ULBP2 and RAET1E NKG2D ligands are independent predictors of poor prognosis in ovarian cancer patients

Identification and validation of immune-related gene signature models for predicting prognosis and immunotherapy response in hepatocellular carcinoma

Background

This study seeks to enhance the accuracy and efficiency of clinical diagnosis and therapeutic decision-making in hepatocellular carcinoma (HCC), as well as to optimize the assessment of immunotherapy response.

Methods

A training set comprising 305 HCC cases was obtained from The Cancer Genome Atlas (TCGA) database. Initially, a screening process was undertaken to identify prognostically significant immune-related genes (IRGs), followed by the application of logistic regression and least absolute shrinkage and selection operator (LASSO) regression methods for gene modeling. Subsequently, the final model was constructed using support vector machines-recursive feature elimination (SVM-RFE). Following model evaluation, quantitative polymerase chain reaction (qPCR) was employed to examine the gene expression profiles in tissue samples obtained from our cohort of 54 patients with HCC and an independent cohort of 231 patients, and the prognostic relevance of the model was substantiated. Thereafter, the association of the model with the immune responses was examined, and its predictive value regarding the efficacy of immunotherapy was corroborated through studies involving three cohorts undergoing immunotherapy. Finally, the study uncovered the potential mechanism by which the model contributed to prognosticating HCC outcomes and assessing immunotherapy effectiveness.

Results

SVM-RFE modeling was applied to develop an OS prognostic model based on six IRGs (CMTM7, HDAC1, HRAS, PSMD1, RAET1E, and TXLNA). The performance of the model was assessed by AUC values on the ROC curves, resulting in values of 0.83, 0.73, and 0.75 for the predictions at 1, 3, and 5 years, respectively. A marked difference in OS outcomes was noted when comparing the high-risk group (HRG) with the low-risk group (LRG), as demonstrated in both the initial training set (P <0.0001) and the subsequent validation cohort (P <0.0001). Additionally, the SVMRS in the HRG demonstrated a notable positive correlation with key immune checkpoint genes (CTLA-4, PD-1, and PD-L1). The results obtained from the examination of three cohorts undergoing immunotherapy affirmed the potential capability of this model in predicting immunotherapy effectiveness.

Conclusions

The HCC predictive model developed in this study, comprising six genes, demonstrates a robust capability to predict the OS of patients with HCC and immunotherapy effectiveness in tumor management.

Soluble NKG2DLs Are Elevated in Breast Cancer Patients and Associate with Disease Outcome

Ligands of the natural killer group 2D (NKG2DL) family are expressed on malignant cells and are usually absent from healthy tissues. Recognition of NKG2DLs such as MICA/B and ULBP1-3 by the activating immunoreceptor NKG2D, expressed by NK and cytotoxic T cells, stimulates anti-tumor immunity in breast cancer. Upregulation of membrane-bound NKG2DLs in breast cancer has been demonstrated by immunohistochemistry. Tumor cells release NKG2DLs via proteolytic cleavage as soluble (s)NKG2DLs, which allows for effective immune escape and is associated with poor prognosis. In this study, we collected serum from 140 breast cancer (BC) and 20 ductal carcinoma in situ (DCIS) patients at the time of initial diagnosis and 20 healthy volunteers (HVs). Serum levels of sNKG2DLs were quantified through the use of ELISA and correlated with clinical data. The analyzed sNKG2DLs were low to absent in HVs and significantly higher in BC patients. For some of the ligands analyzed, higher sNKG2DLs serum levels were associated with the classification of malignant tumor (TNM) stage and grading. Low sMICA serum levels were associated with significantly longer progression-free (PFS) and overall survival (OS). In conclusion, we provide the first insights into sNKG2DLs in BC patients and suggest their potential role in tumor immune escape in breast cancer. Furthermore, our observations suggest that serum sMICA levels may serve as a prognostic parameter in the patients analyzed in this study.

Multiomics-Based Feature Extraction and Selection for the Prediction of Lung Cancer Survival

Lung cancer is a global health challenge, hindered by delayed diagnosis and the disease's complex molecular landscape. Accurate patient survival prediction is critical, motivating the exploration of various -omics datasets using machine learning methods. Leveraging multi-omics data, this study seeks to enhance the accuracy of survival prediction by proposing new feature extraction techniques combined with unbiased feature selection. Two lung adenocarcinoma multi-omics datasets, originating from the TCGA and CPTAC-3 projects, were employed for this purpose, emphasizing gene expression, methylation, and mutations as the most relevant data sources that provide features for the survival prediction models. Additionally, gene set aggregation was shown to be the most effective feature extraction method for mutation and copy number variation data. Using the TCGA dataset, we identified 32 molecular features that allowed the construction of a 2-year survival prediction model with an AUC of 0.839. The selected features were additionally tested on an independent CPTAC-3 dataset, achieving an AUC of 0.815 in nested cross-validation, which confirmed the robustness of the identified features.

Killer instincts: natural killer cells as multifactorial cancer immunotherapy

Natural killer (NK) cells integrate heterogeneous signals for activation and inhibition using germline-encoded receptors. These receptors are stochastically co-expressed, and their concurrent engagement and signaling can adjust the sensitivity of individual cells to putative targets. Against cancers, which mutate and evolve under therapeutic and immunologic pressure, the diversity for recognition provided by NK cells may be key to comprehensive cancer control. NK cells are already being trialled as adoptive cell therapy and targets for immunotherapeutic agents. However, strategies to leverage their naturally occurring diversity and agility have not yet been developed. In this review, we discuss the receptors and signaling pathways through which signals for activation or inhibition are generated in NK cells, focusing on their roles in cancer and potential as targets for immunotherapies. Finally, we consider the impacts of receptor co-expression and the potential to engage multiple pathways of NK cell reactivity to maximize the scope and strength of antitumor activities.

Identification and validation of a novel NK cells-related signature to predict prognosis and immune microenvironment in LUAD

BACKGROUND

The prevalence and fatality rates of lung cancer are experiencing a rapid escalation. Natural Killer (NK) cells have been established to have a crucial role in both tumor initiation and progression. Nevertheless, uncertainties persist regarding their precise implications in the prognosis of LUAD.

METHODS

The data were obtained from reputable sources, such as the Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO) database, and our internally generated sequencing data. Utilizing the TCGA data as a background, we selected intersecting genes, validated by cluster analysis, to establish a Cox model and validated it using the GEO datasets. Furthermore, we conducted extensive analyses to investigate the significance of potential biomarkers in relation to immune cell infiltration, single-cell data, differential gene expression, and drug sensitivity.

RESULTS

67 immune-related genes associated with NK cells (NK-IRGs) were identified in the TCGA datasets, whose research potential was demonstrated by cluster analysis. A prognostic signature was identified utilizing the univariate and multivariate Cox model, resulting in the identification of five genes, which was validated using GEO datasets. Additionally, the nomogram's calibration curve demonstrated exceptional concordance between the projected and actual survival rates. Subsequent investigations uncovered that this prognostic signature demonstrated its independence as a risk factor. Notably, in the low-risk group, NK cells exhibited elevated levels of immune checkpoint molecules, indicating heightened sensitivity to immune therapy. These findings highlight the potential of utilizing this signature as a valuable tool in the selection of patients who could benefit from targeted immune interventions.

The Role and Regulation of the NKG2D/NKG2D Ligand System in Cancer

The family of human NKG2D ligands (NKG2DL) consists of eight stress-induced molecules. Over 80% of human cancers express these ligands on the surface of tumour cells and/or associated stromal elements. In mice, NKG2D deficiency increases susceptibility to some types of cancer, implicating this system in immune surveillance for malignancy. However, NKG2DL can also be shed, released via exosomes and trapped intracellularly, leading to immunosuppressive effects. Moreover, NKG2D can enhance chronic inflammatory processes which themselves can increase cancer risk and progression. Indeed, tumours commonly deploy a range of countermeasures that can neutralise or even corrupt this surveillance system, tipping the balance away from immune control towards tumour progression. Consequently, the prognostic impact of NKG2DL expression in human cancer is variable. In this review, we consider the underlying biology and regulation of the NKG2D/NKG2DL system and its expression and role in a range of cancer types. We also consider the opportunities for pharmacological modulation of NKG2DL expression while cautioning that such interventions need to be carefully calibrated according to the biology of the specific cancer type.

Investigating the Effects of Olaparib on the Susceptibility of Glioblastoma Multiforme Tumour Cells to Natural Killer Cell-Mediated Responses

Glioblastoma multiforme (GBM) is the most common adult primary brain malignancy, with dismal survival rates of ~14.6 months. The current standard-of-care consists of surgical resection and chemoradiotherapy, however the treatment response is limited by factors such as tumour heterogeneity, treatment resistance, the blood-brain barrier, and immunosuppression. Several immunotherapies have undergone clinical development for GBM but demonstrated inadequate efficacy, yet future combinatorial approaches are likely to hold more promise. Olaparib is FDA-approved for BRCA-mutated advanced ovarian and breast cancer, and clinical studies have revealed its utility as a safe and efficacious radio- and chemo-sensitiser in GBM. The ability of Olaparib to enhance natural killer (NK) cell-mediated responses has been reported in prostate, breast, and lung cancer. This study examined its potential combination with NK cell therapies in GBM by firstly investigating the susceptibility of the GBM cell line T98G to NK cells and, secondly, examining whether Olaparib can sensitise T98G cells to NK cell-mediated responses. Here, we characterise the NK receptor ligand profile of T98G cells and demonstrate that Olaparib does not dampen T98G susceptibility to NK cells or elicit immunomodulatory effects on the function of NK cells. This study provides novel insights into the potential combination of Olaparib with NK cell therapies for GBM.

NKG2D discriminates diverse ligands through selectively mechano-regulated ligand conformational changes

Stimulatory immune receptor NKG2D binds diverse ligands to elicit differential anti-tumor and anti-virus immune responses. Two conflicting degeneracy recognition models based on static crystal structures and in-solution binding affinities have been considered for almost two decades. Whether and how NKG2D recognizes and discriminates diverse ligands still remain unclear. Using live-cell-based single-molecule biomechanical assay, we characterized the in situ binding kinetics of NKG2D interacting with different ligands in the absence or presence of mechanical force. We found that mechanical force application selectively prolonged NKG2D interaction lifetimes with the ligands MICA and MICB, but not with ULBPs, and that force-strengthened binding is much more pronounced for MICA than for other ligands. We also integrated steered molecular dynamics simulations and mutagenesis to reveal force-induced rotational conformational changes of MICA, involving formation of additional hydrogen bonds on its binding interface with NKG2D, impeding MICA dissociation under force. We further provided a kinetic triggering model to reveal that force-dependent affinity determines NKG2D ligand discrimination and its downstream NK cell activation. Together, our results demonstrate that NKG2D has a discrimination power to recognize different ligands, which depends on selective mechanical force-induced ligand conformational changes.

Immunotherapeutic targeting of activating natural killer cell receptors and their ligands in cancer

Natural killer (NK) cells exert an important role in cancer immune surveillance. Recognition of malignant cells and controlled activation of effector functions are facilitated by the expression of activating and inhibitory receptors, which is a complex interplay that allows NK cells to discriminate malignant cells from healthy tissues. Due to their unique profile of effector functions, the recruitment of NK cells is attractive in cancer treatment and a key function of NK cells in antibody therapy is widely appreciated. In recent years, besides the low-affinity fragment crystallizable receptor for immunoglobulin G (FcγRIIIA), the activating natural killer receptors p30 (NKp30) and p46 (NKp46), as well as natural killer group 2 member D (NKG2D), have gained increasing attention as potential targets for bispecific antibody-derivatives to redirect NK cell cytotoxicity against tumors. Beyond modulation of the receptor activity on NK cells, therapeutic targeting of the respective ligands represents an attractive approach. Here, novel therapeutic approaches to unleash NK cells by engagement of activating NK-cell receptors and alternative strategies targeting their tumor-expressed ligands in cancer therapy are summarized.

Immune ULBP1 is Elevated in Colon Adenocarcinoma and Predicts Prognosis

Background: Colon adenocarcinoma (COAD) is still the main cause of cancer deaths worldwide. Although immunotherapy has made progress in recent years, there is still a need to improve diagnosis, prognosis, and treatment tools. UL-16 binding protein 1 (ULBP1) is a ligand that activates the receptor natural killer cell group 2 receptor D (NKG2D) and plays an important immunomodulatory role. We aimed to investigate the clinical significance of ULBP1 in COAD.

Methods: We obtained the relevant data from The Cancer Genome Atlas (TCGA). A total of 438 patients with COAD were included in this study, with a mean age of 67.1 ± 13.03 years old, of which 234 (53.42%) were male. The diagnostic value of COAD tumor tissues and adjacent tissues was analyzed by ROC curve. Univariate and multivariate survival analysis investigated the prognostic value of ULBP1 gene, and Gene Set Enrichment Analysis (GSEA) curve was performed to analyze the biological process and enriched enrichment pathway of ULBP1 in COAD. Combination survival analysis investigated the combined prognostic effect of prognostic genes.

Results:ULBP1 gene had a high diagnostic value in COAD [AUC (TCGA) = 0.959; AUC (Guangxi) = 0.898]. Up-regulated ULBP1 gene of patients with COAD predicted a worse prognosis compared to those patients with down-regulated ULBP1 gene (Adjusted HR = 1.544, 95% CI = 1.020–2.337, p = 0.040). The GSEA showed that ULBP1 was involved in the apoptotic pathway and biological process of T cell mediated cytotoxicity, regulation of natural killer cell activation, and T cell mediated immunity of COAD. The combination survival analysis showed that the combination of high expression of ULBP1, AARS1, and DDIT3 would increase the 2.2-fold death risk of COAD when compared with those of low expression genes.

Conclusion: The immune-related ULBP1 gene had diagnostic and prognostic value in COAD. The combination of ULBP1, AARS1, and DDIT3 genes could improve the prognostic prediction performance in COAD.

Cancer Stem Cells in Ovarian Cancer-A Source of Tumor Success and a Challenging Target for Novel Therapies

Ovarian cancer is the most lethal neoplasm of the female genital organs. Despite indisputable progress in the treatment of ovarian cancer, the problems of chemo-resistance and recurrent disease are the main obstacles for successful therapy. One of the main reasons for this is the presence of a specific cell population of cancer stem cells. The aim of this review is to show the most contemporary knowledge concerning the biology of ovarian cancer stem cells (OCSCs) and their impact on chemo-resistance and prognosis in ovarian cancer patients, as well as to present the treatment options targeted exclusively on the OCSCs. The review presents data concerning the role of cancer stem cells in general and then concentrates on OCSCs. The surface and intracellular OCSCs markers and their meaning both for cancer biology and clinical prognosis, signaling pathways specifically activated in OCSCs, the genetic and epigenetic regulation of OCSCs function including the recent studies on the non-coding RNA regulation, cooperation between OCSCs and the tumor microenvironment (ovarian cancer niche) including very specific environment such as ascites fluid, the role of shear stress, autophagy and metabolic changes for the function of OCSCs, and finally mechanisms of OCSCs escape from immune surveillance, are described and discussed extensively. The possibilities of anti-OCSCs therapy both in experimental settings and in clinical trials are presented, including the recent II phase clinical trials and immunotherapy. OCSCs are a unique population of cancer cells showing a great plasticity, self-renewal potential and resistance against anti-cancer treatment. They are responsible for the progression and recurrence of the tumor. Several completed and ongoing clinical trials have tested different anti-OCSCs drugs which, however, have shown unsatisfactory efficacy in most cases. We propose a novel approach to ovarian cancer diagnosis and therapy.

MICA/B-targeted antibody promotes NK cell-driven tumor immunity in patients with intrahepatic cholangiocarcinoma

The major histocompatibility complex-class I chain related proteins A and B (MICA/B) is upregulated because of cellular stress and MICA/B shedding by cancer cells causes escape from NKG2D recognition favoring the emergence of cancers. Cholangiocarcinoma (CCA) is a relatively rare, though increasingly prevalent, primary liver cancer characterized by a late clinical presentation and a dismal prognosis. We explored the NKG2D-MICA/B axis in NK cells from 41 patients with intrahepatic cholangiocarcinoma (iCCA). The MICA/B-specific 7C6 mAb was used for ex vivo antibody-dependent cytotoxicity (ADCC) experiments using circulating, non tumor liver- and tumor-infiltrating NK cells against the HuCCT-1 cell line and patient-derived primary iCCA cells as targets. MICA/B were more expressed in iCCA than in non-tumoral tissue, MICA transcription being higher in moderately-differentiated compared with poorly-differentiated cancer. Serum MICA was elevated in iCCA patients in line with higher expression of ADAM10 and ADAM17 that are responsible for proteolytic release of MICA/B from tumor. Addition of 7C6 significantly boosted peripheral, liver- and tumor-infiltrating-NK cell degranulation and IFNγ production toward MICA/B-expressing established cell lines and autologous iCCA patient target cells. Our data show that anti-MICA/B drives NK cell anti-tumor activity, and provide preclinical evidence in support of 7C6 as a potential immunotherapeutic tool for iCCA.

NKG2D Ligands in Liquid Biopsy: The Importance of Soluble and Vesicle-Bound Proteins for Immune Modulation

The identification of biomarkers allowing diagnostics, prognostics and patient classification is still a challenge in oncological research for patient management. Improvements in patient survival achieved with immunotherapies substantiate that biomarker studies rely not only on cellular pathways contributing to the pathology, but also on the immune competence of the patient. If these immune molecules can be studied in a non-invasive manner, the benefit for patients and clinicians is obvious. The immune receptor Natural Killer Group 2 Member D (NKG2D) represents one of the main systems involved in direct recognition of tumor cells by effector lymphocytes (T and Natural Killer cells), and in immune evasion. The biology of NKG2D and its ligands comprises a complex network of cellular pathways leading to the expression of these tumor-associated ligands on the cell surface or to their release either as soluble proteins, or in extracellular vesicles that potently inhibit NKG2D-mediated responses. Increased levels of NKG2D-ligands in patient serum correlate with tumor progression and poor prognosis; however, most studies did not test the biochemical form of these molecules. Here we review the biology of the NKG2D receptor and ligands, their role in cancer and in patient response to immunotherapies, as well as the changes provoked in this system by non-immune cancer therapies. Further, we discuss the use of NKG2D-L in liquid biopsy, including methods to analyse vesicle-associated proteins. We propose that the evaluation in cancer patients of the whole NKG2D system can provide crucial information about patient immune competence and risk of tumor progression.

Stress Signal ULBP4, an NKG2D Ligand, Is Upregulated in Multiple Sclerosis and Shapes CD8+ T-Cell Behaviors

BACKGROUND AND OBJECTIVES

We posit the involvement of the natural killer group 2D (NKG2D) pathway in multiple sclerosis (MS) pathology via the presence of specific NKG2D ligands (NKG2DLs). We aim to evaluate the expression of NKG2DLs in the CNS and CSF of patients with MS and to identify cellular stressors inducing the expression of UL16-binding protein 4 (ULBP4), the only detectable NKG2DL. Finally, we evaluate the impact of ULBP4 on functions such as cytokine production and motility by CD8⁺ T lymphocytes, a subset largely expressing NKG2D, the cognate receptor.

METHODS

Human postmortem brain samples and CSF from patients with MS and controls were used to evaluate NKG2DL expression. In vitro assays using primary cultures of human astrocytes and neurons were performed to identify stressors inducing ULBP4 expression. Human CD8⁺ T lymphocytes from MS donors and age/sex-matched healthy controls were isolated to evaluate the functional impact of soluble ULBP4.

RESULTS

We detected mRNA coding for the 8 identified human NKG2DLs in brain samples from patients with MS and controls, but only ULBP4 protein expression was detectable by Western blot. ULBP4 levels were greater in patients with MS, particularly in active and chronic active lesions and normal-appearing white matter, compared with normal-appearing gray matter from MS donors and white and gray matter from controls. Soluble ULBP4 was also detected in CSF of patients with MS and controls, but a smaller shed/soluble form of 25 kDa was significantly elevated in CSF from female patients with MS compared with controls and male patients with MS. Our data indicate that soluble ULBP4 affects various functions of CD8⁺ T lymphocytes. First, it enhanced the production of the proinflammatory cytokines GM-CSF and interferon-γ (IFNγ). Second, it increased CD8⁺ T lymphocyte motility and favored a kinapse-like behavior when cultured in the presence of human astrocytes. CD8⁺ T lymphocytes from patients with MS were especially altered by the presence of soluble ULBP4 compared with healthy controls.

DISCUSSION

Our study provides new evidence for the involvement of NKG2D and its ligand ULBP4 in MS pathology. Our results point to ULBP4 as a viable target to specifically block 1 component of the NKG2D pathway without altering immune surveillance involving other NKG2DL.

Barriers to Immunotherapy in Ovarian Cancer: Metabolic, Genomic, and Immune Perturbations in the Tumour Microenvironment

A lack of explicit early clinical signs and effective screening measures mean that ovarian cancer (OC) often presents as advanced, incurable disease. While conventional treatment combines maximal cytoreductive surgery and platinum-based chemotherapy, patients frequently develop chemoresistance and disease recurrence. The clinical application of immune checkpoint blockade (ICB) aims to restore anti-cancer T-cell function in the tumour microenvironment (TME). Disappointingly, even though tumour infiltrating lymphocytes are associated with superior survival in OC, ICB has offered limited therapeutic benefits. Herein, we discuss specific TME features that prevent ICB from reaching its full potential, focussing in particular on the challenges created by immune, genomic and metabolic alterations. We explore both recent and current therapeutic strategies aiming to overcome these hurdles, including the synergistic effect of combination treatments with immune-based strategies and review the status quo of current clinical trials aiming to maximise the success of immunotherapy in OC.

Leveraging NKG2D Ligands in Immuno-Oncology

Immune checkpoint inhibitors (ICI) revolutionized the field of immuno-oncology and opened new avenues towards the development of novel assets to achieve durable immune control of cancer. Yet, the presence of tumor immune evasion mechanisms represents a challenge for the development of efficient treatment options. Therefore, combination therapies are taking the center of the stage in immuno-oncology. Such combination therapies should boost anti-tumor immune responses and/or target tumor immune escape mechanisms, especially those created by major players in the tumor microenvironment (TME) such as tumor-associated macrophages (TAM). Natural killer (NK) cells were recently positioned at the forefront of many immunotherapy strategies, and several new approaches are being designed to fully exploit NK cell antitumor potential. One of the most relevant NK cell-activating receptors is NKG2D, a receptor that recognizes 8 different NKG2D ligands (NKG2DL), including MICA and MICB. MICA and MICB are poorly expressed on normal cells but become upregulated on the surface of damaged, transformed or infected cells as a result of post-transcriptional or post-translational mechanisms and intracellular pathways. Their engagement of NKG2D triggers NK cell effector functions. Also, MICA/B are polymorphic and such polymorphism affects functional responses through regulation of their cell-surface expression, intracellular trafficking, shedding of soluble immunosuppressive isoforms, or the affinity of NKG2D interaction. Although immunotherapeutic approaches that target the NKG2D-NKG2DL axis are under investigation, several tumor immune escape mechanisms account for reduced cell surface expression of NKG2DL and contribute to tumor immune escape. Also, NKG2DL polymorphism determines functional NKG2D-dependent responses, thus representing an additional challenge for leveraging NKG2DL in immuno-oncology. In this review, we discuss strategies to boost MICA/B expression and/or inhibit their shedding and propose that combination strategies that target MICA/B with antibodies and strategies aimed at promoting their upregulation on tumor cells or at reprograming TAM into pro-inflammatory macrophages and remodeling of the TME, emerge as frontrunners in immuno-oncology because they may unleash the antitumor effector functions of NK cells and cytotoxic CD8 T cells (CTL). Pursuing several of these pipelines might lead to innovative modalities of immunotherapy for the treatment of a wide range of cancer patients.

Expression of NKG2D ligands is downregulated by β-catenin signalling and associates with HCC aggressiveness

BACKGROUND & AIMS

The NKG2D system is a potent immunosurveillance mechanism in cancer, wherein the activating NK cell receptor (NKG2D) on immune cells recognises its cognate ligands on tumour cells. Herein, we evaluated the expression of NKG2D ligands in hepatocellular carcinoma (HCC), in both humans and mice, taking the genomic features of HCC tumours into account.

METHODS

The expression of NKG2D ligands (MICA, MICB, ULBP1 and ULBP2) was analysed in large human HCC datasets by Fluidigm TaqMan and RNA-seq methods, and in 2 mouse models (mRNA and protein levels) reproducing the features of both major groups of human tumours.

RESULTS

We provide compelling evidence that expression of the MICA and MICB ligands in human HCC is associated with tumour aggressiveness and poor patient outcome. We also found that the expression of ULBP1 and ULBP2 was associated with poor patient outcome, and was downregulated in CTNNB1-mutated HCCs displaying low levels of inflammation and associated with a better prognosis. We also found an inverse correlation between ULBP1/2 expression levels and the expression of β-catenin target genes in patients with HCC, suggesting a role for β-catenin signalling in inhibiting expression. We showed in HCC mouse models that β-catenin signalling downregulated the expression of Rae-1 NKG2D ligands, orthologs of ULBPs, through TCF4 binding.

CONCLUSIONS

We demonstrate that the expression of NKG2D ligands is associated with aggressive liver tumorigenesis and that the downregulation of these ligands by β-catenin signalling may account for the less aggressive phenotype of CTNNB1-mutated HCC tumours.

LAY SUMMARY

The NKG2D system is a potent immunosurveillance mechanism in cancer. However, its role in hepatocellular carcinoma development has not been widely investigated. Herein, we should that the expression of NKG2D ligands by tumour cells is associated with a more aggressive tumour subtype.

Investigation and verification of the clinical significance and perspective of natural killer group 2 member D ligands in colon adenocarcinoma

This study investigated and verified the diagnostic and prognostic values of natural killer group 2 member D ligand (NKG2DL) genes in colon adenocarcinoma (COAD). We downloaded NKG2DLs expression data and corresponding clinical parameters from The Cancer Genome Atlas (TCGA) and used bioinformatics techniques to investigate the values of NKG2DLs in COAD. Then, we used the GSE40967 cohort to verify the prognostic value of NKG2DLs. Finally, we verified the ULBP2 expression level in tissues, and also investigated the diagnostic and prognostic values of ULBP2 in COAD. The diagnostic receiver operating characteristic curves showed that ULBP1, ULBP2, ULBP3, and RAET1L had high diagnostic values in COAD [Area Under Curve (AUC) > 0.9]. In TCGA cohort, the univariate and multivariate survival analyses suggested that ULBP2 was correlated with the prognosis of COAD recurrence-free survival (RFS) and overall survival (OS). In GSE40967 cohort, ULBP2 was associated with CC RFS and OS. Reverse transcription-quantitative polymerase chain reaction and immunohistochemistry results showed that ULBP2 was highly expressed in COAD tumor tissues (P < 0.05) and both had diagnostic values (AUC > 0.7). Validated survival analysis showed that the high expression of ULBP2 had a worse prognosis in COAD OS and RFS. Thus, ULBP2 might be an independent diagnostic and prognostic biomarker of COAD.

High-throughput proteomics of breast cancer interstitial fluid: identification of tumor subtype-specific serologically relevant biomarkers

Despite significant advancements in breast cancer (BC) research, clinicians lack robust serological protein markers for accurate diagnostics and tumor stratification. Tumor interstitial fluid (TIF) accumulates aberrantly externalized proteins within the local tumor space, which can potentially gain access to the circulatory system. As such, TIF may represent a valuable starting point for identifying relevant tumor-specific serological biomarkers. The aim of the study was to perform comprehensive proteomic profiling of TIF to identify proteins associated with BC tumor status and subtype. A liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis of 35 TIFs of three main subtypes: luminal (19), Her2 (4), and triple-negative (TNBC) (12) resulted in the identification of > 8800 proteins. Unsupervised hierarchical clustering segregated the TIF proteome into two major clusters, luminal and TNBC/Her2 subgroups. High-grade tumors enriched with tumor infiltrating lymphocytes (TILs) were also stratified from low-grade tumors. A consensus analysis approach, including differential abundance analysis, selection operator regression, and random forest returned a minimal set of 24 proteins associated with BC subtypes, receptor status, and TIL scoring. Among them, a panel of 10 proteins, AGR3, BCAM, CELSR1, MIEN1, NAT1, PIP4K2B, SEC23B, THTPA, TMEM51, and ULBP2, was found to stratify the tumor subtype-specific TIFs. In particular, upregulation of BCAM and CELSR1 differentiates luminal subtypes, while upregulation of MIEN1 differentiates Her2 subtypes. Immunohistochemistry analysis showed a direct correlation between protein abundance in TIFs and intratumor expression levels for all 10 proteins. Sensitivity and specificity were estimated for this protein panel by using an independent, comprehensive breast tumor proteome dataset. The results of this analysis strongly support our data, with eight of the proteins potentially representing biomarkers for stratification of BC subtypes. Five of the most representative proteomics databases currently available were also used to estimate the potential for these selected proteins to serve as putative serological markers.

Transcriptomic analysis of micropapillary high grade T1 urothelial bladder cancer

No consensus currently exist on the optimal treatment of patients with high-risk nonmuscle invasive (HGT1) micropapillary variant of bladder cancer (MPBC). Transcripsome analysis may allow stratification of MPBC-HGT1 enabling prediction of recurrence and guide therapeutic management for individual patients. Whole transcriptome RNA-Sequencing of tumors from 23 patients with MPBC-HGT1 and 64 conventional urothelial carcinomas (cUC) (reference set) was performed. Differentially expressed genes between MPBC-HGT1 and cUC-HGT1 were explored. Cox proportional hazard models and Kapplan–Meier methods were used to assess the relation between time to progression (TTP) and individual gene expression adjusting for clinical covariates. Over 3000 genes were differentially expressed in MPBC-HGT1 as compared with cUC-HGT1 and a 26-gene signature is characteristic of MPBC within HGT1. A set of three genes; CD36, FAPB3 and RAETE1; were significantly associated with TTP. High expression of FABP3 and CD36 were associated with shorter TTP (p = 0.045 and p = 0.08) as was low expression of RAET1E (p = 0.01). Our study suggest that a 26-gene signature can define MPBC-HGT1 within conventional urothelial carcinomas. A prognostic risk index of three genes (FABP3, CD36 and RAET1E) was found to be associated with shorter TTP and may help classify a group of patients with MPBC-HGT1 with high-risk of early progression. These observations might have implications in terms of radical cystectomy recommendation in MPBC patients.

Epithelial Ovarian Cancer and the Immune System: Biology, Interactions, Challenges and Potential Advances for Immunotherapy

Recent advances in the understanding of immune function and the interactions with tumour cells have led to the development of various cancer immunotherapies and strategies for specific cancer types. However, despite some stunning successes with some malignancies such as melanomas and lung cancer, most patients receive little or no benefit from immunotherapy, which has been attributed to the tumour microenvironment and immune evasion. Although the US Food and Drug Administration have approved immunotherapies for some cancers, to date, only the anti-angiogenic antibody bevacizumab is approved for the treatment of epithelial ovarian cancer. Immunotherapeutic strategies for ovarian cancer are still under development and being tested in numerous clinical trials. A detailed understanding of the interactions between cancer and the immune system is vital for optimisation of immunotherapies either alone or when combined with chemotherapy and other therapies. This article, in two main parts, provides an overview of: (1) components of the normal immune system and current knowledge regarding tumour immunology, biology and their interactions; (2) strategies, and targets, together with challenges and potential innovative approaches for cancer immunotherapy, with attention given to epithelial ovarian cancer.

Antibody targeting tumor-derived soluble NKG2D ligand sMIC reprograms NK cell homeostatic survival and function and enhances melanoma response to PDL1 blockade therapy

BACKGROUND

Melanoma patients who have detectable serum soluble NKG2D ligands either at the baseline or post-treatment of PD1/PDL1 blockade exhibit poor overall survival. Among families of soluble human NKG2D ligands, the soluble human MHC I chain-related molecule (sMIC) was found to be elevated in melanoma patients and mostly associated with poor response to PD1/PDL1 blockade therapy.

METHODS

In this study, we aim to investigate whether co-targeting tumor-released sMIC enhances the therapeutic outcome of PD1/PDL1 blockade therapy for melanoma. We implanted sMIC-expressing B16F10 melanoma tumors into syngeneic host and evaluated therapeutic efficacy of anti-sMIC antibody and anti-PDL1 antibody combination therapy in comparison with monotherapy. We analyzed associated effector mechanism. We also assessed sMIC/MIC prevalence in metastatic human melanoma tumors.

RESULTS

We found that the combination therapy of the anti-PDL1 antibody with an antibody targeting sMIC significantly improved animal survival as compared to monotherapies and that the effect of combination therapy depends significantly on NK cells. We show that combination therapy significantly increased IL-2Rα (CD25) on NK cells which sensitizes NK cells to low dose IL-2 for survival. We demonstrate that sMIC negatively reprograms gene expression related to NK cell homeostatic survival and proliferation and that antibody clearing sMIC reverses the effect of sMIC and reprograms NK cell for survival. We further show that sMIC/MIC is abundantly present in metastatic human melanoma tumors.

CONCLUSIONS

Our findings provide a pre-clinical proof-of-concept and a new mechanistic understanding to underscore the significance of antibody targeting sMIC to improve therapeutic efficacy of anti-PD1/PDL1 antibody for MIC/sMIC⁺ metastatic melanoma patients.

Rae1 drives NKG2D binding-dependent tumor development in mice by activating mTOR and STAT3 pathways in tumor cells

Natural killer group 2 member D (NKG2D) ligands (NKG2DLs) on tumor cells engage NKG2D and mediate killing by NKG2D⁺ immune cells. However, tumor cells with high levels of NKG2DLs are still malignant and proliferate rapidly. We investigated the reason for NKG2DL-expressing cell progression. Tumor cells in mice were assessed for their NKG2DL expression, ability to attract immune cells, tumorigenicity, mTOR, and signal transducer and activator of transcription 3 (STAT3) signaling activation. Antibody blockade was used to determine the effect of NKG2DL-NKG2D interaction on signaling activation in vitro. Retinoic acid early inducible gene 1 (Rae1) was related to the expression of other NKG2DLs, the promotion of tumorigenicity, Mmp2 expression, mTOR and STAT3 phosphorylation in GL261 cells, and the recruitment of NKG2D⁺ cells in mice. Rae1 also induced NKG2DL expression, mTOR, and STAT3 phosphorylation in GL261 cells and LLC cells, but not in B16 and Pan02 cells, which did not express NKG2DLs, when cocultured with PBMCs; the induced phosphorylation was eliminated by Rae1-NKG2D blockade. Inhibition of mTOR and/or STAT3 decreased PBMC-induced migration and proliferation of GL261 cells in vitro. Rae1, a NKG2DL on tumor cells, plays a driving role in the expression of other NKG2DLs and in tumor development in mice by activating mTOR and STAT3 pathways, relying on its interaction with NKG2D on immune cells.

The Ovarian Cancer Tumor Immune Microenvironment (TIME) as Target for Therapy: A Focus on Innate Immunity Cells as Therapeutic Effectors

Ovarian cancer (OvCA) accounts for one of the leading causes of death from gynecologic malignancy. Despite progress in therapy improvements in OvCA, most patients develop a recurrence after first-line treatments, dependent on the tumor and non-tumor complexity/heterogeneity of the neoplasm and its surrounding tumor microenvironment (TME). The TME has gained greater attention in the design of specific therapies within the new era of immunotherapy. It is now clear that the immune contexture in OvCA, here referred as tumor immune microenvironment (TIME), acts as a crucial orchestrator of OvCA progression, thus representing a necessary target for combined therapies. Currently, several advancements of antitumor immune responses in OvCA are based on the characterization of tumor-infiltrating lymphocytes, which have been shown to correlate with a significantly improved clinical outcome. Here, we reviewed the literature on selected TIME components of OvCA, such as macrophages, neutrophils, γδ T lymphocytes, and natural killer (NK) cells; these cells can have a role in either supporting or limiting OvCA, depending on the TIME stimuli. We also reviewed and discussed the major (immune)-therapeutic approaches currently employed to target and/or potentiate macrophages, neutrophils, γδ T lymphocytes, and NK cells in the OvCA context.

Papillary Thyroid Carcinoma Variants are Characterized by Co-dysregulation of Immune and Cancer Associated Genes

Papillary thyroid carcinoma (PTC) variants exhibit different prognosis, but critical characteristics of PTC variants that contribute to differences in pathogenesis are not well-known. This study aims to characterize dysregulated immune-associated and cancer-associated genes in three PTC subtypes to explore how the interplay between cancer and immune processes causes differential prognosis. RNA-sequencing data from The Cancer Genome Atlas (TCGA) were used to identify dysregulated genes in each variant. The dysregulation profiles of the subtypes were compared using functional pathways clustering and correlations to relevant clinical variables, genomic alterations, and microRNA regulation. We discovered that the dysregulation profiles of classical PTC (CPTC) and the tall cell variant (TCPTC) are similar and are distinct from that of the follicular variant (FVPTC). However, unique cancer or immune-associated genes are associated with clinical variables for each subtype. Cancer-related genes MUC1, FN1, and S100-family members were the most clinically relevant in CPTC, while APLN and IL16, both immune-related, were clinically relevant in FVPTC. RAET-family members, also immune-related, were clinically relevant in TCPTC. Collectively, our data suggest that dysregulation of both cancer and immune associated genes defines the gene expression landscapes of PTC variants, but different cancer or immune related genes may drive the phenotype of each variant.

NKG2D-ligands: Putting everything under the same umbrella can be misleading

NKG2D is a key receptor for the activation of immune effector cells, mainly Natural Killer cells and T lymphocytes, in infection, cancer and autoimmune diseases. Since the detection of ligands for NKG2D in sera of cancer patients is, in many human models, indicative of prognosis, a large number of studies have been undertaken to improve understanding of the biology regulating this receptor and its ligands, with the aim of translating this knowledge into clinical practice. Although it is becoming clear that the NKG2D system can be used as a tool for diagnosis and manipulated for therapy, some questions remain open due to the complexity associated with the existence of a large number of ligands, each one of them displaying distinct biological properties. In this review, we have highlighted some key aspects of this system that differ between humans and mice, including the properties of NKG2D, as well as the genetic and biochemical complexity of NKG2D-ligands. All of these features affect the characteristics of the immune response exerted by NKG2D-expressing cells and are likely to be important factors in the clearance of a tumour or the development of autoimmunity. Implementation of more global analyses, including information on genotype, transcription and protein properties (cellular vs released to the blood stream) of NKG2D-ligands expressed in patients will be necessary to fully understand the links between this system and disease progression.

The Paradoxical Role of NKG2D in Cancer Immunity

The activating receptor NKG2D and its ligands are recognized as a potent immune axis that controls tumor growth and microbial infections. With regards to cancer surveillance, various studies have demonstrated the antitumor function mediated by NKG2D on natural killer cells and on conventional and unconventional T cells. The use of NKG2D-deficient mice established the importance of NKG2D in delaying tumor development in transgenic mouse models of cancer. However, we recently demonstrated an unexpected, flip side to this coin, the ability for NKG2D to contribute to tumor growth in a model of inflammation-driven liver cancer. With a focus on the liver, here, we review current knowledge of NKG2D-mediated tumor surveillance and discuss evidence supporting a dual role for NKG2D in cancer immunity. We postulate that in certain advanced cancers, expression of ligands for NKG2D can drive cancer progression rather than rejection. We propose that the nature of the microenvironment within and surrounding tumors impacts the outcome of NKG2D activation. In a form of autoimmune attack, NKG2D promotes tissue damage, mostly in the inflamed tissue adjacent to the tumor, facilitating tumor progression while being ineffective at rejecting transformed cells in the tumor bed.

Decreased expression of the NKG2D ligand ULBP4 may be an indicator of poor prognosis in patients with nasopharyngeal carcinoma

U16-binding protein 4 (ULBP4), a human ligand for natural killer group 2, member D (NKG2D) receptor on NK cells and subsets of T cells, is thought to activate anticancer immune responses. However, the expression pattern and prognostic effect of ULBP4 in nasopharyngeal carcinoma (NPC) has not been investigated. We first compared ULBP4 expression between archival 15 NPC tissues and 8 normal nasopharynx (NP) tissues using qPCR. Then ULBP4 expression among 111 NPC specimens was validated on immunohistochemical examination. In addition, the association of ULBP4 expression with clinical characteristics and survival outcomes was analyzed. Furthermore, the impact of ULBP4 expression in NPC cells on the cytotoxic activity of NK cells was investigated. Both mRNA and protein ULBP4 expressions of NPC tissues were significantly lower than those in normal NP tissues. However, no association of ULBP4 expression with clinical characteristics was observed. Patients with NPC having decreased expression of UBLP4 had significantly poorer overall survival (OS), progression-free survival (PFS), and distant metastasis-free survival (DMFS) than those with preserved levels of ULBP4. On multivariate analyses, low expression of ULBP4 was of borderline significance for OS, PFS, and DMFS (P = 0.060, 0.053, and 0.076, respectively). Further, LDH analysis demonstrated that the cytotoxic activitity of NK cells against C666-1 or 5-8F NPC cells with lenti-ULBP4 was considerably increased as compared to those with lenti-vector at various E/T ratios. Hence, restoration of ULBP4 expression may be a novel therapeutic strategy for treatment of NPC. However, further study is required to confirm these findings.

Cutting an NKG2D Ligand Short: Cellular Processing of the Peculiar Human NKG2D Ligand ULBP4

Stress-induced cell surface expression of MHC class I-related glycoproteins of the MIC and ULBP families allows for immune recognition of dangerous "self cells" by human cytotoxic lymphocytes via the NKG2D receptor. With two MIC molecules (MICA and MICB) and six ULBP molecules (ULBP1-6), there are a total of eight human NKG2D ligands (NKG2DL). Since the discovery of the NKG2D-NKG2DL system, the cause for both redundancy and diversity of NKG2DL has been a major and ongoing matter of debate. NKG2DL diversity has been attributed, among others, to the selective pressure by viral immunoevasins, to diverse regulation of expression, to differential tissue expression as well as to variations in receptor interactions. Here, we critically review the current state of knowledge on the poorly studied human NKG2DL ULBP4. Summarizing available facts and previous studies, we picture ULBP4 as a peculiar ULBP family member distinct from other ULBP family members by various aspects. In addition, we provide novel experimental evidence suggesting that cellular processing gives rise to mature ULBP4 glycoproteins different to previous reports. Finally, we report on the proteolytic release of soluble ULBP4 and discuss these results in the light of known mechanisms for generation of soluble NKG2DL.

Fusion Proteins of NKG2D/NKG2DL in Cancer Immunotherapy

NKG2D (natural killer group 2, member D) is an important activating receptor in natural killer (NK) cells and some T cells. NKG2D ligands (NKG2DLs) are specifically expressed on most tumor cells. The engagement of these ligands on tumor cells to NKG2D on NK cells will induce cell-mediated cytotoxicity and have target cells destroyed. This gives NKG2D/NKG2DLs great potential in cancer therapeutic application. The creation of NKG2D/NKG2DL-based multi-functional fusion proteins is becoming one of the most promising strategies in immunotherapy for cancer. Antibodies, cytokines, and death receptors have been fused with NKG2D or its ligands to produce many powerful fusion proteins, including NKG2D-based chimeric antigen receptors (CARs). In this article, we review the recent developments of the fusion proteins with NKG2D/NKG2DL ligands in cancer immunotherapy.

Structural Analysis and Epitope Prediction of MHC Class-1-Chain Related Protein-A for Cancer Vaccine Development

Major histocompatibility complex class 1 chain-related gene sequence A is a polymorphic gene found at about 46.6 kb centromeric to HLA-B. It encodes a transmembrane protein, which is a non-classical human leukocyte antigen whose expression is normally induced by stress conditions like cancer and viral infections. The expression of MIC-A leads to the activation of NKG2D receptors of natural killer and T cells, leading to the generation of innate immune response that can easily eliminate/cleanse tumour cells and other cells that express the protein. Several bioinformatics and immunoinformatics tools were used to analyse the sequence and structure of the MIC-A protein. These tools were used in building and evaluating modelled structure of MIC-A, and to predict several antigenic determinant sites on the protein. The MIC-A protein structure generated an average antigenic propensity of 1.0289. Additionally, the hydrophilic regions on the surface of the MIC-A protein where antibodies can be attached were revealed. A total of fourteen antigenic epitopes were predicted, with six found in the transmembrane protein topology, and are predicted to play a role in the development of vaccines that can reactivate the functionalities of the MIC-A protein on the surface of cancer cells in order to elicit a desired immune response.

The immune system in cancer metastasis: friend or foe?

Metastatic disease is the leading cause of death among cancer patients and involves a complex and inefficient process. Every step of the metastatic process can be rate limiting and is influenced by non-malignant host cells interacting with the tumor cell. Over a century ago, experiments first indicated a link between the immune system and metastasis. This phenomenon, called concomitant immunity, indicates that the primary tumor induces an immune response, which may not be sufficient to destroy the primary tumor, but prevents the growth of a secondary tumor or metastases. Since that time, many different immune cells have been shown to play a role in both inhibiting and promoting metastatic disease. Here we review classic and new observations, describing the links between the immune system and metastasis that inform the development of cancer therapies.

Soluble NKG2D ligands in the ovarian cancer microenvironment are associated with an adverse clinical outcome and decreased memory effector T cells independent of NKG2D downregulation

The immune receptor NKG2D is predominantly expressed on NK cells and T cell subsets and confers anti-tumor activity. According to the current paradigm, immune surveillance is counteracted by soluble ligands shed into the microenvironment, which down-regulate NKG2D receptor expression. Here, we analyzed the clinical significance of the soluble NKG2D ligands sMICA and sULBP2 in the malignancy-associated ascites of ovarian cancer. We show that high levels of sMICA and sULBP2 in ascites were associated with a poor prognosis. Ascites inhibited the activation of normal NK cells, which, in contrast to the prevailing notion, was not associated with decreased NKG2D expression. Of note, an inverse correlation of soluble NKG2D ligands with effector memory T cells and a direct correlation with pro-tumorigenic CD163⁺CD206⁺ macrophages was observed. Thus, the role of soluble NKG2D ligands within the ovarian cancer microenvironment is more complex than anticipated and does not exclusively function via NKG2D downregulation.

Exploiting natural killer group 2D receptors for CAR T-cell therapy

Chimeric antigen receptors (CARs) are genetically engineered proteins that combine an extracellular antigen-specific recognition domain with one or several intracellular T-cell signaling domains. When expressed in T cells, these CARs specifically trigger T-cell activation upon antigen recognition. While the clinical proof of principle of CAR T-cell therapy has been established in hematological cancers, CAR T cells are only at the early stages of being explored to tackle solid cancers. This special report discusses the concept of exploiting natural killer cell receptors as an approach that could broaden the specificity of CAR T cells and potentially enhance the efficacy of this therapy against solid tumors. New data demonstrating feasibility of this approach in humans and supporting the ongoing clinical trial are also presented.

STAT3 inhibition by STA21 increases cell surface expression of MICB and the release of soluble MICB by gastric adenocarcinoma cells

NKG2D is an activating receptor expressed on NK cells that binds to a variety of ligands, including MICA and MICB. These cell surface glycoproteins are overexpressed under cellular transformation, thus playing an important role in cell-mediated immune response to tumors. STAT3 is a transcription factor that is constitutively active in cancer. It negatively regulates MICA expression on target cells, while its inhibition enhances NK cell cytotoxicity against tumors. In this work, we aimed to describe the effect of STAT3 signaling inhibition by STA21 on the regulation of MICB expression in gastric adenocarcinoma cells and its effect on the cytotoxic function of NK cells. Treatment of gastric adenocarcinoma cells with STA21 induced an increase in MICB expression and soluble MICB secretion, as well as a variable pattern on effector cell degranulation. Soluble MICB secretion by gastric adenocarcinoma cells was not affected by metalloprotease inhibition. We also observed that primary gastric adenocarcinoma tissue released soluble MICB into the extracellular milieu. Recombinant MICB induced a significant decrease in the levels of NKG2D receptor on effector NK and CD8+ T cells, which correlated with an impaired cytotoxic function. Altogether, our data provide evidence that STAT3 signaling pathway regulates MICB expression on gastric adenocarcinoma cells and that recombinant soluble MICB compromises the cytolytic activity of NK cells.

Control of Tumor Initiation by NKG2D Naturally Expressed on Ovarian Cancer Cells

Cancer cells may co-opt the NKG2D lymphocyte receptor to complement the presence of its ligands for autonomous stimulation of oncogenic signaling. Previous studies raise the possibility that cancer cell NKG2D may induce high malignancy traits, but its full oncogenic impact is unknown. Using epithelial ovarian cancer as model setting, we show here that ex vivo NKG2D⁺ cancer cells have stem-like capacities, and provide formal in vivo evidence linking NKG2D stimulation with the development and maintenance of these functional states. NKG2D⁺ ovarian cancer cell populations harbor substantially greater capacities for self-renewing in vitro sphere formation and in vivo tumor initiation in immunodeficient (NOD scid gamma) mice than NKG2D⁻ controls. Sphere formation and tumor initiation are impaired by NKG2D silencing or ligand blockade using antibodies or a newly designed pan ligand-masking NKG2D multimer. In further support of pathophysiological significance, a prospective study of 47 high-grade serous ovarian cancer cases revealed that the odds of disease recurrence were significantly greater and median progression-free survival rates higher among patients with above and below median NKG2D⁺ cancer cell frequencies, respectively. Collectively, our results define cancer cell NKG2D as an important regulator of tumor initiation in ovarian cancer and presumably other malignancies and thus challenge current efforts in immunotherapy aimed at enhancing NKG2D function.

Phenotypic characterization and anticancer capacity of CD8+ cytokine-induced killer cells after antigen-induced expansion

Cytokine-induced killer cells (CIK) have been used in clinic for adoptive immunotherapy in a variety of malignant tumors and have improved the prognosis of cancer patients. However, there are individual differences in the CIK cell preparations including the obvious differences in the ratio of effector CIK cells among different cancer patients. Infusion of such heterogeneous immune cell preparation is an important factor that would affect the therapeutic efficacy. We report here the enrichment and expansion of CD8+ cells from CIK cells cultured for one week using magnetic activated cell sorting (MACS). These enriched CD8+ CIK cells expressed T cell marker CD3 and antigen recognition receptor NKG2D. Phenotypic analysis showed that CD8+ CIK cells contained 32.4% of CD3+ CD56+ natural killer (NK)-like T cells, 23.6% of CD45RO+ CD28+, and 50.5% of CD45RA+ CD27+ memory T cells. In vitro cytotoxic activity assay demonstrated that the enriched CD8+ CIK cells had significant cytotoxic activity against K562 cells and five ovarian cancer cell lines. Intriguingly, CD8+ CIK cells had strong cytotoxic activity against OVCAR3 cells that has weak binding capability to NKG2D. Flow cytometry and quantitative RT-PCR analysis revealed that OVCAR3 cells expressed HLA-I and OCT4 and Sox2, suggesting that CD8+ CIK cells recognize surface antigen via specific T cell receptor and effectively kill the target cells. The results suggest that transplantation of such in vitro enriched and expanded OCT4-specific CD8+ CIK cells may improve the specific immune defense mechanism against cancer stem cells, providing a novel avenue of cancer stem cell targeted immunotherapy for clinical treatment of ovarian cancer.

Implication of combined PD-L1/PD-1 blockade with cytokine-induced killer cells as a synergistic immunotherapy for gastrointestinal cancer

Cytokine-induced killer (CIK) cells represent a realistic approach in cancer immunotherapy with confirmed survival benefits in the context of metastatic solid tumors. However, therapeutic effects are limited to a fraction of patients. In this study, immune-resistance elements and ideal combination therapies were explored. Initially, phenotypic analysis was performed to document CD3, CD56, NKG2D, DNAM-1, PD-L1, PD-1, CTLA-4, TIM-3, 2B4, and LAG-3 on CIK cells. Upon engagement of CIK cells with the tumor cells, expression of PD-1 on CIK cells and PD-L1 on both cells were up-regulated. Over-expression of PD-L1 levels on tumor cells via lentiviral transduction inhibited tumoricidal activity of CIK cells, and neutralizing of PD-L1/PD-1 signaling axis could enhance their tumor-killing effect. Conversely, blockade of NKG2D, a major activating receptor of CIK cells, largely caused dysfunction of CIK cells. Functional study showed an increase of NKG2D levels along with PD-L1/PD-1 blockade in the presence of other immune effector molecule secretion. Additionally, combined therapy of CIK infusion and PD-L1/PD-1 blockade caused a delay of in vivo tumor growth and exhibited a survival advantage over untreated mice. These results provide a preclinical proof-of-concept for simultaneous PD-L1/PD-1 pathways blockade along with CIK infusion as a novel immunotherapy for unresectable cancers.

Altered Expression of Natural Cytotoxicity Receptors and NKG2D on Peripheral Blood NK Cell Subsets in Breast Cancer Patients

Human natural killer (NK) cells are considered professional cytotoxic cells that are integrated into the effector branch of innate immunity during antiviral and antitumoral responses. The purpose of this study was to examine the peripheral distribution and expression of NK cell activation receptors from the fresh peripheral blood mononuclear cells of 30 breast cancer patients prior to any form of treatment (including surgery, chemotherapy, and radiotherapy), 10 benign breast pathology patients, and 24 control individuals. CD3⁻CD56^dimCD16^bright NK cells (CD56^dim NK) and CD3⁻CD56^brightCD16^dim/− NK cells (CD56^bright NK) were identified using flow cytometry. The circulating counts of CD56^dim and CD56^bright NK cells were not significantly different between the groups evaluated, nor were the counts of other leukocyte subsets between the breast cancer patients and benign breast pathology patients. However, in CD56^dim NK cells, NKp44 expression was higher in breast cancer patients (P = .0302), whereas NKp30 (P = .0005), NKp46 (P = .0298), and NKG2D (P = .0005) expression was lower with respect to healthy donors. In CD56^bright NK cells, NKp30 (P = .0007), NKp46 (P = .0012), and NKG2D (P = .0069) expression was lower in breast cancer patients compared with control group. Only NKG2D in CD56^bright NK cells (P = .0208) and CD56^dim NK cells (P = .0439) showed difference between benign breast pathology and breast cancer patients. Collectively, the current study showed phenotypic alterations in activation receptors on CD56^dim and CD56^bright NK cells, suggesting that breast cancer patients have decreased NK cell cytotoxicity.

Expression and prognostic significance of unique ULBPs in pancreatic cancer

Background

Pancreatic cancer is one of the most lethal cancers worldwide, due to the lack of efficient therapy and difficulty in early diagnosis. ULBPs have been shown to behave as important protectors with prognostic significance in various cancers.

Materials and methods

Immunohistochemistry and enzyme-linked immunosorbent assays were used to explore the expression of ULBPs in cancer tissue and in serum, while survival analysis was used to evaluate the subsequent clinical value of ULBPs.

Results

Statistics showed that high expression of membrane ULBP1 was a good biomarker of overall survival (18 months vs 13 months), and a high level of soluble ULBP2 was deemed an independent poor indicator for both overall survival (P<0.001) and disease-free survival (P<0.001).

Conclusion

ULBP1 provides additional information for early diagnosis, and soluble ULBP2 can be used as a novel tumor marker to evaluate the risk of pancreatic cancer patients.

Genetics, genomics, and evolutionary biology of NKG2D ligands

Human and mouse NKG2D ligands (NKG2DLs) are absent or only poorly expressed by most normal cells but are upregulated by cell stress, hence, alerting the immune system in case of malignancy or infection. Although these ligands are numerous and highly variable (at genetic, genomic, structural, and biochemical levels), they all belong to the major histocompatibility complex class I gene superfamily and bind to a single, invariant, receptor: NKG2D. NKG2D (CD314) is an activating receptor expressed on NK cells and subsets of T cells that have a key role in the recognition and lysis of infected and tumor cells. Here, we review the molecular diversity of NKG2DLs, discuss the increasing appreciation of their roles in a variety of medical conditions, and propose several explanations for the evolutionary force(s) that seem to drive the multiplicity and diversity of NKG2DLs while maintaining their interaction with a single invariant receptor.

Adoptive immunotherapy against ovarian cancer

The standard front-line therapy for epithelial ovarian cancer (EOC) is combination of debulking surgery and platinum-based chemotherapy. Nevertheless, the majority of patients experience disease recurrence. Although extensive efforts to find new therapeutic options, cancer cells invariably develop drug resistance and disease progression. New therapeutic strategies are needed to improve prognosis of patients with advanced EOC.

Recently, several preclinical and clinical studies investigated feasibility and activity of adoptive immunotherapy in EOC. Our aim is to highlight prospective of adoptive immunotherapy in EOC, focusing on HLA-restricted Tumor Infiltrating Lymphocytes (TILs), and MHC-independent immune effectors such as natural killer (NK), and cytokine-induced killer (CIK). Adoptive cell therapy (ACT) has shown activity in several pre-clinical models. Available preclinical and clinical data suggest that adoptive cell therapy may provide the best benefit in settings of low tumor burden, minimal residual disease, or maintenance therapy. Further studies are needed to better define the optimal clinical setting.

Overexpression of natural killer group 2 member D ligands predicts favorable prognosis in cholangiocarcinoma

The natural killer group 2 member D (NKG2D) receptor and its ligands are important mediators of immune responses to tumors. NKG2D ligands are overexpressed in several malignant tumor types; however, the prognostic value of these ligands is unclear. Here, we aimed to elucidate the role of NKG2D ligands in extrahepatic cholangiocarcinoma (EHCC). We therefore investigated the expression of the NKG2D receptor and its ligands MHC class I chain-related proteins A and B (MICA/B), unique long 16 binding protein (ULBP) 1, and ULBP2/5/6 in resected specimens from 82 patients with EHCC. All NKG2D ligands were highly expressed in EHCC. High expression of MICA/B or ULBP2/5/6 correlated with overall and disease-free survival. In contrast, high expression of ULBP1 was significantly associated with improved overall survival, but not disease-free survival. Concurrent high expression of multiple NKG2D ligands revealed significantly better overall and disease-free survival than that observed with the overexpression of any one NKG2D ligand. Co-expression of multiple NKG2D ligands was an independent prognostic indicator of improved survival. Furthermore, co-overexpression of multiple NKG2D ligands was significantly correlated with high expression of the NKG2D receptor. Inhibiting interactions between multiple NKG2D ligands and the NKG2D receptor might be a promising approach for controlling cancer progression and improving patient prognosis in EHCC.

Clinical significance of tumor expression of major histocompatibility complex class I-related chains A and B (MICA/B) in gastric cancer patients

Gastric cancer (GC) is the third most common cause of cancer death worldwide. Natural killer cells play an important role in the immune defense against transformed cells. They express the activating receptor NKG2D, whose ligands belong to the MIC and ULBP/RAET family. Although it is well established that these ligands are generally expressed in tumors, the association between their expression in the tumor and gastric mucosa and clinical parameters and prognosis of GC remains to be addressed. In the present study, MICA and MICB expression was analyzed, by flow cytometry, in 23 and 20 pairs of gastric tumor and adjacent non-neoplasic gastric mucosa, respectively. Additionally, ligands expression in 13 tumors and 7 gastric mucosa samples from GC patients were evaluated by immunohistochemistry. The mRNA levels of MICA in 9 pairs of tumor and mucosa were determined by quantitative PCR. Data were associated with the clinicopathological characteristics and the patient outcome. MICA expression was observed in 57% of tumors (13/23) and 44% of mucosal samples (10/23), while MICB was detected in 50% of tumors (10/20) and 45% of mucosal tissues (9/20). At the protein level, ligand expression was significantly higher in the tumor than in the gastric mucosa. MICA mRNA levels were also increased in the tumor as compared to the mucosa. However, clinicopathological analysis indicated that, in patients with tumors >5 cm, the expression of MICA and MICB in the tumor did not differ from that of the mucosa, and tumors >5 cm showed significantly higher MICA and MICB expression than tumors ≤5 cm. Patients presenting tumors >5 cm that expressed MICA and MICB had substantially shorter survival than those with large tumors that did not express these ligands. Our results suggest that locally sustained expression of MICA and MICB in the tumor may contribute to the malignant progression of GC and that expression of these ligands predicts an unfavorable prognosis in GC patients presenting large tumors.

Abnormal expression levels of sMICA and NKG2D are correlated with poor prognosis in pancreatic cancer

Soluble major histocompatibility complex class I-related chain A molecules (sMICA) and natural-killer group 2 member D (NKG2D) not only correlate with tumorigenesis and progression, but also with tumor invasion and metastasis. In this study, we used immunohistochemistry to investigate the correlation and prognostic significance of the differential expression of sMICA and NKG2D in pancreatic carcinoma and paracarcinoma tissues from 70 patients with pancreatic carcinomas. The results showed that sMICA expression was significantly (P<0.05) higher in tumor tissues (67.1%) than that in adjacent nontumor tissues (31.4%), whereas NKG2D expression was significantly (P<0.001) lower in tumor tissues (32.9%) than that in adjacent nontumor tissues (60.0%). Spearman’s rank correlation test showed a negative correlation between the expression of sMICA and that of NKG2D (r=−0.676, P<0.001). Kaplan–Meier survival analysis showed that a high sMICA expression was significantly correlated with decreased disease-free survival (DFS) (P<0.001) and overall survival (OS) (P<0.001), while a high NKG2D expression was significantly associated with increased DFS (P=0.001) and OS (P=0.001) of the patients. Multivariate analysis showed that a high sMICA expression was an independent predictive factor for poor DFS (P<0.001) and OS (P=0.012); but low NKG2D expression was not an independent prognostic factor for poor DFS (P=0.238) and OS (P=0.574). In conclusion, our findings suggest that the expression levels of sMICA and NKG2D are abnormal and negatively correlated with one another in pancreatic carcinoma tissues; they may be considered as valuable biomarkers for the prognosis of pancreatic carcinoma.

Characterization of 5' promoter and exon 1-3 polymorphism of the RAET1E gene

NKG2D is an activating receptor utilized by natural killer (NK) cells that recognizes upregulated ligands on infected, tumorigenic and damaged cells, leading to their cytolysis. However, the NKG2D ligand (NKG2DL) system is very complex with eight known gene loci encoding slightly different molecules. Furthermore, most NKG2DL gene loci such as MICA and MICB are highly polymorphic with potential for functional differences. NKG2DL expression on tumors varies depending on the malignancy and tumors can also release soluble NKG2DL that exert anergic effects on NK cells when engagement with NKG2D occurs, allowing escape from NK cell immunosurveillance. We carried out RAET1E typing of IHW cell line DNA, including a 580 bp proximal promoter fragment and exons 1-3 identifying 13 of 15 known RAET1E alleles. We determined 7 polymorphisms within the promoter region, including 2 already known that contributed to 9 promoter types. RAET1E alleles with variability in the extracellular region also differed with respect to promoter type and one allele, RAET1E(∗)003, associated with 5 promoter types. We then identified putative transcription factor binding sites for RAET1E, and found 5 of the 7 promoter polymorphisms may disrupt these sites, abrogating binding of transcription factors and varying the potential level of expression.

MTA2 enhances colony formation and tumor growth of gastric cancer cells through IL-11

Background

We have preliminarily reported MTA2 expression in gastric cancer and its biological functions by using knockdown cell models, while the molecular mechanisms of MTA2 in regulating malignant behaviors are still unclear.

Methods

MTA2 overexpression models were established by transfection assay in gastric cancer cells BGC-823 and MKN28. Cell proliferation assay, colony formation in soft agar, wound-healing assay and transwell migration assay were performed with MTA2 overexpression and negative control (NC) cells. Subcutaneous xenografts and pulmonary metastasis models by BGC-823/MTA2 and BGC-823/NC cells were used to observe the capacity of growth and metastasis in vivo. Differential gene expression in MTA2 knockdown and overexpression cells was analyzed by microarrays. IL-11, which demonstrated as differential expression in microarray, was detected by real-time PCR, western blot, ELISA and immunohistochemistry staining. Recombinant human IL-11 (rhIL-11) was administrated in cell proliferation and colony formation as rescue assay.

Results

The numbers of colonies in soft agar were significantly more in BGC-823/MTA2 and MKN28/MTA2 cells, comparing with those in their NC cells. Capabilities of cell proliferation, wound-healing and cell migration were not significantly changed in MTA2 overexpression cells. The sizes of subcutaneous xenografts and pulmonary metastases of BGC-832/MTA2 cells were significantly larger than those in BGC-823/NC group. Differential expression of IL-11 was identified by genome expression microarray both in MTA2 knockdown and overexpression cells. IL-11 expression was elevated in BGC-823/MTA2 cells, whereas reduced in SGC-7901/shMTA2 cells. Administration of rhIL-11 recovered colony formation capacity of SGC-7901/shMTA2 cells.

Conclusions

MTA2 overexpression enhances colony formation and tumor growth of gastric cancer cells, but not plays important role in cancer cell migration and metastasis. IL-11 is one of the downstream effectors of MTA2 in regulating gastric cancer cells growth.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1366-y) contains supplementary material, which is available to authorized users.

NKG2D Ligands in Tumor Immunity: Two Sides of a Coin

The activating/co-stimulatory receptor NKG2D (natural-killer group 2, member D) is expressed on the surface of all human NK, NKT, CD8(+) T, and subsets of γδ(+) T cells. The significance of NKG2D function in tumor immunity has been well demonstrated in experimental animal models. However, the role of human NKG2D ligands in regulating tumor immunity and cancer prognosis had been controversial in the literature. In this review, we summarize the latest advancement, discuss the controversies, and present evidence that membrane-bound and soluble NKG2D ligands oppositely regulate tumor immunity. We also discuss new perspectives of targeting NKG2D ligands for cancer immunotherapy.

MICA/B and ULBP1 NKG2D ligands are independent predictors of good prognosis in cervical cancer

BACKGROUND

NKG2D (natural killer group 2, member D) is thought to play an important role in mediating the activation of anticancer immune response. Expression of NKG2D ligands (NKG2DLs) is pronounced in malignancies and the heterogeneity of NKG2DL expression remains unclear. Here, we investigate the expression and clinical significance of NKG2DLs in cervical cancer.

METHODS

Immunohistochemical analyses of MICA/B, ULBP1, ULBP2, ULBP3, RAET1E, and RAET1G were performed using tissue microarray analysis of 200 cervical cancers, 327 high-grade cervical intraepithelial neoplasias (CINs), 99 low-grade CINs, and 541 matched nonadjacent normal cervical epithelial tissues and compared the data with clinicopathologic variables, including the survival of cervical cancer patients.

RESULTS

MICA/B, ULBP1, and RAET1E expression was higher in cervical cancer than in low-grade CIN (p<0.001, p=0.012, p=0.013, respectively) and normal cervix (all p<0.001). Among these markers, expression of ULBP1 was significantly different depending on patient tumor stage (p=0.010) and tumor size (p=0.045). ULBP1 expression was correlated with MICA/B (p<0.001) and ULBP2 (p=0.002) expression in cervical cancer. While MICA/B+ or ULBP1+ patients had improved disease-free survival time (p=0.027 and p=0.009, respectively) relative to that of the low expression group, RAET1E+ or RAET1G+ was correlated with shorter survival time (p=0.018 and p=0.029, respectively). However, in terms of overall survival, the ULBP1+ group had significantly longer survival time than the low expression group (p=0.009). Multivariate analysis indicated that MICA/B+/ULBP1+ (HR=0.16, p=0.015) and ULBP1+ (HR=0.31, p=0.024) are independent prognostic factors of disease-free survival in cervical cancer.

CONCLUSIONS

High expression of either ULBP1 or MICA/B and ULBP1 combined is an indicator of good prognosis in cervical cancer, suggesting their potential utility as prognostic tests in clinical assessment.