High expression of HLA-E in colorectal carcinoma is associated with a favorable prognosis

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

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

Monalizumab efficacy correlates with HLA-E surface expression and NK cell activity in head and neck squamous carcinoma cell lines

PURPOSE

NKG2A, an inhibitory receptor expressed on NK cells and T cells, leads to immune evasion by binding to HLA-E expressed on cancer cells. Here, we investigated the relationship between HLA-E surface expression on head and neck squamous cell carcinoma (HNSCC) cell lines and the efficacy of monalizumab, an NKG2A inhibitor, in promoting NK cell activity.

METHODS

Six HNSCC cell lines were used as target cells. After exposure to IFN- γ, HLA-E surface expression on HNSCC cell lines was measured by flow cytometry. Peripheral blood mononuclear cells (PBMCs) from healthy donors and isolated NK cells were used as effector cells. NK cells were stimulated by treatment with IL-2 and IL-15 for 5 days, and NK cell-induced cytotoxicity was analyzed by CD107a degranulation and 51Cr release assays.

RESULTS

We confirmed that HLA-E expression was increased by IFN-γ secreted by NK cells and that HLA-E expression was different for each cell line upon exposure to IFN-γ. Cell lines with high HLA-E expression showed stronger inhibition of NK cell cytotoxicity, and efficacy of monalizumab was high. Combination with cetuximab increased the efficacy of monalizumab. In addition, stimulation of isolated NK cells with IL-2 and IL-15 increased the efficacy of monalizumab, even in the HLA-E low groups.

CONCLUSION

Monalizumab efficacy was correlated with HLA-E surface expression and was enhanced when NK cell activity was increased by cetuximab or cytokines. These results suggest that monalizumab may be potent against HLA-E-positive tumors and that monalizumab efficacy could be improved by promoting NK cell activity.

Cell Surface B2m-Free Human Leukocyte Antigen (HLA) Monomers and Dimers: Are They Neo-HLA Class and Proto-HLA?

Cell surface HLA-I molecules (Face-1) consist of a polypeptide heavy chain (HC) with two groove domains (G domain) and one constant domain (C-domain) as well as a light chain, B2-microglobulin (B2m). However, HCs can also independently emerge unfolded on the cell surface without peptides as B2m-free HC monomers (Face-2), B2m-free HC homodimers (Face 3), and B2m-free HC heterodimers (Face-4). The transport of these HLA variants from ER to the cell surface was confirmed by antiviral antibiotics that arrest the release of newly synthesized proteins from the ER. Face-2 occurs at low levels on the normal cell surface of the lung, bronchi, epidermis, esophagus, breast, stomach, ilium, colorectum, gall bladder, urinary bladder, seminal vesicles ovarian epithelia, endometrium, thymus, spleen, and lymphocytes. They are upregulated on immune cells upon activation by proinflammatory cytokines, anti-CD3 antibodies, antibiotics (e.g., ionomycin), phytohemagglutinin, retinoic acid, and phorbol myristate acetate. Their density on the cell surface remains high as long as the cells remain in an activated state. After activation-induced upregulation, the Face-2 molecules undergo homo- and hetero-dimerization (Face-3 and Face-4). Alterations in the redox environment promote dimerization. Heterodimerization can occur among and between the alleles of different haplotypes. The glycosylation of these variants differ from that of Face-1, and they may occur with bound exogenous peptides. Spontaneous arthritis occurs in HLA-B27+ mice lacking B2m (HLA-B27+ B2m-/-) but not in HLA-B27+ B2m+/- mice. The mice with HLA-B27 in Face-2 spontaneous configuration develop symptoms such as changes in nails and joints, hair loss, and swelling in paws, leading to ankyloses. Anti-HC-specific mAbs delay disease development. Some HLA-I polyreactive mAbs (MEM series) used for immunostaining confirm the existence of B2m-free variants in several cancer cells. The upregulation of Face-2 in human cancers occurs concomitantly with the downregulation of intact HLAs (Face-1). The HLA monomeric and dimeric variants interact with inhibitory and activating ligands (e.g., KIR), growth factors, cytokines, and neurotransmitters. Similarities in the amino acid sequences of the HLA-I variants and HLA-II β-chain suggest that Face-2 could be the progenitor of both HLA classes. These findings may support the recognition of these variants as a neo-HLA class and proto-HLA.

Development of prognostic indicator based on NAD+ metabolism related genes in glioma

Background

Studies have shown that Nicotinamide adenine dinucleotide (NAD+) metabolism can promote the occurrence and development of glioma. However, the specific effects and mechanisms of NAD+ metabolism in glioma are unclear and there were no systematic researches about NAD+ metabolism related genes to predict the survival of patients with glioma.

Methods

The research was performed based on expression data of glioma cases in the Cancer Genome Atlas (TCGA) and Chinese Glioma Genome Atlas (CGGA) databases. Firstly, TCGA-glioma cases were classified into different subtypes based on 49 NAD+ metabolism-related genes (NMRGs) by consensus clustering. NAD+ metabolism-related differentially expressed genes (NMR-DEGs) were gotten by intersecting the 49 NMRGs and differentially expressed genes (DEGs) between normal and glioma samples. Then a risk model was built by Cox analysis and the least shrinkage and selection operator (LASSO) regression analysis. The validity of the model was verified by survival curves and receiver operating characteristic (ROC) curves. In addition, independent prognostic analysis of the risk model was performed by Cox analysis. Then, we also identified different immune cells, HLA family genes and immune checkpoints between high and low risk groups. Finally, the functions of model genes at single-cell level were also explored.

Results

Consensus clustering classified glioma patients into two subtypes, and the overall survival (OS) of the two subtypes differed. A total of 11 NAD+ metabolism-related differentially expressed genes (NMR-DEGs) were screened by overlapping 5,995 differentially expressed genes (DEGs) and 49 NAD+ metabolism-related genes (NMRGs). Next, four model genes, PARP9, BST1, NMNAT2, and CD38, were obtained by Cox regression and least absolute shrinkage and selection operator (Lasso) regression analyses and to construct a risk model. The OS of high-risk group was lower. And the area under curves (AUCs) of Receiver operating characteristic (ROC) curves were >0.7 at 1, 3, and 5 years. Cox analysis showed that age, grade G3, grade G4, IDH status, ATRX status, BCR status, and risk Scores were reliable independent prognostic factors. In addition, three different immune cells, Mast cells activated, NK cells activated and B cells naive, 24 different HLA family genes, such as HLA-DPA1 and HLA-H, and 8 different immune checkpoints, such as ICOS, LAG3, and CD274, were found between the high and low risk groups. The model genes were significantly relevant with proliferation, cell differentiation, and apoptosis.

Conclusion

The four genes, PARP9, BST1, NMNAT2, and CD38, might be important molecular biomarkers and therapeutic targets for glioma patients.

Myeloid cell tropism enables MHC-E-restricted CD8+ T cell priming and vaccine efficacy by the RhCMV/SIV vaccine

The strain 68-1 rhesus cytomegalovirus (RhCMV)-based vaccine for simian immunodeficiency virus (SIV) can stringently protect rhesus macaques (RMs) from SIV challenge by arresting viral replication early in primary infection. This vaccine elicits unconventional SIV-specific CD8+ T cells that recognize epitopes presented by major histocompatibility complex (MHC)-II and MHC-E instead of MHC-Ia. Although RhCMV/SIV vaccines based on strains that only elicit MHC-II- and/or MHC-Ia-restricted CD8+ T cells do not protect against SIV, it remains unclear whether MHC-E-restricted T cells are directly responsible for protection and whether these responses can be separated from the MHC-II-restricted component. Using host microRNA (miR)-mediated vector tropism restriction, we show that the priming of MHC-II and MHC-E epitope-targeted responses depended on vector infection of different nonoverlapping cell types in RMs. Selective inhibition of RhCMV infection in myeloid cells with miR-142-mediated tropism restriction eliminated MHC-E epitope-targeted CD8+ T cell priming, yielding an exclusively MHC-II epitope-targeted response. Inhibition with the endothelial cell-selective miR-126 eliminated MHC-II epitope-targeted CD8+ T cell priming, yielding an exclusively MHC-E epitope-targeted response. Dual miR-142 + miR-126-mediated tropism restriction reverted CD8+ T cell responses back to conventional MHC-Ia epitope targeting. Although the magnitude and differentiation state of these CD8+ T cell responses were generally similar, only the vectors programmed to elicit MHC-E-restricted CD8+ T cell responses provided protection against SIV challenge, directly demonstrating the essential role of these responses in RhCMV/SIV vaccine efficacy.

Natural Killer Cells in the Malignant Niche of Multiple Myeloma

Natural killer (NK) cells represent a subset of CD3- CD7+ CD56+/dim lymphocytes with cytotoxic and suppressor activity against virus-infected cells and cancer cells. The overall potential of NK cells has brought them to the spotlight of targeted immunotherapy in solid and hematological malignancies, including multiple myeloma (MM). Nonetheless, NK cells are subjected to a variety of cancer defense mechanisms, leading to impaired maturation, chemotaxis, target recognition, and killing. This review aims to summarize the available and most current knowledge about cancer-related impairment of NK cell function occurring in MM.

HLA-E and HLA-F Are Overexpressed in Glioblastoma and HLA-E Increased After Exposure to Ionizing Radiation

BACKGROUND/AIM

Glioblastoma (GBM) is one of the deadliest human cancers responding very poorly to therapy. Although the central nervous system has been traditionally considered an immunologically privileged site with an enhanced immune response, GBM appears to benefit from this immunosuppressive milieu. Immunomodulatory molecules play an important role in immune tumor-host interactions. Non-classical human leukocyte antigens (HLA) class Ib molecules HLA-E, HLA-F, and HLA-G have been previously described to be involved in protecting semi-allogeneic fetal allografts from the maternal immune response and in transplant tolerance as well as tumoral immune escape. Unfortunately, their role in GBM remains poorly understood. Our study, therefore, aimed to characterize the relationship between the expression of these molecules in GBM on the transcriptional level and clinicopathological and molecular features of GBM as well as the effect of ionizing radiation.

MATERIALS AND METHODS

We performed the analysis of HLA-E, HLA-F, and HLA-G mRNA expression in 69 GBM tissue samples and 21 non-tumor brain tissue samples (controls) by reverse transcription polymerase chain reaction. Furthermore, two primary GBM cell cultures had been irradiated to identify the effect of ionizing radiation on the expression of non-classical HLA molecules.

RESULTS

Analyses revealed that both HLA-E and HLA-F are significantly up-regulated in GBM samples. Subsequent survival analysis showed a significant association between low expression of HLA-E and shorter survival of GBM patients. The dysregulated expression of both molecules was also observed between patients with methylated and unmethylated O-6-methylguanine-DNA methyltransferase (MGMT) promoter. Finally, we showed that ionizing radiation increased HLA-E expression level in GBM cells in vitro.

CONCLUSION

HLA-E and HLA-F play an important role in GBM biology and could be used as diagnostic biomarkers, and in the case of HLA-E also as a prognostic biomarker.

Four Faces of Cell-Surface HLA Class-I: Their Antigenic and Immunogenic Divergence Generating Novel Targets for Vaccines

Leukocyte cell-surface HLA-I molecules, involved in antigen presentation of peptides to CD8+ T-cells, consist of a heavy chain (HC) non-covalently linked to β2-microglobulin (β2m) (Face-1). The HC amino acid composition varies across all six isoforms of HLA-I, while that of β2m remains the same. Each HLA-allele differs in one or more amino acid sequences on the HC α1 and α2 helices, while several sequences among the three helices are conserved. HCs without β2m (Face-2) are also observed on human cells activated by malignancy, viral transformation, and cytokine or chemokine-mediated inflammation. In the absence of β2m, the monomeric Face-2 exposes immunogenic cryptic sequences on these cells as confirmed by HLA-I monoclonal antibodies (LA45, L31, TFL-006, and TFL-007). Furthermore, such exposure enables dimerization between two Face-2 molecules by SH-linkage, salt linkage, H-bonding, and van der Waal forces. In HLA-B27, the linkage between two heavy chains with cysteines at position of 67 of the amino acid residues was documented. Similarly, several alleles of HLA-A, B, C, E, F and G express cysteine at 67, 101, and 164, and additionally, HLA-G expresses cysteine at position 42. Thus, the monomeric HC (Face-2) can dimerize with another HC of its own allele, as homodimers (Face-3), or with a different HC-allele, as heterodimers (Face-4). The presence of Face-4 is well documented in HLA-F. The post-translational HLA-variants devoid of β2m may expose several cryptic linear and non-linear conformationally altered sequences to generate novel epitopes. The objective of this review, while unequivocally confirming the post-translational variants of HLA-I, is to highlight the scientific and clinical importance of the four faces of HLA and to prompt further research to elucidate their functions and their interaction with non-HLA molecules during inflammation, infection, malignancy and transplantation. Indeed, these HLA faces may constitute novel targets for passive and active specific immunotherapy and vaccines.

Prognostic significance of natural killer cell-associated markers in gastric cancer: quantitative analysis using multiplex immunohistochemistry

Background

Natural killer (NK) cells mediate the anti-tumoral immune response as an important component of innate immunity. The aim of this study was to investigate the prognostic significance and functional implication of NK cell-associated surface receptors in gastric cancer (GC) by using multiplex immunohistochemistry (mIHC).

Methods

We performed an mIHC on tissue microarray slides, including 55 GC tissue samples. A total of 11 antibodies including CD57, NKG2A, CD16, HLA-E, CD3, CD20, CD45, CD68, CK, SMA, and ki-67 were used. CD45 + CD3-CD57 + cells were considered as CD57 + NK cells.

Results

Among CD45 + immune cells, the proportion of CD57 + NK cell was the lowest (3.8%), whereas that of CD57 + and CD57- T cells (65.5%) was the highest, followed by macrophages (25.4%), and B cells (5.3%). CD57 + NK cells constituted 20% of CD45 + CD57 + immune cells while the remaining 80% were CD57 + T cells. The expression of HLA-E in tumor cells correlated with that in tumoral T cells, B cells, and macrophages, but not CD57 + NK cells. The higher density of tumoral CD57 + NK cells and tumoral CD57 + NKG2A + NK cells was associated with inferior survival.

Conclusions

Although the number of CD57 + NK cells was lower than that of other immune cells, CD57 + NK cells and CD57 + NKG2A + NK cells were significantly associated with poor outcomes, suggesting that NK cell subsets play a critical role in GC progression. NK cells and their inhibitory receptor, NKG2A, may be potential targets in GC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03203-8.

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

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

Selection, Expansion, and Unique Pretreatment of Allogeneic Human Natural Killer Cells with Anti-CD38 Monoclonal Antibody for Efficient Multiple Myeloma Treatment

Cellular immunotherapy is becoming a new pillar in cancer treatment after recent striking results in different clinical trials with chimeric antigen receptor T cells. However, this innovative therapy is not exempt from challenges such as off-tumor toxicity, tumor recurrence in heterogeneous tumors, and affordability. To surpass these limitations, we exploit the unique anti-tumor characteristics of natural killer (NK) cells. In this study, we aimed to obtain a clinically relevant number of allogeneic NK cells derived from peripheral blood (median of 14,050 million cells from a single donor) to target a broad spectrum of solid and liquid tumor types. To boost their anti-tumor activity, we combined allogeneic NK cells with the approved anti-cluster of differentiation 38 (CD-38) monoclonal antibody Daratumumab to obtain a synergistic therapeutic effect against incurable multiple myeloma. The combination therapy was refined with CD16 polymorphism donor selection and uncomplicated novel in vitro pretreatment to avoid undesired fratricide, increasing the in vitro therapeutic effect against the CD-38 positive multiple myeloma cell line by more than 20%. Time-lapse imaging of mice with established human multiple myeloma xenografts revealed that combination therapy of selected and pretreated NK cells with Daratumumab presented tumor volumes 43-fold smaller than control ones. Combination therapy with an allogeneic source of fully functional NK cells could be beneficial in future clinical settings to circumvent monoclonal antibodies' low therapeutic efficiency due to NK cell dysfunctionality in MM patients.

Trained Immunity for Personalized Cancer Immunotherapy: Current Knowledge and Future Opportunities

Memory formation, guided by microbial ligands, has been reported for innate immune cells. Epigenetic imprinting plays an important role herein, involving histone modification after pathogen-/danger-associated molecular patterns (PAMPs/DAMPs) recognition by pattern recognition receptors (PRRs). Such "trained immunity" affects not only the nominal target pathogen, yet also non-related targets that may be encountered later in life. The concept of trained innate immunity warrants further exploration in cancer and how these insights can be implemented in immunotherapeutic approaches. In this review, we discuss our current understanding of innate immune memory and we reference new findings in this field, highlighting the observations of trained immunity in monocytic and natural killer cells. We also provide a brief overview of trained immunity in non-immune cells, such as stromal cells and fibroblasts. Finally, we present possible strategies based on trained innate immunity that may help to devise host-directed immunotherapies focusing on cancer, with possible extension to infectious diseases.

Vaccine-Mediated Inhibition of the Transporter Associated with Antigen Processing Is Insufficient To Induce Major Histocompatibility Complex E-Restricted CD8+ T Cells in Nonhuman Primates

Major histocompatibility complex E (MHC-E) is a highly conserved nonclassical MHC-Ib molecule that tightly binds peptides derived from leader sequences of classical MHC-Ia molecules for presentation to natural killer cells. However, MHC-E also binds diverse foreign and neoplastic self-peptide antigens for presentation to CD8+ T cells. Although the determinants of MHC-E-restricted T cell priming remain unknown, these cells are induced in humans infected with pathogens containing genes that inhibit the transporter associated with antigen processing (TAP). Indeed, mice vaccinated with TAP-inhibited autologous dendritic cells develop T cells restricted by the murine MHC-E homologue, Qa-1b. Here, we tested whether rhesus macaques (RM) vaccinated with viral constructs expressing a TAP inhibitor would develop insert-specific MHC-E-restricted CD8+ T cells. We generated viral constructs coexpressing SIVmac239 Gag in addition to one of three TAP inhibitors: herpes simplex virus 2 ICP47, bovine herpes virus 1 UL49.5, or rhesus cytomegalovirus Rh185. Each TAP inhibitor reduced surface expression of MHC-Ia molecules but did not reduce surface MHC-E expression. In agreement with modulation of surface MHC-Ia levels, TAP inhibition diminished presentation of MHC-Ia-restricted CD8+ T cell epitopes without impacting presentation of peptide antigen bound by MHC-E. Vaccination of macaques with vectors dually expressing SIVmac239 Gag with ICP47, UL49.5, or Rh185 generated Gag-specific CD8+ T cells classically restricted by MHC-Ia but not MHC-E. These data demonstrate that, in contrast to results in mice, TAP inhibition alone is insufficient for priming of MHC-E-restricted T cell responses in primates and suggest that additional unknown mechanisms govern the induction of CD8+ T cells recognizing MHC-E-bound antigen.IMPORTANCE Due to the near monomorphic nature of MHC-E in the human population and inability of many pathogens to inhibit MHC-E-mediated peptide presentation, MHC-E-restricted T cells have become an attractive vaccine target. However, little is known concerning how these cells are induced. Understanding the underlying mechanisms that induce these T cells would provide a powerful new vaccine strategy to an array of neoplasms and viral and bacterial pathogens. Recent studies have indicated a link between TAP inhibition and induction of MHC-E-restricted T cells. The significance of our research is in demonstrating that TAP inhibition alone does not prime MHC-E-restricted T cell generation and suggests that other, currently unknown mechanisms regulate their induction.

HLA-G, HLA-E, and IDO overexpression predicts a worse survival of Tunisian patients with vulvar squamous cell carcinoma

Little is known about non-classical HLA molecules in vulvar squamous cell carcinoma (VSCC). Because of the indoleamine-2,3-dioxygenase (IDO) immune tolerant role in association with HLA-G, we evaluated the clinical and prognostic value of HLA-G, HLA-E, and IDO in VSCC. HLA-G, HLA-E, and IDO expression was determined by immunohistochemistry in VSCC and associated with clinicopathological parameters and disease outcome. These three molecules were highly represented in tumoral tissues vs healthy matched vulvar tissues (P = 0.0001). Significant differences in HLA-G expression in stages, tumor size, tumor invasion depth, and resection margins subgroups were reported (P < 0.05). At 5 years, the cumulative survival rates was of 79.8% in patients with HLA-Glow expression vs 12.5% in those with HLA-Ghigh expression (P < 3 × 10-5 ). Similarly, patients with IDOhigh expression were at a significantly reduced overall survival (OS) and disease-free survival (DFS) rates (P = 0.011 and 0.045, respectively). The overexpression of the three molecules together worsen survival rates of VSCC patients (OS: P = 0.000038, DFS: P = 0.000085). Altogether, our results showed that HLA-G, HLA-E, and IDO may represent novel candidate markers for patients' prognosis and potential targets for VSCC therapy.

European Patent in Immunoncology: From Immunological Principles of Implantation to Cancer Treatment

The granted European patent EP 2 561 890 describes a procedure for an immunological treatment of cancer. It is based on the principles of the HLA-supported communication of implantation and pregnancy. These principles ensure that the embryo is not rejected by the mother. In pregnancy, the placenta, more specifically the trophoblast, creates an “interface” between the embryo/fetus and the maternal immune system. Trophoblasts do not express the “original” HLA identification of the embryo/fetus (HLA-A to -DQ), but instead show the non-classical HLA groups E, F, and G. During interaction with specific receptors of NK cells (e.g., killer-immunoglobulin-like receptors (KIR)) and lymphocytes (lymphocyte-immunoglobulin-like receptors (LIL-R)), the non-classical HLA groups inhibit these immunocompetent cells outside pregnancy. However, tumors are known to be able to express these non-classical HLA groups and thus make use of an immuno-communication as in pregnancies. If this occurs, the prognosis usually worsens. This patent describes, in a first step, the profiling of the non-classical HLA groups in primary tumor tissue as well as metastases and recurrent tumors. The second step comprises tailored antibody therapies, which is the subject of this patent. In this review, we analyze the underlying mechanisms and describe the currently known differences between HLA-supported communication of implantation and that of tumors.

Enhancing Natural Killer and CD8+ T Cell-Mediated Anticancer Cytotoxicity and Proliferation of CD8+ T Cells with HLA-E Monospecific Monoclonal Antibodies

Cytotoxic NK/CD8+ T cells interact with MHC-I ligands on tumor cells through either activating or inhibiting receptors. One of the inhibitory receptors is CD94/NKG2A. The NK/CD8+ T cell cytotoxic capability is lost when tumor-associated human leukocyte antigen, HLA-E, binds the CD94/NKG2A receptor, resulting in tumor progression and reduced survival. Failure of cancer patients to respond to natural killer (NK) cell therapies could be due to HLA-E overexpression in tumor tissues. Preventing the inhibitory receptor-ligand interaction by either receptor- or ligand-specific monoclonal antibodies (mAbs) is an innovative passive immunotherapeutic strategy for cancer. Since receptors and ligands can be monomeric or homo- or heterodimeric proteins, the efficacy of mAbs may rely on their ability to distinguish monospecific (private) functional epitopes from nonfunctional common (public) epitopes. We developed monospecific anti-HLA-E mAbs (e.g., TFL-033) that recognize only HLA-E-specific epitopes, but not epitopes shared with other HLA class-I loci as occurs with currently available polyreactive anti-HLA-E mAbs. Interestingly the amino acid sequences in the α1 and α2 helices of HLA-E, critical for the recognition of the mAb TFL-033, are strikingly the same sequences recognized by the CD94/NKG2A inhibitory receptors on NK/CD8+ cells. Such monospecific mAbs can block the CD94/NKG2A interaction with HLA-E to restore NK cell and CD8+ anticancer cell cytotoxicity. Furthermore, the HLA-E monospecific mAbs significantly promoted the proliferation of the CD4-/CD8+ T cells. These monospecific mAbs are also invaluable for the specific demonstration of HLA-E on tumor biopsies, potentially indicating those tumors most likely to respond to such therapy. Thus, they can be used to enhance passive immunotherapy once phased preclinical studies and clinical trials are completed. On principle, we postulate that NK cell passive immunotherapy should capitalize on both of these features of monospecific HLA-E mAbs, that is, the specific determination HLA-E expression on a particular tumor and the enhancement of NK cell/CD8+ cytotoxicity if HLA-E positive.

Unconventional T Cell Targets for Cancer Immunotherapy

Most studies on the immunotherapeutic potential of T cells have focused on CD8 and CD4 T cells that recognize peptide antigens (Ag) presented by polymorphic major histocompatibility complex (MHC) class I and MHC class II molecules, respectively. However, unconventional T cells, which interact with MHC class Ib and MHC-I like molecules, are also implicated in tumor immunity, although their role therein is unclear. These include unconventional T cells targeting MHC class Ib molecules such as HLA-E and its murine ortholog Qa-1b, natural killer T (NKT) cells, mucosal associated invariant T (MAIT) cells, and γδ T cells. Here, we review the current understanding of the roles of these unconventional T cells in tumor immunity and discuss why further studies into the immunotherapeutic potential of these cells is warranted.

The prognostic benefit of tumour-infiltrating Natural Killer cells in endometrial cancer is dependent on concurrent overexpression of Human Leucocyte Antigen-E in the tumour microenvironment

BACKGROUND

Human Leucocyte Antigen- E (HLA-E) has been reported as both a positive and negative prognostic marker in cancer. This apparent discrepancy may be due to opposing actions of HLA-E on tumour-infiltrating immune cells. Therefore, we evaluated HLA-E expression and survival in relation to the presence of intratumoural natural killer (NK) cells and cytotoxic T cells (CTLs).

METHODS

Tissue microarrays (TMAs) of endometrial tumours were used for immunohistochemical staining of parameters of interest. The combined impact of clinical, pathological and immune parameters on survival was analysed using log rank testing and Cox regression analyses.

RESULTS

Upregulation of HLA-E was associated with an improved disease-free and disease-specific survival in univariate analysis (HR 0.58 95% CI 0.37-0.89; HR 0.42 95% CI 0.25-0.73, respectively). In multivariate analysis, the presence of NK cells predicts survival with a hazard ratio (HR) 0.28 (95% confidence interval (CI) 0.09-0.91) when HLA-E expression is upregulated; but it is associated with a worse prognosis when HLA-E expression is normal (HR 13.43, 95% CI 1.70-106.14). By contrast, the prognostic benefit of T cells was not modulated by HLA-E expression.

CONCLUSIONS

Taken together, we demonstrate that the prognostic benefit of NK cells, but not T-cells, is influenced by HLA-E expression in endometrial cancer (EC) and propose a model to explain our observations.

In vivo CRISPR screening identifies Ptpn2 as a cancer immunotherapy target

Immunotherapy with PD-1 checkpoint blockade is effective in only a minority of patients with cancer, suggesting that additional treatment strategies are needed. Here we use a pooled in vivo genetic screening approach using CRISPR-Cas9 genome editing in transplantable tumours in mice treated with immunotherapy to discover previously undescribed immunotherapy targets. We tested 2,368 genes expressed by melanoma cells to identify those that synergize with or cause resistance to checkpoint blockade. We recovered the known immune evasion molecules PD-L1 and CD47, and confirmed that defects in interferon-γ signalling caused resistance to immunotherapy. Tumours were sensitized to immunotherapy by deletion of genes involved in several diverse pathways, including NF-κB signalling, antigen presentation and the unfolded protein response. In addition, deletion of the protein tyrosine phosphatase PTPN2 in tumour cells increased the efficacy of immunotherapy by enhancing interferon-γ-mediated effects on antigen presentation and growth suppression. In vivo genetic screens in tumour models can identify new immunotherapy targets in unanticipated pathways.

LILRB receptor-mediated regulation of myeloid cell maturation and function

The leukocyte immunoglobulin-like receptor (LILR) family comprises a set of paired immunomodulatory receptors expressed among human myeloid and lymphocyte cell populations. While six members of LILR subfamily A (LILRA) associate with membrane adaptors to signal via immunoreceptor tyrosine-based activating motifs (ITAM), LILR subfamily B (LILRB) members signal via multiple cytoplasmic immunoreceptor tyrosine-based inhibitory motifs (ITIM). Ligand specificity of some LILR family members has been studied in detail, but new perspective into the immunoregulatory aspects of this receptor family in human myeloid cells has been limited. LILRB receptors and the murine ortholog, paired immunoglobulin-like receptor B (PIRB), have been shown to negatively regulate maturation pathways in myeloid cells including mast cells, neutrophils, dendritic cells, as well as B cells. Our laboratory further demonstrated in mouse models that PIRB regulated functional development of myeloid-derived suppressor cell and the formation of a tumor-permissive microenvironment. Based on observations from the literature and our own studies, our laboratory is focusing on how LILRs modulate immune homeostasis of human myeloid cells and how these pathways may be targeted in disease states. Integrity of this pathway in tumor microenvironments, for example, permits a myeloid phenotype that suppresses antitumor adaptive immunity. This review presents the evidence supporting a role of LILRs as myeloid cell regulators and ongoing efforts to understand the functional immunology surrounding this family.

Novel avenues in immunotherapies for colorectal cancer

Since it is known that the immune system affects tumor growth, it has been studied if immunotherapy can be developed to combat cancer. While some successes have been claimed, the increasing knowledge on tumor-immune interactions has, however, also shown the limitations of this approach. Tumors may show selective outgrowth of cells escaped from immune control. Escape variants arise spontaneously due to the genetically instable nature of tumor cells. This is one of the most obvious limitations of cancer immunotherapy. However, new therapies are becoming available, designed to respond to tumor-immune escape.

High NKG2A expression contributes to NK cell exhaustion and predicts a poor prognosis of patients with liver cancer

Background and Aims: As the predominant lymphocyte subset in the liver, natural killer (NK) cells have been shown to be highly associated with the outcomes of patients with chronic hepatitis B virus infection (CHB) and hepatocellular carcinoma (HCC). Previously, we reported that NKG2A, a checkpoint candidate, mediates human and murine NK cell dysfunction in CHB. However, NK cell exhaustion and, particularly, the level of NKG2A expression within liver tumors have not been reported. Methods: In this study, we analyzed NKG2A expression and the related dysfunction of NK cells located in intra- or peritumor regions of liver tissue samples from 207 HCC patients, in addition to analyzing disease outcomes. Results: The expression of NKG2A in NK cells and the NKG2A ligand, HLA-E, in intratumor HCC tissues was observed to be increased. These NK cells, and particularly CD56^dim NK cells, with higher NKG2A expression showed features of functional exhaustion and were associated with a poor prognosis. The increase in NKG2A expression might be induced by IL-10, which was present at a high level in the plasma of HCC patients. Blocking IL-10 could specifically inhibit NKG2A expression in NK cells. Conclusions: These findings indicate that NKG2A expression is influenced by factors from cancer nests and contributes to NK cell exhaustion, suggesting that NKG2A blockade has the potential to restore immunity against liver tumors by reversing NK cell exhaustion.

A comparison of cancer stem cell markers and nonclassical major histocompatibility complex antigens in colorectal tumor and noncancerous tissues

Colorectal carcinoma (CRC) is one of the most fatal types of cancer in both women and men, and, unfortunately, patients are often diagnosed at an advanced stage. Cancer stem cells (CSCs) are associated with poor prognosis, metastasis, and recurrence, as well as chemotherapy and radiotherapy resistance. Therefore, different treatment alternatives are needed to facilitate the elimination of CSCs. One such approach is immunotherapy; however, tumor cells can evade immune cells by alteration of the expression patterns of human leukocyte antigens (HLA). In this study, we immunohistochemically investigated the expression patterns of CSC-specific markers CD44, CD133, Nanog, and Oct3/4, and immunosuppressive molecules HLA-G and -E in advanced CRC tumor tissues and noncancerous colon biopsies. We found significantly increased CD44, Nanog, Oct3/4, HLA-G, and HLA-E expression in the CRC tumor tissues compared with the noncancerous colon biopsies. These findings suggest that some tumor cells may be CSC-like and that the increased expression of HLA-G and HLA-E may be considered as an immune-evasive adaptation. Therefore, the nonclassical major histocompatibility complex class Ib antigens HLA-G and HLA-E may be potential targets in the elimination of CRC-CSCs. However, more detailed studies are required to support our findings.

Involvement of IL-10 and TGF-β in HLA-E-mediated neuroblastoma migration and invasion

Human leukocyte antigen (HLA)-E is highly expressed in a variety of tumors and, in addition to immune escape, may promote tumor growth via other mechanisms. However, the role of HLA-E in neuroblastoma (NB) migration and invasion is unknown. In the present study, HLA-E expression in human NB tumors was measured by immunohistochemistry. The effect of HLA-E on NB cell migration and invasion was studied in vitro and in vivo, as well as the effect of HLA-E on natural killer (NK)-cell cytotoxicity. HLA-E was expressed in 70.2% of the NB tumor tissues examined. HLA-E expression by NB cells inhibited NK-cell cytotoxicity and induced the release of interleukin (IL)-10 and transforming growth factor (TGF)-β1. HLA-E and the released cytokines enhanced the ability of NB cells migration and invasion. NK cell infusion did not inhibit the growth of NB cells with high HLA-E expression but instead increased the number of metastatic cells in the bone marrow. Taken together, the results indicate that IL-10 and TGF-β are involved in HLA-E-mediated NB migration and invasion. Thus, HLA-E may be a new treatment target in NB.

The Immunogenicity of Colorectal Cancer in Relation to Tumor Development and Treatment

Although most cancer types have been viewed as immunologically silent until recently, it has become increasingly clear that the immune system plays key roles in the course of tumor development. Remarkable progress towards understanding cancer immunogenicity and tumor-immune system interactions has revealed important implications for the design of novel immune-based therapies. Natural immune responses, but also therapeutic interventions, can modulate the tumor phenotype due to selective outgrowth of resistant subtypes. This is the result of heterogeneity of tumors, with genetic instability as a driving force, and obviously changes the immunogenicity of tumors. In this review, we discuss the immunogenicity of colorectal cancer (CRC) in relation to tumor development and treatment. As most tumors, CRC activates the immune system in various ways, and is also capable of escaping recognition and elimination by the immune system. Tumor-immune system interactions underlie the balance between immune control and immune escape, and may differ in primary tumors, in the circulation, and in liver metastases of CRC. Since CRC immunogenicity varies between tumors and individuals, novel immune-based therapeutic strategies should not only anticipate the molecular profile, but also the immunological profile of a specific tumor.

Loss of PTEN Promotes Resistance to T Cell-Mediated Immunotherapy

T cell-mediated immunotherapies are promising cancer treatments. However, most patients still fail to respond to these therapies. The molecular determinants of immune resistance are poorly understood. We show that loss of PTEN in tumor cells in preclinical models of melanoma inhibits T cell-mediated tumor killing and decreases T-cell trafficking into tumors. In patients, PTEN loss correlates with decreased T-cell infiltration at tumor sites, reduced likelihood of successful T-cell expansion from resected tumors, and inferior outcomes with PD-1 inhibitor therapy. PTEN loss in tumor cells increased the expression of immunosuppressive cytokines, resulting in decreased T-cell infiltration in tumors, and inhibited autophagy, which decreased T cell-mediated cell death. Treatment with a selective PI3Kβ inhibitor improved the efficacy of both anti-PD-1 and anti-CTLA-4 antibodies in murine models. Together, these findings demonstrate that PTEN loss promotes immune resistance and support the rationale to explore combinations of immunotherapies and PI3K-AKT pathway inhibitors.

SIGNIFICANCE

This study adds to the growing evidence that oncogenic pathways in tumors can promote resistance to the antitumor immune response. As PTEN loss and PI3K-AKT pathway activation occur in multiple tumor types, the results support the rationale to further evaluate combinatorial strategies targeting the PI3K-AKT pathway to increase the efficacy of immunotherapy.

Loss of PTEN Promotes Resistance to T Cell-Mediated Immunotherapy

T cell-mediated immunotherapies are promising cancer treatments. However, most patients still fail to respond to these therapies. The molecular determinants of immune resistance are poorly understood. We show that loss of PTEN in tumor cells in preclinical models of melanoma inhibits T cell-mediated tumor killing and decreases T-cell trafficking into tumors. In patients, PTEN loss correlates with decreased T-cell infiltration at tumor sites, reduced likelihood of successful T-cell expansion from resected tumors, and inferior outcomes with PD-1 inhibitor therapy. PTEN loss in tumor cells increased the expression of immunosuppressive cytokines, resulting in decreased T-cell infiltration in tumors, and inhibited autophagy, which decreased T cell-mediated cell death. Treatment with a selective PI3Kβ inhibitor improved the efficacy of both anti-PD-1 and anti-CTLA-4 antibodies in murine models. Together, these findings demonstrate that PTEN loss promotes immune resistance and support the rationale to explore combinations of immunotherapies and PI3K-AKT pathway inhibitors.

SIGNIFICANCE

This study adds to the growing evidence that oncogenic pathways in tumors can promote resistance to the antitumor immune response. As PTEN loss and PI3K-AKT pathway activation occur in multiple tumor types, the results support the rationale to further evaluate combinatorial strategies targeting the PI3K-AKT pathway to increase the efficacy of immunotherapy.

Loss of PTEN Promotes Resistance to T Cell-Mediated Immunotherapy

T cell-mediated immunotherapies are promising cancer treatments. However, most patients still fail to respond to these therapies. The molecular determinants of immune resistance are poorly understood. We show that loss of PTEN in tumor cells in preclinical models of melanoma inhibits T cell-mediated tumor killing and decreases T-cell trafficking into tumors. In patients, PTEN loss correlates with decreased T-cell infiltration at tumor sites, reduced likelihood of successful T-cell expansion from resected tumors, and inferior outcomes with PD-1 inhibitor therapy. PTEN loss in tumor cells increased the expression of immunosuppressive cytokines, resulting in decreased T-cell infiltration in tumors, and inhibited autophagy, which decreased T cell-mediated cell death. Treatment with a selective PI3Kβ inhibitor improved the efficacy of both anti-PD-1 and anti-CTLA-4 antibodies in murine models. Together, these findings demonstrate that PTEN loss promotes immune resistance and support the rationale to explore combinations of immunotherapies and PI3K-AKT pathway inhibitors.

SIGNIFICANCE

This study adds to the growing evidence that oncogenic pathways in tumors can promote resistance to the antitumor immune response. As PTEN loss and PI3K-AKT pathway activation occur in multiple tumor types, the results support the rationale to further evaluate combinatorial strategies targeting the PI3K-AKT pathway to increase the efficacy of immunotherapy.

Up-regulation of activating and inhibitory NKG2 receptors in allogeneic and autologous hematopoietic stem cell grafts

Background

Hematopoietic Stem Cell Transplantation (HSCT) is known to induce the inhibitory immune receptor NKG2A on NK cells of donor origin. This occurs in allogeneic recipients, in both the haploidentical and HLA-matched settings.

Methods

To gain further insight, not only NKG2A, but also the activating receptors NKG2C and NKG2D were assessed by flow cytometry. Immunophenotyping was carried out not only on CD56⁺ but also on CD8⁺ lymphocytes from leukemia and lymphoma patients, receiving both HLA-matched (n = 7) and autologous (n = 5) HSCT grafts. Moreover, cognate NKG2 ligands (HLA-E, MICA, ULBP-1, ULBP-2 and ULBP-3) were assessed by immunohistochemistry in diagnostic biopsies from three autotransplanted patients, and at relapse in one case.

Results

All the NKG2 receptors were simultaneously up-regulated in all the allotransplanted patients on CD8⁺ and/or CD56⁺ cells between 30 and 90 days post-transplant, coinciding with, or following, allogeneic engraftment. Up-regulation was of lesser entity and restricted to CD8⁺ cells in the autotransplantation setting. The phenotypic expression ratio between activating and inhibitory NKG2 receptors was remarkably similar in all the patients, except two outliers (a long survivor and a short survivor) who surprisingly displayed a similar NKG2 activation immunophenotype. Tumor expression of 2 to 3 out of the 5 tested NKG2 ligands was observed in 3/3 diagnostic biopsies, and 3 ligands were up-regulated post-transplant in a patient.

Conclusions

Altogether, these results are consistent with a dual (activation-inhibition) NK cell re-education mode, an innate-like T cell re-tuning, and a ligand:receptor interplay between the tumor and the immune system following HSCT including, most interestingly, the up-regulation of several activating NKG2 ligands. Turning the immune receptor balance toward activation on both T and NK cells of donor origin may complement ex vivo NK cell expansion/activation strategies in unmanipulated patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-015-0213-y) contains supplementary material, which is available to authorized users.

Monoclonal antibodies to HLA-E bind epitopes carried by unfolded β2 m-free heavy chains

Since HLA-E heavy chains accumulate free of their light β2 -microglobulin (β2 m) subunit, raising mAbs to folded HLA-E heterodimers has been difficult, and mAb characterization has been controversial. Herein, mAb W6/32 and 5 HLA-E-restricted mAbs (MEM-E/02, MEM-E/07, MEM-E/08, DT9, and 3D12) were tested on denatured, acid-treated, and natively folded (both β2 m-associated and β2 m-free) HLA-E molecules. Four distinct conformations were detected, including unusual, partially folded (and yet β2 m-free) heavy chains reactive with mAb DT9. In contrast with previous studies, epitope mapping and substitution scan on thousands of overlapping peptides printed on microchips revealed that mAbs MEM-E/02, MEM-E/07, and MEM-E/08 bind three distinct α1 and α2 domain epitopes. All three epitopes are linear since they span just 4-6 residues and are "hidden" in folded HLA-E heterodimers. They contain at least one HLA-E-specific residue that cannot be replaced by single substitutions with polymorphic HLA-A, HLA-B, HLA-C, HLA-F, and HLA-G residues. Finally, also the MEM-E/02 and 3D12 epitopes are spatially distinct. In summary, HLA-E-specific residues are dominantly immunogenic, but only when heavy chains are locally unfolded. Consequently, the available mAbs fail to selectively bind conformed HLA-E heterodimers, and HLA-E expression may have been inaccurately assessed in some previous oncology, reproductive immunology, virology, and transplantation studies.

HLA-E regulates NKG2C+ natural killer cell function through presentation of a restricted peptide repertoire

NK cells interact with the HLA-E molecule via the inhibitory receptor NKG2A and the activating receptor NKG2C. Hence, HLA-E can have a dual role in the immune response. In the present study, we aim to investigate the functional consequences of HLA-E for NKG2A and NKG2C expressing NK cell subsets by using a panel of HLA-E binding peptides derived from CMV, Hsp60 and HLA class I. PBMC derived from healthy subjects were used as targets for isolated NK cells and NK cell activation was examined by analysis of the expression of the degranulation marker CD107a. Peptide induced HLA-E expression inhibited degranulation of NKG2A+ NK cell subsets with almost all peptides, whereas NKG2A- NKG2C+ NK cell responses were enhanced only after incubation with four peptides; 1.3-fold with CMV(I), A80 and B13 and 3.2-fold with HLA-G derived peptide. In addition, the HLA-E:G peptide complex triggered NKG2C receptor internalization, as evidenced by reduction in the percentage of NKG2C+ NK cells when incubated with the peptide, which could be restored by addition of Bafilomycin.

IN CONCLUSION

in contrast to NKG2A, NKG2C is regulated by HLA-E only when HLA-E is in complex with a restricted peptide repertoire, especially in combination with the HLA-G leader peptide.

Immunotherapy of Metastatic Colorectal Cancer: Prevailing Challenges and New Perspectives

Patients with recurring or metastatic colorectal cancer (mCRC) have strikingly low long-term survival, while conventional treatments such as chemotherapeutic intervention and radiation therapy marginally improve longevity. Although, many factors involving immunosurveillance and immunosuppression were recently validated as important for patient prognosis and care, a multitude of experimental immunotherapies designed to combat unresectable mCRC have, in few cases, successfully mobilized antitumor immune cells against malignancies, nor conclusively or consistently granted protection, complete remission, and/or stable disease from immunotherapy - of which benefit less than 10% of those receiving therapy. After decades of progress, however, new insights into the mechanisms of immunosuppression, tolerance, and mutation profiling established novel therapies that circumvent these immunological barriers. This review underlines the most exciting methods to date that manipulate immune cells to curb mCRC, including adoptive cell therapy, dendritic cell vaccines, and checkpoint inhibitor antibodies - of which hint at effective and enduring protection against disease progression and undetected micrometastases.

Predictive value of HLA-G and HLA-E in the prognosis of colorectal cancer patients

HLA-G and HLA-E are non-classical HLA Ib molecules. Recently, increasingly more reports have shown that HLA-G is highly expressed in different malignancies. In this article, we detected the expression levels of HLA-G and HLA-E in primary colorectal cancer patients. Our results showed that 70.6% and 65.7% of the colorectal cancer tissues had positive HLA-G or HLA-E expression, respectively, and that 46.1% positively expressed both molecules. We also analyzed the correlations between the expression levels of HLA-G, HLA-E or both combined and the clinical outcomes of the patients. Kaplan-Meier analysis results showed that the expression levels of HLA-G or HLA-E alone and the combined expression of both molecules were all statistically correlated with the overall survival of colorectal cancer patients. Cox multivariate analysis showed that only HLA-G expression can serve as independent factor for OS. Our results also showed that the expression of HLA-E was significantly correlated with tumor metastasis.

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.

Prognostic value of HLA class I, HLA-E, HLA-G and Tregs in rectal cancer: a retrospective cohort study

BACKGROUND

Evasion of immune surveillance and suppression of the immune system are important hallmarks of tumorigenesis. The goal of this study was to establish distinct patterns that reflect a rectal tumors' immune-phenotype and to determine their relation to patient outcome.

METHODS

The study population consisted of 495 Stage I-IV non-preoperatively treated rectal cancer patients of which a tissue micro array (TMA) was available. Sections of this TMA were immunohistochemically stained and quantified for presence of Foxp3+ cells (Tregs) and tumor expression of HLA Class I and non-classical HLA-E and HLA-G. All markers were, separate and combined, analyzed for clinical prognostic value.

RESULTS

Expression of HLA class I (DFS HR 0.637 (0.458-0.886), p = 0.013), Foxp3+ infiltration above median (OS HR 0.637 (0.500-0.813), p < 0.001 and DFS HR 0.624 (0.491-0.793), p < 0.001) and expression of HLA-G (DFS HR 0.753 (0.574-0.989), p = 0.042) were related to a better clinical prognosis. When these markers were combined, patients with 2 or 3 markers associated with poor prognosis (loss of HLA Class I, Foxp3+ below median, and weak HLA-G expression), showed a significantly worse survival (OS and DFS p < 0.001). This immune-phenotype was an independent predictor for DFS (HR 1.56 (1.14-2.14), p = 0.019).

CONCLUSIONS

In conclusion, rectal tumors showing loss of HLA class I expression, Foxp3+ infiltration below median and weak HLA-G expression were related to a worse OS and DFS. Combining these immune markers lead to the creation of tumor immune-phenotypes , which related to patient outcome and were significant independent clinical prognostic markers in rectal cancer.

Gastric cancer progression may involve a shift in HLA-E profile from an intact heterodimer to β2-microglobulin-free monomer

Phenotypic expression of human leukocyte antigen (HLA)-E on the surface of tumor lesions includes intact heterodimer [HLA-E heavy chain and β2-microglobulin (β2m)] and β2m-free monomer. Anti-HLA-E monoclonal antibodies (mAbs), MEM-E/02 or 3D12 bind to the peptide sequences in β2m-free HLA-E, which is common and shared with HLA-Ia monomers. A newly developed monospecific anti-HLA-E mAb (TFL-033) recognizes HLA-E-restricted peptide sequences on α1 and α2 helices away from β2-m-site. Tumor progression may involve shedding of β2-m from HLA-E or overexpression of β2m-free monomers. There is a need to identify and distinguish the different phenotypic expression of HLA-E, particularly the intact heterodimer from the β2m-free monomer on the surface of tumor lesions. Because of the unique peptide-binding affinities of the mAbs, it is hypothesized that TFL-033 and MEM-E/02 may distinguish the phenotypic expressions of cell surface HLA-E during stages of tumor progression. Only TFL-033 stained diffusely the cytoplasm of normal mucosa. The incidence and intensity of TFL-033 staining of the cell surface in early stages, poorly or undifferentiated and non-nodal lesions and in diffuse carcinoma is greater than that of MEM-E/02. Whereas MEM-E/02 stained terminal stages, adenocarcinoma and lymph node metastatic lesions intensely, either owing to increased expression of β2m-free HLA-E with tumor progression or owing to expression of HLA-Ia molecules. Our study evaluates the relative diagnostic potential of HLA-E-monospecific TFL-033 and the HLA-Ia-reactive MEM-E/02 for determining the specific distribution and immunodiagnosis of different phenotypic expression HLA-E in tumor lesions, and the structural and functional alterations undergone by HLA-E during tumor progression.

A melanoma immune response signature including Human Leukocyte Antigen-E

Paired cultures of early-passage melanoma cells and melanocytes were established from metastatic lesions and the uninvolved skin of five patients. In this stringent autologous setting, cDNA profiling was used to analyze a subset of 1477 genes selected by the Gene Ontology term 'immune response'. Human Leukocyte Antigen E (HLA-E) was ranked 19th among melanoma-overexpressed genes and was embedded in a transformation signature including its preferred peptide ligand donors HLA-A, HLA-B, HLA-C, and HLA-G. Mostly undetectable in normal skin and 39 nevi (including rare and atypical lesions), HLA-E was detected by immunohistochemistry in 17/30 (57%) and 32/48 (67%) primary and metastatic lesions, respectively. Accordingly, surface HLA-E was higher on melanoma cells than on melanocytes and protected the former (6/6 cell lines) from lysis by natural killer (NK) cells, functionally counteracting co-expressed triggering ligands. Although lacking HLA-E, melanocytes (4/4 cultures) were nevertheless (and surprisingly) fully protected from NK cell lysis.

Role of non-classical MHC class I molecules in cancer immunosuppression

Growing neoplasms employ various mechanisms to evade immunosurveillance. The expression of non-classical MHC class I molecules by both immune and malignant cells in the tumor microenvironment constitute of the strategies used by tumors to circumvent the cytotoxic activity of effector cells of the immune system. The overexpression of HLA-G, -E, and -F is a common finding across a variety of malignancies. However, while the presence of HLA-G and HLA-E has been recently correlated with poor clinical outcome, information on the clinicopathological significance of HLA-F is limited. In the present review, we summarize studies on non-classical MHC class I molecules with special emphasis on their role in the modulation of anticancer immune responses.

HLA-dependent tumour development: a role for tumour associate macrophages?

HLA abnormalities on tumour cells for immune escape have been widely described. In addition, cellular components of the tumour microenvironment, in particular myeloid derived suppressor cells (MDSC) and alternatively activated M2 tumour-associated macrophages (TAMs), are involved in tumour promotion, progression, angiogenesis and suppression of anti-tumour immunity. However, the role of HLA in these activities is poorly understood. This review details MHC class I characteristics and describes MHC class I receptors functions. This analysis established the basis for a reflection about the crosstalk among the tumour cells, the TAMs and the cells mediating an immune response.The tumour cells and TAMs exploit MHC class I molecules to modulate the surrounding immune cells. HLA A, B, C and G molecules down-regulate the macrophage myeloid activation through the interaction with the inhibitory LILRB receptors. HLA A, B, C are able to engage inhibitory KIR receptors negatively regulating the Natural Killer and cytotoxic T lymphocytes function while HLA-G induces the secretion of pro-angiogenic cytokines and chemokine thanks to an activator KIR receptor expressed by a minority of peripheral NK cells. The open conformer of classical MHC-I is able to interact with LILRA receptors described as being associated to the Th2-type cytokine response, triggering a condition for the M2 like TAM polarization. In addition, HLA-E antigens on the surface of the TAMs bind the inhibitory receptor CD94/NKG2A expressed by a subset of NK cells and activated cytotoxic T lymphocytes protecting from the cytolysis.Furthermore MHC class II expression by antigen presenting cells is finely regulated by factors provided with immunological capacities. Tumour-associated macrophages show an epigenetically controlled down-regulation of the MHC class II expression induced by the decoy receptor DcR3, a member of the TNFR, which further enhances the M2-like polarization. BAT3, a positive regulator of MHC class II expression in normal macrophages, seems to be secreted by TAMs, consequently lacking its intracellular function, it looks like acting as an immunosuppressive factor.In conclusion HLA could cover a considerable role in tumour-development orchestrated by tumour-associated macrophages.

Differential expression of immune-modulatory molecule HLA-E in non-neoplastic and neoplastic lesions of the thyroid

Human leukocyte antigen (HLA)–E is a non-classical molecule of the histocompatibility complex that functions as one of the main ligands of the Natural Killer (NK) cell inhibitory receptor CD94/NKG2A and inhibits its potent cytotoxic activity. Due to the important role of NK cells in combating neoplasm, we hypothesized that the differential expression of HLA-E could favor the progression of heterogeneous thyroid tumors.Using an immunohistochemistry technique in 143 biopsies of thyroid tumors, including benign and malignant neoplasms and goiters, we evaluated the expression of HLA-E among various tumor types and its association with the clinicopathological factors of diseases. We verified high HLA-E expression in all types of neoplastic tumors, although no significant differences between the groups were found. Low expression was observed in 95 percent of the goiter samples, showing significant differences between neoplastic and non-neoplastic lesions. Furthermore, a significant result was found with regard to the tumor size, with high HLA-E expression being related to smaller tumors. Therefore, our data suggest that an increase in HLA-E may be associated with the establishment of thyroid neoplasms, with either benign or malignant features.

Major histocompatibility complex class i and tumour immuno-evasion: how to fool T cells and natural killer cells at one time

Cytotoxic T lymphocytes (ctls) and natural killer (nk) cells lyse tumours expressing and lacking, respectively, properly conformed class i molecules of the major histocompatibility complex [mhc-i (Figure 1)] [...]

T and NK cells: two sides of tumor immunoevasion

Natural Killer (NK) cells are known to reject several experimental murine tumors, but their antineoplastic activity in humans is not generally agreed upon, as exemplified by an interesting correspondence recently appeared in Cancer Research. In the present commentary, we join the discussion and bring to the attention of the readers of the Journal of Translational Medicine a set of recent, related reports. These studies demonstrate that effectors of the adaptive and innate immunity need to actively cooperate in order to reject tumors and, conversely, tumors protect themselves by dampening both T and NK cell responses. The recently reported ability of indoleamine 2,3-dioxygenase (IDO) and prostaglandin E2 (PGE2) expressed by melanoma cells to down-regulate activating NK receptors is yet another piece of evidence supporting combined and highly effective T/NK cell disabling. Major Histocompatibility Complex class I (MHC-I) molecules, including Human Leukocyte Antigen E (HLA-E), represent another class of shared activating/inhibitory ligands. Ongoing clinical trials with small molecules interfering with IDO and PGE2 may be exploiting an immune bonus to control cancer. Conversely, failure to simultaneously engage effectors of both the innate and the adaptive immunity may contribute to explain the limited clinical efficacy of T cell-only vaccination trials. Shared (T/NK cells) natural immunosuppressants and activating/inhibitory ligands expressed by tumor cells may provide mechanistic insight into impaired gathering and function of immune effectors at the tumor site.

Correlations between cytoplasmic CSE1L in neoplastic colorectal glands and depth of tumor penetration and cancer stage

Background

Colorectal carcinomas spread easily to nearby tissues around the colon or rectum, and display strong potential for invasion and metastasis. CSE1L, the chromosome segregation 1-like protein, is implicated in cancer progression and is located in both the cytoplasm and nuclei of tumor cells. We investigated the prognostic significance of cytoplasmic vs. nuclear CSE1L expression in colorectal cancer.

Methods

The invasion- and metastasis-stimulating activities of CSE1L were studied by in vitro invasion and animal experiments. CSE1L expression in colorectal cancer was assayed by immunohistochemistry, with tissue microarray consisting of 128 surgically resected specimens; and scored using a semiquantitative method. The correlations between CSE1L expression and clinicopathological parameters were analyzed.

Results

CSE1L overexpression was associated with increased invasiveness and metastasis of cancer cells. Non-neoplastic colorectal glands showed minimal CSE1L staining, whereas most colorectal carcinomas (99.2%, 127/128) were significantly positive for CSE1L staining. Cytoplasmic CSE1L was associated with cancer stage (P=0.003) and depth of tumor penetration (P=0.007). Cytoplasmic CSE1L expression also correlated with lymph node metastasis of the disease in Cox regression analysis

Conclusions

CSE1L regulates the invasiveness and metastasis of cancer cells, and immunohistochemical analysis of cytoplasmic CSE1L in colorectal tumors may provide a useful aid to prognosis.

High Ran level is correlated with poor prognosis in patients with colorectal cancer

BACKGROUND

The Ras-like nuclear protein (Ran) is involved in the regulation of nuclear transport, microtubule nucleation and dynamics, and spindle assembly. Its fundamental function is nucleocytoplasmic transport of RNA and proteins. The expression and potential role of Ran in colorectal cancer (CRC) remain unclear. The aim of this study was to investigate the relationship between Ran expression and CRC characteristics. The potential role of Ran as a prognostic indicator was also evaluated.

METHODS

We used immunohistochemistry and western blotting to detect Ran expression in 287 CRC tissues. The relationships between Ran expression and clinicopathological characteristics and overall survival rate were statistically analyzed.

RESULTS

CRC tissues had significantly higher Ran expression than normal colorectal epithelial cells. Ran was positively correlated with depth of invasion, lymph node metastases, distant metastases, tumor differentiation, and tumor-node-metastasis stage. However, no correlation was found between Ran expression and patient age or sex. The overall survival rate was consistently and significantly lower in patients with Ran-positive tumors than in those with Ran-negative tumors.

CONCLUSION

Our findings emphasize the important role of Ran in differentiation, disease stage, and metastasis in human CRC. Ran may play an important role in the development of CRC and may serve as a novel prognostic indicator of CRC.

HLA-E expression in cervical adenocarcinomas: association with improved long-term survival

BACKGROUND

Cervical cancer is the third most common cancer in women worldwide. The most common histopathological subtype is cervical squamous cell carcinoma (SCC, 75-80%), followed by adenocarcinoma (AC) and adenosquamous carcinoma (ASC; together 15-20%). Rising incidence rates of AC have been observed relative and absolute to SCC and evidence is accumulating that cervical AC is a distinct clinical entity. Cervical SCC, ASC, and AC are caused by a persistent infection with high-risk human papillomavirus (HPV) and failed control of the immune system plays a pivotal role in the carcinogenesis of all three histopathological subtypes. Human leukocyte antigen E (HLA-E), a non-classical HLA class Ib molecule, plays an important role in immune surveillance and immune escape of virally infected cells. In this study we investigated HLA-E expression in three well-defined cohorts of cervical AC, ASC, and SCC patients, and determined whether HLA-E expression was associated with histopathological parameters and patient survival.

METHODS AND RESULTS

HLA-E expression was assessed by immunohistochemistry on formalin-fixed, paraffin-embedded tissue sections of 79 SCC, 38 ASC, and 75 AC patients. All patients included were International Federation of Gynaecology and Obstetrics stage I-II and underwent radical hysterectomy with lymphadenectomy as primary treatment. Significant differences between the histopathological subgroups were detected for age distribution, HPV positivity, HPV type distribution, tumour size, tumour infiltration depth, lymph-vascular space invasion, and adjuvant radiotherapy. High expression of HLA-E was found in 107/192 (56%) cervical carcinomas, with significantly more overexpression in cervical AC compared to SCC and ASC (37/79 SCC, 18/38 ASC, and 52/75 AC; P = 0.010). High HLA-E expression in cervical AC was associated with favourable long term disease-specific and recurrence-free survival (P = 0.005 and P = 0.001, respectively).

CONCLUSION

High expression of HLA-E occurred in the majority of all histopathological subtypes of cervical cancer; especially in cervical AC. High HLA-E expression in cervical AC was associated with improved patient survival. This study also highlights the importance of careful evaluation of cervical carcinomas to distinguish histopathological subtypes. In the future, insight into the biological behaviour and distinct molecular carcinogenetic processes of the AC, ASC, and SCC subtypes may contribute to the development of more tumour-specific treatment strategies.