Interferon regulatory factor 1 (IRF-1) and IRF-2 regulate PD-L1 expression in hepatocellular carcinoma (HCC) cells

Liquid Biopsy Assessment of Circulating Tumor Cell PD-L1 and IRF-1 Expression in Patients with Advanced Solid Tumors Receiving Immune Checkpoint Inhibitor

BACKGROUND

Reliable biomarkers that can be serially monitored to predict treatment response to immune checkpoint inhibitors (ICIs) are still an unmet need. Here, we present a multiplex immunofluorescence (IF) assay that simultaneously detects circulating tumor cells (CTCs) and assesses CTC expression of programmed death ligand-1 (PD-L1) and interferon regulatory factor 1 (IRF-1) as a candidate biomarker related to ICI use.

OBJECTIVE

To assess the potential of CTC PD-L1 and IRF-1 expression as candidate biomarkers for patients with advanced epithelial solid tumors receiving ICIs.

PATIENTS AND METHODS

We tested the IF CTC assay in a pilot study of 28 patients with advanced solid tumors who were starting ICI. Blood for CTC evaluation was obtained prior to starting ICI, after a single cycle of therapy, and at the time of radiographic assessment or treatment discontinuation.

RESULTS

At baseline, patients with 0-1 CTCs had longer progression-free survival (PFS) compared to patients with ≥ 2 CTCs (4.3 vs 1.3 months, p = 0.01). The presence of any PD-L1+ CTCs after a single dose of ICI portended shorter PFS compared to patients with no CTCs or PD-L1- CTCs (1.2 vs 4.2 months, p = 0.02); the presence of any PD-L1+ or IRF-1+ CTCs at time of imaging assessment or treatment discontinuation also was associated with shorter PFS (1.9 vs 5.5 months, p < 0.01; 1.6 vs 4.7 months, p = 0.05). CTC PD-L1 and IRF-1 expression did not correlate with tumor tissue PD-L1 or IRF-1 expression. Strong IRF-1 expression in tumor tissue was associated with durable (≥ 1 year) radiographic response (p = 0.02).

CONCLUSIONS

Based on these results, CTC PD-L1 and IRF-1 expression is of interest in identifying ICI resistance and warrants further study.

The Role of Interferon Regulatory Factors in Non-Alcoholic Fatty Liver Disease and Non-Alcoholic Steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is becoming the most common chronic liver disease with many metabolic comorbidities, such as obesity, diabetes, and cardiovascular diseases. Non-alcoholic steatohepatitis (NASH), an advanced form of NAFLD, accompanies the progression of hepatic steatosis, inflammation, cell death, and varying degree of liver fibrosis. Interferons (IFNs) have been shown to play important roles in the pathogenesis of NAFLD and NASH. Their regulating transcriptional factors such as interferon regulatory factors (IRFs) can regulate IFN expression, as well as genes involved in macrophage polarization, which are implicated in the pathogenesis of NAFLD and advanced liver disease. In this review, the roles of IRF-involved signaling pathways in hepatic inflammation, insulin resistance, and immune cell activation are reviewed. IRFs such as IRF1 and IRF4 are also involved in the polarization of macrophages that contribute to critical roles in NAFLD or NASH pathogenesis. In addition, IRFs have been shown to be regulated by treatments including microRNAs, PPAR modulators, anti-inflammatory agents, and TLR agonists or antagonists. Modulating IRF-mediated factors through these treatments in chronic liver disease can ameliorate the progression of NAFLD to NASH. Furthermore, adenoviruses and CRISPR activation plasmids can also be applied to regulate IRF-mediated effects in chronic liver disease. Pre-clinical and clinical trials for evaluating IRF regulators in NAFLD treatment are essential in the future direction.

Comprehensive Landscape of ARID Family Members and Their Association with Prognosis and Tumor Microenvironment in Hepatocellular Carcinoma

As one of the most lethal forms of cancers, hepatocellular carcinoma (HCC) claims many lives around the world, and it is especially common in China. The ARID family plays key roles in the pathogenesis and development of human cancers. The potential of several functional genes used as novel biomarkers has attracted more and more attention. However, the prognostic values of the ARID family in HCC patients are rarely known by people. In this study, we performed comprehensive analysis using TCGA datasets, finding that the expressions of ARID4B, ARID2, ARID3B, JARID2, ARID1A, ARID1B, and ARID3A were increased in HCC specimens compared to nontumor specimens, while the expressions of ARID4A and ARID3C were decreased in HCC specimens. According to the Pearson correlation data, the methylation levels of the majority of ARID members were negatively correlated. Upregulation of ARID3A, ARID5B, and ARID1A was related to a poor HCC outcome according to the data of multivariate assays. Then, we built a LASSO Cox regression model based on ARID3A, ARID5B, and ARID1A in HCC. Overall survival rates were considerably lower for those with high risk scores compared to those with low risk scores. Finally, we studied the associations between risk scores and several types of infiltrating immune cells. The data revealed that the risk score was positively related to the infiltration of CD8+ T cells, B cell, T cell CD8+, neutrophil, macrophage, and myeloid dendritic cell. This study conducted a thorough analysis of the ARID members, resulting in new insights for further examination of the ARID family members as prospective targets in the treatment of HCC.

Predictive biomarkers of response to immune checkpoint inhibitors in hepatocellular carcinoma

INTRODUCTION

Hepatocellular carcinoma (HCC) is the most common primary liver cancer and fourth leading cause of cancer death. While drug discovery to improve disease survival was historically poor, there is now evidence of significant potential for immune checkpoint inhibitors (ICPIs) in treatment of the disease, and indeed such drug approvals are beginning to emerge.

AREAS COVERED

HCC typically arises in the context of cirrhosis and chronic liver disease (CLD), and HCC exhibits significant biological heterogeneity, in part reflecting the broad range of aetiologies of CLD. Different classes and combinations of ICPI-based therapy exist, but not all patients will respond and predictive biomarkers are not yet available to guide clinician decision making, unlike some other cancer types. In this review, we discuss the emerging biomarkers for ICPI sensitivity in HCC, including tumour genomic features, perturbation of the gut microbiome and systemic inflammatory markers.

EXPERT OPINION

Additional profiling studies are required to appreciate existing trends with clinical outcome and to further drive clinical studies in disease stratification by response. This will only be possible within collaborative and international efforts, especially regarding biopsy collection. A close collaboration between basic scientists and clinicians will be the key to shape the next future of HCC biomarker research.

Mechanisms of MHC-I Downregulation and Role in Immunotherapy Response

Immunotherapy has become a key therapeutic strategy in the treatment of many cancers. As a result, research efforts have been aimed at understanding mechanisms of resistance to immunotherapy and how anti-tumor immune response can be therapeutically enhanced. It has been shown that tumor cell recognition by the immune system plays a key role in effective response to T cell targeting therapies in patients. One mechanism by which tumor cells can avoid immunosurveillance is through the downregulation of Major Histocompatibility Complex I (MHC-I). Downregulation of MHC-I has been described as a mechanism of intrinsic and acquired resistance to immunotherapy in patients with cancer. Depending on the mechanism, the downregulation of MHC-I can sometimes be therapeutically restored to aid in anti-tumor immunity. In this article, we will review current research in MHC-I downregulation and its impact on immunotherapy response in patients, as well as possible strategies for therapeutic upregulation of MHC-I.

IRF-2 inhibits cancer proliferation by promoting AMER-1 transcription in human gastric cancer

BACKGROUND

Interferon regulatory factor 2 (IRF-2) acts as an anti-oncogene in gastric cancer (GC); however, the underlying mechanism remains unknown.

METHODS

This study determined the expression of IRF-2 in GC tissues and adjacent non-tumor tissues using immunohistochemistry (IHC) and explored the predictive value of IRF-2 for the prognoses of GC patients. Cell function and xenograft tumor growth experiments in nude mice were performed to test tumor proliferation ability, both in vitro and in vivo. Chromatin immunoprecipitation sequencing (ChIP-Seq) assay was used to verify the direct target of IRF-2.

RESULTS

We found that IRF-2 expression was downregulated in GC tissues and was negatively correlated with the prognoses of GC patients. IRF-2 negatively affected GC cell proliferation both in vitro and in vivo. ChIP-Seq assay showed that IRF-2 could directly activate AMER-1 transcription and regulate the Wnt/β-catenin signaling pathway, which was validated using IHC, in both tissue microarray and xenografted tumor tissues, western blot analysis, and cell function experiments.

CONCLUSIONS

Increased expression of IRF-2 can inhibit tumor growth and affect the prognoses of patients by directly regulating AMER-1 transcription in GC and inhibiting the Wnt/β-catenin signaling pathway.

Interferon regulatory factor-1 regulates cisplatin-induced apoptosis and autophagy in A549 lung cancer cells

This study aimed to investigate the expression and function of interferon regulatory factor-1 (IRF-1) in non-small cell lung cancer (NSCLC). IRF-1 expression and its prognostic value were investigated through bioinformatic analysis. The protein expression levels of IRF-1, cleaved caspase 3, and LC3-I/II were analyzed by western blotting. A lentiviral vector was used to overexpress or knockdown IRF-1 in vitro. Mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) were analyzed by JC-1 and DCFH-DA staining, respectively. ATP, SOD, MDA, cell viability, LDH release, and caspase 3 activity were evaluated using commercial kits. Compared to the levels in normal tissues, IRF-1 expression was significantly lower in lung cancer tissues and was a prognostic factor for NSCLC. Cisplatin treatment-induced IRF-1 activation, ROS production, ATP depletion, SOD consumption, and MDA accumulation in A549 lung cancer cells. IRF-1 overexpression promoted mitochondrial depolarization, oxidative stress, and apoptotic cell death and inhibited autophagy in A549 cells, and these effects could be reversed by IRF-1 knockdown. These data suggest that IRF-1 regulates apoptosis, autophagy and oxidative stress, which might be served as a potential target for increasing chemotherapy sensitivity of lung cancer.

Comprehensive analysis of expression profile and prognostic significance of interferon regulatory factors in pancreatic cancer

BACKGROUND

Pancreatic cancer (PC) is a highly lethal disease and an increasing cause of cancer-associated mortality worldwide. Interferon regulatory factors (IRFs) play vital roles in immune response and tumor cellular biological processes. However, the specific functions of IRFs in PC and tumor immune response are far from systematically clarified. This study aimed to explorer the expression profile, prognostic significance, and biological function of IRFs in PC.

RESULTS

We observed that the levels of IRF2, 6, 7, 8, and 9 were elevated in tumor compared to normal tissues in PC. IRF7 expression was significantly associated with patients' pathology stage in PC. PC patients with high IRF2, low IRF3, and high IRF6 levels had significantly poorer overall survival. High mRNA expression, amplification and, deep deletion were the three most common types of genetic alterations of IRFs in PC. Low expression of IRF2, 4, 5, and 8 was resistant to most of the drugs or small molecules from Genomics of Drug Sensitivity in Cancer. Moreover, IRFs were positively correlated with the abundance of tumor infiltrating immune cells in PC, including B cells, CD8+ T cells, CD4+ T cells, macrophages, Neutrophil, and Dendritic cells. Functional analysis indicated that IRFs were involved in T cell receptor signaling pathway, immune response, and Toll-like receptor signaling pathway.

CONCLUSIONS

Our results indicated that certain IRFs could serve as potential therapeutic targets and prognostic biomarkers for PC patients. Further basic and clinical studies are needed to validate our findings and generalize the clinical application of IRFs in PC.

IRF7 is a Prognostic Biomarker and Associated with Immune Infiltration in Stomach Adenocarcinoma

Background

Stomach adenocarcinoma (STAD) is one of the most prevalent malignances, ranking fifth in incidence and third in mortality among all malignances. Interferon regulatory factors (IRFs) play a vital role in immune response and tumor cellular biological process. The roles of IRFs in STAD are far from being systematically clarified.

Methods

A series of bioinformatics tools, including GEPIA, UALCAN, TIMER, Kaplan–Meier plotter and LinkedOmics, were applied to explore the expression and clinical significance of IRFs in STAD.

Results

IRF3/7 expression were upregulated in STAD in sub-group analyses based on race, gender, age, H. Pylori infection status, histological subtypes, tumor grade, individual cancer stages, and nodal metastasis status. High IRF3/7 expression were associated with poor overall survival (OS), post-progression survival (PFPS) and first progression (FP) in STAD. IRF3 and IRF7 were altered in 5% and 6% of all TCGA STAD patients. Further analysis revealed that IRF7 was significantly associated with the abundance of immune cells (B cells, Neutrophils and Dendritic cells) and the expression of most immune biomarkers. Enrichment analysis indicated that IRF7 was mainly involved in adaptive immune response, NOD-like receptor signaling pathway, Necroptosis, and Toll-like receptor signaling pathway. We also identified several IRF7-associated kinase and miRNA targets in STAD. The result of verified experiment revealed that ITF7 expression was increased in STAD tissues compared with normal tissues and prognosis analysis revealed that STAD patients with high IRF7 expression had a poor overall survival.

Conclusion

IRF7 is upregulated in STAD and associated with poor OS, PPS and FP. Moreover, IRF7 is significantly associated with the abundance of immune cells and the expression of most immune biomarkers, suggesting that IRF7 is as a prognostic biomarker and associated with immune infiltration in STAD.

Various Uses of PD1/PD-L1 Inhibitor in Oncology: Opportunities and Challenges

The occurrence and development of cancer are closely related to the immune escape of tumor cells and immune tolerance. Unlike previous surgical, chemotherapy, radiotherapy and targeted therapy, tumor immunotherapy is a therapeutic strategy that uses various means to stimulate and enhance the immune function of the body, and ultimately achieves the goal of controlling tumor cells.With the in-depth understanding of tumor immune escape mechanism and tumor microenvironment, and the in-depth study of tumor immunotherapy, immune checkpoint inhibitors represented by Programmed Death 1/Programmed cell Death-Ligand 1(PD-1/PD-L1) inhibitors are becoming increasingly significant in cancer medication treatment. employ a variety of ways to avoid detection by the immune system, a single strategy is not more effective in overcoming tumor immune evasion and metastasis. Combining different immune agents or other drugs can effectively address situations where immunotherapy is not efficacious, thereby increasing the chances of success and alternative access to alternative immunotherapy. Immune combination therapies for cancer have become a hot topic in cancer treatment today. In this paper, several combination therapeutic modalities of PD1/PD-L1 inhibitors are systematically reviewed. Finally, an analysis and outlook are provided in the context of the recent advances in combination therapy with PD1/PD-L1 inhibitors and the pressing issues in this field.

[CDK1, CCNB1 and NDC80 are associated with prognosis and progression of hepatitis B virus-associated hepatocellular carcinoma: a bioinformatic analysis]

OBJECTIVE

To identify the key genes involved in the transformation of hepatitis B virus (HBV) into hepatocellular carcinoma (HCC) and explore the underlying molecular mechanisms.

METHODS

We analyzed the mRNA microarray data of 119 HBV-related HCC tissues and 252 HBV-related non-tumor tissues in GSE55092, GSE84044 and GSE121248 from the GEO database, and the "sva" R package was used to remove the batch effects. Integration analysis was performed to identify the differentially expressed genes (DEGs) in HBV-related liver cancer and liver tissues with HBV infection. The significant DEGs were functionally annotated using GO and KEGG analyses, and the most important modules and hub genes were explored with STRING analysis. Kaplan-Meier and Oncomine databases were used to verify the HCC gene expression data in the TCGA database to explore the correlations of the hub genes with the occurrence, progression and prognosis of HCC. We also examined the expressions of the hub genes in 17 pairs of surgical specimens of HCC and adjacent tissues using RT-qPCR.

RESULTS

We identified a total of 121 DEGs and 3 genetic markers in HCC (P < 0.01). These DEGs included cyclin1 (CDK1), cyclin B1 (CCNB1), and nuclear division cycle 80 (NDC80), which participated in cell cycle, pyrimidine metabolism and DNA replication and were highly correlated (P < 0.05). Analysis of the UALCAN database confirmed high expressions of these 3 genes in HCC tissues, which were correlated with a low survival rate of the patients, as shown by Kaplan-Meier analysis of the prognostic data from the UALCAN database. CDK1, CCNB1 and NDC80 were all correlated with the clinical grading of HCC (P < 0.05). The results of RT-qPCR on the surgical specimens verified significantly higher expressions of CDK1, CCNB1 and NDC80 mRNA in HCC tissues than in the adjacent tissues.

CONCLUSION

CDK1, CCNB1 and NDC80 genes can be used as prognostic markers of HBV-related HCC and may serve as potential targets in preclinical studies and clinical treatment of HCC.

Intratumor heterogeneity: the hidden barrier to immunotherapy against MSI tumors from the perspective of IFN-γ signaling and tumor-infiltrating lymphocytes

In this era of precision medicine, with the help of biomarkers, immunotherapy has significantly improved prognosis of many patients with malignant tumor. Deficient mismatch repair (dMMR)/microsatellite instability (MSI) status is used as a biomarker in clinical practice to predict favorable response to immunotherapy and prognosis. MSI is an important characteristic which facilitates mutation and improves the likelihood of a favorable response to immunotherapy. However, many patients with dMMR/MSI still respond poorly to immunotherapies, which partly results from intratumor heterogeneity propelled by dMMR/MSI. In this review, we discuss how dMMR/MSI facilitates mutations in tumor cells and generates intratumor heterogeneity, especially through type II interferon (IFN-γ) signaling and tumor-infiltrating lymphocytes (TILs). We discuss the mechanism of immunotherapy from the perspective of dMMR/MSI, molecular pathways and TILs, and we discuss how intratumor heterogeneity hinders the therapeutic effect of immunotherapy. Finally, we summarize present techniques and strategies to look at the tumor as a whole to design personalized regimes and achieve favorable prognosis.

Comparative Analysis of Six IRF Family Members in Alveolar Epithelial Cell-Intrinsic Antiviral Responses

Host cell-intrinsic antiviral responses are largely mediated by pattern-recognition receptor (PRR) signaling and the interferon (IFN) system. The IFN regulatory factor (IRF) family of transcription factors takes up a central role in transcriptional regulation of antiviral innate immunity. IRF3 and IRF7 are known to be key players downstream of PRRs mediating the induction of type I and III IFNs. IFN signaling then requires IRF9 for the expression of the full array of interferon stimulated genes (ISGs) ultimately defining the antiviral state of the cell. Other members of the IRF family clearly play a role in mediating or modulating IFN responses, such as IRF1, IRF2 or IRF5, however their relative contribution to mounting a functional antiviral response is much less understood. In this study, we systematically and comparatively assessed the impact of six members of the IRF family on antiviral signaling in alveolar epithelial cells. We generated functional knockouts of IRF1, -2, -3, -5, -7, and -9 in A549 cells, and measured their impact on the expression of IFNs and further cytokines, ISGs and other IRFs, as well as on viral replication. Our results confirmed the vital importance of IRF3 and IRF9 in establishing an antiviral state, whereas IRF1, 5 and 7 were largely dispensable. The previously described inhibitory activity of IRF2 could not be observed in our experimental system.

Current understanding of cancer-intrinsic PD-L1: regulation of expression and its protumoral activity

In the last decade, we have witnessed an unprecedented clinical success in cancer immunotherapies targeting the programmed cell-death ligand 1 (PD-L1) and programmed cell-death 1 (PD-1) pathway. Besides the fact that PD-L1 plays a key role in immune regulation in tumor microenvironment, recently a plethora of reports has suggested a new perspective of non-immunological functions of PD-L1 in the regulation of cancer intrinsic activities including mesenchymal transition, glucose and lipid metabolism, stemness, and autophagy. Here we review the current understanding on the regulation of expression and intrinsic protumoral activity of cancer-intrinsic PD-L1.

Overexpression of IRF3 Predicts Poor Prognosis in Clear Cell Renal Cell Carcinoma

Background

Growing findings have demonstrated that interferon regulatory transcription factor (IRF) family members are linked to the progression of various cancers. However, the roles of IRFs in clear cell renal cell carcinoma (ccRCC) remain undefined. Herein, we conducted a comprehensive analysis using the bioinformatics method to evaluate the expression patterns, clinical significance, and regulation of IRFs-related mechanisms in patients with ccRCC.

Methods

Data from the Cancer Genome Atlas (TCGA), International Cancer Genome Consortium (ICGA), and Gene Expression Omnibus (GEO) databases were used for investigation comprehensively. Specifically, we carried out a series of analyses to identify the candidate IRF and to explore its potential action mechanisms using the gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. What is more, we emphatically investigate the association of candidate IRF with tumor immunity in ccRCC through the CIBERSORT algorithm, TIMER and GEPIA databases.

Results

Herein, IRF3 was identified as candidate IRF, which was highly expressed in ccRCC, and its overexpression was significantly associated with worse clinical outcomes and adverse overall survival. Uni- and multi-variate Cox regression analysis demonstrated that IRF3 overexpression was an independent predictor of worse prognosis. Functional enrichment analysis showed that IRF3 might participate in several cancer-related biological processes and signaling pathways, thereby promoting the progression of ccRCC. Additionally, we found that IRF3 was remarkably associated with tumor-infiltrating immune cells (TIICs) and various immune-related genes.

Conclusion

Herein, we identified IRF3 from the IRF gene family members, which could serve as promising prognostic marker and therapeutic target in ccRCC.

IRF1 Inhibits Autophagy-Mediated Proliferation of Colorectal Cancer via Targeting ATG13

IRF1 is a nuclear transcription factor that mediates interferon effects and appears to have anti-tumor activity. To determine the roles of IRF1 in colorectal cancer (CRC), we investigated the effects of IRF1 in CRC cells. We found that IRF1 inhibit cell proliferation and tumor growth. Under starvation conditions, IRF1 enhanced apoptosis and reduced autophagic flux. ATG13, an important factor of autophagy complex, was confirmed as a target of IRF1. These findings indicated that IRF1 function as a tumor suppressor in CRC and inhibit autophagy through ATG13, targeting this pathway may provide new insights into the molecular mechanisms of CRC progression.

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.

Hepatic IFNL4 Gene Activation in Hepatocellular Carcinoma Patients with Regard to Etiology

Hepatocellular carcinoma (HCC) is a malignancy with a leading lethality. The etiology is quite diverse, ranging from viral infections to metabolic disorders or intoxications, and associates with specific somatic mutational patterns and specific host immunological phenotypes. Particularly, hepatitis C virus (HCV)-infected liver is featured by an activation of interferon (IFN)-stimulated genes (ISGs; IFN signature), which we suppose is driven by type III IFNL4. Taking advantage of the TCGA collection of HCC patients of various different etiologies, this study aimed at validating our previous findings on hepatic IFNL4 gene activation in HCV infection in an independent and larger cohort of patients with advanced liver disease. In a cohort of n = 377 cases, the entirety of the sequencing data was used to assess the IFNL genotypes, and the cases were stratified for etiology. The number of IFNL4 transcripts within nonmalignant and malignant tissues was found to be more abundant in patients with HCV or HCV/HBV infections when compared to other risk factors. Moreover, in patients with HCV infection as a risk factor, a close, positive relationship was found between ISG activation and the number of functional IFNL4 transcripts. Data on this independent TCGA sample support the concept of an IFNL4-dependent HCV-driven activation of hepatic ISGs. In addition to that, they add to the understanding of etiology-related host immunological phenotypes in HCC.

Disrupting Mitochondrial Electron Transfer Chain Complex I Decreases Immune Checkpoints in Murine and Human Acute Myeloid Leukemic Cells

Oxidative metabolism is crucial for leukemic stem cell (LSC) function and drug resistance in acute myeloid leukemia (AML). Mitochondrial metabolism also affects the immune system and therefore the anti-tumor response. The modulation of oxidative phosphorylation (OxPHOS) has emerged as a promising approach to improve the therapy outcome for AML patients. However, the effect of mitochondrial inhibitors on the immune compartment in the context of AML is yet to be explored. Immune checkpoints such as ectonucleotidase CD39 and programmed dead ligand 1 (PD-L1) have been reported to be expressed in AML and linked to chemo-resistance and a poor prognosis. In the present study, we first demonstrated that a novel selective electron transfer chain complex (ETC) I inhibitor, EVT-701, decreased the OxPHOS metabolism of murine and human cytarabine (AraC)-resistant leukemic cell lines. Furthermore, we showed that while AraC induced an immune response regulation by increasing CD39 expression and by reinforcing the interferon-γ/PD-L1 axis, EVT-701 reduced CD39 and PD-L1 expression in vitro in a panel of both murine and human AML cell lines, especially upon AraC treatment. Altogether, this work uncovers a non-canonical function of ETCI in controlling CD39 and PD-L1 immune checkpoints, thereby improving the anti-tumor response in AML.

Regulatory mechanisms of immune checkpoints PD-L1 and CTLA-4 in cancer

The cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4)/B7 and programmed death 1 (PD-1)/ programmed cell death-ligand 1 (PD-L1) are two most representative immune checkpoint pathways, which negatively regulate T cell immune function during different phases of T-cell activation. Inhibitors targeting CTLA-4/B7 and PD1/PD-L1 pathways have revolutionized immunotherapies for numerous cancer types. Although the combined anti-CTLA-4/B7 and anti-PD1/PD-L1 therapy has demonstrated promising clinical efficacy, only a small percentage of patients receiving anti-CTLA-4/B7 or anti-PD1/PD-L1 therapy experienced prolonged survival. Regulation of the expression of PD-L1 and CTLA-4 significantly impacts the treatment effect. Understanding the in-depth mechanisms and interplays of PD-L1 and CTLA-4 could help identify patients with better immunotherapy responses and promote their clinical care. In this review, regulation of PD-L1 and CTLA-4 is discussed at the levels of DNA, RNA, and proteins, as well as indirect regulation of biomarkers, localization within the cell, and drugs. Specifically, some potential drugs have been developed to regulate PD-L1 and CTLA-4 expressions with high efficiency.

Interferon regulatory factor 1 (IRF-1) downregulates Checkpoint kinase 1 (CHK1) through miR-195 to upregulate apoptosis and PD-L1 expression in Hepatocellular carcinoma (HCC) cells

BACKGROUND

CHK1 is considered an oncogene with overexpression in numerous cancers. However, CHK1 signalling regulation in hepatocellular carcinoma (HCC) remains unclear.

METHODS

CHEK1 mRNA, protein, pri-miR-195 and miR-195 expression in HCC tissue was determined by qPCR, WB and IF staining assay. Survival analyses in HCC with high- and low-CHEK1 mRNA expression was performed using TCGA database. Relative luciferase activity was investigated in HCC cells transfected with p-CHEK1 3'UTR. Apoptosis was detected by TUNEL assay. NK and CD8+ T cells were analysed by flow cytometry.

RESULTS

CHK1 is increased in human HCC tumours compared with non-cancerous liver. High CHK1 predicts worse prognosis. IFN-γ suppresses CHK1 via IRF-1 in HCC cells. The molecular mechanism of IRF-1 suppressing CHK1 is post-transcriptional by promoting miR-195 binding to CHEK1 mRNA 3'UTR, which exerts a translational blockade. Upregulated IRF-1 inhibits CHK1, which induces apoptosis of HCC cells. Likewise, CHK1 inhibition augments cellular apoptosis in HCC tumours. This effect may be a result of increased tumour NK cell infiltration. However, IRF-1 expression or CHK1 inhibition also upregulates PD-L1 expression via increased STAT3 phosphorylation.

CONCLUSIONS

IRF-1 induces miR-195 to suppress CHK1 protein expression. Both increased IRF-1 and decreased CHK1 upregulate cellular apoptosis and PD-L1 expression in HCC.

Interferon regulatory factor 1(IRF-1) activates anti-tumor immunity via CXCL10/CXCR3 axis in hepatocellular carcinoma (HCC)

Interferon regulatory factor 1 (IRF-1) is a tumor suppressor gene in cancer biology with anti-proliferative and pro-apoptotic effect on cancer cells, however mechanisms of IRF-1 regulating tumor microenvironment (TME) in hepatocellular carcinoma (HCC) remain only partially characterized. Here, we investigated that IRF-1 regulates C-X-C motif chemokine 10 (CXCL10) and chemokine receptor 3 (CXCR3) to activate anti-tumor immunity in HCC. We found that IRF-1 mRNA expression was positively correlated with CXCL10 and CXCR3 through qRT-PCR assay in HCC tumors and in analysis of the TCGA database. IRF-1 response elements were identified in the CXCL10 promoter region, and ChIP-qPCR confirmed IRF-1 binding to promote CXCL10 transcription. IRF-2 is a competitive antagonist for IRF-1 mediated transcriptional effects, and overexpression of IRF-2 decreased basal and IFN-γ induced CXCL10 expression. Although IRF-1 upregulated CXCR3 expression in HCC cells, it inhibited proliferation and exerted pro-apoptotic effects, which overcome proliferation partly mediated by activating the CXCL10/CXCR3 autocrine axis. In vitro and in vivo studies showed that IRF-1 increased CD8⁺ T cells, NK and NKT cells migration, and activated IFN-γ secretion in NK and NKT cells to induce tumor apoptosis through the CXCL10/CXCR3 paracrine axis. Conversely, this effect was markedly abrogated in HCC tumor bearing mice deficient in CXCR3. Therefore, the IRF-1/CXCL10/CXCR3 axis contributes to the anti-tumor microenvironment in HCC.

Regulation of PD-L1 expression in the tumor microenvironment

Programmed death-ligand 1 (PD-L1) on cancer cells engages with programmed cell death-1 (PD-1) on immune cells, contributing to cancer immune escape. For multiple cancer types, the PD-1/PD-L1 axis is the major speed-limiting step of the anti-cancer immune response. In this context, blocking PD-1/PD-L1 could restore T cells from exhausted status and eradicate cancer cells. However, only a subset of PD-L1 positive patients benefits from α-PD-1/PD-L1 therapies. Actually, PD-L1 expression is regulated by various factors, leading to the diverse significances of PD-L1 positivity. Understanding the mechanisms of PD-L1 regulation is helpful to select patients and enhance the treatment effect. In this review, we focused on PD-L1 regulators at the levels of transcription, post-transcription, post-translation. Besides, we discussed the potential applications of these laboratory findings in the clinic.

Increased Expression of Programmed Death Ligand 1 in Hepatocellular Carcinoma of Patients with Hepatitis B Virus Pre-S2 Mutant

Purpose

Chronic hepatitis B virus (HBV) infection is a major risk factor for hepatocellular carcinoma (HCC), a leading cause of cancer-related death worldwide. The HCC patients who harbor HBV pre-S2 mutant, an oncoprotein that plays key roles in HCC development, have been closely associated with a worse prognosis after curative surgical resection, suggesting an urgent need for alternative therapeutic options to improve their survival. In this study, we aimed to evaluate the expression profiles of programmed death 1 (PD-1) and programmed death ligand 1 (PD-L1), two of the most well-studied immune checkpoint molecules that promote tumor immune evasion, in tumor of the pre-S2 mutant-positive/high HCC patients.

Methods

We classified 40 HBV-related HCC patients into the pre-S2-positive/high and -negative/low groups by a next-generation sequencing-based approach. The fluorescent immunohistochemistry staining was performed to detect the expression of PD-1 and PD-L1 in HCC tissues of patients.

Results

We showed that patients with either deletion spanning pre-S2 gene segment or high percentage of pre-S2 plus pre-S1+pre-S2 deletion (the pre-S2 mutant-positive/high group) exhibited a significantly higher density of PD-L1-positive cells in HCC tissues than those without. Moreover, the percentage of pre-S2 plus pre-S1+pre-S2 deletion displayed a high positive correlation with the density of PD-L1-positive cells in HCC tissues.

Conclusion

The increased expression of PD-L1 in tumor tissues of the pre-S2 mutant-positive HCC patients suggest that pre-S2 mutant may play a potential role in dysregulation of tumor immune microenvironment in the progression of HBV-related HCC, implicating for the development of future therapeutic strategies.

Transcriptional Regulation of Cancer Immune Checkpoints: Emerging Strategies for Immunotherapy

The study of immune evasion has gained a well-deserved eminence in cancer research by successfully developing a new class of therapeutics, immune checkpoint inhibitors, such as pembrolizumab and nivolumab, anti-PD-1 antibodies. By aiming at the immune checkpoint blockade (ICB), these new therapeutics have advanced cancer treatment with notable increases in overall survival and tumor remission. However, recent reports reveal that 40-60% of patients fail to benefit from ICB therapy due to acquired resistance or tumor relapse. This resistance may stem from increased expression of co-inhibitory immune checkpoints or alterations in the tumor microenvironment that promotes immune suppression. Because these mechanisms are poorly elucidated, the transcription factors that regulate immune checkpoints, known as "master regulators", have garnered interest. These include AP-1, IRF-1, MYC, and STAT3, which are known to regulate PD/PD-L1 and CTLA-4. Identifying these and other potential master regulators as putative therapeutic targets or biomarkers can be facilitated by mining cancer literature, public datasets, and cancer genomics resources. In this review, we describe recent advances in master regulator identification and characterization of the mechanisms underlying immune checkpoints regulation, and discuss how these master regulators of immune checkpoint molecular expression can be targeted as a form of auxiliary therapeutic strategy to complement traditional immunotherapy.