Expression of Programmed Cell Death-Ligands in Hepatocellular Carcinoma: Correlation With Immune Microenvironment and Survival Outcomes

Targeting immune checkpoints on tumor-associated macrophages in tumor immunotherapy

Unprecedented breakthroughs have been made in cancer immunotherapy in recent years. Particularly immune checkpoint inhibitors have fostered hope for patients with cancer. However, immunotherapy still exhibits certain limitations, such as a low response rate, limited efficacy in certain populations, and adverse events in certain tumors. Therefore, exploring strategies that can improve clinical response rates in patients is crucial. Tumor-associated macrophages (TAMs) are the predominant immune cells that infiltrate the tumor microenvironment and express a variety of immune checkpoints that impact immune functions. Mounting evidence indicates that immune checkpoints in TAMs are closely associated with the prognosis of patients with tumors receiving immunotherapy. This review centers on the regulatory mechanisms governing immune checkpoint expression in macrophages and strategies aimed at improving immune checkpoint therapies. Our review provides insights into potential therapeutic targets to improve the efficacy of immune checkpoint blockade and key clues to developing novel tumor immunotherapies.

Navigating through the PD-1/PDL-1 Landscape: A Systematic Review and Meta-Analysis of Clinical Outcomes in Hepatocellular Carcinoma and Their Influence on Immunotherapy and Tumor Microenvironment

This systematic review aimed to assess the prognostic significance of programmed cell death-ligand 1 (PDL-1) and programmed cell death protein 1 (PD-1) in hepatocellular carcinoma (HCC). Medline, EMBASE, and Cochrane Library database searches were conducted, revealing nine relevant cohort studies (seven PDL-1 and three PD-1). Our meta-analysis showed that PD-1/PDL-1 was a marker of poor survival, regardless of the assessment method (PD-1 overall survival (OS): hazard ratio (HR) 2.40; 95% confidence interval (CI), 1.30–4.42; disease-free survival (DFS): HR 2.12; 95% CI, 1.45–3.10; PDL-1: OS: HR 3.61; 95% CI, 2.75–4.75; and DFS: HR 2.74; 95% CI, 2.09–3.59). Additionally, high level of PD-1/PDL-1 expression was associated with aging, multiple tumors, high alpha-fetoprotein levels, and advanced Barcelona Clinic Liver Cancer stage. This high level significantly predicted a poor prognosis for HCC, suggesting that anti-PD-1 therapy is plausible for patients with HCC. Furthermore, HIF-1 induces PD-1 expression, and PD1lowSOCS3high is associated with a better prognosis. Taken together, combination therapy may be the key to effective immunotherapy. Thus, exploring other markers, such as HIF-1 and SOCS3, along with PD-1/PDL-1 immunotherapy, may lead to improved outcomes.

Soluble programmed death ligand-1-induced immunosuppressive effects on chimeric antigen receptor-natural killer cells targeting Glypican-3 in hepatocellular carcinoma

Although the pre-clinical study of chimeric antigen receptor (CAR)-natural killer (NK) cell was effective against various tumours, immunosuppression mediated by tumour microenvironment hampers their application and several efforts have been explored to improve their effect in combating solid tumours. Glypican 3 (GPC3) is a promising target for hepatocellular carcinoma (HCC), and CAR-T cells targeting GPC3 have been tested in clinical trials. Based on an affinity-enhanced antibody (hYP7) targeting GPC3, we constructed GPC3-CAR-NK cells to explore their potential function in the treatment of HCC. We found that patients with HCC secreted high levels of soluble programmed death-ligand 1 (sPD-L1), which inhibits the function of CAR-NK cells targeting GPC3. In addition, we combined high-affinity sPD-L1 variant (L3C7c-Fc) with GPC3-CAR-NK cells to solve the problem of GPC3-CAR-NK inhibition. Our studies demonstrated that L3C7c-Fc could enhance the therapeutic effect of CAR-NK cells by reversing the suppression of sPD-L1, which provides the experimental evidence for the subsequent development of HCC immunotherapy strategies.

Turning adversity into opportunity: Small extracellular vesicles as nanocarriers for tumor-associated macrophages re-education

Currently, small extracellular vesicles (sEV) as a nanoscale drug delivery system, are undergoing biotechnological scaling and clinical validation. Nonetheless, preclinical pharmacokinetic studies revealed that sEV are predominantly uptaken by macrophages. Although this "sEV-macrophage" propensity represents a disadvantage in terms of sEV targeting and their bioavailability as nanocarriers, it also represents a strategic advantage for those therapies that involve macrophages. Such is the case of tumor-associated macrophages (TAMs), which can reprogram/repolarize their predominantly immunosuppressive and tumor-supportive phenotype toward an immunostimulatory and anti-tumor phenotype using sEV as nanocarriers of TAMs reprogramming molecules. In this design, sEV represents an advantageous delivery system, providing precision to the therapy by simultaneously matching their tropism to the therapeutic cell target. Here, we review the current knowledge of the role of TAMs in the tumoral microenvironment and the effect generated by the reprogramming of these phagocytic cells fate using sEV. Finally, we discuss how these vesicles can be engineered by different bioengineering techniques to improve their therapeutic cargo loading and preferential uptake by TAMs.

Recent progress in molecular mechanisms of postoperative recurrence and metastasis of hepatocellular carcinoma

Hepatectomy is currently considered the most effective option for treating patients with early and intermediate hepatocellular carcinoma (HCC). Unfortunately, the postoperative prognosis of patients with HCC remains unsatisfactory, predominantly because of high postoperative metastasis and recurrence rates. Therefore, research on the molecular mechanisms of postoperative HCC metastasis and recurrence will help develop effective intervention measures to prevent or delay HCC metastasis and recurrence and to improve the long-term survival of HCC patients. Herein, we review the latest research progress on the molecular mechanisms underlying postoperative HCC metastasis and recurrence to lay a foundation for improving the understanding of HCC metastasis and recurrence and for developing more precise prevention and intervention strategies.

Hepatic macrophage mediated immune response in liver steatosis driven carcinogenesis

Obesity confers an independent risk for carcinogenesis. Classically viewed as a genetic disease, owing to the discovery of tumor suppressors and oncogenes, genetic events alone are not sufficient to explain the progression and development of cancers. Tumor development is often associated with metabolic and immunological changes. In particular, obesity is found to significantly increase the mortality rate of liver cancer. As its role is not defined, a fundamental question is whether and how metabolic changes drive the development of cancer. In this review, we will dissect the current literature demonstrating that liver lipid dysfunction is a critical component driving the progression of cancer. We will discuss the involvement of inflammation in lipid dysfunction driven liver cancer development with a focus on the involvement of liver macrophages. We will first discuss the association of steatosis with liver cancer. This will be followed with a literature summary demonstrating the importance of inflammation and particularly macrophages in the progression of liver steatosis and highlighting the evidence that macrophages and macrophage produced inflammatory mediators are critical for liver cancer development. We will then discuss the specific inflammatory mediators and their roles in steatosis driven liver cancer development. Finally, we will summarize the molecular pattern (PAMP and DAMP) as well as lipid particle signals that are involved in the activation, infiltration and reprogramming of liver macrophages. We will also discuss some of the therapies that may interfere with lipid metabolism and also affect liver cancer development.

Immune cell infiltration and immunotherapy in hepatocellular carcinoma

Hepatocellular carcinoma is a highly malignant tumor and patients yield limited benefits from the existing treatments. The application of immune checkpoint inhibitors is promising but the results described in the literature are not favorable. It is therefore urgent to systematically analyze the immune microenvironment of HCC and screen the population best suited for the application of immune checkpoint inhibitors to provide a basis for clinical treatment. In this study, we collected The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC)-related data sets to evaluate the immune microenvironment and immune cell infiltration (ICI) in HCC. Three independent ICI subtypes showing significant differences in survival were identified. Further, TCGA-LIHC immunophenoscore (IPS) was used to identify the differentially expressed genes between high- and low-IPS in HCC, so as to identify the immune gene subtypes in HCC tumors. The ICI score model for HCC was constructed, whereby we divided HCC samples into high- and low-score groups based on the median ICI score. The differences between these groups in genomic mutation load and immunotherapy benefit in HCC were examined in detail to provide theoretical support for accurate immunotherapy strategy in HCC. Finally, four genes were screened, which could accurately predict the subtype based on the tumor immune infiltration score. The findings may provide a basis and simplify the process for screening clinical drugs suitable for relevant subgroups.

Synergistic antitumor efficacy of PD-1-conjugated PTX- and ZSQ-loaded nanoliposomes against multidrug-resistant liver cancers

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide with poor chemotherapeutic efficiency due to multidrug resistance (MDR); it is very important to develop a targeted nanocarrier for the treatment of HCC. In this study, a programmed death ligand 1 (PD-L1)-conjugated nanoliposome was constructed for co-delivery of paclitaxel (PTX) and P-glycoprotein (P-gp) inhibitor zosuquidar (ZSQ) to overcome MDR in human HCC cells and tumors in vivo. Transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA) were used to examine the nanoparticles morphology and size; PD-1-conjugated PTX and ZSQ-loaded nanoliposomes (PD-PZLP) revealed a spherical shape with a size of 139.5 ± 10.7 nm. Then, the physicochemical properties, as well as the drug loading capacity, release profile, cellular uptake, and cytotoxicity of the dual drug-encapsulated nanoliposomes were characterized. PD-PZLP displayed a high drug loading capacity of 20 ~ 30% for both PTX and ZSQ; the drug release of PTX and ZSQ in pH 5.0 was significantly faster than in pH 7.4. Cellular uptake study demonstrated PD-PZLP had higher internalization efficiency than non-targeted PZLP. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining and reactive oxygen species (ROS) analysis demonstrated that PD-PZLP triggered an excessive ROS reaction and cell apoptosis compared with that of free PTX or ZSQ, which was also consistent with the cell antiproliferative effects in MTT assay. Furthermore, PD-PZLP could enhance synergistic antitumor effects on 7721/ADM xenograft tumor model, which also significantly alleviated hepatotoxicity as evident from the decreased aspartate transaminase (AST) and alanine transaminase (ALT) levels. Overall, PD-PZLP exhibited high loading capacity, significant synergistic effects, promising antitumor efficacy, and the lowest toxicity, which provide a promising strategy to overcome MDR in HCC.

Clinicopathological and Prognostic Value of Programmed Cell Death 1 Expression in Hepatitis B Virus-related Hepatocellular Carcinoma: A Meta-analysis

BACKGROUND AND AIMS

The efficacy of targeted programmed cell death 1/programmed death ligand 1 (PD-1/PD-L1) monoclonal antibodies (mAbs) has been confirmed in many solid malignant tumors. The overexpression of PD-1/PD-L1 serves as a biomarker to predict prognosis and clinical progression. However, the role of PD-1 in patients with hepatitis B virus-related hepatocellular carcinoma (HBV-HCC) remains indeterminate. Given that HBV is the most important cause for HCC, this study aimed to investigate the prognostic and clinicopathological value of PD-1 in HBV-HCC via a meta-analysis.

METHODS

We searched PubMed, Embase, Scopus, the Cochrane Library, Web of Science and Google Scholar up to January 2021 for studies on the correlation between clinicopathology/prognosis and PD-1 in patients with HBV-HCC. The pooled hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated to investigate the prognostic significance of PD-1 expression. The odds ratios (ORs) and 95% CIs were determined to explore the association between PD-1 expression and clinicopathological features.

RESULTS

Our analysis included seven studies with 658 patients, which showed that high PD-1 expression was statistically correlated with poorer overall survival (HR=2.188, 95% CI: [1.262-3.115], p<0.001) and disease-free survival (HR=2.743, 95% CI: [1.980-3.506], p<0.001). PD-1 overexpression was correlated with multiple tumors (OR=2.268, 95% CI: [1.209-4.257], p=0.011), high level of alpha fetoprotein (AFP; OR=1.495, 95% CI: [1.005-2.223], p=0.047) and advanced Barcelona Clinic Liver Cancer (BCLC) stage (OR=3.738, 95% CI: [2.101-6.651], p<0.001).

CONCLUSIONS

Our meta-analysis revealed that the high level of PD-1 expression was associated with multiple tumors, high level of AFP and advanced BCLC stage. It significantly predicted a poor prognosis of HBV-HCC, which suggests that anti-PD-1 therapy for HBV-HCC patients is plausible.

Identification of Gene-Set Signature in Early-Stage Hepatocellular Carcinoma and Relevant Immune Characteristics

Background

The incidence of hepatocellular carcinoma (HCC) is rising worldwide, and there is limited therapeutic efficacy due to tumor microenvironment heterogeneity and difficulty in early-stage screening. This study aimed to develop and validate a gene set-based signature for early-stage HCC (eHCC) patients and further explored specific marker dysregulation mechanisms as well as immune characteristics.

Methods

We performed an integrated bioinformatics analysis of genomic, transcriptomic, and clinical data with three independent cohorts. We systematically reviewed the crosstalk between specific genes, tumor prognosis, immune characteristics, and biological function in the different pathological stage samples. Univariate and multivariate survival analyses were performed in The Cancer Genome Atlas (TCGA) patients with survival data. Diethylnitrosamine (DEN)-induced HCC in Wistar rats was employed to verify the reliability of the predictions.

Results

We identified a Cluster gene that potentially segregates patients with eHCC from non-tumor, through integrated analysis of expression, overall survival, immune cell characteristics, and biology function landscapes. Immune infiltration analysis showed that lower infiltration of specific immune cells may be responsible for significantly worse prognosis in HCC (hazard ratio, 1.691; 95% CI: 1.171–2.441; p = 0.012), such as CD8 Tem and cytotoxic T cells (CTLs) in eHCC. Our results identified that Cluster C1 signature presented a high accuracy in predicting CD8 Tem and CTL immune cells (receiver operating characteristic (ROC) = 0.647) and cancerization (ROC = 0.946) in liver. As a central member of Cluster C1, overexpressed PRKDC was associated with the higher genetic alteration in eHCC than advanced-stage HCC (aHCC), which was also connected to immune cell-related poor prognosis. Finally, the predictive outcome of Cluster C1 and PRKDC alteration in DEN-induced eHCC rats was also confirmed.

Conclusions

As a tumor prognosis-relevant gene set-based signature, Cluster C1 showed an effective approach to predict cancerization of eHCC and its related immune characteristics with considerable clinical value.

Comprehensive Analysis of YTH Domain Family in Lung Adenocarcinoma: Expression Profile, Association with Prognostic Value, and Immune Infiltration

Background

All YTH domain family members are m⁶A reader proteins accounting for the methylation modulation involved in the process of tumorgenesis and tumor progression. However, the expression profiles and roles of the YTH domain family in lung adenocarcinoma (LUAD) remain to be further illustrated.

Methods

GEPIA2 and TNMplot databases were used to generate the expression profiles of the YTH family. Kaplan-Meier plotter database was employed to analysis the prognostic value of the YTH family. Coexpression profiles and genetic alterations analysis of the YTH family were undertaken using the cBioPortal database. YTH family protein-associated protein-protein interaction (PPI) network was identified by using STRING. Functional enrichment analysis was performed with the help of the WebGestalt database. The correlation analysis between the YTH family and immune cell infiltration in LUAD was administrated by using the TIMER2.0 database.

Results

mRNA expression of YTHDC1 and YTHDC2 was significantly lower in LUAD, whereas YTHDF1, YTHDF2, and YTHDF3 with apparently higher expression. YTHDF2 expression was observed to be the highest in the nonsmoker subgroup, and its expression gradually decreased with the increased severity of smoking habit. LUAD patients with low expression of YTHDC2, YTHDF1, and YTHDF2 were correlated with a better overall survival (OS) time. The YTHDF1 genetic alteration rate was 26%, which was the highest in the YTH family. The major cancer-associated functions of YTH family pointed in the direction of immunomodulation, especially antigen processing and presentation. Most of the YTH family members were significantly correlated with the infiltration of CD4+ T cells, CD8+ T cells, macrophages, and neutrophils, indicating the deep involvement of the YTH domain family in the immune cell infiltration in LUAD.

Conclusion

The molecular and expression profiles of the YTH family were dysregulated in LUAD. YTH family members (especially YTHDC2) were promising biomarkers and potential therapeutic targets that may bring benefit for the patients with LUAD.

Combination therapy for hepatocellular carcinoma with diacylglycerol kinase alpha inhibition and anti-programmed cell death-1 ligand blockade

Activation of diacylglycerol kinase alpha (DGKα) augments proliferation and suppresses apoptosis of cancer cells and induces T lymphocyte anergy. We investigated the dual effects of DGKα inhibition on tumorigenesis and anti-tumor immunity with the aim of establishing a novel therapeutic strategy for cancer. We examined the effects of a DGKα inhibitor (DGKAI) on liver cancer cell proliferation and cytokine production by immune cells in vitro and on tumorigenesis and host immunity in a hepatocellular carcinoma (HCC) mouse model. Oral DGKAI significantly suppressed tumor growth and prolonged survival in model mice. Tumor infiltration of T cells and dendritic cells was also enhanced in mice treated with DGKAI, and the production of cytokines and cytotoxic molecules by CD4⁺ and CD8⁺ T cells was increased. Depletion of CD8⁺ T cells reduced the effect of DGKAI. Furthermore, interferon-γ stimulation augmented the expression of programmed cell death-1 ligand (PD-L1) on cancer cells, and DGKAI plus an anti-PD-L1 antibody strongly suppressed the tumor growth. These results suggest that DGKα inhibition may be a promising new treatment strategy for HCC.

The Role of Immunotherapy in a Tolerogenic Environment: Current and Future Perspectives for Hepatocellular Carcinoma

In contrast to several tumors whose prognoses are radically affected by novel immunotherapeutic approaches and/or targeted therapies, the outcomes of advanced hepatocellular carcinoma (HCC) remain poor. The underlying cirrhosis that is frequently associated with it complicates medical treatment and often determines survival. The landscape of HCC treatment had included sorafenib as the only drug available for ten years, until 2018, when lenvatinib was approved for treatment. The second-line systemic treatments available for hepatocellular carcinoma include regorafenib, cabozantinib, ramucirumab, and, more recently, immune checkpoint inhibitors. However, the median survival remains below 15 months. The results obtained in clinics should be interpreted whilst considering the peculiar role of the liver as an immune organ. A healthy liver microenvironment ordinarily experiences stimulation by gut-derived antigens. This setup elucidates the response to chronic inflammation and the altered balance between tolerance and immune response in HCC development. This paper provides an overview of the mechanisms involved in HCC pathogenesis, with a special focus on the immune implications, along with current and future clinical perspectives.

Immunotherapy against programmed death-1/programmed death ligand 1 in hepatocellular carcinoma: Importance of molecular variations, cellular heterogeneity, and cancer stem cells

Hepatocellular carcinoma (HCC) is a heterogeneous malignancy related to diverse etiological factors. Different oncogenic mechanisms and genetic variations lead to multiple HCC molecular classifications. Recently, an immune-based strategy using immune checkpoint inhibitors (ICIs) was presented in HCC therapy, especially with ICIs against the programmed death-1 (PD-1) and its ligand PD-L1. However, despite the success of anti-PD-1/PD-L1 in other cancers, a substantial proportion of HCC patients fail to respond. In this review, we gather current information on biomarkers of anti-PD-1/PD-L1 treatment and the contribution of HCC heterogeneity and hepatic cancer stem cells (CSCs). Genetic variations of PD-1 and PD-L1 are associated with chronic liver disease and progression to cancer. PD-L1 expression in tumoral tissues is differentially expressed in CSCs, particularly in those with a close association with the tumor microenvironment. This information will be beneficial for the selection of patients and the management of the ICIs against PD-1/PD-L1.

Identification of m6A methyltransferase-related lncRNA signature for predicting immunotherapy and prognosis in patients with hepatocellular carcinoma

N6-methyladenosine (m6A) methyltransferase has been shown to be an oncogene in a variety of cancers. Nevertheless, the relationship between the long non-coding RNAs (lncRNAs) and hepatocellular carcinoma (HCC) remains elusive. We integrated the gene expression data of 371 HCC and 50 normal tissues from The Cancer Genome Atlas (TCGA) database. Differentially expressed protein-coding genes (DE-PCGs)/lncRNAs (DE-lncRs) analysis and univariate regression and Kaplan–Meier (K–M) analysis were performed to identify m6A methyltransferase-related lncRNAs. Three prognostic lncRNAs were selected by univariate and LASSO Cox regression analyses to construct the m6A methyltransferase-related lncRNA signature. Multivariate Cox regression analyses illustrated that this signature was an independent prognostic factor for overall survival (OS) prediction. The Gene Set Enrichment Analysis (GSEA) suggested that the m6A methyltransferase-related lncRNAs were involved in the immune-related biological processes (BPs) and pathways. Besides, we discovered that the lncRNAs signature was correlated with the tumor microenvironment (TME) and the expression of critical immune checkpoints. Tumor Immune Dysfunction and Exclusion (TIDE) analysis revealed that the lncRNAs could predict the clinical response to immunotherapy. Our study had originated a prognostic signature for HCC based on the potential prognostic m6A methyltransferase-related lncRNAs. The present study had deepened the understanding of the TME status of HCC patients and laid a theoretical foundation for the choice of immunotherapy.

Exploration of prognostic index based on immune-related genes in patients with liver hepatocellular carcinoma

The present study aimed to screen the immune-related genes (IRGs) in patients with liver hepatocellular carcinoma (LIHC) and construct a synthetic index for indicating the prognostic outcomes. The bioinformatic analysis was performed on the data of 374 cancer tissues and 50 normal tissues, which were downloaded from TCGA database. We observed that 17 differentially expressed IRGs were significantly associated with survival in LIHC patients. These LIHC-specific IRGs were validated with function analysis and molecular characteristics. Cox analysis was applied for constructing a RiskScore for predicting the survival. The RiskScore involved six IRGs and corresponding coefficients, which was calculated with the following formula: RiskScore = [Expression level of FABP5 *(0.064)] + [Expression level of TRAF3 * (0.198)] + [Expression level of CSPG5 * (0.416)] + [Expression level of IL17D * (0.197)] + [Expression level of STC2 * (0.036)] + [Expression level of BRD8 * (0.140)]. The RiskScore was positively associated with the poor survival, which was verified with the dataset from ICGC database. Further analysis revealed that the RiskScore was independent of any other clinical feature, while it was linked with the infiltration levels of six types of immune cells. Our study reported the survival-associated IRGs in LIHC and then constructed IRGs-based RiskScore as prognostic indicator for screening patients with high risk of short survival. Both the screened IRGs and IRGs-based RiskScore were clinically significant, which may be informative for promoting the individualized immunotherapy against LIHC.

Identification of PD-1 ligands: PD-L1 and PD-L2 on macrophages in lung cancer milieu by flow cytometry

Background

The efficacy of immune checkpoint inhibitors (ICIs) remains unexpected and in some patients the resistance to anti-programmed death-1 (anti-PD-1) and anti-programmed death ligand 1 (anti-PD-L1) agents is observed. One of possible explanation may be PD-L2 activity. PD-1 ligands: PD-L1 and PD-L2 are present on cancer cells but also, not without significance, on alveolar macrophages (AMs) contributing to immune-suppression in the tumor microenvironment. The aim of this study was to analyse PD-L2, PD-L1 expression on AMs in bronchoalveolar lavage fluid (BALF) in relation to PD-1 positive T lymphocytes.

Methods

Seventeen patients with lung cancer were investigated. BALF cells from the lung with cancer (clBALF) and from the opposite “healthy” lung (hlBALF) and peripheral blood (PB) lymphocytes were investigated. Flow cytometry method was used.

Results

We found that 100% of CD68+ AMs from the clBALF were PD-L1 and PD-L2-positive. Unexpectedly, fluorescence minus one (FMO) PD-L1 and PD-L2 stained controls and isotype controls also showed strong autofluorescence. The hlBALF AMs exhibited a similar PD-L1 and PD-L2 autofluorescence. The median proportion of PD-1+ T lymphocytes was higher in the clBALF than the hlBALF and PB (28.9 vs. 23.4% vs. 15.6%, P=0.0281).

Conclusions

We discussed the opportunities of exploring the PD-1-PD-L1/PD-L2 pathway in the lung cancer environment, which may help to find new potential biomarkers for immunotherapy. We concluded that precise identification by flow cytometry of macrophages in the BALF is possible, but our study showed that the autofluorescence of macrophages did not allow to assess a real expression of PD-L2 as well as PD-L1 on AMs.

Prognostic significance and immune infiltration of microenvironment-related signatures in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is 1 of the highly fatal and most aggressive types of malignancies and accounts for the vast majority of Pancreatic Cancer. Numerous studies have reported that the tumor microenvironment (TME) was significantly correlated with the oncogenesis, progress, and prognosis of various malignancies. Therefore, mining of TME-related genes is reasonably important to improve the overall survival of patients with PDAC.The Estimation of STromal and Immune cells in MAlignant Tumor tissues using Expression data algorithm was applied to identify differential expressed genes. Functional and pathway enrichment analyses, protein-protein interaction network construction and module analysis, overall survival analysis and tumor immune estimation resource database analysis were then performed on differential expressed genes.Data analysis indicated that higher immune scores were correlated with better overall survival (P = 0.033). Differential expression analysis obtained 90 intersection genes influencing both stromal and immune scores. Among these intersection genes, CA9, EBI3, SPOCK2, WDFY4, CD1D, and CCL22 were significantly correlated with overall survival in PDAC patients. Moreover, multivariate Cox analysis revealed that CA9, SPOCK2, and CD1D were the most significant prognostic genes, and were closely correlated with immune infiltration in TCGA cohort. Further analysis indicated that CD1D were significantly related with immune cell biomarkers for PDAC patients.In summary, our findings provide a more comprehensive insight into TME and show a list of prognostic immune associated genes in PDAC. However, further studies on these genes need to be performed to gain additional understanding of the association between TME and prognosis in PDAC.

Targeting tumor-associated macrophages to synergize tumor immunotherapy

The current treatment strategies in advanced malignancies remain limited. Notably, immunotherapies have raised hope for a successful control of these advanced diseases, but their therapeutic responses are suboptimal and vary considerably among individuals. Tumor-associated macrophages (TAMs) are a major component of the tumor microenvironment (TME) and are often correlated with poor prognosis and therapy resistance, including immunotherapies. Thus, a deeper understanding of the complex roles of TAMs in immunotherapy regulation could provide new insight into the TME. Furthermore, targeting of TAMs is an emerging field of interest due to the hope that these strategies will synergize with current immunotherapies. In this review, we summarize recent studies investigating the involvement of TAMs in immune checkpoint inhibition, tumor vaccines and adoptive cell transfer therapies, and discuss the therapeutic potential of targeting TAMs as an adjuvant therapy in tumor immunotherapies.

PKM2-Induced the Phosphorylation of Histone H3 Contributes to EGF-Mediated PD-L1 Transcription in HCC

High expression of programmed death-ligand-1 (PD-L1) in hepatocellular carcinoma (HCC) cells usually inhibits the proliferation and functions of T cells, leading to immune suppression in tumor microenvironment. However, very little has been described regarding the mechanism of PD-L1 overexpression in HCC cells. In the present study, we found epidermal growth factor (EGF) stimulation promoted the expression of PD-L1 mRNA and protein in HCC cells. Inhibition of epidermal growth factor receptor (EGFR) could reverse EGF-induced the expression of PD-L1 mRNA and protein. Subsequently, we also observed that the phosphorylation level of Pyruvate kinase isoform M2 (PKM2) at Ser³⁷ site was also increased in response to EGF stimulation. Expression of a phosphorylation-mimic PKM2 S37D mutant stimulated PD-L1 expression as well as H3-Thr¹¹ phosphorylation in HCC cells, while inhibition of PKM2 significantly blocked EGF-induced PD-L1 expression and H3-Thr¹¹ phosphorylation. Furthermore, mutation of Thr¹¹ of histone H3 into alanine abrogated EGF-induced mRNA and protein expression of PD-L1, Chromatin immunoprecipitation (ChIP) assay also suggested that EGF treatment resulted in enhanced H3-Thr¹¹ phosphorylation at the PD-L1 promoter. In a diethylnitrosamine (DEN)-induced rat model of HCC, we found that the expression of phosphorylated EGFR, PKM2 nuclear expression, H3-Thr¹¹ phosphorylation as well as PD-L1 mRNA and protein was higher in the livers than that in normal rat livers. Taken together, our study suggested that PKM2-dependent histone H3-Thr¹¹ phosphorylation was crucial for EGF-induced PD-L1 expression at transcriptional level in HCC. These findings may provide an alternative target for the treatment of hepatocellular carcinoma.

Fibrinogen-like protein 2 promotes the accumulation of myeloid-derived suppressor cells in the hepatocellular carcinoma tumor microenvironment

The tumor microenvironment in hepatocellular carcinoma can be classified into cellular and non-cellular components. Myeloid-derived suppressor cells (MDSCs) are cellular components of this microenvironment that serve an important role in the progression of hepatocellular carcinoma. Fibrinogen-like protein 2 (FGL2) has been demonstrated to promote tumor progression by regulating cellular components of the tumor microenvironment in various types of malignant tumor. The present study aimed to determine the expression of FGL2 in hepatocellular carcinoma and its effect on the tumor microenvironment in order to determine novel targets for liver cancer treatment. Immunohistochemistry and reverse transcription quantitative PCR were performed to determine the expression level of FGL2 and the correlation with surface markers of human MDSCs in hepatocellular carcinoma. Furthermore, a mouse hepatocellular carcinoma cell line overexpressing FGL2 was established by stable transfection of a lentivirus expressing FGL2. In addition, fresh bone marrow cells extracted from mouse femurs were in vitro cultured using conditioned medium derived from the cell line overexpressing FGL2. An orthotopic hepatocellular carcinoma mouse model was also established. The results demonstrated that FGL2 expression level in hepatocellular carcinoma tissues was closely associated with tumor size. FGL2 level was positively correlated with the expression level of the MDSC surface markers CD11b and CD33 in hepatocellular carcinoma. The in vitro results demonstrated that FGL2 could maintain the undifferentiated state of bone marrow cells, therefore promoting MDSC accumulation. Furthermore, in the orthotopic hepatocellular carcinoma mouse model, we observed that overexpression of FGL2 could promote tumor growth and significantly increase the number of MDSCs in the tumors and spleen. Taken together, these findings suggested that FGL2 may promote hepatocellular carcinoma tumor growth by promoting the accumulation of MDSCs in the tumor microenvironment.

Prognostic and clinicopathological utility of PD-L2 expression in patients with digestive system cancers: A meta-analysis

OBJECTIVE

Programmed death ligand-2 (PD-L2)has been detected in various cancers. However, its prognostic value in digestive system cancers (DSCs) remains unclear. Accordingly, this meta-analysis investigated the prognostic and clinicopathological utility of PD-L2 in patients with DSCs.

METHODS

We systematically searched PubMed, EMBASE, Web of Science, ClinicalTrials.gov., Scopus, and Cochrane Library databases for eligible studies up to April 30, 2020. The hazard ratio (HR), odds ratio (OR), and corresponding 95% confidence interval (CI) of the outcomes were calculated.

RESULTS

Twenty two studies with 4886 patients were included in this meta-analysis. The pooled results showed that PD-L2 overexpression was significantly associated with poor overall survival (OS) (HR 1.470, 95% CI: 1.252-1.728, p < 0.001) and worse disease-free survival (DFS) (HR1.598, 95% CI: 1.398-1.826, p < 0.001). Subgroup analysis revealed that elevated PD-L2 was a significant prognostic indicator of worse OS in hepatocellular carcinoma (HR 1.703, 95% CI: 1.456-1.991, p < 0.001) and colorectal cancer (HR 3.811, 95% CI: 1.718-8.454, p = 0.001). Concerning clinicopathologic factors, PD-L2 overexpression was associated with lymphatic metastasis (OR 1.394., 95% CI: 1.101-1.764, p = 0.006), tumor metastasis (OR 1.599, 95% CI: 1.072-2.383, p = 0.021), and the histopathological stage (OR 0.704, 95% CI: 0.566-0.875, p = 0.002).

CONCLUSION

PD-L2 overexpression in DSCs after surgery might predict a poor prognosis, especially in hepatocellular carcinoma and colorectal cancer. Larger patient cohorts are needed to validate its prognostic role.

Immuno-oncology for Hepatocellular Carcinoma: The Present and the Future

Hepatocellular carcinoma is a highly prevalent and lethal cancer that many therapeutics are being tested for this disease. It has the potential to be a highly immune-responsive tumor given its inflammatory origins. The first immunotherapies were anti-programmed death-1 monotherapies, which improved response rates and survival. Novel immunotherapy combinations and immunotherapy show promise in frontline treatment. The novel antibody therapy combination of atezolizumab and bevacizumab may be practice changing. Although these landmark studies seem to offer new treatment options, the role of immunotherapy in the liver transplant setting is uncertain until the safety of this approach is defined.

A Molecular Subtype Model for Liver HBV-Related Hepatocellular Carcinoma Patients Based on Immune-Related Genes

Hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the world with a very poor prognosis. Immunotyping is of great significance for predicting HCC outcomes and guiding immunotherapy. Therefore, we sought to establish a reliable prognostic model for HBV-related HCC based on immune scores. We identified immune-related modules of The Cancer Genome Atlas LIHC and GSE14520 data sets through weighted gene co-expression network analysis and evaluated HCC through a non-negative matrix factorization algorithm. Through further bioinformatics analyses, we identified causes for prognostic differences between subtypes. The results illustrate a significant difference in prognosis based on immunotypes, which may stem from metabolic disorders and increased tumor invasion associated with the high expression of genes related to stem cell characteristics. In conclusion, we identified a novel HBV-related HCC immune subtype and determined its immunological characteristics, which provides ideas for further individualized immunotherapy research.

Correlation Patterns Among B7 Family Ligands and Tryptophan Degrading Enzymes in Hepatocellular Carcinoma

Mechanisms of dysfunctional T cell immunity in Hepatocellular Carcinoma (HCC) need to be well defined. B7 family molecules provide both co-stimulatory and co-inhibitory signals to T cells while tryptophan degrading enzymes like Indoleamine 2,3 dioxygenase (IDO) and Tryptophan 2,3 Dioxygenase (TDO) mediate tumor immune tolerance. It is necessary to identify their in situ correlative expression, which informs targets for combined immunotherapy approaches. We investigated B7 family molecules, IDO, TDO and immune responsive effectors in the tumor tissues of patients with HCC (n = 28) using a pathway-focused quantitative nanoscale chip real-time PCR. Four best correlative expressions, namely (1) B7-1 & PD-L2, (2) B7-H2 & B7-H3, (3) B7-2 & PD-L1, (4) PD-L1 & PD-L2, were identified among B7 family ligands, albeit they express at different levels. Although TDO expression is higher than IDO, PD-L1 correlates only with IDO but not TDO. Immune effector (Granzyme B) and suppressive (PD-1 and TGF-β) genes correlate with IDO and B7-1, B7-H5, PD-L2. Identification of the in situ correlation of PD-L1, PD-L2 and IDO suggest their cumulative immuno suppressive role in HCC. The distinct correlations among B7-1, B7-2, B7-H2, and B7-H3, correlation of PD-1 with non-cognate ligands such as B7-1 and B7-H5, and correlation of tumor lytic enzyme Granzyme B with IDO and PD-L2 suggest that HCC microenvironment is complexly orchestrated with both stimulatory and inhibitory molecules which together neutralize and blunt anti-HCC immunity. Functional assays demonstrate that both PDL-1 and IDO synergistically inhibit T cell responses. Altogether, the present data suggest the usage of combined immune checkpoint blocking strategies targeting co-inhibitory B7 molecules and IDO for HCC management.

Increasing the expression of programmed death ligand 2 (PD-L2) but not 4-1BB ligand in colorectal cancer cells

Immune checkpoint (ICP) molecules modulate the immune response by either inducing or preventing T cell activation. Over-expression of some ICPs on malignant cells has been shown to regulate anti-tumor immune responses. We aimed to investigate the expression levels of two immune checkpoint molecules which have not been studied extensively in patients with colorectal cancer (CRC). Programmed Death Ligand 2 (co-inhibitory) and 4-1BB ligand (co-stimulatory) were assessed in tumor tissues of CRC patients compared to the adjacent normal tissues. Following tissue excision during surgical operation from 21 CRC patients, RNA extraction, cDNA synthesis and semi-quantitative real-time PCR were done for measuring the expressions of PD-L2 and 4-1BBL genes. In protein level, indirect immunohistochemistery (IHC) was performed on tissue sections. We revealed that PD-L2 was expressed in about 81% CRCs and insignificantly correlated with the tumor differentiation grade. Although a 3.25-fold change in the gene expression of PD-L2 was found in tumor tissues compared to the adjacent normal tissues (P = 0.005), but decreased level of 4-1BBL in counterpart tissues was not significant. Our results were confirmed by IHC for PDL-2 (P = 0.02) and 4-1BBL, however it was not statistically significant for the latter one. Although not significant, we could find an association between the elevated expression of PD-L2 and the tumor differentiation grade. Increased expression of negative regulator of the anti-tumor immune responses like PD-L2, as a prominent way of tumor escape, can be considered for cancer immunotherapy approaches in CRC patients using blocking monoclonal antibodies.

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.

Inflammatory Mechanisms of HCC Development

HCC (hepatocellular carcinoma) is the second leading cause of cancer deaths worldwide, with several etiologic causes, mostly inflammation-associated. Different inflammatory responses in the liver can be triggered by different etiological agents. The inflammatory process can be resolved or be persistent, depending on the etiology and multiple other factors. Chronic inflammation, tissue remodeling, genetic alterations, and modifications in cellular signaling are considered to be key processes promoting immunosuppression. The progressive immunosuppression leads to the inactivation of anti-tumor immunity involved in HCC carcinogenesis and progression. Tumor cellular processes including DNA damage, necrosis, and ER (endoplasmic reticulum) stress can affect both immune-surveillance and cancer-promoting inflammation, supporting a mutual interdependence. Here, we review the current understanding of how chronic liver injury and inflammation is triggered and sustained, and how inflammation is linked to HCC. The identification of many hepatic microenvironmental inflammatory processes and their effector molecules, has resulted in extensive translational work and promising clinical trials of new immunomodulatory agents.

Spatiotemporal Changes in Checkpoint Molecule Expression

Immune checkpoint inhibitors (ICIs), particularly PD-1/PD-L1 blockade, have led to therapeutic breakthrough in patients with advanced malignancy, covering the lung, breast, gastrointestinal, head and neck, urinary system, lymphoma, and solid tumor harboring MSI/dMMR. In certain cancer types, the expression level of immune checkpoint molecule will be required if the immune-based approaches are considered, especially the PD-L1 expression. However, in other types, survival benefit has been proven regardless of PD-L1 expression. It raises a question of how to select patients for immune therapy and whether the expression of immune checkpoint molecules will be optimal biomarkers. Before answering this question, a comprehensive map for the expression of immune checkpoint molecules is needed. In this chapter, we describe our current knowledge on the spatiotemporal changes in the expression of checkpoint molecules. We discuss the different frequencies of expression depending on tumor types and stages, the different patterns between primary and metastatic tumors, as well as the change of expression before and after treatment. The expression of PD-L1 has been most studied, but the threshold that separate "positive" and "negative" PD-L1 expressions and the consistency of testing platform remain under debate. Better understanding on the tumor microenvironment and expression of checkpoint molecules will help to identify patients who will benefit from checkpoint blockade therapy.

Exosomal PD-L1: New Insights Into Tumor Immune Escape Mechanisms and Therapeutic Strategies

As a classical immune checkpoint molecule, PD-L1 on the surface of tumor cells plays a pivotal role in tumor immunosuppression, primarily by inhibiting the antitumor activities of T cells by binding to its receptor PD-1. PD-1/PD-L1 inhibitors have demonstrated unprecedented promise in treating various human cancers with impressive efficacy. However, a significant portion of cancer patients remains less responsive. Therefore, a better understanding of PD-L1-mediated immune escape is imperative. PD-L1 can be expressed on the surface of tumor cells, but it is also found to exist in extracellular forms, such as on exosomes. Recent studies have revealed the importance of exosomal PD-L1 (ExoPD-L1). As an alternative to membrane-bound PD-L1, ExoPD-L1 produced by tumor cells also plays an important regulatory role in the antitumor immune response. We review the recent remarkable findings on the biological functions of ExoPD-L1, including the inhibition of lymphocyte activities, migration to PD-L1-negative tumor cells and immune cells, induction of both local and systemic immunosuppression, and promotion of tumor growth. We also discuss the potential implications of ExoPD-L1 as a predictor for disease progression and treatment response, sensitive methods for detection of circulating ExoPD-L1, and the novel therapeutic strategies combining the inhibition of exosome biogenesis with PD-L1 blockade in the clinic.