PD-L1 (CD274) and PD-L2 (PDCD1LG2) promoter methylation is associated with HPV infection and transcriptional repression in head and neck squamous cell carcinomas

The dynamic role of immune checkpoint molecules in diagnosis, prognosis, and treatment of head and neck cancers

Head and neck cancer (HNC) is the sixth most common cancer type, accounting for approximately 277,597 deaths worldwide. Recently, the Food and Drug Administration (FDA) has approved immune checkpoint blockade (ICB) agents targeting programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) as a treatment regimen for head and neck squamous cell carcinomas (HNSCC). Studies have reported the role of immune checkpoint inhibitors as targeted therapeutic regimens that unleash the immune response against HNSCC tumors. However, the overall response rates to immunotherapy vary between 14-32% in recurrent or metastatic HNSCC, with clinical response and treatment success being unpredictable. Keeping this perspective in mind, it is imperative to understand the role of T cells, natural killer cells, and antigen-presenting cells in modulating the immune response to immunotherapy. In lieu of this, these immune molecules could serve as prognostic and predictive biomarkers to facilitate longitudinal monitoring and understanding of treatment dynamics. These immune biomarkers could pave the path for personalized monitoring and management of HNSCC. In this review, we aim to provide updated immunological insight on the mechanism of action, expression, and the clinical application of immune cells' stimulatory and inhibitory molecules as prognostic and predictive biomarkers in HNC. The review is focused mainly on CD27 and CD137 (members of the TNF-receptor superfamily), natural killer group 2 member D (NKG2D), tumor necrosis factor receptor superfamily member 4 (TNFRSF4 or OX40), S100 proteins, PD-1, PD-L1, PD-L2, T cell immunoglobulin and mucin domain 3 (TIM-3), cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), lymphocyte-activation gene 3 (LAG-3), indoleamine-pyrrole 2,3-dioxygenase (IDO), B and T lymphocyte attenuator (BTLA). It also highlights the importance of T, natural killer, and antigen-presenting cells as robust biomarker tools for understanding immune checkpoint inhibitor-based treatment dynamics. Though a comprehensive review, all aspects of the immune molecules could not be covered as they were beyond the scope of the review; Further review articles can cover other aspects to bridge the knowledge gap.

Towards system genetics analysis of head and neck squamous cell carcinoma using the mouse model, cellular platform, and clinical human data

Head and neck squamous cell cancer (HNSCC) is a leading global malignancy. Every year, More than 830 000 people are diagnosed with HNSCC globally, with more than 430 000 fatalities. HNSCC is a deadly diverse malignancy with many tumor locations and biological characteristics. It originates from the squamous epithelium of the oral cavity, oropharynx, nasopharynx, larynx, and hypopharynx. The most frequently impacted regions are the tongue and larynx. Previous investigations have demonstrated the critical role of host genetic susceptibility in the progression of HNSCC. Despite the advances in our knowledge, the improved survival rate of HNSCC patients over the last 40 years has been limited. Failure to identify the molecular origins of development of HNSCC and the genetic basis of the disease and its biological heterogeneity impedes the development of new therapeutic methods. These results indicate a need to identify more genetic factors underlying this complex disease, which can be better used in early detection and prevention strategies. The lack of reliable animal models to investigate the underlying molecular processes is one of the most significant barriers to understanding HNSCC tumors. In this report, we explore and discuss potential research prospects utilizing the Collaborative Cross mouse model and crossing it to mice carrying single or double knockout genes (e.g. Smad4 and P53 genes) to identify genetic factors affecting the development of this complex disease using genome-wide association studies, epigenetics, microRNA, long noncoding RNA, lncRNA, histone modifications, methylation, phosphorylation, and proteomics.

PD-L1 (CD274) promoter hypomethylation predicts immunotherapy response in metastatic urothelial carcinoma

PD-L1 status assessed by immunohistochemistry (IHC) has failed to reliably predict outcomes for patients with metastatic urothelial carcinoma (mUC) on immune checkpoint blockade (ICB). PD-L1 promoter methylation is an epigenetic mechanism that has been shown to regulate PD-L1 mRNA expression in various malignancies. The aim of our present study was to evaluate the predictive potential of PD-L1 promoter methylation status (mPD-L1) in ICB-treated mUC compared to conventional IHC-based PD-L1 assessment. We quantified mPD-L1 in formalin-fixed and paraffin-embedded tissue sections using an established quantitative methylation-specific PCR assay (qMSP) in a well-characterized multicenter ICB-treated cohort comprising N = 107 patients with mUC. Additionally, PD-L1 protein expression in tumor tissues was assessed using regulatory approved IHC protocols. The effect of pharmacological hypomethylation by the DNA methyltransferase inhibitor decitabine in combination with interferon-γ stimulation in urothelial carcinoma cell lines was investigated by IHC and FACS. mPD-L1 hypomethylation predicted objective response rate at the first staging on ICB. Patients with tumors categorized as PD-L1 hypomethylated (lower quartile) showed significantly prolonged progression-free (PFS) and overall survival (OS) after ICB initiation. In contrast, PD-L1 protein expression status neither correlated with response nor survival. In multivariable Cox regression analyses, PD-L1 promoter hypermethylation remained an independent predictor of unfavorable PFS and OS. In urothelial carcinoma cell lines, pharmacological demethylation led to an upregulation of membranous PD-L1 expression and an enhanced inducibility of PD-L1 expression by interferon γ. Hypomethylation of the PD-L1 promoter is a promising predictive biomarker for response to ICB in patients with mUC.

Manipulating TGF-β signaling to optimize immunotherapy for cervical cancer

Cervical cancer is a serious threat to women's health globally. Therefore, identifying key molecules associated with cervical cancer progression is essential for drug development, disease monitoring, and precision therapy. Recently, TGF-β (transforming growth factor-beta) has been identified as a promising target for cervical cancer treatment. For advanced cervical cancer, TGF-β participates in tumor development by improving metastasis, stemness, drug resistance, and immune evasion. Accumulating evidence demonstrates that TGF-β blockade effectively improves the therapeutic effects, especially immunotherapy. Currently, agents targeting TGF-β and immune checkpoints such as PD-L1 have been developed and tested in clinical studies. These bispecific antibodies might have the potential as therapeutic agents for cervical cancer treatment in the future.

Examination of the Functional Relationship between PD-L1 DNA Methylation and mRNA Expression in Non-Small-Cell Lung Cancer

Immunotherapy targeting the interaction between programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) is a treatment option for patients with non-small-cell lung cancer (NSCLC). The expression of PD-L1 by the NSCLC cells determines treatment effectiveness, but the relationship between PD-L1 DNA methylation and expression has not been clearly described. We investigated PD-L1 DNA methylation, mRNA expression, and protein expression in NSCLC cell lines and tumor biopsies. We used clustered regularly interspaced short palindromic repeats-associated protein 9 (CRISPR-Cas9) to modify PD-L1 genetic contexts and endonuclease deficient Cas9 (dCas9) fusions with ten-eleven translocation methylcytosine dioxygenase 1 (TET1) and DNA (cytosine-5)-methyltransferase 3A (DNMT3A) to manipulate PD-L1 DNA methylation. In NSCLC cell lines, we identified specific PD-L1 CpG sites with methylation levels inversely correlated with PD-L1 mRNA expression. However, inducing PD-L1 mRNA expression with interferon-γ did not decrease the methylation level for these CpG sites, and using CRISPR-Cas9, we found that the CpG sites did not directly confer a negative regulation. dCas9-TET1 and dCas9-DNMT3A could induce PD-L1 hypo- and hyper-methylation, respectively, with the latter conferring a decrease in expression showing the functional impact of methylation. In NSCLC biopsies, the inverse correlation between the methylation and expression of PD-L1 was weak. We conclude that there is a regulatory link between PD-L1 DNA methylation and expression. However, since these measures are weakly associated, this study highlights the need for further research before PD-L1 DNA methylation can be implemented as a biomarker and drug target for measures to improve the effectiveness of PD-1/PD-L1 immunotherapy in NSCLC.

IKZF3 is a novel prognostic biomarker for head and neck squamous cell carcinoma: A study based on bioinformatics analysis

In the past few years, immunotherapy of tumors has become an extensive research hotspot, and the value of IKZF family genes in the tumor microenvironment has also been increasingly recognized. However, the expression of the IKAROS family zinc finger 3 (IKZF3) gene in human head and neck squamous cell carcinoma (HNSCC) and its prognostic value were not reported for the main subset until now. In the present study, we analyzed the relationship between IKZF3 gene expression and the survival of HNSCC patients. To evaluate the potential of IKZF3 as a prognostic biomarker for HNSCC comprehensively, multiple online analysis tools, including UALCAN, cBioPortal, GEPIA, WebGestalt, String, Genomic Data Commons, and TIMER databases were utilized in our study. We observed that the HNSCC patients with higher IKZF3 expression tended to exhibit longer overall survival. Univariate and multivariate Cox regression analyses indicated that age and grade were independent prognostic indicators in HNSCC. Moreover, Gene Ontology and KEGG function enrichment analyses showed that several pathways in HNSCC might be pivotal pathways regulated by IKZF3, which revealed that IKZF3 was probably participating in the occurrence and development of HNSCC. Furthermore, the hypomethylation of the IKZF3 gene was closely associated with genes that observed mutation in HNSCC. IKZF3 was significantly correlated with several immune cells in HNSCC (e.g., CD8+ T cell, CD4+ cell, and dendritic cell). We explored the potential prognostic values and roles of the IKZF3 in HNSCC, revealing that IKZF3 was probably a novel and reliable prognostic biomarker for patients with HNSCC.

Tumor immune checkpoints and their associated inhibitors

Immunological evasion is one of the defining characteristics of cancers, as the immune modification of an immune checkpoint (IC) confers immune evasion capabilities to tumor cells. Multiple ICs, such as programmed cell death protein-1 (PD-1) and cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), can bind to their respective receptors and reduce tumor immunity in a variety of ways, including blocking immune cell activation signals. IC blockade (ICB) therapies targeting these checkpoint molecules have demonstrated significant clinical benefits. This is because antibody-based IC inhibitors and a variety of specific small molecule inhibitors can inhibit key oncogenic signaling pathways and induce durable tumor remission in patients with a variety of cancers. Deciphering the roles and regulatory mechanisms of these IC molecules will provide crucial theoretical guidance for clinical treatment. In this review, we summarize the current knowledge on the functional and regulatory mechanisms of these IC molecules at multiple levels, including epigenetic regulation, transcriptional regulation, and post-translational modifications. In addition, we provide a summary of the medications targeting various nodes in the regulatory pathway, and highlight the potential of newly identified IC molecules, focusing on their potential implications for cancer diagnostics and immunotherapy.

Current insight into the regulation of PD-L1 in cancer

The molecular mechanisms underlying cancer immune escape are a core topic in cancer immunology research. Cancer cells can escape T cell-mediated cellular cytotoxicity by exploiting the inhibitory programmed cell-death protein 1 (PD-1)/programmed cell death ligand 1 (PD-L1, CD274) immune checkpoint. Studying the PD-L1 regulatory pattern of tumor cells will help elucidate the molecular mechanisms of tumor immune evasion and improve cancer treatment. Recent studies have found that tumor cells regulate PD-L1 at the transcriptional, post-transcriptional, and post-translational levels and influence the anti-tumor immune response by regulating PD-L1. In this review, we focus on the regulation of PD-L1 in cancer cells and summarize the underlying mechanisms.

Tissue and circulating PD-L2: moving from health and immune-mediated diseases to head and neck oncology

Amongst the chief targets of immune-checkpoint inhibitors (ICIs), namely the Programmed cell death protein 1 (PD-1)/PD-Ligands (Ls) axis, most research has focused on PD-L1, while to date PD-L2 is still under-investigated. However, emerging data support PD-L2 relevant expression in malignancies of the head and neck area, mostly in head and neck squamous cell carcinoma (HNSCC) and salivary gland cancers (SGCs). In this context, ICIs have achieved highly heterogeneous outcomes, emphasizing an urgent need for the identification of predictive biomarkers. With the present review, we aimed at describing PD-L2 biological significance by focusing on its tissue expression, its binding to PD-1 and RGMb receptors, and its impact on physiological and anti-cancer immune response. Specifically, we reported PD-L2 expression rates and significant clinical correlates among different head and neck cancer histotypes. Finally, we described the biology of soluble PD-L2 form and its potential application as a prognostic and/or predictive circulating biomarker.

CD274 (PD-L1) Methylation is an Independent Predictor for Bladder Cancer Patients' Survival

This study was carried out to demonstrate the prognostic value of CD274 (PD-L1 promoter gene) methylation in bladder cancer patients. UCSC Xena database was searched for relevant information of PD-L1 (CD274) methylation and PD-L1 mRNA expression in bladder cancer. 407 bladder patients were included in our analyses. Multivariate analysis revealed that PD-L1 methylation was an independent predictor for OS (P = 0.037). Moreover, PD-L1 methylation might be a prognostic biomarker for immunotherapy response. However, PD-L1 methylation and PD-L1 mRNA expression were not statistically associated with chemotherapy response. In conclusion, PD-L1 methylation was an independent prognostic factor for bladder cancer patients.

Effect of CMNa combined with radiotherapy on the tumor immune microenvironment of mouse cervical cancer cell transplantation tumor model

In this study, we construct a subcutaneous tumor mice model of U14 cells, observe the tumor growth, and detect the expression of Foxp3 and VISTA in cervical cancer tissues and adjacent tissues during CMNa-enhancing radiotherapy.From the 15th day, compared with the control group, the tumor volume changes in each treatment group were significant (P < 0.01). CMNa combined with radiotherapy had an interactive effect and a positive effect in inhibiting tumor volume growth. There was no significant difference in the expression of Foxp3 and VISTA in mouse cervical cancer tissues and adjacent tissues in each group. The Foxp3 level in the RT group was the highest, and the CMNa group was the lowest. The VISTA level of the CMNa+RT group was the highest, the RT group is followed by, and the Control group is the lowest. The Foxp3 level of the CMNa group did not change much at each different point. The Foxp3 level in RT and CMNa+RT group gradually decreased after a transient increase, and the VISTA level in the CMNa+RT group increased more.Our results show that CMNa can enhance the efficacy of radiotherapy, and at the same time can reduce the compensatory increase in regulatory T cell Foxp3 levels caused by radiotherapy, and reduce the radiotherapy response. However, in the course of the treatment of the two, there may be a substantial increase in the level of VISTA, and the combined application of VISTA inhibitors may increase the anti-tumor response.

Head and Neck Cancers Are Not Alike When Tarred with the Same Brush: An Epigenetic Perspective from the Cancerization Field to Prognosis

Simple Summary

Squamous cell carcinomas affect different head and neck subsites and, although these tumors arise from the same epithelial lining and share risk factors, they differ in terms of clinical behavior and molecular carcinogenesis mechanisms. Differences between HPV-negative and HPV-positive tumors are those most frequently explored, but further data suggest that the molecular heterogeneity observed among head and neck subsites may go beyond HPV infection. In this review, we explore how alterations of DNA methylation and microRNA expression contribute to head and neck squamous cell carcinoma (HNSCC) development and progression. The association of these epigenetic alterations with risk factor exposure, early carcinogenesis steps, transformation risk, and prognosis are described. Finally, we discuss the potential application of the use of epigenetic biomarkers in HNSCC.

Abstract

Head and neck squamous cell carcinomas (HNSCC) are among the ten most frequent types of cancer worldwide and, despite all efforts, are still diagnosed at late stages and show poor overall survival. Furthermore, HNSCC patients often experience relapses and the development of second primary tumors, as a consequence of the field cancerization process. Therefore, a better comprehension of the molecular mechanisms involved in HNSCC development and progression may enable diagnosis anticipation and provide valuable tools for prediction of prognosis and response to therapy. However, the different biological behavior of these tumors depending on the affected anatomical site and risk factor exposure, as well as the high genetic heterogeneity observed in HNSCC are major obstacles in this pursue. In this context, epigenetic alterations have been shown to be common in HNSCC, to discriminate the tumor anatomical subsites, to be responsive to risk factor exposure, and show promising results in biomarker development. Based on this, this review brings together the current knowledge on alterations of DNA methylation and microRNA expression in HNSCC natural history, focusing on how they contribute to each step of the process and on their applicability as biomarkers of exposure, HNSCC development, progression, and response to therapy.

Immunoprofiles and DNA Methylation of Inflammatory Marker Genes in Ulcerative Colitis-Associated Colorectal Tumorigenesis

Immunological and epigenetic changes are interconnected and contribute to tumorigenesis. We determined the immunoprofiles and promoter methylation of inflammation-related genes for colitis-associated colorectal carcinomas (CA-CRC). The results were compared with Lynch syndrome (LS)-associated colorectal tumors, which are characterized by an active immune environment through inherited mismatch repair defects. CA-CRCs (n = 31) were immunohistochemically evaluated for immune cell scores (ICSs) and PDCD1 and CD274 expression. Seven inflammation-associated genes (CD274, NTSR1, PPARG, PTGS2, PYCARD, SOCS1, and SOCS2), the repair gene MGMT, and eight standard marker genes for the CpG Island Methylator Phenotype (CIMP) were investigated for promoter methylation in CA-CRCs, LS tumors (n = 29), and paired normal mucosae by multiplex ligation-dependent probe amplification. All but one CA-CRCs were microsatellite-stable and all LS tumors were microsatellite-unstable. Most CA-CRCs had a high ICS (55%) and a positive CD274 expression in immune cells (52%). NTSR1 revealed frequent tumor-specific hypermethylation in CA-CRC and LS. When compared to LS mucosae, normal mucosae from patients with CA-CRC showed significantly higher methylation of NTSR1 and most CIMP markers. In conclusion, CA-CRCs share a frequent ICS^high/CD274^pos expression pattern with LS tumors. Elevated methylation in normal mucosa may indicate field cancerization as a feature of CA-CRC-associated tumorigenesis.

Expression and clinicopathological significance of Foxp3 and VISTA in cervical cancer

OBJECTIVE

To detect the expression differences of Foxp3 and VISTA in chronic cervical inflammation, cervical intraepithelial neoplasia, and cervical cancer, and to explore the role of Foxp3 and VISTA in the development of cervical cancer and the effect of Foxp3 and VISTA on the prognosis of cervical cancer, to provide a theoretical basis for clinical immunotherapy of cervical cancer.

METHODS

We collected 130 paraffin specimens of cervical tissue, which included 70 cases of cervical cancer tissue, 40 cases of cervical intraepithelial neoplasia tissues and 20 cases of chronic cervicitis. The expression of Foxp3 and VISTA in each group was detected, and the study was conducted based on the clinicopathological characteristics of the patients. The patients were followed up and the prognosis was statistically analyzed.

RESULT

1. The expression of Foxp3 and VISTA was statistically different between the cervical cancer group and other groups. 2. Expressions of Foxp3 and VISTA were significantly correlated. 3. In 70 cases of cervical cancer, the expression of Foxp3 and VISTA was related to the clinical stage. 4. The 3-year survival rate of 70 patients with cervical cancer was 72.9%, and there were no factors affecting 3-year OS found. The expression of Foxp3 and VISTA was significantly correlated with the prognosis of cervical cancer. Foxp3 and VISTA double positive expression group had the worst prognosis.

CONCLUSION

1. In cervical cancer, the expression of Foxp3 and VISTA was significantly higher than that of cervical intraepithelial neoplasia and chronic cervicitis, which suggested that they were closely related to the occurrence and growth of cervical cancer. 2. The expression of Foxp3 and VISTA was significantly related. 3. The positive expression of Foxp3 and VISTA could be used as independent prognostic factors for cervical cancer prognosis providing a strong basis for cervical cancer immunotherapy.

Epitranscriptomic Approach: To Improve the Efficacy of ICB Therapy by Co-Targeting Intracellular Checkpoint CISH

Cellular immunotherapy has recently emerged as a fourth pillar in cancer treatment co-joining surgery, chemotherapy and radiotherapy. Where, the discovery of immune checkpoint blockage or inhibition (ICB/ICI), anti-PD-1/PD-L1 and anti-CTLA4-based, therapy has revolutionized the class of cancer treatment at a different level. However, some cancer patients escape this immune surveillance mechanism and become resistant to ICB-therapy. Therefore, a more advanced or an alternative treatment is required urgently. Despite the functional importance of epitranscriptomics in diverse clinico-biological practices, its role in improving the efficacy of ICB therapeutics has been limited. Consequently, our study encapsulates the evidence, as a possible strategy, to improve the efficacy of ICB-therapy by co-targeting molecular checkpoints especially N6A-modification machineries which can be reformed into RNA modifying drugs (RMD). Here, we have explained the mechanism of individual RNA-modifiers (editor/writer, eraser/remover, and effector/reader) in overcoming the issues associated with high-dose antibody toxicities and drug-resistance. Moreover, we have shed light on the importance of suppressor of cytokine signaling (SOCS/CISH) and microRNAs in improving the efficacy of ICB-therapy, with brief insight on the current monoclonal antibodies undergoing clinical trials or already approved against several solid tumor and metastatic cancers. We anticipate our investigation will encourage researchers and clinicians to further strengthen the efficacy of ICB-therapeutics by considering the importance of epitranscriptomics as a personalized medicine.

CXCL10 Produced by HPV-Positive Cervical Cancer Cells Stimulates Exosomal PDL1 Expression by Fibroblasts via CXCR3 and JAK-STAT Pathways

Persistent infection with human papillomavirus (HPV) and immune surveillance failure may be the initiating factors for the carcinogenesis of cervical squamous cell carcinoma (CSCC). HPV infection might affect the innate immune pathway of cervical epithelial cells that constitute the “microenvironment” for tumor cells. Programmed death-ligand 1 (PD-L1) has been reported to be an immunosuppressor that helps cancer cells escape the actions of T cells. In the present study, CXCL10 was substantially upregulated both in cervical tissues of HPV infected patients with cervical intraepithelial neoplasia (CIN) or CSCC, as well as in HPV16 E6/E7 transgenic murine cervix. The HPV-positive (HPV+) cervical cancer cell lines SiHa and Caski secreted increased levels of CXCL10 compared to human foreskin fibroblasts (HFF-1), and its receptor CXCR3 was overexpressed in HFF-1. After co-culture with SiHa or Caski, the JAK-STAT signaling pathway and exosomal PD-L1 expression were both upregulated in HFF-1. Recombinant human CXCL10 induced JAK-STAT and PD-L1, while the CXCL10-CXCR3 and JAK-STAT inhibitors AMG487 or ruxolitinib reduced the expression of PD-L1 in HFF-1 cells. Furthermore, the upregulated expression of PD-L1 was verified in HPV+ but not HPV-negative (HPV-) patients with cervical cancers by analysis of tissue microarray cores in 25 cervical lesion patients (P < 0.05). The results indicate that HPV infection can induce cervical cancer cells to secrete CXCL10, which binds to CXCR3 in the surrounding fibroblast cells,leading to JAK-STAT pathway activation and the subsequent upregulated expression of exosomal PD-L1. These mechanisms may help HPV to escape immune response attack, leading to carcinogenesis.

Characterizing DNA methylation signatures and their potential functional roles in Merkel cell carcinoma

BACKGROUND

Merkel cell carcinoma (MCC) is a rare but aggressive skin cancer with limited treatment possibilities. Merkel cell tumors display with neuroendocrine features and Merkel cell polyomavirus (MCPyV) infection in the majority (80%) of patients. Although loss of histone H3 lysine 27 trimethylation (H3K27me3) has been shown during MCC tumorigenesis, epigenetic dysregulation has largely been overlooked.

METHODS

We conducted global DNA methylation profiling of clinically annotated MCC primary tumors, metastatic skin tumors, metastatic lymph node tumors, paired normal tissues, and two human MCC cell lines using the Illumina Infinium EPIC DNA methylation BeadArray platform.

RESULTS

Significant differential DNA methylation patterns across the genome are revealed between the four tissue types, as well as based on MCPyV status. Furthermore, 964 genes directly regulated by promoter or gene body DNA methylation were identified with high enrichment in neuro-related pathways. Finally, our findings suggest that loss of H3K27me3 occupancy in MCC is attributed to KDM6B and EZHIP overexpression as a consequence of promoter DNA hypomethylation.

CONCLUSIONS

We have demonstrated specific DNA methylation patterns for primary MCC tumors, metastatic MCCs, and adjacent-normal tissues. We have also identified DNA methylation markers that not only show potential diagnostic or prognostic utility in MCC management, but also correlate with MCC tumorigenesis, MCPyV expression, neuroendocrine features, and H3K27me3 status. The identification of DNA methylation alterations in MCC supports the need for further studies to understand the clinical implications of epigenetic dysregulation and potential therapeutic targets in MCC.

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.

Targeting the PD-1 Axis with Pembrolizumab for Recurrent or Metastatic Cancer of the Uterine Cervix: A Brief Update

Even though cervical cancer is partly preventable, it still poses a great public health problem throughout the world. Current therapies have vastly improved the clinical outcomes of cervical cancer patients, but progress in new systemic treatment modalities has been slow in the last years. Especially for patients with advanced disease this is discouraging, as their prognosis remains very poor. The pathogen-induced nature, the considerable mutational load, the involvement of genes regulating the immune response, and the high grade of immune infiltration, suggest that immunotherapy might be a promising strategy to treat cervical cancer. In this literature review, we focus on the use of PD-1 blocking therapy in cervical cancer, pembrolizumab in particular, as it is the only approved immunotherapy for this disease. We discuss why it has great clinical potential, how it opens doors for personalized treatment in cervical cancer, and which trials are aiming to expand its clinical use.

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.

Identification of functional methylated CpG loci in PD-L1 promoter as the novel epigenetic biomarkers for primary gastric cancer

Gastric cancer (GC) is considered one of the most lethal malignancies worldwide due to poor prognosis. Aberrant methylation has been demonstrated to be involved in PD-L1 dysregulated expression in human cancers and possesses a great value as a diagnostic biomarker. Given that, in this study, we investigated the methylation status of PD-L1 as a promising biomarker in primary gastric tumors and identified functional CpG loci undergoing aberrant methylation through tumorigenesis of GC. PD-L1 methylation was initially evaluated in-silico using TCGA-STAD dataset. Pearson's correlation analysis was further employed to identify the most significant functional methylated CpG loci of PD-L1 gene in TCGA-STAD patient cohort. Methylation status and its correlation with PD-L1 expression were also validated using q-MSP and qRT-PCR in a set of internal samples, including 25 paired primary gastric tumors and adjacent normal tissues. The obtained results from TCGA-STAD showed that PD-L1 is significantly hypermethylated through gastric tumorigenesis, mostly in two CpG loci overlapping with cg19724470 and cg15837913 probes. Besides, PD-L1 DNA methylation was negatively correlated with PD-L1 expression in tumor samples. Furthermore, hypermethylation of cg19724470 and cg15837913 regions was validated in primary gastric tumors compared to adjacent normal samples. Also, ROC curve analysis illustrated the high diagnostic value of PD-L1 methylation for early detection of GC (AUC = 0.8110). In conclusion, the findings of this study suggested that PD-L1 expression is regulated by methylation in functional CpG loci and its methylation could be considered as a valuable diagnostic target for GC.

The DNA methylation landscape of PD-1 (PDCD1) and adjacent lncRNA AC131097.3 in head and neck squamous cell carcinoma

Aims: PD-1 expression is associated with DNA methylation in head and neck squamous cell carcinomas (HNSCCs). We performed methylation analysis at single CpG site resolution in order to understand epigenetic regulation. Materials and methods: CpG methylation analysis of PD-1 and long non-coding RNA (lncRNA) AC131097.3 was performed in n = 528 HNSCCs and n = 50 normal adjacent tissues provided by The Cancer Genome Atlas and in isolated leukocytes. Results: PD-1 mRNA and AC131097.3 lncRNA expression correlated inversely with promoter and positively with gene body CpG methylation. PD-1 and AC131097.3 are co-expressed. Methylation was sequence-contextually associated with human papillomavirus prognosis, mutational load, and immune infiltrates. Conclusions: The significance of PD-1 and AC131097.3 methylation is highly sequence-contextual. AC131097.3 might play a role in HNSCC.

Using Machine Learning Modeling to Explore New Immune-Related Prognostic Markers in Non-Small Cell Lung Cancer

OBJECTIVE

To find new immune-related prognostic markers for non-small cell lung cancer (NSCLC).

METHODS

We found GSE14814 is related to NSCLC in GEO database. The non-small cell lung cancer observation (NSCLC-OBS) group was evaluated for immunity and divided into high and low groups for differential gene screening according to the score of immune evaluation. A single factor COX regression analysis was performed to select the genes related to prognosis. A prognostic model was constructed by machine learning, and test whether the model has a test efficacy for prognosis. A chip-in-chip non-small cell lung cancer chemotherapy (NSCLC-ACT) sample was used as a validation dataset for the same validation and prognostic analysis of the model. The coexpression genes of hub genes were obtained by pearson analysis and gene enrichment, function enrichment and protein interaction analysis. The tumor samples of patients with different clinical stages were detected by immunohistochemistry and the expression difference of prognostic genes in tumor tissues of patients with different stages was compared.

RESULTS

By screening, we found that LYN, C3, COPG2IT1, HLA.DQA1, and TNFRSF17 is closely related to prognosis. After machine learning, we constructed the immune prognosis model from these 5 genes, and the model AUC values were greater than 0.9 at three time periods of 1, 3, and 5 years; the total survival period of the low-risk group was significantly better than that of the high-risk group. The results of prognosis analysis in ACT samples were consistent with OBS groups. The coexpression genes are mainly involved B cell receptor signaling pathway and are mainly enriched in apoptotic cell clearance. Prognostic key genes are highly correlated with PDCD1, PDCD1LG2, LAG3, and CTLA4 immune checkpoints. The immunohistochemical results showed that the expression of COPG2IT1 and HLA.DQA1 in stage III increased significantly and the expression of LYN, C3, and TNFRSF17 in stage III decreased significantly compared with that of stage I. The experimental results are consistent with the previous analysis.

CONCLUSION

LYN, C3, COPG2IT1, LA.DQA1, and NFRSF17 may be new immune markers to judge the prognosis of patients with non-small cell lung cancer.

The Extrinsic and Intrinsic Roles of PD-L1 and Its Receptor PD-1: Implications for Immunotherapy Treatment

Programmed death-ligand 1 (PD-L1) is an immune checkpoint inhibitor that binds to its receptor PD-1 expressed by T cells and other immune cells to regulate immune responses; ultimately preventing exacerbated activation and autoimmunity. Many tumors exploit this mechanism by overexpressing PD-L1 which often correlates with poor prognosis. Some tumors have also recently been shown to express PD-1. On tumors, PD-L1 binding to PD-1 on immune cells promotes immune evasion and tumor progression, primarily by inhibition of cytotoxic T lymphocyte effector function. PD-1/PD-L1-targeted therapy has revolutionized the cancer therapy landscape and has become the first-line treatment for some cancers, due to their ability to promote durable anti-tumor immune responses in select patients with advanced cancers. Despite this clinical success, some patients have shown to be unresponsive, hyperprogressive or develop resistance to PD-1/PD-L1-targeted therapy. The exact mechanisms for this are still unclear. This review will discuss the current status of PD-1/PD-L1-targeted therapy, oncogenic expression of PD-L1, the new and emerging tumor-intrinisic roles of PD-L1 and its receptor PD-1 and how they may contribute to tumor progression and immunotherapy responses as shown in different oncology models.

PD-1, CTLA4, PD-L1 and PD-L2 DNA methylation in papillary thyroid carcinoma

Aim: We investigated DNA methylation patterns of immune checkpoint genes PD-1, PD-L1, PD-L2, CTLA4 and an adjacent long noncoding RNA in papillary thyroid carcinoma (PTC). Materials & methods: DNA methylation and mRNA expression were examined in PTCs. DNA methylation was correlated with mRNA expression, BRAF and RAS mutational status, and immune cell infiltration. Results: Inverse correlations between DNA methylation and mRNA expression were observed. Immune checkpoint expression correlated positively, and DNA methylation negatively, with immune cell infiltration. Higher DNA methylation levels accompanied by lower immune checkpoint expression were observed in RAS-mutated tumors. Conclusion: We suggest epigenetic regulation of immune checkpoints in PTC. Methylation was associated with BRAF and RAS mutation status. DNA methylation might be a promising biomarker candidate in the context of immunotherapies in PTC.

Role of Epigenetic Modifications in Inhibitory Immune Checkpoints in Cancer Development and Progression

A balance between co-inhibitory and co-stimulatory signals in the tumor microenvironment (TME) is critical to suppress tumor development and progression, primarily via maintaining effective immunosurveillance. Aberrant expression of immune checkpoints (ICs), including programmed cell death protein 1 (PD-1), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), T cell immunoglobulin and mucin-domain containing-3 (TIM-3), lymphocyte-activation gene 3 (LAG-3) and T cell immunoreceptor with Ig and ITIM domains (TIGIT), can create an immune-subversive environment, which helps tumor cells to evade immune destruction. Recent studies showed that epigenetic modifications play critical roles in regulating the expression of ICs and their ligands in the TME. Reports showed that the promoter regions of genes encoding ICs/IC ligands can undergo inherent epigenetic alterations, such as DNA methylation and histone modifications (acetylation and methylation). These epigenetic aberrations can significantly contribute to the transcriptomic upregulation of ICs and their ligands. Epigenetic therapeutics, including DNA methyltransferase and histone deacetylase inhibitors, can be used to revert these epigenetic anomalies acquired during the progression of disease. These discoveries have established a promising therapeutic modality utilizing the combination of epigenetic and immunotherapeutic agents to restore the physiological epigenetic profile and to re-establish potent host immunosurveillance mechanisms. In this review, we highlight the roles of epigenetic modifications on the upregulation of ICs, focusing on tumor development, and progression. We discuss therapeutic approaches of epigenetic modifiers, including clinical trials in various cancer settings and their impact on current and future anti-cancer therapies.

[Prognostic and predictive methylation biomarkers in HNSCC : Epigenomic diagnostics for head and neck squamous cell carcinoma (HNSCC)]

BACKGROUND

Prognostic and predictive biomarkers for personalized treatment management in head and neck squamous cell carcinoma (HNSCC) are of great clinical interest.

OBJECTIVE

DNA methylation is an epigenetic process involved in gene regulation and could be a source of potential prognostic and predictive biomarkers.

METHODS

This study comprises literature research in PubMed and own studies.

RESULTS

Gene methylation, e.g. of PITX2, is a strong, human papillomavirus (HPV)-independent prognostic biomarker. SHOX2 and SEPT9 methylation in circulating cell-free DNA within blood plasma correlates with tumor stage and prognosis. Methylation of diverse immune checkpoints, e.g., PD‑1, PD-L1, and CTLA4, is also prognostic and correlates with gene expression.

CONCLUSION

DNA methylation is a source of efficient prognostic blood plasma- and tissue-based biomarkers. However, prior to clinical implementation, studies must prove that biomarker-guided treatment selection can lead to better outcomes or reduced toxicity. The applicability of DNA methylation as a predictive biomarker for targeted drug-based cancer therapy seems promising, although further validation is needed.

Prognostic and predictive value of PD-L2 DNA methylation and mRNA expression in melanoma

BACKGROUND

PD-L1 (programmed cell death 1 ligand 1) expression in melanoma has been associated with a better response to anti-PD-1 (programmed cell death 1) therapy. However, patients with PD-L1-negative melanomas can respond to anti-PD-1 blockade, suggesting that the other PD-1 ligand, PD-L2 (programmed cell death 1 ligand 2), might also be relevant for efficacy of PD-1 inhibition. We investigated PD-L2 expression and methylation as a prognostic and predictive biomarker in melanoma.

METHODS

DNA methylation at five CpG loci and gene expression of PD-L2 were evaluated with regard to survival in 470 melanomas from The Cancer Genome Atlas. PD-L2 promoter methylation in correlation with PD-L2 mRNA and protein expression was analyzed in human melanoma cell lines. Prognostic and predictive value of PD-L2 methylation was validated using quantitative methylation-specific PCR in a multicenter cohort of 129 melanoma patients receiving anti-PD-1 therapy. mRNA sequencing data of 121 melanoma patients receiving anti-PD-1 therapy provided by Liu et al. were analyzed for PD-L2 mRNA expression.

RESULTS

We found significant correlations between PD-L2 methylation and mRNA expression levels in melanoma tissues and cell lines. Interferon-γ inducible PD-L2 protein expression correlated with PD-L2 promoter methylation in melanoma cells. PD-L2 DNA promoter hypomethylation and high mRNA expression were found to be strong predictors of prolonged overall survival. In pre-treatment melanoma samples from patients receiving anti-PD-1 therapy, low PD-L2 DNA methylation and high PD-L2 mRNA expression predicted longer progression-free survival.

CONCLUSION

PD-L2 expression seems to be regulated via DNA promoter methylation. PD-L2 DNA methylation and mRNA expression may predict progression-free survival in melanoma patients receiving anti-PD-1 immunotherapy. Assessment of PD-L2 should be included in further clinical trials with anti-PD-1 antibodies.

HPV Involvement in the Tumor Microenvironment and Immune Treatment in Head and Neck Squamous Cell Carcinomas

Head and neck squamous cell carcinomas (HNSCC) are one of the most prevalent cancers worldwide. Active human papillomavirus (HPV) infection has been identified as an important additional risk factor and seems to be associated with a better prognosis in non-drinker and non-smoker young patients with oropharyngeal SCC. The better response of the immune system against the HPV-induced HNSCC is suspected as a potential explanation for the better prognosis of young patients. To further assess this hypothesis, our review aims to shed light the current knowledge about the impact of HPV infection on the immune response in the context of HNSCC, focusing on the innate immune system, particularly highlighting the role of macrophages, Langerhans and myeloid cells, and on the adaptative immune system, pointing out the involvement of T regulatory, T CD8 and T CD4 lymphocytes. In addition, we also review the preventive (HPV vaccines) and therapeutic (checkpoint inhibitors) strategies against HPV-related HNSCC, stressing the use of anti-CTLA4, PD-L1, PD-L2 antibodies alone and in combination with other agents able to modulate immune responses.

Ultrasound-Mediated Co-Delivery of miR-34a and sPD-1 Complexed with Microbubbles for Synergistic Cancer Therapy

Background

miR-34a was downregulated and PD-L1 was upregulated in cervical cancer; however, the treatment of cervical cancer lacks precision and targeting. This study explored the ultrasound-mediated co-delivery of miR-34a and sPD-1 complexes with microbubbles for synergistic cancer therapy.

Methods

Cationic lipid microbubbles (CLMBs) were prepared by membrane hydration and mechanical oscillation. U14 subcutaneous xenograft mice were injected with CLMBs-loaded sPD-1 and miR-34a combined with ultrasound targeted destruction, and tumor volume and tumor weight of mice were measured. TUNEL apoptosis test and the mRNA expression of apoptosis-related gene Bcl-2 and Bax were analyzed by qRT-PCR. Antitumor immune-related cytokines IFN-γ were investigated by qRT-PCR, LDH Cytotoxicity Assay Kit were performed to test cytotoxic T lymphocytes (CTL).

Results

CLMBs were successfully prepared and the plasmid bound to its surface. The tumor volume and weight were specifically decreased by ultrasound-mediated co-delivery of miR-34a and sPD-1 complexes with microbubbles, apoptosis was induced and the apoptosis suppressor gene Bcl-2 was downregulated and proapoptotic gene Bax were upregulated. qRT-PCR analysis revealed that antitumor immunity-related IFN-γ was strongly upregulated in mice, which were treated with CLMBs-loaded sPD-1 and miR-34a combined with ultrasound targeted destruction, and the percentage of CTL was increased.

Conclusion

These findings from the study demonstrated that CLMBs could deliver miR-34a and sPD-1, combined with ultrasound targeted destruction, could suppress the tumor tissue growing, induce apoptosis and enhance antitumor immunity in U14 subcutaneous xenograft mice.

Regulation of PD-L1 expression in cancer and clinical implications in immunotherapy

PD-1/PD-L1 immune checkpoint blockade therapy has become an effective method for the treatment of cancers in the clinic. It has great clinical advantages and therapeutic effects in the treatment of various cancers. However, a considerable number of cancer patients currently have relatively low response rates and drug resistance to PD-1/PD-L1 immunotherapy. Therefore, an in-depth understanding of the regulatory mechanism of PD-L1 expression in tumor cells will provide new insights into PD-1/PD-L1 immunotherapy. This review will systematically review the regulatory mechanisms of PD-L1 including genomic amplification, epigenetic regulation, transcriptional regulation, translational regulation and posttranslational modification. We will also discuss PD-L1 expression regulation in clinical applications. Finally, we hope to provide new routes for PD-1/PD-L1 immunotherapy in the clinic.

Humanized Mice as an Effective Evaluation System for Peptide Vaccines and Immune Checkpoint Inhibitors

Peptide vaccination was developed for the prevention and therapy of acute and chronic infectious diseases and cancer. However, vaccine development is challenging, because the patient immune system requires the appropriate human leukocyte antigen (HLA) recognition with the peptide. Moreover, antigens sometimes induce a low response, even if the peptide is presented by antigen-presenting cells and T cells recognize it. This is because the patient immunity is dampened or restricted by environmental factors. Even if the immune system responds appropriately, newly-developed immune checkpoint inhibitors (ICIs), which are used to increase the immune response against cancer, make the immune environment more complex. The ICIs may activate T cells, although the ratio of responsive patients is not high. However, the vaccine may induce some immune adverse effects in the presence of ICIs. Therefore, a system is needed to predict such risks. Humanized mouse systems possessing human immune cells have been developed to examine human immunity in vivo. One of the systems which uses transplanted human peripheral blood mononuclear cells (PBMCs) may become a new diagnosis strategy. Various humanized mouse systems are being developed and will become good tools for the prediction of antibody response and immune adverse effects.

Genome-Wide Profiling of Acquired Uniparental Disomy Reveals Prognostic Factors in Head and Neck Squamous Cell Carcinoma

Acquired uniparental disomy (aUPD) leads to homozygosity facilitating identification of monoallelically expressed genes. We analyzed single-nucleotide polymorphism array-based genotyping data of 448 head and neck squamous cell carcinoma (HNSCC) samples from The Cancer Genome Atlas to determine the frequency and distribution of aUPD regions and their association with survival, as well as to gain a better understanding of their influence on the tumor genome. We used expression data from the same dataset to identify differentially expressed genes between groups with and without aUPD. Univariate and multivariable Cox proportional hazards models were performed for survival analysis. We found that 82.14% of HNSCC samples carried aUPD; the most common regions were in chromosome 17p (31.25%), 9p (30.13%), and 9q (27.46%). In univariate analysis, five independent aUPD regions at chromosome 9p, two regions at chromosome 9q, and the CDKN2A region were associated with poor overall survival in all groups, including training and test sets and human papillomavirus (HPV)-negative samples. Forty-three genes in areas of aUPD including PD-L1 and CDKN2A were differentially expressed in samples with aUPD compared to samples without aUPD. In multivariable analysis, aUPD at the CDKN2A region was a significant predictor of overall survival in the whole cohort and in patients with HPV-negative HNSCC. aUPD at specific regions in the genome influences clinical outcomes of HNSCC and may be beneficial for selection of personalized therapy to prolong survival in patients with this disease.

Epigenetic Modifications in Head and Neck Cancer

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common human malignancy in the world, with high mortality and poor prognosis for patients. Among the risk factors are tobacco and alcohol intake, human papilloma virus, and also genetic and epigenetic modifications. Many studies show that epigenetic events play an important role in HNSCC development and progression, including DNA methylation, chromatin remodeling, histone posttranslational covalent modifications, and effects of non-coding RNA. Epigenetic modifications may influence silencing of tumor suppressor genes by promoter hypermethylation, regulate transcription by microRNAs and changes in chromatin structure, or induce genome instability through hypomethylation. Moreover, getting to better understand aberrant patterns of methylation may provide biomarkers for early detection and diagnosis, while knowledge about target genes of microRNAs may improve the therapy of HNSCC and extend overall survival. The aim of this review is to present recent studies which demonstrate the role of epigenetic regulation in the development of HNSCC.

DNA methylation of indoleamine 2,3-dioxygenase 1 (IDO1) in head and neck squamous cell carcinomas correlates with IDO1 expression, HPV status, patients' survival, immune cell infiltrates, mutational load, and interferon γ signature

Background

The immune checkpoint, indoleamine 2,3-dioxygenase 1, is under investigation as target of novel immunotherapies for cancers, including head and neck squamous cell carcinomas (HNSCC). The aim of our study was to analyze DNA methylation of the encoding gene (IDO1) in HNSCC.

Methods

Methylation of three CpG sites within the promoter, promoter flank, and gene body was investigated and correlated with mRNA expression, immune cell infiltration, mutational burden, human papillomavirus (HPV)-status, and overall survival in a cohort of N = 528 HNSCC patients obtained from The Cancer Genome Atlas. In addition, IDO1 immunohistochemistry and DNA methylation analysis was performed in an independent cohort of N = 138 HNSCC samples.

Findings

Significant inverse correlations of IDO1 methylation and IDO1 mRNA expression were found in the promoter and promoter flank region (Spearman's ρ = −0.163 and ρ = −0.377, respectively) while a positive correlation was present in the gene body (ρ = 0.502; all P < 0.001). IDO1 DNA methylation significantly correlated with IDO1 protein expressing immune cells as well as tumor cells. IDO1 promoter flank hypermethylation was significantly associated with poor overall survival (P < 0.001). In addition, we discovered significant correlations between IDO1 methylation and expression with RNA signatures of immune cell infiltrates and with HPV-status, mutational load (methylation only), and interferon γ signature.

Interpretation

Our results suggest IDO1 expression levels are epigenetically regulated by DNA methylation. This study provides rationale to test IDO1 methylation as potential biomarker for prediction of response to IDO1 immune checkpoint inhibitors in HNSCC.

Immunotherapy for Uterine Cervical Cancer

Cervical cancer is a malignant neoplastic disease that is the fourth most commonly occurring cancer in women worldwide. Since the introduction of angiogenesis inhibitors, treatments for recurrent and advanced cervical cancers have improved significantly in the past five years. However, the median overall survival in advanced cervical cancer is 16.8 months, with a 5-year overall survival rate of 68% for all stages, indicating that the effects of the treatment are still unsatisfactory. The development of a new treatment method is therefore imperative. Recently, in the clinical oncology field, remarkable progress has been made in immunotherapy. Immunotherapy is already established as standard therapy in some fields and in some types of cancers, and its clinical role in all areas, including the gynecology field, will change further based on the outcomes of currently ongoing clinical trials. This manuscript summarizes the results from previous clinical trials in cervical cancer and describes the ongoing clinical trials, as well as future directions.

Recent Findings in the Regulation of Programmed Death Ligand 1 Expression

With the recent approvals for the application of monoclonal antibodies that target the well-characterized immune checkpoints, immune therapy shows great potential against both solid and hematologic tumors. The use of these therapeutic monoclonal antibodies elicits inspiring clinical results with durable objective responses and improvements in overall survival. Agents targeting programmed cell death protein 1 (PD-1; also known as PDCD1) and its ligand (PD-L1) achieve a great success in immune checkpoints therapy. However, the majority of patients fail to respond to PD-1/PD-L1 axis inhibitors. Expression of PD-L1 on the membrane of tumor and immune cells has been shown to be associated with enhanced objective response rates to PD-1/PD-L1 inhibition. Thus, an improved understanding of how PD-L1 expression is regulated will enable us to better define its role as a predictive marker. In this review, we summarize recent findings in the regulation of PD-L1 expression.

Clinicopathological, immune and molecular correlates of PD-L2 methylation in gastric adenocarcinomas

Aim: We investigated the significance of PD-L2 DNA methylation in gastric adenocarcinomas. Methods: We analyzed the methylation at different CpG sites within the PD-L2-encoding gene PDCD1LG2 with regard to correlations and associations with gene expression, clinicopathological parameters, molecular features and immune cell infiltrates in two publicly available cohorts (The Cancer Genome Atlas and Singapore cohorts) of a total of 594 gastric adenocarcinoma patients. Results: PD-L2 methylation is significantly associated with transcriptional activity, survival, Epstein–Barr virus infection, PD-L2 gene amplification, CD8+ T-cell infiltration, microsatellite instability and high mutational load (tumor mutational burden, hypermutation). Conclusion: PD-L2 methylation is associated with known predictive biomarkers of response to anti-PD-1 immunotherapies.

Integration of microbiology, molecular pathology, and epidemiology: a new paradigm to explore the pathogenesis of microbiome-driven neoplasms

Molecular pathological epidemiology (MPE) is an integrative transdisciplinary field that addresses heterogeneous effects of exogenous and endogenous factors (collectively termed 'exposures'), including microorganisms, on disease occurrence and consequences, utilising molecular pathological signatures of the disease. In parallel with the paradigm of precision medicine, findings from MPE research can provide aetiological insights into tailored strategies of disease prevention and treatment. Due to the availability of molecular pathological tests on tumours, the MPE approach has been utilised predominantly in research on cancers including breast, lung, prostate, and colorectal carcinomas. Mounting evidence indicates that the microbiome (inclusive of viruses, bacteria, fungi, and parasites) plays an important role in a variety of human diseases including neoplasms. An alteration of the microbiome may be not only a cause of neoplasia but also an informative biomarker that indicates or mediates the association of an epidemiological exposure with health conditions and outcomes. To adequately educate and train investigators in this emerging area, we herein propose the integration of microbiology into the MPE model (termed 'microbiology-MPE'), which could improve our understanding of the complex interactions of environment, tumour cells, the immune system, and microbes in the tumour microenvironment during the carcinogenic process. Using this approach, we can examine how lifestyle factors, dietary patterns, medications, environmental exposures, and germline genetics influence cancer development and progression through impacting the microbial communities in the human body. Further integration of other disciplines (e.g. pharmacology, immunology, nutrition) into microbiology-MPE would expand this developing research frontier. With the advent of high-throughput next-generation sequencing technologies, researchers now have increasing access to large-scale metagenomics as well as other omics data (e.g. genomics, epigenomics, proteomics, and metabolomics) in population-based research. The integrative field of microbiology-MPE will open new opportunities for personalised medicine and public health. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

PD-1/PD-L1 Inhibitors in Cervical Cancer

Cervical cancer is one of the most common gynecological tumors, and the majority of early-stage cervical cancer patients achieve good recovery through surgical treatment and concurrent chemoradiotherapy (CCRT). However, for patients with recurrent, persistent, metastatic cervical cancer, effective treatment is rare, except for bevacizumab combined with chemotherapy. Programmed cell death-1/programmed cell death-ligand 1 (PD-1/PD-L1) inhibitors might be a novel choice to improve the clinical outcomes of these patients. Thus far, some pivotal trials, including Keynote 028, Keynote 158 and Checkmate 358, have indicated established clinical benefit of PD-1/PD-L1 inhibitors in cervical cancer. In light of these data, the FDA has approved pembrolizumab for patients with recurrent or metastatic cervical cancer with disease progression during or after chemotherapy. There are also some ongoing studies that may provide more evidence for the PD-1/PD-L1 pathway as a therapeutic target in cervical cancer. In this review, we have summarized the status and application of PD-1/PD-L1 inhibitors in clinical trials for the treatment of cervical cancer and suggested some future directions in this field.

Gene code CD274/PD-L1: from molecular basis toward cancer immunotherapy

The programmed death 1 receptor (PD-1) and its ligand (PD-L1) are key molecules of immune checkpoint mechanisms in cancer and actually represent one of the main targets of immunotherapy. The predictive and prognostic values of PD-L1 expression alone in cancer patients is currently under debate due to the methodological assessment of PD-L1 expression and its temporal variations. Better detailed studies about the molecular basis of immunotherapy biomarkers are necessary. Here we summarize the current knowledge of PD-L1 gene modifications at genetic and epigenetic levels in different tumors, thus highlighting their reported correlation with cellular processes and potential impact on patient outcomes.

Epigenetic regulators of programmed death-ligand 1 expression in human cancers

The programmed cell death protein 1-programmed death-ligand 1 (PD-L1) axis has been successfully targeted in clinics and the use of immune check-point inhibitors have shown durable antitumor response in untreated or heavily treated advanced stage cancer. PD-L1 upregulation has been found to correlate with poor prognosis in multiple cancer types and expression of PD-L1 in intratumoral compartment has been suggested to influence immune response and act as a key determinant of checkpoint immunotherapy efficacy. Hence it becomes critical to understand the regulation of PD-L1 expression in cancer. Role of oncogenic signaling pathways and transcription factors such as PI3K-AKT, MEK-ERK, JAK-STAT, MYC, HIF-1α, AP-1 and NF-κB is well established in inducing PD-L1 expression. Even the structural variations resulting in the truncation of the 3' untranslated region (UTR) of PD-L1 has been shown to upregulate PD-L1 expression in multiple cancer types. Since microRNAs carry out post-transcriptional gene silencing by binding to the 3' UTR of its target messenger RNA, truncation of PD-L1 3' UTR can result in alleviation of PD-L1 suppression mediated by microRNA, leading to its overexpression. Other epigenetic modifications, such as promoter DNA methylation and histone modifications can also play crucial role in regulating PD-L1 expression. Here, we review recent findings and evidence on epigenetic mechanisms that regulate PD-L1 expression and the biological and clinical implications of such regulation in cancer.

PD-L1 methylation regulates PD-L1 expression and is associated with melanoma survival

The aim of this study is to determine the significance of programmed death ligand 1 (PD-L1 or CD274) methylation in relation to PD-L1 expression and survival in melanoma. Despite the clinical importance of therapies targeting the PD-1/PD-L1 immune checkpoint in melanoma, factors regulating PD-L1 expression, including epigenetic mechanisms, are not completely understood. In this study, we examined PD-L1 promoter methylation in relation to PD-L1 expression and overall survival in melanoma patients. Our results suggest that DNA methylation regulates PD-L1 expression in melanoma, and we identify the key methylated CpG loci in the PD-L1 promoter, establish PD-L1 methylation as an independent survival prognostic factor, provide proof of concept for altering PD-L1 expression by hypomethylating agents, and uncover that PD-L1 methylation is associated with an interferon signaling transcriptional phenotype. Based on our findings, measuring and altering PD-L1 promoter DNA methylation may have potential prognostic and therapeutic applications in melanoma.

PD-1 (PDCD1) Promoter Methylation Is a Prognostic Factor in Patients With Diffuse Lower-Grade Gliomas Harboring Isocitrate Dehydrogenase (IDH) Mutations

Immune checkpoints are important targets for immunotherapies. However, knowledge on the epigenetic modification of immune checkpoint genes is sparse. In the present study, we investigated promoter methylation of CTLA4, PD-L1, PD-L2, and PD-1 in diffuse lower-grade gliomas (LGG) harboring isocitrate dehydrogenase (IDH) mutations with regard to mRNA expression levels, clinicopathological parameters, previously established methylation subtypes, immune cell infiltrates, and survival in a cohort of 419 patients with IDH-mutated LGG provided by The Cancer Genome Atlas. PD-L1, PD-L2, and CTLA-4 mRNA expression levels showed a significant inverse correlation with promoter methylation (PD-L1: p=0.005; PD-L2: p<0.001; CTLA-4: p<0.001). Furthermore, immune checkpoint methylation was significantly associated with age (PD-L2: p=0.003; PD-1: p=0.015), molecular alterations, i.e. MGMT methylation (PD-L1: p<0.001; PD-L2: p<0.001), ATRX mutations (PD-L2: p<0.001, PD-1: p=0.001), and TERT mutations (PD-L1: p=0.035, PD-L2: p<0.001, PD-1: p<0.001, CTLA4: p<0.001) as well as methylation subgroups and immune cell infiltrates. In multivariate Cox proportional hazard analysis, PD-1 methylation qualified as strong prognostic factor (HR=0.51 [0.34-0.76], p=0.001). Our findings suggest an epigenetic regulation of immune checkpoint genes via DNA methylation in LGG. PD-1 methylation may assist the identification of patients that might benefit from an alternative treatment, particularly in the context of emerging immunotherapies.