MICA/B expression is inhibited by unfolded protein response and associated with poor prognosis in human hepatocellular carcinoma

Molecular profiling in the management of hepatocellular carcinoma

PURPOSE OF REVIEW

The purpose of this review is to both summarize the current knowledge of hepatocellular carcinoma molecular biology and to suggest a framework in which to prospectively translate this knowledge into patient care. This is timely as recent guidelines recommend increased use of these technologies to advance personalized liver cancer care.

RECENT FINDINGS

The main themes covered here address germline and somatic genetic alterations recently discovered in hepatocellular carcinoma, largely owing to next generation sequencing technologies, and nascent efforts to translate these into contemporary practice.

SUMMARY

Early efforts of translating molecular profiling to hepatocellular carcinoma care demonstrate a growing number of potentially actionable alterations. Still lacking are a consensus on what biomarkers and technologies to adopt, at what scale and cost, and how to integrate them most effectively into care.

Establishment and verification of a prognostic risk score model based on immune genes for hepatocellular carcinoma in an Asian population

Background

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide, with the highest incidence in East Asia, and hepatitis B virus (HBV) infection is the most common cause of HCC in Asian population. The immune system is closely related to the development of HCC and plays an important role in the treatment of this disease. In this study, we analyzed the data of HCC from The Cancer Genome Atlas (TCGA) database and constructed a risk-score prognostic model based on immune genes of an Asian HCC population, aiming to provide new perspectives for clinical treatment and management of HCC in Asian population.

Methods

Data concerning clinical attributes and transcriptomic profiles of individuals in the Asian population diagnosed with HCC were retrieved from the TCGA database. Concurrently, immune-related genes were sourced from the Immport database for incorporation into our analysis. A total of 265 immune-related genes displaying differential expression were identified through wilcoxTest analysis in R. Further refinement using univariate and multivariate Cox regression analysis led to the identification of 15 genes that exhibited strong associations with prognosis. MICB/PSMD14/TRAF3/SP1/NDRG1/HDAC1/HRAS/NRAS/SEMA5B/GMFB/ACVR2B/BRD8/MMP12/KITLG/DCK, and a prognostic risk score model was constructed based on the above genes.

Results

The findings demonstrated notable differences in survival rates between the low-risk and high-risk groups, as depicted by the Kaplan-Meier (K-M) survival curves (P<0.001). Furthermore, the model's predictive capability was evidenced by receiver operating characteristic (ROC) curves, with area under the curve (AUC) =0.901. Finally, the relationship of the model with each clinical trait and immune cells was assessed by correlation analysis.

Conclusions

The prognostic risk score model constructed by immune genes based on the Asian HCC population has certain predictive capacity.

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.

A signature based on NKG2D ligands to predict the recurrence of hepatocellular carcinoma after radical resection

INTRODUCTION

Due to the high recurrence, the HCC prognosis remains poor. Yet, the biomarkers for predicting the recurrence of high-risk patients are currently lacking. We aimed to develop a signature to predict the recurrence of HCC based on NKG2D ligands.

METHODS

The multivariate Cox proportional hazards regression was used to select recurrence-related variables of NKG2D ligands in HCC patients from The Cancer Genome Atlas (TCGA). HCC patients from the OEP000321 dataset and Guilin cohort were used to validate the predictive signature. The mRNA expression of NKG2D ligands was measured by QRT-PCR. Immunohistochemistry analysis of HCC tissue microarray samples was used to identify the expression of NKG2D ligands.

RESULTS

In this study, NKG2D ligands expression in the mRNA and protein level was both abnormally expressed in HCC and associated with recurrence-free survival (RFS). Then, the recurrence-related variables of NKG2D ligands in HCC were selected by the multivariate Cox proportional hazards regression. Among the eight NKG2D ligands, MICA (HR = 1.347; 95% CI = 1.012-1.793; p = 0.041), ULBP3 (HR = 0.453; 95% CI = 0.231-0.889; p = 0.021) and ULBP5 (HR = 3.617; 95% CI = 1.819-7.194; p < 0.001) were significantly correlated with RFS in the TCGA-LIHC cohort. Then, the signature was constructed by the three NKG2D ligands. The predictive effectiveness of this signature was also validated in the OEP000321 dataset and Guilin cohort. Further, HCC patients were classified into low-risk and high-risk subgroups by the predictive score. Compared with the low-risk group, the high-risk group had poor RFS in both training and validation cohorts. Importantly, compared with the low-risk patients with the G1-G2 stage, the levels of infiltrated NK-activated cells and NKG2D expression were both lower in the high-risk patients.

CONCLUSIONS

The signature based on MICA, ULBP3, and ULBP5 could predict HCC recurrence.

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.

Overcoming the therapeutic resistance of hepatomas by targeting the tumor microenvironment

Hepatocellular carcinoma (HCC) accounts for the majority of primary liver cancers and is the third leading cause of cancer-related mortality worldwide. Multifactorial drug resistance is regarded as the major cause of treatment failure in HCC. Accumulating evidence shows that the constituents of the tumor microenvironment (TME), including cancer-associated fibroblasts, tumor vasculature, immune cells, physical factors, cytokines, and exosomes may explain the therapeutic resistance mechanisms in HCC. In recent years, anti-angiogenic drugs and immune checkpoint inhibitors have shown satisfactory results in HCC patients. However, due to enhanced communication between the tumor and TME, the effect of heterogeneity of the microenvironment on therapeutic resistance is particularly complicated, which suggests a more challenging research direction. In addition, it has been reported that the three-dimensional (3D) organoid model derived from patient biopsies is more intuitive to fully understand the role of the TME in acquired resistance. Therefore, in this review, we have focused not only on the mechanisms and targets of therapeutic resistance related to the contents of the TME in HCC but also provide a comprehensive description of 3D models and how they contribute to the exploration of HCC therapies.

Expressional regulation of NKG2DLs is associated with the tumor development and shortened overall survival in lung adenocarcinoma

Natural killer group 2D ligands (NKG2DLs) are expressed on tumor cells as a ligand for Natural killer group 2D (NKG2D) receptors. NKG2DLs interact with NKG2D to induce immune cell-mediated cytotoxicity for eliminating tumors. Studies demonstrated that tumor cells can reduce NKG2DLs' expression to escape from anti-tumor immunity, leading to an aggressive cancer phenotype and poor prognosis in some cancers. However, these studies are limited and there is no comprehensive work on the regulation of NKG2DLs in lung adenocarcinoma (LUAD) which is one of the deadliest cancers worldwide. Here, we conducted an in silico analysis to evaluate the changes in NKG2DLs in LUAD by analyzing The Cancer Genome Atlas and the Gene Expression Omnibus datasets including tumor vs. normal comparisons, TNM stages, survival and infiltrating immune estimation profile. Results indicated that some members of NKG2DL were downregulated in LUAD as compared to normal samples. We determined that MICA (MHC class I polypeptide-related sequence A) was the most and significantly downregulated ligand among others and the results were nearly consistent with the different datasets which we used. Furthermore, survival analysis revealed that down-regulated MICA transcript expression might be one of the prognostic indicators of LUAD. Interestingly, according to the immune cell infiltrating analysis, there wasn't a direct correlation between the MICA transcript expression and immune cell infiltration, while for MICB there was. In addition, in genetic alteration, DNA methylation and miRNA analyses, we did not observe critical outcomes that would clarify the down-regulated MICA expression in detail. Regardless, this study is highly comprehensive and contributes valuable suggestions to further functional studies about the regulation of NKG2DLs and promising immunotherapeutic approaches in LUAD.

The Prognostic Value of Natural Killer Cells and Their Receptors/Ligands in Hepatocellular Carcinoma: A Systematic Review and Meta-Analysis

Background

Natural killer (NK) cells play major roles in eliminating tumor cells. Preliminary studies have shown that NK cells and their receptors/ligands have prognostic value in malignant tumors. However, the relevance of NK cells and their receptors/ligands level to the prognosis of hepatocellular carcinoma (HCC) remains unclear.

Methods

Several electronic databases were searched from database inception to November 8, 2021. Random effects were introduced to this meta-analysis. The relevance of NK cells and their receptors/ligands level to the prognosis of HCC was evaluated using hazard ratios (HRs) with 95% confidence interval (95%CI).

Results

26 studies were included in the analysis. The pooled results showed that high NK cells levels were associated with better overall survival (HR=0.70, 95%CI 0.57–0.86, P=0.001) and disease-free survival (HR=0.61, 95%CI 0.40-0.93, P=0.022) of HCC patients. In subgroup analysis for overall survival, CD57⁺ NK cells (HR=0.70, 95%CI 0.55-0.89, P=0.004) had better prognostic value over CD56⁺ NK cells (HR=0.69, 95%CI 0.38-1.25, P=0.224), and intratumor NK cells had better prognostic value (HR=0.71, 95%CI 0.55-0.90, P=0.005) over peripheral NK cells (HR=0.66, 95%CI 0.41-1.06, P=0.088). In addition, high level of NK cell inhibitory receptors predicted increased recurrence of HCC, while the prognostic role of NK cell activating receptors remained unclear.

Conclusion

NK cells and their inhibitory receptors have prognostic value for HCC. The prognostic role of NK cell activating receptors is unclear and more high-quality prospective studies are essential to evaluate the prognostic value of NK cells and their receptors/ligands for HCC.

Genetic Susceptibility to Enteric Fever in Experimentally Challenged Human Volunteers

Infections with Salmonella enterica serovars Typhi and Paratyphi A cause an estimated 14 million cases of enteric fever annually. Here, the controlled nature of challenge studies is exploited to identify genetic variants associated with enteric fever susceptibility. Human challenge participants were genotyped by Illumina OmniExpress-24 BeadChip array (n = 176) and/or transcriptionally profiled by RNA sequencing (n = 174). While the study was underpowered to detect any single nucleotide polymorphisms (SNPs) significant at the whole-genome level, two SNPs within CAPN14 and MIATNB were identified with P < 10-5 for association with development of symptoms or bacteremia following oral S. Typhi or S. Paratyphi A challenge. Imputation of classical human leukocyte antigen (HLA) types from genomic and transcriptomic data identified HLA-B*27:05, previously associated with nontyphoidal Salmonella-induced reactive arthritis, as the HLA type most strongly associated with enteric fever susceptibility (P = 0.011). Gene sets relating to the unfolded protein response/heat shock and endoplasmic reticulum-associated protein degradation were overrepresented in HLA-B*27:05+ participants following challenge. Furthermore, intracellular replication of S. Typhi is higher in C1R cells transfected with HLA-B*27:05 (P = 0.02). These data suggest that activation of the unfolded protein response by HLA-B*27:05 misfolding may create an intracellular environment conducive to S. Typhi replication, increasing susceptibility to enteric fever.

EZH2, a prominent orchestrator of genetic and epigenetic regulation of solid tumor microenvironment and immunotherapy

Immune checkpoint blockade (ICB) is regarded as a promising strategy for cancer therapy. The histone methyltransferase, Enhancer of Zeste Homolog 2 (EZH2), has been implicated in the carcinogenesis of numerous solid tumors. However, the underlying mechanism of EZH2 in cancer immunotherapeutic resistance remains unknown. EZH2 orchestrates the regulation of the innate and adaptive immune systems of the tumor microenvironment (TME). Profound epigenetic and transcriptomic changes induced by EZH2 in tumor cells and immune cells mobilize the elements of the TME, leading to immune-suppressive activity of solid tumors. In this review, we summarized the dynamic functions of EZH2 on the different components of the TME, including tumor cells, T cells, macrophages, natural killer cells, myeloid-derived suppressor cells, dendritic cells, fibroblasts, and mesenchymal stem cells. Several ongoing anti-tumor clinical trials using EZH2 inhibitors have also been included as translational perspectives. In conclusion, based combinational therapy to enable ICB could offer a survival benefit in patients with cancer.

Recent updates on chimeric antigen receptor T cell therapy for hepatocellular carcinoma

Chimeric antigen receptor T cell (CAR-T) therapy is novel tumor immunotherapy that enables T cells to specifically recognize tumor-associated antigens through genetic engineering technology, thus exerting antitumor effects, and it has achieved encouraging outcomes in leukemia and lymphoma. Building on excellent progress, CAR-T therapy is also expected to work well in solid tumors. Hepatocellular carcinoma (HCC), the most common primary liver cancer, is usually diagnosed at an advanced stage. Current management options for HCC remain limited, and although previous studies have indicated the feasibility of CAR-T cells, ideal therapeutic effects have not yet been achieved. This is, in part, due to the heterogeneity of tumor antigens, high intratumor pressure, immunosuppressive microenvironment, CAR-T cell exhaustion, and serious adverse reactions, which compromise the therapeutic efficiency of CAR-T immunotherapy in HCC. To overcoming these challenges, many ongoing preclinical and clinical studies were conducted. This review summarizes current CAR-T therapy targets in the treatment of HCC, discusses current obstacles and possible solutions in the process, and describes potential strategies to improve the efficacy of CAR-T cells for patients with HCC.

Bufalin enhances the killing efficacy of NK cells against hepatocellular carcinoma by inhibiting MICA shedding

Bufalin, as a Chinese traditional anti-tumor agent, has been studied about inhibiting proliferation and promoting apoptosis of liver cancer, however, there are few reports on immune modulating function. We used the human liver cancer cell lines along with 91 pathologically-verified postoperative hepatocellular carcinoma (HCC) specimens to assess immune modulating function of bufalin. We found that bufalin directly balances stimulatory and inhibitory receptors on the surface of NK cells and indirectly activates natural killer (NK) cells by inhibiting MICA shedding, which prevented immune escape and indirectly enhanced NKG2D-dependent immune surveillance. This study showed that bufalin can directly or indirectly regulate the immune response, which provides a new theoretical basis for the clinical application of "Huachansu injection".

A Co-Expression Network Reveals the Potential Regulatory Mechanism of lncRNAs in Relapsed Hepatocellular Carcinoma

Background

The mechanistic basis for relapsed hepatocellular carcinoma (HCC) remains poorly understood. Recent research has highlighted the important roles of long non-coding RNAs (lncRNAs) in HCC. However, there are only a few studies on the association between lncRNAs and HCC relapse.

Methods

Differentially expressed lncRNAs and mRNAs between a primary HCC group and relapsed HCC group were identified using the edge R package to analyze the GSE101432 dataset. The differentially expressed lncRNAs and mRNAs were used to construct a lncRNA–mRNA co-expression network. Weighted gene co-expression network analysis followed by Gene Ontology (GO) enrichment analyses were conducted on the database. Furthermore, correlation and survival analyses were performed using The Cancer Genome Atlas database, and expression in the clinical samples was verified by qRT-PCR. Thereafter, we inputted the genes from the two groups into the HCC TNM stage and tumor grade database from TCGA. Finally, we performed Kaplan–Meier survival analysis on the lncRNAs related to relapsed HCC.

Results

In this study, lncRNAs and mRNAs associated with HCC relapse were identified. Two gene modules were found to be closely linked to this. The GO terms in the yellow and black modules were related to cell proliferation, differentiation, and survival, as well as some transcription-related biological processes. Through qRT-PCR, we found that the expression levels of LINC00941 and LINC00668 in relapsed HCC were higher than those in primary HCC. Further, mRNA levels of LOX, OTX1, MICB, NDUFA4L2, BAIAP2L2, and KCTD17 were changed in relapsed HCC compared to levels in primary HCC. In addition, we verified that these genes could predict the overall survival and recurrence-free survival of HCC. Moreover, we found that LINC00668 and LINC00941 could affect tumor grade and TNM stages. In total, we identified and validated two lncRNAs (LINC00941 and LINC00668) and six mRNAs (LOX, MICB, OTX1, BAIAP2L2, KCTD17, NDUFA4L2) associated with HCC relapse.

Conclusion

In summary, we identified the key gene modules and central genes associated with relapsed HCC and constructed lncRNA–mRNA networks related to this. These genes are likely to have potential prognostic value for relapsed HCC and might shed new light on novel biomarkers or diagnostic targets for relapsed HCC.

Natural Killer Cells and Type 1 Innate Lymphoid Cells in Hepatocellular Carcinoma: Current Knowledge and Future Perspectives

Natural killer (NK) cells and type 1 innate lymphoid cells (ILC1) are specific innate lymphoid cell subsets that are key for the detection and elimination of pathogens and cancer cells. In liver, while they share a number of characteristics, they differ in many features. These include their developmental pathways, tissue distribution, phenotype and functions. NK cells and ILC1 contribute to organ homeostasis through the production of key cytokines and chemokines and the elimination of potential harmful bacteria and viruses. In addition, they are equipped with a wide range of receptors, allowing them to detect “stressed cells’ such as cancer cells. Our understanding of the role of innate lymphoid cells in hepatocellular carcinoma (HCC) is growing owing to the development of mouse models, the progress in immunotherapeutic treatment and the recent use of scRNA sequencing analyses. In this review, we summarize the current understanding of NK cells and ILC1 in hepatocellular carcinoma and discuss future strategies to take advantage of these innate immune cells in anti-tumor immunity. Immunotherapies hold great promise in HCC, and a better understanding of the role and function of NK cells and ILC1 in liver cancer could pave the way for new NK cell and/or ILC1-targeted treatment.

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.

The diterpenoid adenanthin upregulates the expression of natural killer group 2D receptor ligands in hepatocellular carcinoma cells

OBJECTIVE

The natural killer (NK) group 2D (NKG2D) receptor plays a crucial role in NK cell-mediated anti-tumor immunity. NKG2D anti-proliferative effect is mediated by direct interactions of the receptor with its ligands that may be considered as a potential target for NK-based immunotherapeutic strategy in cancer cells.

METHODS

Here we report that a natural product adenanthin significantly promotes NKG2D ligands expression in hepatoma cells. The effect was determined using flow cytometry analysis. The activity of NK cell was evaluated by measuring its degranulation activity and cytotoxicity.

RESULTS

Our data indicates that the induction of NKG2D ligand binding to liver cancer cell surface receptors greatly improves the killing activity of NK cells against the cancer cells.

CONCLUSIONS

This is the first report of a new mechanism anti-cancer effects of adenanthin mediated by an indirect activation of NK cells. Our data suggests that adenanthin may be used to sensitize NK cells in tumor immunotherapy.

A five-gene signature for predicting overall survival of esophagus adenocarcinoma

Esophageal adenocarcinoma (EAC) is common and aggressive with increasing trend of incidence. Urgent need for an effective signature to assess EAC prognosis and facilitate tailored treatment is required.Differentially expressed mRNAs (DEMs) were identified by analyzing EAC tissues and adjacent normal samples from The Cancer Genome Atlas (TCGA). Then univariate regression analyses were performed to confirm prognostic DEMs. We used least absolute shrinkage and selection operator (LASSO) to build a prognostic mRNA signature whose performance was assessed by Kaplan-Meier curve, receiver operating characteristic (ROC). GSE72874 were used as an external test set. The performances of the signature were also validated in internal TCGA and external test sets. Gene set enrichment analysis (GSEA) and tumor immunity analysis were performed to decipher the biological mechanisms of the signature.A 5-mRNA signature consisted of SLC26A9, SINHCAF, MICB, KRT19, and MT1X was developed to predict prognosis of EAC. The 5-mRNA signature was promising as a biomarker for predicting 3-year survival rate of EAC in the internal test set, the entire TCGA set, and the external test set with areas under the curve (AUC) = 0.849, 0.924, and 0.747, respectively. Patients were divided into low- and high-risk groups based on risk scores of the signature. The high-risk group was mainly associated with cancer-related pathways and low levels of B cell infiltration.The 5-mRNA prognostic signature we identified can reliably predict prognosis and facilitate individualized treatment decisions for EAC patients.

Targeting unfolded protein response: a new horizon for disease control

Unfolded protein response (UPR) is an evolutionarily conserved pathway triggered during perturbation of endoplasmic reticulum (ER) homeostasis in response to the accumulation of unfolded/misfolded proteins under various stress conditions like viral infection, diseased states etc. It is an adaptive signalling cascade with the main purpose of relieving the stress from the ER, which may otherwise lead to the initiation of cell death via apoptosis. ER stress if prolonged, contribute to the aetiology of various diseases like cancer, type II diabetes, neurodegenerative diseases, viral infections etc. Understanding the role of UPR in disease progression will help design pharmacological drugs targeting the sensors of signalling cascade acting as potential therapeutic agents against various diseases. The current review aims at highlighting the relevance of different pathways of UPR in disease progression and control, including the available pharmaceutical interventions responsible for ameliorating diseased state via modulating UPR pathways.

Exploring the Emerging Role of the Gut Microbiota and Tumor Microenvironment in Cancer Immunotherapy

The tumor microenvironment (TME) is a complex ecosystem, which includes many different types of cells, abnormal vascular systems, and immunosuppressive cytokines. TME serves an important function in tumor tolerance and escapes from immune surveillance leading to tumor progression. Indeed, there is increasing evidence that gut microbiome is associated with cancer in a variety of ways, as specific microbial signatures are known to promote cancer development and influence safety, tolerability, and efficacy of therapies. Studies over the past five years have shown that the composition of the intestinal microbiota has a significant impact on the efficacy of anticancer immunosurveillance, which contribute to the therapeutic activity of cancer immunotherapies based on targeting cytotoxic T lymphocyte protein 4 (CTLA-4) or programmed cell death protein 1 (PD-1)-programmed cell death 1 ligand 1 (PD-L1) axis. In this review, we mainly discuss the impact of TME on cancer and immunotherapy through immune-related mechanisms. We subsequently discuss the influence of gut microbiota and its metabolites on the host immune system and the formation of TME. In addition, this review also summarizes the latest research on the role of gut microbiota in cancer immunotherapy.

An Anti-MICA/B Antibody and IL-15 Rescue Altered NKG2D-Dependent NK Cell Responses in Hepatocellular Carcinoma

Natural killer (NK) cells play a pivotal role in cancer immune surveillance, and activating the receptor/ligand interaction may contribute to control the development and evolution of hepatocellular carcinoma (HCC). We investigated the role of the natural killer group 2 member D (NKG2D) activating receptor and its ligand, the major histocompatibility complex class I chain-related protein A and B (MICA/B) in patients with cirrhosis and HCC subjected to surgical resection, patients with cirrhosis and no HCC, and healthy donors (HD). The NKG2D-mediated function was determined in peripheral blood (PB), in tumor-infiltrating lymphocytes (NK-TIL), and in matched surrounding liver tissue (NK-LIL). A group of patients treated with sorafenib because of clinically advanced HCC was also studied. A humanized anti-MICA/B monoclonal antibody (mAb) was used in in vitro experiments to examine NK cell-mediated antibody-dependent cellular cytotoxicity. Serum concentrations of soluble MICA/B were evaluated by ELISA. IL-15 stimulation increased NKG2D-dependent activity which, however, remained dysfunctional in PB NK cells from HCC patients, in line with the reduced NKG2D expression on NK cells. NK-TIL showed a lower degranulation ability than NK-LIL, which was restored by IL-15 stimulation. Moreover, in vitro IL-15 stimulation enhanced degranulation and interferon-γ production by PB NK from patients at month one of treatment with sorafenib. Anti-MICA/B mAb associated with IL-15 was able to induce PB NK cytotoxicity for primary HCC cells in HD and patients with HCC, who also showed NK-TIL degranulation for autologous primary HCC cells. Our findings highlight the key role of the NKG2D-MICA/B axis in the regulation of NK cell responses in HCC and provide evidence in support of a potentially important role of anti-MICA/B mAb and IL-15 stimulation in HCC immunotherapy.

Natural Killer Cell Responses in Hepatocellular Carcinoma: Implications for Novel Immunotherapeutic Approaches

Hepatocellular carcinoma (HCC) still represents a significant complication of chronic liver disease, particularly when cirrhosis ensues. Current treatment options include surgery, loco-regional procedures and chemotherapy, according to specific clinical practice guidelines. Immunotherapy with check-point inhibitors, aimed at rescuing T-cells from exhaustion, has been applied as second-line therapy with limited and variable success. Natural killer (NK) cells are an essential component of innate immunity against cancer and changes in phenotype and function have been described in patients with HCC, who also show perturbations of NK activating receptor/ligand axes. Here we discuss the current status of NK cell treatment of HCC on the basis of existing evidence and ongoing clinical trials on adoptive transfer of autologous or allogeneic NK cells ex vivo or after activation with cytokines such as IL-15 and use of antibodies to target cell-expressed molecules to promote antibody-dependent cellular cytotoxicity (ADCC). To this end, bi-, tri- and tetra-specific killer cell engagers are being devised to improve NK cell recognition of tumor cells, circumventing tumor immune escape and efficiently targeting NK cells to tumors. Moreover, the exciting technique of chimeric antigen receptor (CAR)-engineered NK cells offers unique opportunities to create CAR-NK with multiple specificities along the experience gained with CAR-T cells with potentially less adverse effects.

Immune-based therapies for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third most frequent cause of cancer-related death. The immune-rich contexture of the HCC microenvironment makes this tumour an appealing target for immune-based therapies. Here, we discuss how the functional characteristics of the liver microenvironment can potentially be harnessed for the treatment of HCC. We will review the evidence supporting a therapeutic role for vaccines, cell-based therapies and immune-checkpoint inhibitors and discuss the potential for patient stratification in an attempt to overcome the series of failures that has characterised drug development in this disease area.

Clinicopathological relevance of tumor expression of NK group 2 member D ligands in resected non-small cell lung cancer

UL16-binding protein (ULBP) 1-6 and MHC class I chain-related molecule A and B (MICA/B) are NK group 2, member D (NKG2D) ligands, which are specifically expressed in infected or transformed cells and are recognized by NK cells via NKG2D-NKG2D ligand interactions. We previously reported that MICA/B overexpression predicted improved clinical outcomes in patients with resected non-small cell lung cancer (NSCLC). However, the clinicopathological features and prognostic significance of ULBPs in NSCLC remain unclear. Here,ULBP1-6 expression was evaluated based on immunohistochemistry of 91 NSCLC samples from patients following radical surgery. ULBPs were expressed by the majority of NSCLC. Either ULBP1 or ULBP2/5/6 overexpression was associated with squamous-cell carcinoma histology, whereas ULBP4 overexpression was associated with younger age and adenocarcinoma histology. Although overexpression of ULBP1-6 did not impact clinical outcomes in NSCLC patients, integrative profiling with cluster analysis classified patients into 3 subgroups based on the expression pattern of NKG2D ligands. The subgroup characterized by ULBP1 or ULBP2/5/6 high expressing but ULBP4 low expressing tumors showed poor overall survival. Taken together with previous results, NSCLC histological subtype strongly correlates with NKG2D ligands expression pattern. NKG2D ligands expression levels assessed by multiple immune parameters could predict clinical outcomes of patients with NSCLC.

Eradication of Hepatocellular Carcinoma by NKG2D-Based CAR-T Cells

Despite the great success of chimeric antigen receptor T (CAR-T)-cell therapy in the treatment of hematologic malignancies, CAR-T-cell therapy is limited in solid tumors, including hepatocellular carcinoma (HCC). NK group 2 member D (NKG2D) ligands (NKG2DL) are generally absent on the surface of normal cells but are overexpressed on malignant cells, offering good targets for CAR-T therapy. Indeed, analysis of The Cancer Genome Atlas and HCC tumor samples showed that the expression of most NKG2DLs was elevated in tumors compared with normal tissues. Thus, we designed a novel NKG2D-based CAR comprising the extracellular domain of human NKG2D, 4-1BB, and CD3ζ signaling domains (BBz). NKG2D-BBz CAR-T cells efficiently killed the HCC cell lines SMMC-7721 and MHCC97H in vitro, which express high levels of NKG2DLs, whereas they less efficiently killed NKG2DL-silenced SMMC-7721 cells or NKG2DL-negative Hep3B cells. Overexpression of MICA or ULBP2 in Hep3B improved the killing capacity of NKG2D-BBz CAR-T cells. T cells expressing the NKG2D-BBz CAR effectively eradicated SMMC-7721 HCC xenografts. Collectively, these results suggested that NKG2D-BBz CAR-T cells could potently eliminate NKG2DL-high HCC cells both in vitro and in vivo, thereby providing a promising therapeutic intervention for patients with NKG2DL-positive HCC.

The role of natural killer cells in hepatocellular carcinoma development and treatment: A narrative review

A major obstacle for treatment of HCC is the inadequate efficacy and limitation of the available therapeutic options. Despite the recent advances in developing novel treatment options, HCC still remains one of the major causes of cancer morbidity and mortality around the world. Achieving effective treatment and eradication of HCC is a challenging task, however recent studies have shown that targeting Natural Killer cells, as major regulators of immune system, can help with the complete treatment of HCC, restoration of normal liver function and subsequently higher survival rate of HCC patients. Studies have shown that decrease in the frequency of NK cells, their dysfunction due to several factors such as dysregulation of receptors and their ligands, and imbalance of different types of inhibitory and stimulating microRNA expression is associated with higher rate of HCC progression and development, and poor survival outcome. Here in our review, we mainly focused on the importance of NK cells in HCC development and treatment.

Race-associated expression of MHC class I polypeptide-related sequence A (MICA) in prostate cancer

Despite the lack of a complete understanding of the disparities involved, prostate cancer (PCa) has both higher incidence and death rates in African American Men (AAM) relative to those of Caucasian American Men (CAM). MHC class I polypeptide related sequence A (MICA) is an innate immunity protein involved in tumor immunoevasion. Due to a lack of reports of race-specific expression of MICA in PCa, we evaluated MICA expression in patients' tumors and in cell lines from a racially diverse origin. Immunohistochemistry was done on a tissue microarray (TMA) with antibodies against MICA. Tumor MICA mRNA was assessed by data mining using Oncomine and PROGeneV2. Surface MICA and release rate of soluble (s) MICA was evaluated in PCa cell lines originally derived from African American (MDA-PCa-2b) or Caucasian (LNCaP and DU-145) PCa patients. Prostate tumor tissue had a 1.7-fold higher MICA expression relative to normal tissue (p < .0001). MICA immunoreactivity in PCa tissue from AAM was 24% lower (p = .002) compared to CAM. Survival analysis revealed a marginal association of low MICA with poor overall survival (OS) (p = .058). By data mining analysis, a 2.9-fold higher level of MICA mRNA was evidenced in tumor compared to normal tissue (p < .0001). Tumors from AAM had 24% lower levels of MICA mRNA compared to tumors from CAM (p = .038), and poor prognosis was found for patients with lower MICA mRNA (p = .028). By flow cytometry analysis, cell fraction positive for surface MICA was of 3% in MDA-PCa-2b cells, 54% in DU-145 cells, and 67% in LNCaP cells (p < .0001). sMICA was detected in DU-145 and LNCaP cells, but was not detected in MDA-PCa-2b cells. Both LNCaP and DU-145 cells were sensitive to cytolysis mediated by Natural killer (NK) cells. MDA-PCa-2b cells, however were between 1.3-fold at 10:1 Effector:Target (E:T) ratio (p < .0001) and 2-fold at 50:1 E:T ratio (p < .0001) more resistant to NK-mediated cytolysis relative to cells from Caucasian origin. These results suggest that MICA expression may be related to the aggressive nature of PCa. Our findings also demonstrate for the first time that there are variations in MICA expression in the context of racial differences. This study establishes a rationale for further investigation of MICA as a potential race-specific prognostic marker in PCa.

Natural killer cells involved in tumour immune escape of hepatocellular carcinomar

Natural killer cells are the first line of host immune surveillance and play major roles in the defence against infection and tumours. Hepatic NK cells exhibit unique phenotypic and functional characteristics compared to circulating and spleen NK cells, such as higher levels of cytolytic activity and cytotoxicity mediators against tumour cells. However, the activities of NK cells may be reversed during tumour progression. Recent studies demonstrated that hepatic NK cells were exhausted in hepatocellular carcinoma (HCC) and exhibited impaired cytolytic activity and decreased production of effector cytokines. The present review discusses current knowledge on the role of exhausted NK cells in promoting HCC development and the mechanisms contributing to tumour immune escape, including an imbalance of activating and inhibitory receptors on NK cells, abnormal receptor-ligand interaction, and cross-talk with immune cells and other stromal cells in the tumour environment. We provide a fundamental basis for further study of innate immunity in tumour progression and serve the purpose of exploring new HCC treatment strategies.

Immunogenicity moderation effect of interleukin-24 on myelogenous leukemia cells

Previous studies have shown that interleukin-24 (IL-24) has tumor-suppressing activity by multiple pathways. However, the immunogenicity moderation effect of IL-24 on malignant cells has not been explored extensively. In this study, we investigated the role of IL-24 in immunogenicity modulation of the myelogenous leukemia cells. Data show that myelogenous leukemia cells express low levels of immunogenicity molecules. Treatment with IL-24 could enhance leukemia cell immunogenicity, predominantly regulate leukemia cells to produce immune-associated cytokines, and improve the cytotoxic sensitivity of these cells to immune effector cells. IL-24 expression could retard transplanted leukemia cell tumor growth in vivo in athymic nude mice. Moreover, IL-24 had marked effects on downregulating the expression of angiogenesis-related proteins vascular endothelial growth factor, cluster of differentiation (CD) 31, CD34, collagen IV and metastasis-related factors CD147, membrane type-1 matrix metalloproteinase (MMP), and MMP-2 and MMP-9 in transplanted tumors. These findings indicated novel functions of this antitumor gene and characterized IL-24 as a promising agent for further clinical trial for hematologic malignancy immunotherapy.

NK Cell-Based Immunotherapy in Cancer Metastasis

Metastasis represents the leading cause of cancer-related death mainly owing to the limited efficacy of current anticancer therapies on advanced malignancies. Although immunotherapy is rendering promising results in the treatment of cancer, many adverse events and factors hampering therapeutic efficacy, especially in solid tumors and metastases, still need to be solved. Moreover, immunotherapeutic strategies have mainly focused on modulating the activity of T cells, while Natural Killer (NK) cells have only recently been taken into consideration. NK cells represent an attractive target for cancer immunotherapy owing to their innate capacity to eliminate malignant tumors in a non-Major Histocompatibility Complex (MHC) and non-tumor antigen-restricted manner. In this review, we analyze the mechanisms and efficacy of NK cells in the control of metastasis and we detail the immunosubversive strategies developed by metastatic cells to evade NK cell-mediated immunosurveillance. We also share current and cutting-edge clinical approaches aimed at unleashing the full anti-metastatic potential of NK cells, including the adoptive transfer of NK cells, boosting of NK cell activity, redirecting NK cell activity against metastatic cells and the release of evasion mechanisms dampening NK cell immunosurveillance.

Transcription of the NKG2D ligand MICA is suppressed by the IRE1/XBP1 pathway of the unfolded protein response through the regulation of E2F1

The unfolded protein response (UPR) is an adaptive signaling pathway activated in response to endoplasmic reticulum (ER) stress. The effectors of the UPR are potent transcription activators; however, some genes are suppressed by ER stress at the mRNA level. The mechanisms underlying UPR-mediated gene suppression are less known. Exploration of the effect of UPR on NK cells ligand expression found that the transcription of NK group 2 member D (NKG2D) ligand major histocompatibility complex class I polypeptide-related sequence A/B (MICA/B) is suppressed by the inositol-requiring enzyme 1 (IRE1)/X-box binding protein 1 (XBP1) pathway of the UPR. Deletion of IRE1 or XBP1 was sufficient to promote mRNA and surface levels of MICA. Accordingly, NKG2D played a greater role in the killing of IRE1/XBP1 knockout target cells. Analysis of effectors downstream to XBP1s identified E2F transcription factor 1 (E2F1) as linking UPR and MICA transcription. The inverse correlation between XBP1 and E2F1 or MICA expression was corroborated in RNA-Seq analysis of 470 primary melanoma tumors. While mechanisms that connect XBP1 to E2F1 are not fully understood, we implicate a few microRNA molecules that are modulated by ER stress and possess dual suppression of E2F1 and MICA. Because of the importance of E2F1 and MICA in cancer progression and recognition, these observations could be exploited for cancer therapy by manipulating the UPR in tumor cells.-Obiedat, A., Seidel, E., Mahameed, M., Berhani, O., Tsukerman, P., Voutetakis, K., Chatziioannou, A., McMahon, M., Avril, T., Chevet, E., Mandelboim, O., Tirosh, B. Transcription of the NKG2D ligand MICA is suppressed by the IRE1/XBP1 pathway of the unfolded protein response through the regulation of E2F1.

The role of the unfolded protein response in cancer progression: From oncogenesis to chemoresistance

Tumour cells endure both oncogenic and environmental stresses during cancer progression. Transformed cells must meet increased demands for protein and lipid production needed for rapid proliferation and must adapt to exist in an oxygen- and nutrient-deprived environment. To overcome such challenges, cancer cells exploit intrinsic adaptive mechanisms such as the unfolded protein response (UPR). The UPR is a pro-survival mechanism triggered by accumulation of unfolded or misfolded proteins in the endoplasmic reticulum (ER), a condition referred to as ER stress. IRE1, PERK and ATF6 are three ER anchored transmembrane receptors. Upon induction of ER stress, they signal in a coordinated fashion to re-establish ER homoeostasis, thus aiding cell survival. Over the past decade, evidence has emerged supporting a role for the UPR in the establishment and progression of several cancers, including breast cancer, prostate cancer and glioblastoma multiforme. This review discusses our current knowledge of the UPR during oncogenesis, tumour growth, metastasis and chemoresistance.

Genetic polymorphism analysis of MICB gene in Jing ethnic minority of Southern China

In the present study, the polymorphism in the 5'-upstream regulation region (5'-URR), coding region (exons 2-4), and the 3'-untranslated region (3'-UTR) of MICB gene were investigated for 150 healthy unrelated Jing individuals in Guangxi Zhuang Autonomous Region, by using PCR-SBT method. A total of 14 variation sites in the 5'-URR, 9 in coding region, and 6 in the 3'-UTR were detected in the Jing population. The MICB gene seems to present two different lineages showing functional variations mainly in nucleotides of the promoter region. Nineteen different MICB extended haplotypes (EHs) encompassing the 5'-URR, exons 2-4, and 3'-UTR were found in this population, and the most frequent was EH2 (20.33%). The findings here are of importance for future studies on the potential role of regulation region of MICB gene in disease association, transplantation, viral infection, and tumor progression among Jing population.

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.

Epigenetic Mechanisms Dictating Eradication of Cancer by Natural Killer Cells

Natural killer (NK) cells of the innate immune system are the first line of defense against infectious agents and cancer cells. However, only a few mechanisms that regulate eradication of tumors by NK cells have been identified. In this review, we present an account of epigenetic mechanisms that modulate the ability of NK cells to eradicate cancer cells. To date, several drugs that target epigenetic modifiers have shown clinical efficacy in cancer. Therefore, once a given epigenetic modifier is validated as a regulator of NK cell function, it can be targeted for NK cell-based cancer immunotherapies.

Unresolved endoplasmic reticulum stress engenders immune-resistant, latent pancreatic cancer metastases

The majority of patients with pancreatic ductal adenocarcinoma (PDA) develop metastatic disease after resection of their primary tumor. We found that livers from patients and mice with PDA harbor single disseminated cancer cells (DCCs) lacking expression of cytokeratin 19 (CK19) and major histocompatibility complex class I (MHCI). We created a mouse model to determine how these DCCs develop. Intraportal injection of immunogenic PDA cells into preimmunized mice seeded livers only with single, nonreplicating DCCs that were CK19^- and MHCI^- The DCCs exhibited an endoplasmic reticulum (ER) stress response but paradoxically lacked both inositol-requiring enzyme 1α activation and expression of the spliced form of transcription factor XBP1 (XBP1s). Inducible expression of XBP1s in DCCs, in combination with T cell depletion, stimulated the outgrowth of macrometastatic lesions that expressed CK19 and MHCI. Thus, unresolved ER stress enables DCCs to escape immunity and establish latent metastases.

Inhibition of Enhancer of zeste homolog 2 (EZH2) induces natural killer cell-mediated eradication of hepatocellular carcinoma cells

Natural killer (NK) cell-mediated tumor cell eradication could inhibit tumor initiation and progression. However, the factors that regulate NK cell-mediated cancer cell eradication remain unclear. We determined that hepatocellular carcinoma (HCC) cells exhibit transcriptional down-regulation of NK group 2D (NKG2D) ligands and are largely resistant to NK cell-mediated eradication. Because the down-regulation of NKG2D ligands occurred at the transcriptional level, we tested 32 chemical inhibitors of epigenetic regulators for their ability to re-express NKG2D ligands and enhance HCC cell eradication by NK cells and found that Enhancer of zeste homolog 2 (EZH2) was a transcriptional repressor of NKG2D ligands. The inhibition of EZH2 by small-molecule inhibitors or genetic means enhanced HCC cell eradication by NK cells in a NKG2D ligand-dependent manner. Collectively, these results demonstrate that EZH2 inhibition enhances HCC eradication by NK cells and that EZH2 functions, in part, as an oncogene by inhibiting immune response.

Prognostic value of MICA/B in cancers: a systematic review and meta-analysis

Purpose

MHC class I chain related-proteins A (MICA) and B (MICB) are natural killer group 2D ligands that mediate tumor surveillance. Several studies have suggested that MICA/B levels predict clinical outcomes in patients with cancer; however, this remains contentious. Here, we present a systematic review and meta-analysis of available studies of the prognostic value of MICA/B in cancer.

Materials and Methods

We searched PubMed, Embase, Clinicaltrials.gov, and Cochrane Library to identify studies published from inception to July 2017 that assessed MICA/B in patients with cancer. The hazard ratio (HR) and 95% confidence interval (CI) of MICA/B were extracted for overall survival (OS) analysis.

Results

A total of 19 studies comprising 2,588 patients with 10 different types of cancer were included in the study. Low sMICA/B levels were found associated with significantly longer OS (HR = 1.65, 95% CI [1.42–1.92], P < 0.00001). Patients with cancers of digestive system that exhibited high MICA/B expression had significantly longer OS in (HR = 0.56, 95% CI [0.39–0.80], P = 0.002) compared with those with lower MICA/B expression (I² = 35%, P = 0.18).

Conclusions

Serum soluble MICA/B represents a potential prognostic marker in various human cancers. High cell-surface MICA/B expression in cancers of the digestive system was found associated with increased survival.

The Combined Antitumor Effects of 125I Radioactive Particle Implantation and Cytokine-Induced Killer Cell Therapy on Xenograft Hepatocellular Carcinoma in a Mouse Model

The combination of radiotherapy and immunotherapy has shown great promise in eradicating tumors. For example, ¹²⁵I radioactive particle implantation and cytokine-induced killer cell therapies have demonstrated efficacy in treating hepatocellular carcinoma. However, the mechanism of this combination therapy remains unknown. In this study, we utilized cytokine-induced killer cells obtained from human peripheral blood mononuclear cells along with ¹²⁵I radioactive particle implantation to treat subcutaneous hepatocellular carcinoma xenograft tumors in BALB/c nude mice. The effects of combination therapy on tumor growth, tumor cell apoptosis and proliferation, animal survival, and immune indexes were then assessed. The results indicated that ¹²⁵I radioactive particle implantation combined with cytokine-induced killer cells shows a much greater antitumor therapeutic effect than either of the therapies alone when compared to control treatments. Mice treated with a combination of radiotherapy and immunotherapy displayed significantly reduced tumor growth. ¹²⁵I radioactive particle implantation upregulated the expression of major histocompatibility complex (MHC) class I chain-related gene A in hepatocellular carcinoma cells and enhanced cytokine-induced killer cell–mediated apoptosis through activation of caspase-3. Furthermore, cytokine-induced killer cells supplied immune substrates to induce a strong immune response after ¹²⁵I radioactive particle implantation therapy. In conclusion, ¹²⁵I radioactive particle implantation combined with cytokine-induced killer cell therapy significantly inhibits the growth of human hepatocellular carcinoma cells in vivo and improves animal survival times through mutual promotion of antitumor immunity, presenting a promising therapy for hepatocellular carcinoma.

Emerging Role of the Unfolded Protein Response in Tumor Immunosurveillance

Disruption of endoplasmic reticulum (ER) homeostasis results in ER stress and activation of the unfolded protein response (UPR). This response alleviates cell stress, and is activated in both tumor cells and tumor infiltrating immune cells. The UPR plays a dual function in cancer biology, acting as a barrier to tumorigenesis at the premalignant stage, while fostering cancer maintenance in established tumors. In infiltrating immune cells, the UPR has been involved in both immunosurveillance and immunosuppressive functions. This review aims to decipher the role of the UPR at different stages of tumorigenesis and how the UPR shapes the balance between immunosurveillance and immune escape. This knowledge may improve existing UPR-targeted therapies and the design of novel strategies for cancer treatment.

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.

microRNA-889 is downregulated by histone deacetylase inhibitors and confers resistance to natural killer cytotoxicity in hepatocellular carcinoma cells

Major histocompatibility complex class I chain-related gene B (MICB) is expressed on tumor cells and participates in natural killer (NK) cell-mediated antitumor immune response through engagement with the NKG2D receptor. This study was undertaken to identify novel microRNA (miRNA) regulators of MICB and clarify their functions in NK cell-mediated cytotoxicity to hepatocellular carcinoma (HCC) cells. Bioinformatic analysis and luciferase reporter assay were conducted to search for MICB-targeting miRNAs. Overexpression and knockdown experiments were performed to determine the roles of candidate miRNAs in the susceptibility of HCC cells to NK lysis. miR-889 was identified as a novel MICB-targeting miRNA and overexpression of miR-889 significantly inhibited the mRNA and protein expression of MICB in HepG2 and SMMC7721 HCC cells. miR-889 expression had a negative correlation with MICB mRNA levels in HCC specimens (r = -0.392, P = 0.0146). NK cell-mediated cytotoxicity was reduced in miR-889-overexpressing HCC cells, which was reversed by restoration of MICB expression. In contrast, knockdown of miR-889 led to more pronounced NK cell-mediated lysis in HCC cells. HCC cells exposed to the histone deacetylase (HDAC) inhibitor sodium valproate showed downregulation of miR-889. Enforced expression of miR-889 prevented the upregulation of MICB and enhancement of NK cell-mediated lysis by HDAC inhibitors. In conclusion, miR-889 upregulation attenuates the susceptibility of HCC cells to NK lysis and represents a potential target for improving NK cell-based antitumor therapies.

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.

Silencing NKG2D ligand-targeting miRNAs enhances natural killer cell-mediated cytotoxicity in breast cancer

NKG2D is one of the major activating receptors of natural killer (NK) cells and binds to several ligands (NKG2DLs). NKG2DLs are expressed on malignant cells and sensitize them to early elimination by cytotoxic lymphocytes. We investigated the clinical importance of NKG2DLs and the mechanism of NKG2DL regulation in breast cancer (BC). Among the NKG2DLs MICA/B and ULBP1/2/3, the expression levels of MICA/B in BC tissues were inversely associated with the Tumor Node Metastasis stage. We first found that the high expression of MICB, but not MICA, was an independent prognostic factor for overall survival in patients with BC. Investigation into the mechanism revealed that a group of microRNAs (miRNAs) belonging to the miR-17-92 cluster, especially miR-20a, decreased the expression of ULBP2 and MICA/B. These miRNAs downregulated the expression of MICA/B by targeting the MICA/B 3'-untranslated region and downregulated ULBP2 by inhibiting the MAPK/ERK signaling pathway. Functional analysis showed that the silencing of NKG2DL-targeting miRNAs in BC cells increased NK cell-mediated cytotoxicity in vitro and inhibited immune escape in vivo. In addition, histone deacetylase inhibitors (HDACis) increased NKG2DL expression in BC cells by inhibiting members of the miR-17-92 cluster. Thus, targeting miRNAs with antisense inhibitors or HDACis may represent a novel approach for increasing the immunogenicity of BC.

Novel chemoimmunotherapeutic strategy for hepatocellular carcinoma based on a genome-wide association study

Pharmacotherapeutic options are limited for hepatocellular carcinoma (HCC). Recently, we identified the anti-tumor ligand MHC class I polypeptide-related sequence A (MICA) gene as a susceptibility gene for hepatitis C virus-induced HCC in a genome-wide association study (GWAS). To prove the concept of HCC immunotherapy based on the results of a GWAS, in the present study, we searched for drugs that could restore MICA expression. A screen of the FDA-approved drug library identified the anti-cancer agent vorinostat as the strongest hit, suggesting histone deacetylase inhibitors (HDACis) as potent candidates. Indeed, the HDACi-induced expression of MICA specific to HCC cells enhanced natural killer (NK) cell-mediated cytotoxicity in co-culture, which was further reinforced by treatment with an inhibitor of MICA sheddase. Similarly augmented anti-tumor activity of NK cells via NK group 2D was observed in vivo. Metabolomics analysis revealed HDACi-mediated alterations in energy supply and stresses for MICA induction and HCC inhibition, providing a mechanism for the chemoimmunotherapeutic actions. These data are indicative of promising strategies for selective HCC innate immunotherapy.

MHC class I chain-related molecule A and B expression is upregulated by cisplatin and associated with good prognosis in patients with non-small cell lung cancer

MHC class I chain-related molecule A and B (MICA/B) are NK group 2 member D (NKG2D) ligands, which are broadly expressed in transformed cells. Both DNA damage-induced ataxia-telangiectasia-mutated (ATM)- and ATM and Rad3-related protein kinases (ATM-ATR) signaling and oncogene-induced PI3K-AKT signaling regulate the expression of NKG2D ligands, which promote NK cell-mediated cytotoxicity via NKG2D-NKG2D ligand interactions. NKG2D ligand overexpression was recently reported to be correlated with good prognosis in several types of cancer. However, the prognostic significance of NKG2D ligands in non-small cell lung cancer (NSCLC) remains unclear. Here, MICA/B expression was evaluated based on immunohistochemistry of 91 NSCLC samples from patients following radical surgery. In addition, expression of MICA/B was assessed in NSCLC cell lines treated with cisplatin in order to evaluate the regulatory mechanisms of MICA/B expression. Overall, 28 out of 91 (30.8%) specimens showed high expression level of MICA/B, which was associated with low (18)F-fluorodeoxyglucose uptake and manifestation of adenocarcinoma. After a median follow-up of 48.2 months, high MICA/B expression was associated with good recurrence-free survival (p = 0.037). In vitro assays using cell lines revealed that MICA/B expression was upregulated by cisplatin via ATM-ATR signaling, resulting in enhanced NK cell-mediated cytotoxicity. Upregulated MICA/B expressions in patients with radically resected NSCLC are predictive of good disease prognosis. Cisplatin-induced MICA/B upregulation is possibly an indirect mechanism by which the innate immune system eliminates tumor cells. NKG2D-NKG2D ligand-targeting therapy is a promising avenue for future immune-chemotherapy development.

Scorpion venom activates natural killer cells in hepatocellular carcinoma via the NKG2D-MICA pathway

Previous studies have demonstrated that polypeptides extracted from scorpion venom (PESV) inhibited cell proliferation in several tumors, however, the effect on dysfunctional and exhausted natural killer cells which contribute to tumor escape from immune surveillance remain to be elucidated. In this study, we determined the effect of PESV on NK infiltration into H22 cells orthotopic transplantation tumors and on the expression of MHC class I chain-related proteins A (MICA) in HepG2 cells. We found that tumor growth in mice was significantly inhibited by PESV and the survival time of tumor-bearing mice treated with PESV was significantly prolonged. Moreover, levels of tumor-infiltrating NK cells, NKG2D protein, perforin and granzyme B mRNA were significantly increased in the group treated with PESV compared with the tumor-bearing control group. In addition, In addition, up-regulation of MICA by PESV enhances the susceptibility of HepG2 cells to NK lysis in vitro. These results indicate that the inhibitory effects of PESV on hepatic carcinoma are likely mediated by up-regulation of NK cell activity via the MICA-NKG2D pathway.

HOXD9 promotes epithelial-mesenchymal transition and cancer metastasis by ZEB1 regulation in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common malignant tumor that severely threatens human health. The poor prognosis of HCC is mainly attributed to intrahepatic and extrahepatic metastases. HOXD9 proteins belong to a superfamily that regulates the development and control of many cellular processes, including proliferation, apoptosis, cell shape, and cell migration. HOXD9 can also function as an oncogene in several cancer cells. However, its biological function in human HCC requires further investigation. In this study, HOXD9 exhibited high expression in invasive HCC cells. HOXD9 overexpression can significantly enhance HCC cell migration, invasion, and metastasis, whereas silencing HOXD9 inhibits these processes. HOXD9 also promotes the epithelial-mesenchymal transition (EMT) of HCC cells. Microarray analysis suggests that ZEB1 can function as a downstream factor of HOXD9. HOXD9 can interact with the promoter region of ZEB1 and promotes ZEB1 expression. ZEB1 knockdown inhibits HOXD9-induced migration and invasion, as well as EMT in HCC cells. This study helps elucidates the oncogenic functions of HOXD9 in HCC.

CXCR2-CXCL1 axis is correlated with neutrophil infiltration and predicts a poor prognosis in hepatocellular carcinoma

Background & aims

Inflammation is a hallmark of cancer, yet the mechanisms that regulate immune cell infiltration into tumors remain poorly characterized. This study attempted to characterize the composition, distribution, and prognostic value of CXCR2⁺ cells in hepatocellular carcinoma (HCC) and to examine the CXCR2 ligands that are responsible for local immune infiltration in different areas of HCC tumors.

Methods

Immunohistochemistry and immunofluorescene were used to identify CXCR2⁺ cells in HCC tissues. Kaplan–Meier analysis and Cox regression models were applied to estimate recurrence-free survival (RFS) and overall survival (OS) for 259 HCC patients. The expression levels of CXCR2 ligands (CXCL-1, −2, −5, and −8) were measured by real-time PCR and compared with local immune cell density. The combined prognostic value of the CXCR2–CXCL1 axis was further evaluated.

Results

In HCC tissues, CXCR2⁺ cells were mainly neutrophils that were enriched in the peri-tumoral stroma (PS) region. Kaplan–Meier survival analysis showed that increased CXCR2⁺_PS cells were associated with reduced RFS and OS (P = 0.015 for RFS; P = 0.002 for OS). Multivariate Cox proportional hazards analysis identified CXCR2⁺_PS cell density as an independent prognostic factor for OS (hazard ratio [HR] = 1.737, 95 % confidence interval [CI] = 1.167–2.585, P = 0.006). Furthermore, we detected a positive correlation between the density of CD15⁺ neutrophils and CXCL1 levels in both the peri-tumoral stroma and intra-tumoral regions. The combination of CXCR2 and CXCL1 expression levels represented a powerful predictor of a poor prognosis for patients with HCC.

Conclusions

Our data showed that the CXCR2⁺ cell density was an independent prognostic factor for predicting OS for HCC patients. The CXCR2–CXCL1 axis can regulate neutrophil infiltration into HCC tumor tissues and might represent a useful target for anti-HCC therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-015-0247-1) contains supplementary material, which is available to authorized users.