-Ib antibodies. The disease activity index, Systemic Lupus Erythematosus Disease Activity Index (SLEDAI)-2000, was reflected only in the levels of anti-HLA-F IgG. Anti-HLA-F IgG with MFI level of 500-1999 was associated with active SLE, whereas inactive SLE revealed higher MFI (>2000). When anti-HLA-F IgG were cross-reactive with other HLA-Ib alleles, their reactivity was reflected in the levels of anti-HLA-E and -G IgG. The prevalence of HLA-F-monospecific antibodies in SLE patients was also associated with the clinical disease activity. Anti-HLA-F IgG is possibly involved in the clearance of HLA-F shed from lymphocytes and inflamed tissues to lessen the disease's severity, and thus emerges as a beneficial immune biomarker. Therefore, anti-HLA-Ib IgG should be considered as a biomarker in standard SLE diagnostics.

Cancer stem cells and immunoresistance: clinical implications and solutions

Tumor cells can be contained, but not eliminated, by traditional cancer therapies. A cell minor subpopulation is able to evade attack from therapies and may have cancer stem cell (CSC) characteristics, including self-renewal, multiple differentiation and tumor initiation (tumor initiating cells, or TICs). Thus, CSCs/TICs, aided by the microenvironment, produce more differentiated, metastatic cancer cells which the immune system detects and interacts with. There are three phases to this process: elimination, equilibrium and escape. In the elimination phase the immune system recognizes and destroys most of the tumor cells. Then the latency phase begins, consisting of equilibrium between immunological elimination and tumor cell growth. Finally, a minor attack-resistant subpopulation escapes and forms a clinically detectable tumor mass. Herein we review current knowledge of immunological characterization of CSCs/TICs. Due to the correlation between CTCs/TICs and drug resistance and metastasis, we also comment on the crucial role of key molecules involved in controlling CSCs/TICs properties; such molecules are essential to detect and destroy CSCs/TICs. Monoclonal antibodies, antibody constructs and vaccines have been designed to act against CSCs/TICs, with demonstrated efficacy in human cancer xenografts and some antitumor activity in human clinical studies. Therefore, therapeutic strategies that selectively target CSCs/TICs warrant further investigation. Better understanding of the interaction between CSCs and tumor immunology may help to identify strategies to eradicate the minor subpopulation that escapes conventional therapy attack, thus providing a solution to the problem of drug resistance and metastasis.

Evaluation of soluble human leukocyte antigen-G in peripheral blood of pregnant women with gestational diabetes mellitus

BACKGROUND

Research says that diabetes may develop in over 10% of non-diabetic pregnant women. Diabetes which generally occurs late in second trimester and third trimester of pregnancy, it is called gestational diabetes. Overweight or suffering from obesity before pregnancy is type 2 diabetes risk factor. In most cases, diabetic symptoms disappear after delivery. HLA-G has an important role both in mother and fetus tolerance during pregnancy, it may also be effective in the protection of pancreatic islet cells. In this study, concentration of these molecules in pregnant women with gestational diabetes in comparison with normal pregnant women was investigated.

METHODS

In this case-control study, we measured serum HLA-G levels in 24 pregnant women with gestational diabetes compared with 30 normal pregnant women using sandwich ELISA.

RESULTS

HLA-G levels were significantly low in pregnant women with gestational diabetes in contrast to normal pregnant women (P=0.001).

CONCLUSION

In this study, we found that HLA-G levels were reduced in women with gestational diabetes compared with control group. Therefore, it is suggested that measurement of HLA-G in pregnant women can be considered as an indicator in prognosis of gestational diabetes.

Non-classical HLA-class I expression in serous ovarian carcinoma: Correlation with the HLA-genotype, tumor infiltrating immune cells and prognosis

In our previous studies, we have shown that patients with serous ovarian carcinoma in advanced surgical stage disease have a particularly poor prognosis if they carry the HLA-A*02 genotype. This represent a stronger prognostic factor than loss or downregulation of the MHC class I heavy chain (HC) on tumor cells. In this study, we investigated the expression of the non-classical, immune tolerogenic HLA -G and -E on the tumor cells along with the infiltration of immune cells in the tumor microenvironment. FFPE primary tumors from 72 patients with advanced stages of serous adenocarcinoma and metastatic cells present in ascites fluid from 8 additional patients were included in this study. Both expression of HLA-G and aberrant expression of HLA-E were correlated to a significant worse prognosis in patients with HLA-A*02, but not with different HLA genotypes. Focal cell expression of HLA-G correlated to a site-specific downregulation of classical MHC class I HC products and aberrant HLA-E expression, showing a poor survival. HLA-G was more frequently expressed in metastatic cells than in primary tumor lesions and the expression of HLA-G inversely correlated with the frequency of tumor infiltrating immune cells. All these parameters can contribute together to identify and discriminate subpopulations of patients with extremely poor prognosis and can give them the opportunity to receive, and benefit of individually tailored treatments.

Clinical and immunological significance of HLA-E in stem cell transplantation and cancer

Human leukocyte antigen-E (HLA-E) is a nonclassical HLA class I molecule that canonically binds peptides derived from the leader sequence of classical HLA class I. HLA-E can also bind peptides from stress protein [e.g. heat shock protein 60 (Hsp60)] and pathogens, illustrating the importance of HLA-E for anti-viral and anti-tumor immunity. Like classical HLA class I molecules, HLA-E is ubiquitously expressed, however, it is characterized by only a very limited sequence variability and two dominant protein forms have been described (HLA-E*01:01 and HLA-E*01:03). HLA-E influences both the innate and the adaptive arms of the immune system by the engagement of inhibitory (e.g. NKG2A) and activating receptors [e.g. αβ T cell receptor (αβTCR) or NKG2C] on NK cells and CD8 T cells. The effects of HLA-E on the cellular immune response are therefore complex and not completely understood yet. Here, we aim to provide an overview of the immunological and clinical relevance of HLA-E and HLA-E polymorphism in stem cell transplantation and in cancer. We review novel insights in the mechanism via which HLA-E expression levels are controlled and how the cellular immune response in transplantation and cancer is influenced by HLA-E.

Inhibition of ERK and proliferation in NK cell lines by soluble HLA-E released from Japanese encephalitis virus infected cells

Productive infection of human endothelial cells with Japanese encephalitis virus (JEV), a single stranded RNA virus induces shedding of sHLA-E. We show here that sHLA-E that is released upon infection with this flavivirus can inhibit IL-2 and PMA mediated ERK 1/2 phosphorylation in two NK cell lines, Nishi and NKL. Virus infected or IFN-γ treated cell culture supernatants containing sHLA-E were found to partially inhibit IL-2 mediated induction of CD25 molecules on NKL cells. It was also found that sHLA-E could inhibit IL-2 induced [(3)H]-thymidine incorporation suggesting that, similar to cell surface expressed HLA-E, sHLA-E could also inhibit NK cell responses. Hence JEV-induced shedding of sHLA-E needs further investigation to better understand immune responses in JEV infections since it may have a role in viral evasion of NK cell responses.

NK cell phenotypic modulation in lung cancer environment

Background

Nature killer (NK) cells play an important role in anti-tumor immunotherapy. But it indicated that tumor cells impacted possibly on NK cell normal functions through some molecules mechanisms in tumor microenvironment.

Materials and methods

Our study analyzed the change about NK cells surface markers (NK cells receptors) through immunofluorescence, flow cytometry and real-time PCR, the killed function from mouse spleen NK cell and human high/low lung cancer cell line by co-culture. Furthermore we certificated the above result on the lung cancer model of SCID mouse.

Results

We showed that the infiltration of NK cells in tumor periphery was related with lung cancer patients' prognosis. And the number of NK cell infiltrating in lung cancer tissue is closely related to the pathological types, size of the primary cancer, smoking history and prognosis of the patients with lung cancer. The expression of NK cells inhibitor receptors increased remarkably in tumor micro-environment, in opposite, the expression of NK cells activated receptors decrease magnificently.

Conclusions

The survival time of lung cancer patient was positively related to NK cell infiltration degree in lung cancer. Thus, the down-regulation of NKG2D, Ly49I and the up-regulation of NKG2A may indicate immune tolerance mechanism and facilitate metastasis in tumor environment. Our research will offer more theory for clinical strategy about tumor immunotherapy.

CD8(low)CD28(-) T Cells: A Human CD8 T-Suppressor Subpopulation With Alloantigen Specificity Induced by Soluble HLA-A2 Dimer In Vitro

CD8(+) suppressor T cells have been demonstrated to provide protection of allografts from rejection. We previously reported that soluble peptide/HLA-A2 dimer shows peptide-specific inhibitory effects on alloresponse in a coculture of peptide-pulsed T2 cells with HLA-A2 negative lymphocytes in vitro. Here we found a subset of CD8(low)CD28(-) T cells that was induced in the dimer-treated coculture. Importantly, this population showed hyporesponsiveness to the alloantigen restimulation as well as alloantigen-specific suppression on alloreactive T cells in a cell-cell contact-dependent fashion. The suppressive mechanisms of CD8(low)CD28(-) T cells involved an elevated expression of membrane-bound TGF-β1, but not Foxp3, CTLA-4, or IL-10. Furthermore, an overrepresention of CD8(low)CD28(-) T cells was observed in the patients after allogeneic platelet transfusion and positively correlated with the elevated concentrations of plasma HLA class I antigens. Our findings demonstrated that soluble HLA-A2 dimer could efficiently induce the tolerant CD8(low)CD28(-) T cells with alloantigen-specific suppression on alloreactive T cells. This study might provide a new strategy for preparation of donor-specific suppressor T cells and represent an attractive alternative for induction of allograft tolerance.

Cancer stem cell immunology: key to understanding tumorigenesis and tumor immune escape?

Cancer stem cell (CSC) biology and tumor immunology have shaped our understanding of tumorigenesis. However, we still do not fully understand why tumors can be contained but not eliminated by the immune system and whether rare CSCs are required for tumor propagation.

Long latency or recurrence periods have been described for most tumors. Conceptually, this requires a subset of malignant cells which is capable of initiating tumors, but is neither eliminated by immune cells nor able to grow straight into overt tumors. These criteria would be fulfilled by CSCs. Stem cells are pluripotent, immune-privileged, and long-living, but depend on specialized niches. Thus, latent tumors may be maintained by a niche-constrained reservoir of long-living CSCs that are exempt from immunosurveillance while niche-independent and more immunogenic daughter cells are constantly eliminated.

The small subpopulation of CSCs is often held responsible for tumor initiation, metastasis, and recurrence. Experimentally, this hypothesis was supported by the observation that only this subset can propagate tumors in non-obese diabetic/scid mice, which lack T and B cells. Yet, the concept was challenged when an unexpectedly large proportion of melanoma cells were found to be capable of seeding complex tumors in mice which further lack NK cells. Moreover, the link between stem cell-like properties and tumorigenicity was not sustained in these highly immunodeficient animals. In humans, however, tumor-propagating cells must also escape from immune-mediated destruction. The ability to persist and to initiate neoplastic growth in the presence of immunosurveillance – which would be lost in a maximally immunodeficient animal model – could hence be a decisive criterion for CSCs.

Consequently, integrating scientific insight from stem cell biology and tumor immunology to build a new concept of “CSC immunology” may help to reconcile the outlined contradictions and to improve our understanding of tumorigenesis.

Soluble HLA-I/peptide monomers mediate antigen-specific CD8 T cell activation through passive peptide exchange with cell-bound HLA-I molecules

Accumulating evidence that serum levels of soluble class I HLA molecules (sHLA-I) can, under various pathological conditions, correlate with disease stage and/or patient survival, has stimulated interest in defining whether sHLA-I can exert immunological functions. However, despite a mounting number of publications suggesting the ability of sHLA-I to affect immune effectors in vitro, the precise underlying mechanism still remains controversial. In this article, we address potential functions of both classical and nonclassical sHLA-I, using soluble recombinant HLA-I/peptide monomers, and clearly demonstrate their ability to trigger Ag-specific activation of CD8 T cells in vitro. Furthermore, we provide strong evidence that this behavior results from the passive transfer of peptides from monomers to T cell-bound HLA-I molecules, allowing for fratricide representation and activation. Hence, we proposed a unifying model of T cell activation by HLA-I/peptide monomers, reappraising the potential involvement of sHLA-I molecules in the immune response.

Genotyping of human leukocyte antigen (HLA) ancestral haplotypes as prognostic marker in cancer using PCR analysis

The major histocompatibility complex (MHC) comprises a set of genes that are essential to immunity and surveillance against neoplastic transformation. MHC antigens not only regulate antitumor immune responses in experimental animal models but also directly correlate with survival and prognosis of patients with various types of cancers. Effective recognition of tumor cells by effector T cells may be affected by the genotype and the extent of expression of human leukocyte antigen (HLA)-peptide complexes. Therefore, MHC antigens may serve as potential biomarkers for prognosis and allow selection of cancer patients for specific therapy. We describe PCR-based method to determine the HLA genotype in healthy individuals and patients using blood and tumor tissue as DNA source.

Granzyme B degradation by autophagy decreases tumor cell susceptibility to natural killer-mediated lysis under hypoxia

Recent studies demonstrated that autophagy is an important regulator of innate immune response. However, the mechanism by which autophagy regulates natural killer (NK) cell-mediated antitumor immune responses remains elusive. Here, we demonstrate that hypoxia impairs breast cancer cell susceptibility to NK-mediated lysis in vitro via the activation of autophagy. This impairment was not related to a defect in target cell recognition by NK cells but to the degradation of NK-derived granzyme B in autophagosomes of hypoxic cells. Inhibition of autophagy by targeting beclin1 (BECN1) restored granzyme B levels in hypoxic cells in vitro and induced tumor regression in vivo by facilitating NK-mediated tumor cell killing. Together, our data highlight autophagy as a mechanism underlying the resistance of hypoxic tumor cells to NK-mediated lysis. The work presented here provides a cutting-edge advance in our understanding of the mechanism by which hypoxia-induced autophagy impairs NK-mediated lysis in vitro and paves the way for the formulation of more effective NK cell-based antitumor therapies.

MHC class I antigen processing and presenting machinery: organization, function, and defects in tumor cells

The surface presentation of peptides by major histocompatibility complex (MHC) class I molecules is critical to all CD8(+) T-cell adaptive immune responses, including those against tumors. The generation of peptides and their loading on MHC class I molecules is a multistep process involving multiple molecular species that constitute the so-called antigen processing and presenting machinery (APM). The majority of class I peptides begin as proteasome degradation products of cytosolic proteins. Once transported into the endoplasmic reticulum by TAP (transporter associated with antigen processing), peptides are not bound randomly by class I molecules but are chosen by length and sequence, with peptidases editing the raw peptide pool. Aberrations in APM genes and proteins have frequently been observed in human tumors and found to correlate with relevant clinical variables, including tumor grade, tumor stage, disease recurrence, and survival. These findings support the idea that APM defects are immune escape mechanisms that disrupt the tumor cells' ability to be recognized and killed by tumor antigen-specific cytotoxic CD8(+) T cells. Detailed knowledge of APM is crucial for the optimization of T cell-based immunotherapy protocols.

Reciprocal complementation of the tumoricidal effects of radiation and natural killer cells

The tumor microenvironment is a key determinant for radio-responsiveness. Immune cells play an important role in shaping tumor microenvironments; however, there is limited understanding of how natural killer (NK) cells can enhance radiation effects. This study aimed to assess the mechanism of reciprocal complementation of radiation and NK cells on tumor killing. Various tumor cell lines were co-cultured with human primary NK cells or NK cell line (NK-92) for short periods and then exposed to irradiation. Cell proliferation, apoptosis and transwell assays were performed to assess apoptotic efficacy and cell viability. Western blot analysis and immunoprecipitation methods were used to determine XIAP (X-linked inhibitor of apoptosis protein) and Smac (second mitochondria-derived activator of caspase) expression and interaction in tumor cells. Co-culture did not induce apoptosis in tumor cells, but a time- and dose-dependent enhancing effect was found when co-cultured cells were irradiated. A key role for caspase activation via perforin/granzyme B (Grz B) after cell-cell contact was determined, as the primary radiation enhancing effect. The efficacy of NK cell killing was attenuated by upregulation of XIAP to bind caspase-3 in tumor cells to escape apoptosis. Knockdown of XIAP effectively potentiated NK cell-mediated apoptosis. Radiation induced Smac released from mitochondria and neutralized XIAP and therefore increased the NK killing. Our findings suggest NK cells in tumor microenvironment have direct radiosensitization effect through Grz B injection while radiation enhances NK cytotoxicity through triggering Smac release.

Distribution of several activating and inhibitory receptors on CD3(-)CD56(+) NK cells in regional lymph nodes of melanoma patients

BACKGROUND

Natural killer (NK) cells, as the main effector subpopulation of the innate immune system, play an important role in the control of the rise and spread of malignant tumors. Regional lymph nodes (LN) represent the first immunologic barrier to tumor metastasis. Since there are scarce data on NK cells from regional LN of cancer patients, the aim of this study was to investigate the expression of several activating and inhibitory receptors on the entire NK cell population as well as their CD3(-)CD56(dim) and CD3(-)CD56(bright) functional NK subsets from regional LN of melanoma patients.

MATERIALS AND METHODS

Mononuclear cells were isolated from 50 regional LN of melanoma patients. The expression of several receptors on NK cells and their functional subsets was analyzed by flow cytometry.

RESULTS

We show increased percentages of CD3(-)CD56(+) NK cells in involved LN compared with uninvolved LN, mostly in favor of the CD56(dim) NK cell subset. NK cells in involved LN express similar levels of activating receptor NKG2D, while the level of another activating receptor, CD16, is increased compared with uninvolved LN. Regarding the expression of inhibitory NK cell receptors, we show increased CD158b, but similar low CD158a, inhibitory killer Ig-like cell receptor expression in involved LN compared with uninvolved LN. Furthermore, NK cells in involved compared with uninvolved LN displayed increased CD69 early activation antigen expression.

CONCLUSIONS

Our results indicate that with tumor infiltration into regional LN of melanoma patients, NK cells, mostly of the CD56(dim) subset, are recruited into draining LN. The invading NK cells show counterbalance of the increased expression of CD16 activating receptor and increased CD158b inhibitory killer Ig-like cell receptor.

Shaping of NK cell responses by the tumor microenvironment

Natural killer (NK) cells belong to the innate immune system and are potent cytolytic and cytokine-producing effector cells in response to tumor targets. NK cell based anti-tumor immunotherapy was so far mainly successful in patients with different types of leukemia. For instance, acute myeloid leukemia (AML) patients displayed a prolonged survival if transplanted with haploidentical stem cells giving rise to NK cells with a mismatch in inhibitory killer immunoglobulin receptors (KIRs) and recipients' HLA class I. Although promising results have been achieved with hematological tumors, solid tumors are in most cases poorly controlled by NK cells. Therapeutic protocols that aimed at improving NK cell responses in patients with solid malignancies succeeded in increasing NK cell numbers and functional responses of NK cells isolated from the patients' peripheral blood. However, in the majority of cases tumor progression and overall survival of patients were not significantly improved. There is increasing evidence that tumor-associated NK cells become gradually impaired during tumor progression compared to NK cells from peripheral blood and healthy tissues. Future protocols of NK cell based immunotherapy should integrate three important aspects to improve NK cell anti-tumor activity: facilitating NK cell migration to the tumor site, enhancing their infiltration into the tumor tissue and ensuring subsequent efficient activation in the tumor. This review summarizes the current knowledge of tumor-infiltrating NK cells and the influence of the tumor microenvironment on their phenotype and function.

EphrinA1-EphA2 interaction-mediated apoptosis and FMS-like tyrosine kinase 3 receptor ligand-induced immunotherapy inhibit tumor growth in a breast cancer mouse model

BACKGROUND

The receptor tyrosine kinase EphA2 is overexpressed in several types of cancers and is currently being pursued as a target for breast cancer therapeutics. The EphA2 ligand EphrinA1 induces EphA2 phosphorylation and intracellular internalization and degradation, thus inhibiting tumor progression. The hematopoietic growth factor, FMS-like tyrosine kinase 3 receptor ligand (Flt3L), promotes expansion and mobilization of functional dendritic cells.

METHODS

We tested the EphrinA1-EphA2 interaction in MDA-MB-231 breast cancer cells focusing on the receptor-ligand-mediated apoptosis of breast cancer cells. To determine whether EphrinA1-EphA2 interaction-associated apoptosis and Flt3L-mediated immunotherapy would have an additive effect in inhibiting tumor growth, we used an immunocompetent mouse model of breast cancer to evaluate intratumoral (i.t.) inoculation strategies with human adenovirus (HAd) vectors expressing either EphrinA1 (HAd-EphrinA1-Fc), Flt3L (HAd-Flt3L) or a combination of EphrinA1-Fc + Flt3L (HAd-EphrinA1-Fc + HAd-Flt3L).

RESULTS

In vitro analysis demonstrated that an EphrinA1-EphA2 interaction led to apoptosis-related changes in breast cancer cells. In vivo, three i.t. inoculations of HAd-EphrinA1-Fc showed potent inhibition of tumor growth. Furthermore, increased inhibition in tumor growth was observed with the combination of HAd-EphrinA1-Fc and HAd-Flt3L accompanied by the generation of an anti-tumor adaptive immune response.

CONCLUSIONS

The results obtained in the present study, indicating the induction of apoptosis and inhibition of mammary tumor growth, show the potential therapeutic benefits of HAd-EphrinA1-Fc. In combination with HAd-Flt3L, this represents a promising strategy for effectively inducing mammary tumor regression by HAd vector-based therapy.

Expression of soluble HLA-G in multiple myeloma patients and patients with renal failure

Human lymphocyte antigen-G (HLA-G) is an immunosuppressive molecule that induces functional silencing of immune component cells and can be responsible for immunosuppression in patients with multiple myeloma (MM). Immune dysfunction is an important feature of MM and leads to infections as well as may promote disease progression. Ninety-five patients were included in this study. In MM, the sHLA-G levels were increased when compared to healthy volunteers and the levels of sHLA-G correlated with concentration of creatinine. Interestingly, we detected high levels of sHLA-G in patients with renal insufficiency without any malignant disease but levels were lower than in MM.

Profound coordinated alterations of intratumoral NK cell phenotype and function in lung carcinoma

Both the innate and adaptive immune systems contribute to tumor immunosurveillance in mice and humans; however, there is a paucity of direct evidence of a role for natural killer (NK) cells in this important process. In this study, we investigated the intratumoral phenotypic profile and functions of NK cells in primary human tumor specimens of non-small cell lung carcinoma (NSCLC). We used in situ methods to quantify and localize NK cells using the NKp46 marker and we characterized their phenotype in blood, tumoral, and nontumoral samples of NSCLC patients. Intratumoral NK cells displayed a profound and coordinated alteration of their phenotype, with a drastic reduction of NK cell receptor expression specifically detected in the tumoral region. According to their altered phenotype, intratumoral NK cells exhibited profound defects in the ability to activate degranulation and IFN-γ production. We found that the presence of NK cells did not impact the clinical outcome of patients with NSCLC. Finally, we showed that tumor cells heterogeneously express ligands for both activating and inhibitory NK receptors. Taken together, our results suggest that the NSCLC tumor microenvironment locally impairs NK cells, rendering them less tumorcidal and thereby supportive to cancer progression.

The Human Immunopeptidome Project, a suggestion for yet another postgenome next big thing

The time is ripe for staging the Human Immunopeptidome Project, whose goal is to analyze the full repertoires of peptides bound to the HLA molecules, in both health and disease. Mass spectrometry technologies have matured to enable comprehensive analyses of both the membrane-bound and the plasma soluble immunopeptidomes associated with each of the HLA allomorphs and the different diseases. The expected outcomes of such project will include basic understanding of the molecular mechanisms involved with formation of immunopeptidomes, correlating them with their source cellular proteomes, definition of both the consensus motifs and the scope of each allomorphs-specific immunopeptidomes, and most importantly, identification of disease-related HLA peptides, which may eventually serve as biomarkers or immunotherapeutics. Ideally, the Human Immunopeptidome Project will become public and the gathered data will be shared, as soon as possible. Other immunopeptidome projects, of other animals, will follow suit.