Inflammatory cytokines IL-17 and TNF-α up-regulate PD-L1 expression in human prostate and colon cancer cells

Analysis of m6A-Related Signatures in the Tumor Immune Microenvironment and Identification of Clinical Prognostic Regulators in Adrenocortical Carcinoma

Adrenocortical carcinoma (ACC) is a rare endocrine malignancy with a high rate of mortality and recurrence. N6-methyladenosine methylation (m6A) is the most common modification to affect cancer development, but to date, the potential role of m6A regulators in ACC prognosis is not well understood. In this study, we systematically analyzed 21 m6A regulators in ACC samples from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) database. We identified three m6A modification patterns with different clinical outcomes and discovered a significant relationship between diverse m6A clusters and the tumor immune microenvironment (immune cell types and ESTIMATE algorithm). Additionally, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) revealed that the m6A clusters were strongly associated with immune infiltration in the ACC. Next, to further explore the m6A prognostic signatures in ACC, we implemented Lasso (Least Absolute Shrinkage and Selection Operator) Cox regression to establish an eight-m6A-regulator prognostic model in the TCGA dataset, and the results showed that the model-based high-risk group was closely correlated with poor overall survival (OS) compared with the low-risk group. Subsequently, we validated the key modifications in the GEO datasets and found that high HNRNPA2B1 expression resulted in poor OS and event-free survival (EFS) in ACC. Moreover, to further decipher the molecular mechanisms, we constructed a competing endogenous RNA (ceRNA) network based on HNRNPA2B1, which consists of 12 long noncoding RNAs (lncRNAs) and 1 microRNA (miRNA). In conclusion, our findings indicate the potential role of m6A modification in ACC, providing novel insights into ACC prognosis and guiding effective immunotherapy.

Harnessing Tumor Necrosis Factor Alpha to Achieve Effective Cancer Immunotherapy

Tumor necrosis factor alpha (TNFα) is a pleiotropic cytokine known to have contradictory roles in oncoimmunology. Indeed, TNFα has a central role in the onset of the immune response, inducing both activation and the effector function of macrophages, dendritic cells, natural killer (NK) cells, and B and T lymphocytes. Within the tumor microenvironment, however, TNFα is one of the main mediators of cancer-related inflammation. It is involved in the recruitment and differentiation of immune suppressor cells, leading to evasion of tumor immune surveillance. These characteristics turn TNFα into an attractive target to overcome therapy resistance and tackle cancer. This review focuses on the diverse molecular mechanisms that place TNFα as a source of resistance to immunotherapy such as monoclonal antibodies against cancer cells or immune checkpoints and adoptive cell therapy. We also expose the benefits of TNFα blocking strategies in combination with immunotherapy to improve the antitumor effect and prevent or treat adverse immune-related effects.

Prostate cancer C5a receptor expression and augmentation of cancer cell proliferation, invasion, and PD-L1 expression by C5a

BACKGROUND

The treatment of castration-resistant prostate cancer (CRPC) is a urological issue. Recent studies have revealed cancer promotion via the C5a-C5a receptor (C5aR) system. To establish a new therapeutic target for CRPC, we investigated an association of the system with CRPC progression and evasion from the antitumor immune responses.

METHODS

C5aR and PD-L1 were immunostained in the prostate cancer (PC) tissues. The relationship of PC C5aR expression to clinicopathological parameters was analyzed. CRPC cell lines were examined for C5aR expression by real-time reverse transcription polymerase chain reaction, immunoblotting, and flow cytometry. C5a effects were examined on CRPC cell glutamine consumption, proliferation, invasion, and PD-L1 expression.

RESULTS

PC cells expressed C5aR in 83 of the 161 patients (52%) and in three of the six CRPC patients. Basal cells, but not luminal cells, of noncancerous prostate glands expressed C5aR. Three CRPC cell lines expressed C5aR. C5a increased CRPC cell glutamine consumption 2.1-fold, proliferation 1.3-1.6-fold, and invasion 2-3-fold in a C5a-concentration and a C5aR-dependent manner. High expression of C5aR did not relate to the PC patients' clinical parameters but the PD-L1-positive rate was higher in the C5aR high-expression patients (37.5%) compared to low- or no expression patients (17.8%), and double-positive PC cells were present. C5a increased CRPC cell PD-L1 production 1.4-fold and cell-surface expression 2.6-fold.

CONCLUSIONS

C5aR expression of PC cells in patients' tissues and C5a augmentation of C5aR-dependent CRPC proliferation, invasion, and PD-L1 expression suggested participation of the C5a-C5aR system in CRPC promotion and evasion from antitumor immune responses. Targeting this signaling pathway may provide a useful therapeutic option for CRPC.

The tumor-promoting effects of the adaptive immune system: a cause of hyperprogressive disease in cancer?

Adaptive antitumor immune responses, either cellular or humoral, aim at eliminating tumor cells expressing the cognate antigens. There are some instances, however, where these same immune responses have tumor-promoting effects. These effects can lead to the expansion of antigen-negative tumor cells, tumor cell proliferation and tumor growth, metastatic dissemination, resistance to antitumor therapy and apoptotic stimuli, acquisition of tumor-initiating potential and activation of various forms of survival mechanisms. We describe the basic mechanisms that underlie tumor-promoting adaptive immune responses and try to identify the variables that induce the switching of a tumor-inhibitory, cellular or humoral immune response, into a tumor-promoting one. We suggest that tumor-promoting adaptive immune responses may be at the origin of at least a fraction of hyperprogressive diseases (HPD) that are observed in cancer patients during therapy with immune checkpoint inhibitors (ICI) and, less frequently, with single-agent chemotherapy. We also propose the use of non-invasive biomarkers allowing to predict which patients may undergo HPD during ICI and other forms of antitumor therapy. Eventually, we suggest possibilities of therapeutic intervention allowing to inhibit tumor-promoting adaptive immune responses.

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.

Association between Inflammation and Function of Cell Adhesion Molecules Influence on Gastrointestinal Cancer Development

Gastrointestinal cancer is highly associated with inflammatory processes inducing the release of cytokines from cancer or immune cells, including interferons, interleukins, chemokines, colony-stimulating factors, and growth factors, which promote or suppress tumor progression. Inflammatory cytokines within the tumor microenvironment promote immune cell infiltration. Infiltrating immune, and tumor-surrounding stromal cells support tumor growth, angiogenesis, metastasis, and immunosuppression through communication with inflammatory cytokines and cell adhesion molecules. Notably, infiltrating immune and tumor cells present immunosuppressive molecules, such as programmed death-ligand 1 (PD-L1) and CD80/CD86. Suppression of cytotoxic T cells promotes tumor avoidance of immune surveillance and greater malignancy. Moreover, glycosylation and sialylation of proteins hyperexpressed on the cancer cell surface have been shown to enhance immune escape and metastasis. Cytokine treatments and immune checkpoint inhibitors are widely used in clinical practice. However, the tumor microenvironment is a rapidly changing milieu involving several factors. In this review, we have provided a summary of the interactions of inflammation and cell adhesion molecules between cancer and other cell types, to improve understanding of the tumor microenvironment.

Immune checkpoint molecules are regulated by transforming growth factor (TGF)-β1-induced epithelial-to-mesenchymal transition in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer with a high mortality rate. Epithelial-to-mesenchymal transition (EMT) confers cancer cells with immune evasive ability by modulating the expression of immune checkpoints in many cancers. Thus, the aim of our study is to examine the interplay between EMT and immune checkpoint molecules in HCC. A reversible EMT model was utilised with transforming growth factor (TGF)-β1 as an EMT inducer for HCC cell lines Hep3B and PLC/PRF/5. HCC cells were treated with TGF-β1 for 72 h and the EMT status and immune checkpoint expression were examined. In addition, the migratory ability of HCC cells were examined using wound healing and transwell migration assays in the reversible EMT model. siRNA-mediated knockdown of immune checkpoint molecule, B7-H3, was further utilised to validate the association between TGF-β1-mediated EMT and immune checkpoint expression in HCC. In addition, a web-based platform, SurvExpress, was utilised to evaluate the association between expression of TGF-β1 in combination with immune checkpoint molecules and overall survival in HCC patients. We observed induction of EMT upon treatment of HCC cells with TGF-β1 revealed by reduced expression of epithelial markers along with increased expression of mesenchymal markers. Withdrawal of TGF-β1 reversed the process of EMT with elevated expression of epithelial markers and reduced expression of mesenchymal markers. TGF-β1 treatment elevated the migratory potential of HCC cells which was reversed following reversal assay. Notably, during TGF-β1-induced EMT, there was upregulation of immune checkpoint molecules PD-L1 and B7-H3. However, the reversal of EMT decreased the expression of PD-L1 and B7-H3. In addition, TGF-β1 driven EMT was reversed following knockdown of B7-H3 in both HCC cells further validating the interplay between TGF-β1-mediated EMT and immune checkpoint expression in HCC. Furthermore, the coordinate expression of TGF-β1 with PD-L1 (p=0.01487) and B7-H3 (p=0.009687) was correlated with poor overall survival in 422 HCC patients. Our study has demonstrated a close association between TGF-β1-mediated EMT and regulation of immune checkpoints in HCC.

Britannin stabilizes T cell activity and inhibits proliferation and angiogenesis by targeting PD-L1 via abrogation of the crosstalk between Myc and HIF-1α in cancer

BACKGROUND

Programmed cell death-ligand 1 (PD-L1) is overexpressed in tumor cells, which causes tumor cells to escape T cell killing, and promotes tumor cell survival, cell proliferation, migration, invasion, and angiogenesis. Britannin is a natural product with anticancer pharmacological effects.

PURPOSE

In this work, we studied the anticancer potential of britannin and explored whether britannin mediated its effect by inhibiting the expression of PD-L1 in tumor cells.

METHODS

In vitro, the mechanisms underlying the inhibition of PD-L1 expression by britannin were investigated by MTT assay, homology modeling and molecular docking, RT-PCR, western blotting, co-immunoprecipitation, and immunofluorescence. The changes in tumor killing activity, cell proliferation, cell cycle, migration, invasion, and angiogenesis were analyzed by T cell killing assays, EdU labeling, colony formation, flow cytometry, wound healing, matrigel transwell invasion, and tube formation, respectively. In vivo, the antitumor activity of britannin was evaluated in the HCT116 cell xenograft model.

RESULTS

Britannin reduced the expression of PD-L1 in tumor cells by inhibiting the synthesis of the PD-L1 protein but did not affect the degradation of the PD-L1 protein. Britannin also inhibited HIF-1α expression through the mTOR/P70S6K/4EBP1 pathway and Myc activation through the Ras/RAF/MEK/ERK pathway. Mechanistically, britannin inhibited the expression of PD-L1 by blocking the interaction between HIF-1α and Myc. In addition, britannin could enhance the activity of cytotoxic T lymphocytes and inhibit tumor cell proliferation and angiogenesis by inhibiting PD-L1. Finally, in vivo observations were confirmed by demonstrating the antitumor activity of britannin in a murine xenograft model.

CONCLUSION

Britannin inhibits the expression of PD-L1 by blocking the interaction between HIF-1α and Myc. Moreover, britannin stabilizes T cell activity and inhibits proliferation and angiogenesis by inhibiting PD-L1 in cancer. The current work highlights the anti-tumor effect of britannin, providing insights into the development of cancer therapeutics via PD-L1 inhibition.

Regulation of PD-L1 Expression by NF-κB in Cancer

Immune checkpoints are inhibitory receptor/ligand pairs regulating immunity that are exploited as key targets of anti-cancer therapy. Although the PD-1/PD-L1 pair is one of the most studied immune checkpoints, several aspects of its biology remain to be clarified. It has been established that PD-1 is an inhibitory receptor up-regulated by activated T, B, and NK lymphocytes and that its ligand PD-L1 mediates a negative feedback of lymphocyte activation, contributing to the restoration of the steady state condition after acute immune responses. This loop might become detrimental in the presence of either a chronic infection or a growing tumor. PD-L1 expression in tumors is currently used as a biomarker to orient therapeutic decisions; nevertheless, our knowledge about the regulation of PD-L1 expression is limited. The present review discusses how NF-κB, a master transcription factor of inflammation and immunity, is emerging as a key positive regulator of PD-L1 expression in cancer. NF-κB directly induces PD-L1 gene transcription by binding to its promoter, and it can also regulate PD-L1 post-transcriptionally through indirect pathways. These processes, which under conditions of cellular stress and acute inflammation drive tissue homeostasis and promote tissue healing, are largely dysregulated in tumors. Up-regulation of PD-L1 in cancer cells is controlled via NF-κB downstream of several signals, including oncogene- and stress-induced pathways, inflammatory cytokines, and chemotherapeutic drugs. Notably, a shared signaling pathway in epithelial cancers induces both PD-L1 expression and epithelial–mesenchymal transition, suggesting that PD-L1 is part of the tissue remodeling program. Furthermore, PD-L1 expression by tumor infiltrating myeloid cells can contribute to the immune suppressive features of the tumor environment. A better understanding of the interplay between NF-κB signaling and PD-L1 expression is highly relevant to cancer biology and therapy.

Genomics and prognosis analysis of epithelial-mesenchymal transition in colorectal cancer patients

Background

The epithelial-mesenchymal transition (EMT) plays a pivotal role in various physiological processes, such as embryonic development, tissue morphogenesis, and wound healing. EMT also plays an important role in cancer invasion, metastasis, and chemoresistance. Additionally, EMT is partially responsible for chemoresistance in colorectal cancer (CRC). The aim of this research is to develop an EMT-based prognostic signature in CRC.

Methods

RNA-seq and microarray data, together with clinical information, were downloaded from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) databases. A total of 244 differentially expressed EMT-related genes (ERGs) were obtained by comparing the expression between normal and tumor tissues. An EMT-related signature of 11 genes was identified as crucially related to the overall survival (OS) of patients through univariate Cox proportional hazard analysis, least absolute shrinkage and selection operator (LASSO), and Cox regression analysis. Finally, we established a clinical nomogram to predict the survival possibility of CRC patients by integrating clinical characteristics and the EMT-related gene signature.

Results

Two hundred and forty-four differentially expressed ERGs and their enriched pathways were confirmed. Significant enrichment analysis revealed that EMT-related signaling pathway genes were highly related to CRC. Kaplan-Meier analysis revealed that the 11-EMT signature could significantly distinguish high- and low-risk patients in both TCGA and GEO CRC cohorts. In addition, the calibration curves verified fine concordance between the nomogram prediction model and actual observation.

Conclusion

We developed a novel EMT-related gene signature for the prognosis prediction of CRC patients, which could improve the individualized outcome prediction in CRC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07615-5.

β-Catenin regulates tumor-derived PD-L1

In this issue of JEM, Du et al. (https://doi.org/10.1084/jem.20191115) report that enhancement of the β-catenin signaling by Wnt or EGF treatment increases the expression of PD-L1 in an AKT and β-catenin-dependent manner, and blocking the AKT pathway synergizes with anti-PD-1 in a glioblastoma model.

Blood-based PD-L1 analysis in tumor-derived extracellular vesicles: Applications for optimal use of anti-PD-1/PD-L1 axis inhibitors

Monoclonal antibodies that inhibit the programmed cell death protein 1 axis (anti-PD-1/PD-L1) are part of a new pharmacological strategy aimed at reinforcing the immune response to cancer. Despite the success in several cancer types, a significant percentage of patients do not benefit from treatment with these drugs due to intrinsic or acquired resistance or the occurrence of immune-related adverse reactions. Assessment of PD-L1 expression in tumor tissues is currently used to predict drug response in the clinics; however, there is a growing interest in identifying blood-based biomarkers that, owing to the minimally-invasive nature, can allow a dynamic monitoring of drug response in daily clinical practice. In the current review article, we discuss whether the assessment of PD-L1 mRNA and protein levels in circulating extracellular vesicles may have the potential to predict the likelihood of tumor response to anti-PD-1/PD-L1 antibodies.

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.

H. pylori modulates DC functions via T4SS/TNFα/p38-dependent SOCS3 expression

Background

Helicobacter pylori (H. pylori) is a gram-negative bacterium that chronically infects approximately 50% of the world’s human population. While in most cases the infection remains asymptomatic, 10% of infected individuals develop gastric pathologies and 1–3% progress to gastric cancer. Although H. pylori induces severe inflammatory responses, the host’s immune system fails to clear the pathogen and H. pylori can persist in the human stomach for decades. As suppressor of cytokine signaling (SOCS) proteins are important feedback regulators limiting inflammatory responses, we hypothesized that H. pylori could modulate the host’s immune responses by inducing SOCS expression.

Methods

The phenotype of human monocyte-derived DCs (moDCs) infected with H. pylori was analyzed by flow cytometry and multiplex technology. SOCS expression levels were monitored by qPCR and signaling studies were conducted by means of Western blot. For functional studies, RNA interference-based silencing of SOCS1–3 and co-cultures with CD4⁺ T cells were performed.

Results

We show that H. pylori positive gastritis patients express significantly higher SOCS3, but not SOCS1 and SOCS2, levels compared to H. pylori negative patients. Moreover, infection of human moDCs with H. pylori rapidly induces SOCS3 expression, which requires the type IV secretion system (T4SS), release of TNFα, and signaling via the MAP kinase p38, but appears to be independent of TLR2, TLR4, MEK1/2 and STAT proteins. Silencing of SOCS3 expression in moDCs prior to H. pylori infection resulted in increased release of both pro- and anti-inflammatory cytokines, upregulation of PD-L1, and decreased T-cell proliferation.

Conclusions

This study shows that H. pylori induces SOCS3 via an autocrine loop involving the T4SS and TNFα and p38 signaling. Moreover, we demonstrate that high levels of SOCS3 in DCs dampen PD-L1 expression on DCs, which in turn drives T-cell proliferation.

Extracellular Vesicles Reflect the Efficacy of Wheatgrass Juice Supplement in Colon Cancer Patients During Adjuvant Chemotherapy

Introduction

Colorectal cancer (CC) is the third most common type of cancer, accounting for 10% of all cancer cases. Adjuvant chemotherapy is recommended in stages II–III CC. Wheatgrass juice (WGJ) from wheat seeds has high nutritional values, may induce synergistic benefits to chemotherapy and may attenuate chemotherapy-related side effects. Extracellular vesicles (EVs) are subcellular membrane blebs. EVs include exosomes (generated in the endosome, in size <150 nm) and microvesicles (shed from the plasma cell membrane) provide information on their parental cells and play a role in intercellular communication. We aimed to elucidate the effects of chemotherapy administration with supportive treatment of WGJ on CC patients’ EVs characteristics.

Methods

EVs were isolated from the blood samples of 15 healthy controls (HCs) and 50 CC patients post-surgery, treated by chemotherapy, with or without additional daily WGJ. Blood samples were taken before, during, and at the end of chemotherapy. EVs were characterized by size, concentration, membrane antigens and cytokine content using nanoparticle-tracking analysis, western blot, flow cytometry, and protein array methods.

Results

EVs were found to be similar by size and concentration with reduced levels of exosome markers (CD81) on samples at the end of combined treatment (chemotherapy and WGJ). Higher levels of endothelial EVs, which may indicate impairment of the vascular endothelial cells during treatment, were found in CC patients treated by chemotherapy only compared to those with chemotherapy and daily WGJ. Also, EVs thrombogenicity was lower in patients added WGJ compared to patients who had only chemotherapy (levels of tissue factor p = 0.029 and endothelial protein C receptor p = 0.005). Following treatments, levels of vascular endothelial growth factor receptors (VEGFR-1) and the majority of growth-factors/pro-inflammatory cytokines were higher in EVs of patients treated by chemotherapy only than in EVs obtained from patients with the combined treatment.

Conclusion

Daily consumption of WGJ during chemotherapy may reduce vascular damage and chemotherapy-related thrombogenicity, growth factors and cytokines, as reflected by the characteristics of patient’s EVs.

Estrogen Receptor Downregulates Expression of PD-1/PD-L1 and Infiltration of CD8+ T Cells by Inhibiting IL-17 Signaling Transduction in Breast Cancer

Background: The relationship between the interleukin 17 (IL-17) family of cytokines and breast cancer has been widely studied in recent years. Many studies have revealed increased levels of the cytokine IL-17A in estrogen receptor (ER)-negative or triple-negative breast cancer. Upregulation of IL-17A signaling is associated with increased expression of programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) in breast cancer with low ER expression and may elevate the infiltration of CD8⁺ T cells in tumor tissue. This study aims to determine whether ER downregulates the expression of PD-1/PD-L1, reduces the infiltration of CD8⁺ T cells, and affects the immune microenvironment by decreasing T-helper 17 (Th17) cell infiltration and inhibiting IL-17 signaling in breast cancer.

Methods: Samples in The Cancer Genome Atlas Breast Cancer dataset were grouped by ER status and the PAM50 intrinsic subtype. The expression of IL-17 family cytokines and Th17 cell signature cytokines were compared between groups. IL-17 signaling pathway-related genes that were differentially expressed according to the ER level were identified. The PD-1 and PD-L1 levels were compared between breast cancer samples with different ER statuses and IL-17A/IL-17F expression levels. Correlation analyses of the expression of PD-1/PD-L1 and IL-17 signaling pathway-related genes were performed. The associations of the expression of IL-17 signaling pathway-related genes with the immune microenvironment were investigated.

Results: High levels of ER decreased the expression of IL-17A, IL-17C, and IL-17F but increased the expression of IL-17E (IL25), which acts as a suppressor of IL-17 signaling. The expression levels of Th17 cell signature cytokines were significantly increased in ER-negative breast cancer. The expression levels of genes encoding downstream products of IL-17A/IL-17F signaling were downregulated in breast cancer with high ER expression. Increased expression of PD-1/PD-L1 was associated with ER-negative status, IL-17A-positive status, IL-17F-positive status, and upregulation of IL-17 signaling pathway-related genes in breast cancer. Enhanced IL-17 signal transduction was associated with the elevation of CD8⁺ T cell infiltration and variation of the immune microenvironment of breast cancer.

Conclusion: High estrogen receptor levels decrease PD-1/PD-L1 expression and CD8⁺ T cell infiltration by suppressing Th17 cell infiltration and IL-17 signal transduction in breast cancer.

Identification of hub genes in colon cancer via bioinformatics analysis

Objectives

This study aimed to investigate hub genes and their prognostic value in colon cancer via bioinformatics analysis.

Methods

Differentially expressed genes (DEGs) of expression profiles (GSE33113, GSE20916, and GSE37364) obtained from Gene Expression Omnibus (GEO) were identified using the GEO2R tool and Venn diagram software. Function and pathway enrichment analyses were performed, and a protein–protein interaction (PPI) network was constructed. Hub genes were verified based on The Cancer Genome Atlas (TCGA) and Human Protein Atlas (HPA) databases.

Results

We identified 207 DEGs, 62 upregulated and 145 downregulated genes, enriched in Gene Ontology terms “organic anion transport,” “extracellular matrix,” and “receptor ligand activity”, and in the Kyoto Encyclopedia of Genes and Genomes pathway “cytokine-cytokine receptor interaction.” The PPI network was constructed and nine hub genes were selected by survival analysis and expression validation. We verified these genes in the TCGA database and selected three potential predictors (ZG16, TIMP1, and BGN) that met the independent predictive criteria. TIMP1 and BGN were upregulated in patients with a high cancer risk, whereas ZG16 was downregulated. The immunostaining results from HPA supported these findings.

Conclusion

This study indicates that these hub genes may be promising prognostic indicators or therapeutic targets for colon cancer.

The (Neutrophils + Monocyte)/Lymphocyte Ratio Is an Independent Prognostic Factor for Progression-Free Survival in Newly Diagnosed Multiple Myeloma Patients Treated With BCD Regimen

Objective

Bortezomib is one of the important drugs that have made breakthrough progress in multiple myeloma (MM) in the past 10 years. However, the heterogeneity of its efficacy makes it difficult to predict the risk of disease progression. The purpose of this study is to determine the prognostic significance of the (neutrophils + monocytes)/lymphocytes ratio (NMLR) in newly diagnosed MM patients who received BCD regimen therapy in terms of progression-free survival (PFS).

Methods

A total of 150 patients who fulfilled the International Myeloma Working Group (IMWG) criteria were enrolled in the study retrospectively. The prognostic value of NMLR was evaluated by 150 patients with MM who were treated with BCD (bortezomib + cyclophosphamide + dexamethasone) regimen therapy. NMLR was calculated by the ratio of (neutrophils + monocyte) to lymphocytes. According to receiver operating characteristic curves, the cutoff value was 1.90. The patients were divided into high NMLR group (H-NMLR, NMLR ≥1.90) and low NMLR group (L-NMLR, NMLR <1.90). The clinical characteristics, treatment responses and PFS of the two groups were analyzed.

Results

The median age of the patients was 61 years. Fifty-five (36.67%) patients showed lower NMLR at initial diagnosis. Although NMLR was unable to discriminate prognosis in ISS stage I/II patients, interestingly, the addition of NMLR to the ISS further defined prognosis particularly in stage III. Low-NMLR group who achieved early immune reconstruction significantly higher than that of the high-NMLR group (P < 0.001). NMLR value was 1.98 ± 1.02 for the patients who achieved early immune reconstruction, which was 3.26 ± 2.52 for the patients without immune reconstruction (P < 0.05). Compared with the H-NMLR group, the levels of β2-microglobulin, serum creatinine and calcium were lower, and the very good partial response or better (≥VGPR) ratio was higher in L-NMLR group. The L-NMLR group experienced a superior median PFS compared with the H-NMLR group (24.0 versus 15.5 months; P < 0.001). In addition, several other prognostic factors of PFS were estimated, including the high-risk cytogenetics, β2-microglobulin and the depth of treatment response 3 months after treatment with BCD regimen. Moreover, NMLR was an independent predictor of PFS including non-high risk cytogenetics (0.587; P = 0.031).

Conclusion

In patients with newly diagnosed MM undergoing BCD regimen, the NMLR <1.90 was an independent prognostic factor for PFS as well as early immune reconstruction and lower disease burden.

Intratumoral Copper Modulates PD-L1 Expression and Influences Tumor Immune Evasion

Therapeutic checkpoint antibodies blocking programmed death receptor 1/programmed death ligand 1 (PD-L1) signaling have radically improved clinical outcomes in cancer. However, the regulation of PD-L1 expression on tumor cells is still poorly understood. Here we show that intratumoral copper levels influence PD-L1 expression in cancer cells. Deep analysis of the The Cancer Genome Atlas database and tissue microarrays showed strong correlation between the major copper influx transporter copper transporter 1 (CTR-1) and PD-L1 expression across many cancers but not in corresponding normal tissues. Copper supplementation enhanced PD-L1 expression at mRNA and protein levels in cancer cells and RNA sequencing revealed that copper regulates key signaling pathways mediating PD-L1-driven cancer immune evasion. Conversely, copper chelators inhibited phosphorylation of STAT3 and EGFR and promoted ubiquitin-mediated degradation of PD-L1. Copper-chelating drugs also significantly increased the number of tumor-infiltrating CD8⁺ T and natural killer cells, slowed tumor growth, and improved mouse survival. Overall, this study reveals an important role for copper in regulating PD-L1 and suggests that anticancer immunotherapy might be enhanced by pharmacologically reducing intratumor copper levels. SIGNIFICANCE: These findings characterize the role of copper in modulating PD-L1 expression and contributing to cancer immune evasion, highlighting the potential for repurposing copper chelators as enhancers of antitumor immunity. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/19/4129/F1.large.jpg.

Tumor Microenvironment in Ovarian Cancer: Function and Therapeutic Strategy

Ovarian cancer is one of the leading causes of death in patients with gynecological malignancy. Despite optimal cytoreductive surgery and platinum-based chemotherapy, ovarian cancer disseminates and relapses frequently, with poor prognosis. Hence, it is urgent to find new targeted therapies for ovarian cancer. Recently, the tumor microenvironment has been reported to play a vital role in the tumorigenesis of ovarian cancer, especially with discoveries from genome-, transcriptome- and proteome-wide studies; thus tumor microenvironment may present potential therapeutic target for ovarian cancer. Here, we review the interactions between the tumor microenvironment and ovarian cancer and various therapies targeting the tumor environment.

Ubiquitin C-terminal hydrolase L1 promotes expression of programmed cell death-ligand 1 in non-small-cell lung cancer cells

Programmed cell death‐ligand 1 (PD‐L1) expressed on cancer cells can cause immune escape of non‐small‐cell lung cancer (NSCLC). Elucidation of the regulatory mechanisms of the PD‐L1 expression is a prerequisite for establishing new tumor immunotherapy strategies. Ubiquitin C‐terminal hydrolase L1 (UCHL1) is a regulator of cellular signaling transduction that is aberrantly expressed in NSCLC. However, it is not known whether UCHL1 regulates the expression of PD‐L1 in NSCLC cells. In the present study, we found that UCHL1 promotes the expression of PD‐L1 in NSCLC cell lines. In addition, UCHL1 expressed in NSCLC cells inhibited activation of Jurkat cells through upregulation of PD‐L1 expression in in vitro experiments. Moreover, UCHL1 upregulates PD‐L1 expression through facilitating activation of the AKT‐P65 signaling pathway. In conclusion, these results indicated that UCHL1 promoted PD‐L1 expression in NSCLC cells. This finding implied that inhibition of UCHL1 might suppress immune escape of NSCLC through downregulation of PD‐L1 expression in NSCLC cells.

Programmed cell death-1 (PD-1) and programmed death-ligand 1 (PD-L1) expression in PD-1 inhibitor-associated colitis and its mimics

AIMS

Immune checkpoint inhibitors (ICIs) have revolutionised the treatment of advanced malignancies by boosting immune-mediated destruction of neoplastic cells, but are associated with side effects stemming from generalised immune system activation against normal tissues. Checkpoint ligand expression in non-tumoral cells of tissues affected by immune-related adverse effects has been described in ICI-associated hypophysitis, myocarditis, and acute interstitial nephritis. We aimed to investigate the tissue expression of the immune checkpoint receptor programmed cell death-1 (PD-1) and its ligand, programmed death-ligand 1 (PD-L1), in PD-1 inhibitor-associated colitis (PD1i colitis).

METHODS AND RESULTS

PD-1 and PD-L1 immunohistochemical expression levels were analysed in 15 cases of PD1i colitis and potential mimics-infectious colitis and inflammatory bowel disease (IBD). Increased epithelial expression of PD-L1 was observed in PD1i colitis as compared with normal colon and infectious colitis, but the expression level was lower than that in IBD. Conversely, PD-1 expression in inflammatory cells was higher in infectious colitis, intermediate in IBD, and minimal or absent in normal colon and in patients receiving PD-1 inhibitors.

CONCLUSIONS

Although our results do not justify the use of PD-L1 as a discriminatory marker of PD1i colitis against other entities within the differential diagnosis, they support the concept that PD1i colitis and IBD have similar pathogenetic mechanisms. They also highlight the fact that PD-L1 epithelial overexpression is a commonly used mechanism of the gastrointestinal tract mucosa to protect itself from inflammatory-mediated damage resulting from different aetiologies, which probably underpins the high incidence of gastrointestinal immune-related adverse effects in patients receiving ICI therapies, in whom this mechanism is disrupted.

PD-L1 Expression Affects Neoantigen Presentation

Although PD-L1 expression on tumor is related to the prognosis of immune checkpoint blockade (ICB) therapy, a recent study also demonstrated clinical benefits even in patients without PD-L1 expression. To understand the relationship between innate resistance and antitumor cytotoxic T lymphocyte (CTL) responses especially against neoantigens, the interaction between PD-L1⁺ or genetically PD-L1-deleted colorectal tumors and CTLs was assessed under an ICB therapy, finding the robust CTL activation in PD-L1-deleted tumor-bearing mice. Using antigen libraries based on immunogenomics, we identified three H2-K^b-restricted, somatic-mutated immunogenic neoantigens by utilizing enhanced CTLs responses due to PD-L1 deficiency. Furthermore, we identified three T cell receptor (TCR) repertoires relevant to the neoantigens, confirming the response of TCR-gene-transduced CTLs to parental tumor cells. Notably, neoantigen-pulsed dendritic cell (DC) therapy reversed the tumor tolerance. Thus, innate resistance of tumors determines their responsiveness to neoantigens and mixed neoantigen peptides may be useful in DC therapy against innate resistance type tumor.

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Poor prognosis of PD-L1-expressing tumors in some cancers

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Identification of TCRVα and Vβ repertoire responsive for H2-K^b-restricted neoantigens

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Neoantigen-epitope-pulsed DC therapy demonstrates antitumor effect in vaccine

NF-κB and Its Role in Checkpoint Control

Nuclear factor-κB (NF-κB) has been described as one of the most important molecules linking inflammation to cancer. More recently, it has become clear that NF-κB is also involved in the regulation of immune checkpoint expression. Therapeutic approaches targeting immune checkpoint molecules, enabling the immune system to initiate immune responses against tumor cells, constitute a key breakthrough in cancer treatment. This review discusses recent evidence for an association of NF-κB and immune checkpoint expression and examines the therapeutic potential of inhibitors targeting either NF-κB directly or molecules involved in NF-κB regulation in combination with immune checkpoint blockade.

Serum PD-1/PD-L1 Levels, Tumor Expression and PD-L1 Somatic Mutations in HER2-Positive and Triple Negative Normal-Like Feline Mammary Carcinoma Subtypes

Tumor microenvironment has gained great relevance due to its ability to regulate distinct checkpoints mediators, orchestrating tumor progression. Serum programmed cell death protein-1 (PD-1) and programmed death ligand-1 (PD-L1) levels were compared with healthy controls and with serum cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and tumor necrosis factor-alpha (TNF-α) levels in order to understand the role of PD-1/PD-L1 axis in cats with mammary carcinoma. PD-1 and PD-L1 expression was evaluated in tumor-infiltrating lymphocytes (TILs) and cancer cells, as the presence of somatic mutations. Results showed that serum PD-1 and PD-L1 levels were significantly higher in cats with HER2-positive (p = 0.017; p = 0.032) and triple negative (TN) normal-like mammary carcinomas (p = 0.004; p = 0.015), showing a strong positive correlation between serum CTLA-4 and TNF-α levels. In tumors, PD-L1 expression in cancer cells was significantly higher in HER2-positive samples than in TN normal-like tumors (p = 0.010), as the percentage of PD-L1-positive TILs (p = 0.037). PD-L1 gene sequencing identified two heterozygous mutations in exon 4 (A245T; V252M) and one in exon 5 (T267S). In summary, results support the use of spontaneous feline mammary carcinoma as a model for human breast cancer and suggest that the development of monoclonal antibodies may be a therapeutic strategy.

Adipocytes promote tumor progression and induce PD-L1 expression via TNF-α/IL-6 signaling

Background

Obesity confers increased risk for various types of cancer. PD-L1 is a key molecule in tumor immune evasion by inducing T cell exhaustion. The relationship between obesity and PD-L1 is still ambiguous. This study was designed to reveal the development of hepatocellular carcinoma and melanoma in obese mice and to investigate if adipocytes regulate PD-L1 expression and the underlying mechanism.

Methods

Monosodium glutamate-induced obese mice were inoculated with H22 tumor cells and High fat diet (HFD)-induced obese mice were inoculated with B16-F1 mouse melanoma cells. Human hepatoma HepG2 cells and B16-F1 cells were treated with conditional media from 3T3-L1 adipocytes (adi-CM). Neutralized anti-TNF-α and anti-IL-6 antibodies and inhibitor of NF-κB or STAT3 were used to reveal the mechanism of effect of adi-CM.

Results

In obese mice, H22 and B16-F1 tumor tissues grew faster and PD-L1 expression in tumor tissue was increased. Adi-CM up-regulated PD-L1 level in HepG2 and B16-F1 cells in vitro. Differentiated 3T3-L1 adipocytes secreted TNF-α and IL-6, and neutralizing TNF-α and/or IL-6 reduced PD-L1 expression in adi-CM-treated cells. p-NF-κB/NF-κB level was downregulated in HepG2 and B16-F1 cells, and p-STAT3/STAT3 level was also decreased in HepG2 cells. In addition, inhibitor of NF-κB or STAT3 reversed the effect of adi-CM on PD-L1 expression.

Conclusions

TNF-α and IL-6 secreted by adipocytes up-regulates PD-L1 in hepatoma and B16-F1 cells, which may be at least partially involved in the role of obesity in promoting tumor progression.

NPM1 upregulates the transcription of PD-L1 and suppresses T cell activity in triple-negative breast cancer

Programmed cell death protein-1 (PD-1)/programmed cell death ligand-1 (PD-L1) interaction plays a crucial role in tumor-associated immune escape. Here, we verify that triple-negative breast cancer (TNBC) has higher PD-L1 expression than other subtypes. We then discover that nucleophosmin (NPM1) binds to PD-L1 promoter specifically in TNBC cells and activates PD-L1 transcription, thus inhibiting T cell activity in vitro and in vivo. Furthermore, we demonstrate that PARP1 suppresses PD-L1 transcription through its interaction with the nucleic acid binding domain of NPM1, which is required for the binding of NPM1 at PD-L1 promoter. Consistently, the PARP1 inhibitor olaparib elevates PD-L1 expression in TNBC and exerts a better effect with anti-PD-L1 therapy. Together, our research has revealed NPM1 as a transcription regulator of PD-L1 in TNBC, which could lead to potential therapeutic strategies to enhance the efficacy of cancer immunotherapy.

PD-L1 is highly expressed in triple-negative breast cancers (TNBC). Here, the authors show that nucleophosmin 1 (NPM1) transcriptionally activates PD-L1 expression and inhibits T cell activity in TNBC.

Role of tumor microenvironment in the regulation of PD-L1: A novel role in resistance to cancer immunotherapy

Tumor evasion from the host immune system is a substantial strategy for tumor development and survival. The expression of many immune checkpoint proteins in cancer cells is a mechanism by which tumor cells escape from the immune system. Among the well-known immune checkpoints that can tremendously affect tumor development and cancer therapy are the programmed death-ligand-1/programmed death-1 (PD-L1/PD-1). To tackle this phenomenon and improve the therapeutic strategies in cancer treatment, the blockade of the PD-L1/PD-1 pathway is introduced as a target, but the therapeutic advantage of PD L1/PD-1 blockade has not fulfilled the expectations. This condition may be associated with a different type of resistance in a considerable number of patients. A crucial issue to conquer resistance against immune checkpoint blockade therapy is to understand how PD-L1 level is regulated. However, the mechanisms by which the PD-L1 expression is regulated are complicated, and they can occur at different levels from signaling pathways to posttranscriptional levels. For example, various transcriptional factors, such as hypoxia-inducible factor-1, nuclear factor-κΒ, interferon-γ, STAT3, MYC, and AP-1 can regulate the PD-L1 distribution at the transcriptional level. Herein, we tried to focus on the most important regulatory mechanisms of PD-L1 by inducible agents in the tumor cells, such as signaling pathways, transcriptional factors, and posttranscriptional factors. Finally, these approaches may open up new windows for targeting tumor immune evasion and suggest the novel suppressors of PD-L1 for efficient therapeutics.

Chemosensitization of Therapy Resistant Tumors: Targeting Multiple Cell Signaling Pathways by Lupeol, A Pentacyclic Triterpene

Background:

The resistance of cancer cells to different therapies is one of the major stumbling blocks for successful cancer treatment. Various natural and pharmaceuticals drugs are unable to control drug-resistance cancer cell's growth. Also, chemotherapy and radiotherapy have several side effects and cannot apply to the patient in excess. In this context, chemosensitization to the therapy-resistant cells by non-toxic phytochemicals could be an excellent alternative to combat therapy-resistant cancers.

Objective:

To review the currently available literature on chemosensitization of therapy resistance cancers by Lupeol for clinically approved drugs through targeting different cell signaling pathways.

Methods:

We reviewed relevant published articles in PubMed and other search engines from 1999 to 2019 to write this manuscript. The key words used for the search were “Lupeol and Cancer”, “Lupeol and Chemosensitization”, “Lupeol and Cell Signaling Pathways”, “Cancer Stem Cells and Lupeol” etc. The published results on the chemosensitization of Lupeol were compared and discussed.

Results:

Lupeol chemosensitizes drug-resistant cancer cells for clinically approved drugs. Lupeol alone or in combination with approved drugs inhibits inflammation in different cancer cells through modulation of expression of IL-6, TNF-α, and IFN-γ. Lupeol, through altering the expression levels of BCL-2, BAX, Survivin, FAS, Caspases, and PI3K-AKT-mTOR signaling pathway, significantly induce cell deaths among therapy-resistant cells. Lupeol also modulates the molecules involved in cell cycle regulation such as Cyclins, CDKs, P53, P21, and PCNA in different cancer types.

Conclusion:

Lupeol chemosensitizes the therapy-resistant cancer cells for the treatment of various clinically approved drugs via modulating different signaling pathways responsible for chemoresistance cancer. Thus, Lupeol might be used as an adjuvant molecule along with clinically approved drugs to reduce the toxicity and increase the effectiveness.

Expression of Programmed Death Ligand 1 Is Associated with the Prognosis of Intrahepatic Cholangiocarcinoma

BACKGROUND

Programmed death ligand 1 (PD-L1) is expressed in many malignancies and plays a critical role in escape from immune surveillance through inhibition of its receptor programmed death 1. The role of PD-L1 in intrahepatic cholangiocarcinoma (ICC) and mechanisms of its regulation, however, remain largely unknown.

AIMS

To analyze the expression and prognostic significance of PD-L1 in ICC and to study the regulatory mechanisms of PD-L1.

METHODS

Samples were obtained from 125 patients diagnosed with ICC in the Eastern Hepatobiliary Surgery Hospital from January 2012 to January 2013. The records of each patient were analyzed to examine the relationship between PD-L1 and clinical data. In vitro experiments were performed to investigate the relationship between PD-L1 and the IL-6/mTOR signaling pathway and the feedback mechanism pathway of PD-L1.

RESULTS

Expression of PD-L1 is closely related to tumor vascular invasion, lymphatic metastasis and TNM staging. High PD-L1 expression is closely related to poor prognosis in ICC. Mechanically, IL-6 induces PD-L1 expression through mTOR signaling in ICC cells. In addition, PD-L1 has a negative feedback inhibition effect on AKT signaling.

CONCLUSIONS

In summary, high PD-L1 expression was found to be associated with poor prognosis. The IL-6/mTOR pathway upregulates expression of PD-L1, thus promoting tumor invasion, and PD-L1 negatively inhibits the AKT pathway.

Disruption of SIRT7 Increases the Efficacy of Checkpoint Inhibitor via MEF2D Regulation of Programmed Cell Death 1 Ligand 1 in Hepatocellular Carcinoma Cells

BACKGROUND & AIMS

Immune checkpoint inhibitors have some efficacy in the treatment of hepatocellular carcinoma (HCC). Programmed cell death 1 ligand 1 (PD-L1), expressed on some cancer cells, binds to the receptor programmed cell death 1 (PDCD1, also called PD1) on T cells to prevent their proliferation and reduce the antigen-tumor immune response. Immune cells that infiltrate some types of HCCs secrete interferon gamma (IFNG). Some HCC cells express myocyte enhancer factor 2D (MEF2D), which has been associated with shorter survival times of patients. We studied whether HCC cell expression of MEF2D regulates expression of PD-L1 in response to IFNG.

METHODS

We analyzed immune cells from 20 fresh HCC tissues by flow cytometry. We analyzed 225 fixed HCC tissues (from 2 cohorts) from patients in China by immunohistochemistry and obtained survival data. We created mice with liver-specific knockout of MEF2D (MEF2D^LPC-KO mice). We knocked out or knocked down MEF2D, E1A binding protein p300 (p300), or sirtuin 7 (SIRT7) in SMMC-7721, Huh7, H22, and Hepa1-6 HCC cell lines, some incubated with IFNG. We analyzed liver tissues from mice and cell lines by RNA sequencing, immunoblot, dual luciferase reporter, and chromatin precipitation assays. MEF2D protein acetylation and proteins that interact with MEF2D were identified by coimmunoprecipitation and pull-down assays. H22 cells, with MEF2D knockout or without (controls), were transplanted into BALB/c mice, and some mice were given antibodies to deplete T cells. Mice bearing orthotopic tumors grown from HCC cells, with or without knockout of SIRT7, were given injections of an antibody against PD1. Growth of tumors was measured, and tumors were analyzed by immunohistochemistry and flow cytometry.

RESULTS

In human HCC specimens, we found an inverse correlation between level of MEF2D and numbers of CD4⁺ and CD8⁺ T cells; level of MEF2D correlated with percentages of PD1-positive or TIM3-positive CD8⁺ T cells. Knockout of MEF2D from H22 cells reduced their growth as allograft tumors in immune-competent mice but not in immune-deficient mice or mice with depletion of CD8⁺ T cells. When MEF2D-knockout cells were injected into immune-competent mice, they formed smaller tumors that had increased infiltration and activation of T cells compared with control HCC cells. In human and mouse HCC cells, MEF2D knockdown or knockout reduced expression of PD-L1. MEF2D bound the promoter region of the CD274 gene (encodes PD-L1) and activated its transcription. Overexpression of p300 in HCC cells, or knockout of SIRT7, promoted acetylation of MEF2D and increased its binding, along with acetylated histones, to the promoter region of CD274. Exposure of HCC cells to IFNG induced expression of p300 and its binding MEF2D, which reduced the interaction between MEF2D and SIRT7. MEF2D-induced expression of PD-L1 upon IFNG exposure was independent of interferon-regulatory factors 1 or 9. In HCC cells not exposed to IFNG, SIRT7 formed a complex with MEF2D that attenuated expression of PD-L1. Knockout of SIRT7 reduced proliferation of HCC cells and growth of tumors in immune-deficient mice. Compared with allograft tumors grown from control HCC cells, in immune-competent mice, tumors grown from SIRT7-knockout HCC cells expressed higher levels of PD-L1 and had reduced infiltration and activation of T cells. In immune-competent mice given antibodies to PD1, allograft tumors grew more slowly from SIRT7-knockout HCC cells than from control HCC cells.

CONCLUSIONS

Expression of MEF2D by HCC cells increases their expression of PD-L1, which prevents CD8⁺ T-cell-mediated antitumor immunity. When HCC cells are exposed to IFNG, p300 acetylates MEF2D, causing it to bind the CD274 gene promoter and up-regulate PD-L1 expression. In addition to promoting HCC cell proliferation, SIRT7 reduced acetylation of MEF2D and expression of PD-L1 in HCC cells not exposed to IFNG. Strategies to manipulate this pathway might increase the efficacy of immune therapies for HCC.

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.

Roles of PD-1/PD-L1 Pathway: Signaling, Cancer, and Beyond

Immunotherapies that target PD-1/PD-L1 axis have shown unprecedented success in a wide variety of human cancers. PD-1 is one of the key coinhibitory receptors expressed on T cells upon T cell activation. After engagement with its ligands, mainly PD-L1, PD-1 is activated and recruits the phosphatase SHP-2 in proximity to T cell receptor (TCR) and CD28 signaling. This event results in dephosphorylation and attenuation of key molecules in TCR and CD28 pathway, leading to inhibition of T cell proliferation, activation, cytokine production, altered metabolism and cytotoxic T lymphocytes (CTLs) killer functions, and eventual death of activated T cells. Bodies evolve coinhibitory pathways controlling T cell response magnitude and duration to limit tissue damage and maintain self-tolerance. However, tumor cells hijack these inhibitory pathways to escape host immune surveillance by overexpression of PD-L1. This provides the scientific rationale for clinical application of immune checkpoint inhibitors in oncology. The aberrantly high expression of PD-L1 in tumor microenvironment (TME) can be attributable to the "primary" activation of multiple oncogenic signaling and the "secondary" induction by inflammatory factors such as IFN-γ. Clinically, antibodies targeting PD-1/PD-L1 reinvigorate the "exhausted" T cells in TME and show remarkable objective response and durable remission with acceptable toxicity profile in large numbers of tumors such as melanoma, lymphoma, and mismatch-repair deficient tumors. Nevertheless, most patients are still refractory to anti-PD-1/PD-L1 therapy. Identifying the predictive biomarkers and design rational PD-1-based combination therapy become the priorities in cancer immunotherapy. PD-L1 expression, cytotoxic T lymphocytes infiltration, and tumor mutation burden (TMB) are generally considered as the most important factors affecting the effectiveness of PD-1/PD-L1 blockade. The revolution in cancer immunotherapy achieved by PD-1/PD-L1 blockade offers the paradigm for scientific translation from bench to bedside. The next decades will without doubt witness the renaissance of immunotherapy.

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

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

Genetic alterations of interleukin-17 and related genes in human prostate cancer

Interleukin-17 (IL-17) has been shown to promote development of hormone-naïve prostate cancer (HNPC) and castration-resistant prostate cancer (CRPC) as well as lymph node metastasis in mouse models. Gene alterations of IL-17 family of cytokines and their downstream genes in human prostate cancer have not been investigated. We studied 7 datasets archived in cBioPortal and queried gene alterations in a total of 1303 cases of human prostate cancers. 35 genes were examined, including IL-17 family of cytokines and receptors, IL-17-downstream genes, and genes related to IL-17-downstream genes. We found that 34/35 (97%) genes had significantly more alterations in metastatic prostate cancer (with alteration rates ranging from 3.42% to 13.01%) than primary prostate cancer (with alteration rates ranging from 0.40% to 2.96%). 15/35 (43%) genes had significantly more alterations in primary CRPC than primary HNPC. 34/35 (97%) genes had significantly more alterations in metastatic CRPC than primary HNPC. Only three genes (S100A7, S100A8, and S100A9) had significantly more alterations in metastatic CRPC than primary CRPC. The gene alterations were mostly gene amplifications (97%), while gene deep deletions, missense mutations, and truncating mutations were very rare. 7/35 (20%) genes had significantly more alterations in primary neuroendocrine prostate cancer (NEPC) than primary adenocarcinoma (AC). 23/35 (66%) genes had significantly more alterations in metastatic NEPC than metastatic AC. Only three genes (S100A7, S100A8, and S100A9) had significantly more alterations in metastatic NEPC than metastatic AC with neuroendocrine features. Most of the gene alterations in metastatic NEPC were gene amplifications (80%), while gene deep deletions, missense mutations, and truncating mutations were very rare. Our findings suggest that gene amplifications of IL-17 and related genes are more frequently found in metastatic CRPC and NEPC than primary hormone-naïve prostate adenocarcinomas, implying that IL-17 and related genes may play important roles in the progression from HNPC to CRPC and from primary location to metastasis as well as in development of metastatic NEPC.

Herbal Medicines Attenuate PD-L1 Expression to Induce Anti-Proliferation in Obesity-Related Cancers

Pro-inflammatory hormones and cytokines (leptin, tumor necrosis factor (TNF)-α, and interleukin (IL)-6) rise in obesity. Elevated levels of hormones and cytokines are linked with several comorbidities such as diabetes, heart disease, and cancer. The checkpoint programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) plays an important role in obesity and cancer proliferation. L-thyroxine (T₄) and steroid hormones up-regulate PD-L1 accumulation and promote inflammation in cancer cells and diabetics. On the other hand, resveratrol and other herbal medicines suppress PD-L1 accumulation and reduce diabetic effects. In addition, they induce anti-cancer proliferation in various types of cancer cells via different mechanisms. In the current review, we discuss new findings and visions into the antagonizing effects of hormones on herbal medicine-induced anti-cancer properties.

Efficacy and clinical monitoring strategies for immune checkpoint inhibitors and targeted cytokine immunotherapy for locally advanced and metastatic colorectal cancer

Colorectal cancer (CRC) is the fourth most common cancer type and is the second leading cause of cancer deaths annually in the United States. Conventional treatment options include postoperative (adjuvant) and preoperative (neoadjuvant) chemotherapy and radiotherapy. Although these treatment modalities have shown to decrease tumor burden, a major limitation to chemothearpy/radiotherapy is the high recurrence rate in patients. Immune-modulation strategies have emerged as a promising new therapeutic avenue to reduce this recurrence rate while minimizing undesirable systemic side effects. This review will focus specifically on the mechanisms of monoclonal antibodies: immune checkpoint inhibitors and cytokines, as well as current drugs approved by the Food and Drug Administration (FDA) and new clinical/pre-clinical trials. Finally, this review will investigate emerging methods used to monitor tumor response post-treatment.

Mechanisms Controlling PD-L1 Expression in Cancer

The engagement of programmed cell death protein 1 (PD-1; encoded by the PDCD1 gene) receptor expressed on activated T cells and its ligand, programmed death-ligand 1 (PD-L1; encoded by the CD274 gene), is a major co-inhibitory checkpoint signaling that controls T cell activities. Various types of cancers express high levels of PD-L1 and exploit PD-L1/PD-1 signaling to evade T cell immunity. Blocking the PD-L1/PD-1 pathway has consistently shown remarkable anti-tumor effects in patients with advanced cancers and is recognized as the gold standard for developing new immune checkpoint blockade (ICB) and combination therapies. However, the response rates of anti-PD-L1 have been limited in several solid tumors. Therefore, furthering our understanding of the regulatory mechanisms of PD-L1 can bring substantial benefits to patients with cancer by improving the efficacy of current PD-L1/PD-1 blockade or other ICBs. In this review, we provide current knowledge of PD-L1 regulatory mechanisms at the transcriptional, posttranscriptional, post-translational, and extracellular levels, and discuss the implications of these findings in cancer diagnosis and immunotherapy.

PD-L1 and PD-1 expressed in trigeminal ganglia may inhibit pain in an acute migraine model

BACKGROUND

Neurogenic inflammation, mediated by the activation of primary neurons, is thought to be an important factor in migraine pathophysiology. Programmed cell death ligand-1 (PD-L1) can suppress the immune response through the Programmed cell death-1 receptor. However, the role of PD-L1/PD-1 in migraine remains unclear. In this study we evaluated the expression and role of PD-L1/PD-1 in the trigeminal ganglia in an animal model of acute migraine.

METHODS

Acute nitroglycerin induces acute mechanical hyperalgesia that can be used as a readout of migraine-like pain. We investigated the expression of PD-L1 and PD-1 in the trigeminal ganglia in a mouse model by means of immunofluorescence labeling, quantitative reverse transcription-polymerase chain reaction and western blotting. We explored the effects of PD-1 in a migraine model by the von Frey test and by analyzing the expression of calcitonin gene-related peptide, interleukin-1β (IL-1β), interleukin-18 (IL-18), Tumor Necrosis Factor-α (TNF-α), interleukin-6 (IL-6) and transient receptor potential vanilloid (TRPV4) after the intravenous injection of a PD-1 inhibitor.

RESULTS

PD-L1 and PD-1 immunoreactivity were present in healthy trigeminal ganglia neurons. The mRNA levels of PD-L1 and PD-1 were significantly elevated 2 h, 4 h and 6 h after acute nitroglycerin treatment (p < 0.05). The protein levels of PD-L1 were significantly increased 2 h, 4 h and 6 h after treatment, and PD-1 was significantly increased at 2 h and 6 h. The blockade of PD-1 increased acute nitroglycerin-induced hyperalgesia, and this effect was accompanied by a more significant increase in calcitonin gene-related peptide, IL-1β, TNF-α, IL-6 and IL-18 in the trigeminal ganglia.

CONCLUSION

These findings suggest that PD-L1 and PD-1 might inhibit migraine-like pain by downregulating CGRP and inflammatory factors in the trigeminal ganglia. The use of PD-L1 and PD-1 as analgesics should be further studied.

Uncovering the Anticancer Mechanism of Compound Sophorae Decoction against Ulcerative Colitis-Related Colorectal Cancer in Mice

Compound sophorae decoction (CSD), a traditional Chinese medicine (TCM) formula, has been voluminously used in China to deal with ulcerative colitis and gained significant therapeutic effect. Tremendous explorations have unraveled a contributory role of inflammatory bowel disease (IBD) like ulcerative colitis (UC) and Crohn's disease (CD) at the onset of colorectal cancer, scilicet, and colitis-related cancer (CRC). In light of the anti-inflammatory properties of CSD in UC, we appraised its chemoprevention capacity and underlying mechanism in ulcerative colitis-related colorectal cancer (UCRCC), employing a model of azoxymethane (AOM) plus dextran sulfate sodium- (DSS-) induced colorectal cancer (CRC) in C57BL/6 mice. Rapturously, our results illuminated the ameliorative effect of CSD against UCRCC in mice portrayed by lesser polyps or adenomas, attenuated colonic xenograft tumor growth in company with the preferable well-being of mice in contrast to the Model Group. We examined significant downregulation of proinflammatory cytokines such as TNF-α, NF-κB, IL-6, STAT3, and IL-17 after exposure to CSD, with the concomitant repression of inflammation-associated proteins, including COX-2 and iNOS. Independent of this, treatment with CSD declined the proportion of T helper 17 cells (Th17) and protein level of matrix metallopeptidase 9 (MMP-9). Moreover, transmission electron microscopy (TEM) detected observably suppressed mitophagy in mice administered with CSD and that was paralleled by the pro-apoptotic effect as indicated by upregulating caspase-3 together with caspase-9 and deregulating B-cell lymphoma 2 (Bcl-2). In closing, these findings suggest CSD executes the UCRCC-inhibitory activity through counteracting inflammatory responses and rescuing detuning of apoptosis as well as neutralizing overactive mitophagy, concurring to build up an oncosuppressive microenvironment.

Interleukin-17 is associated with expression of programmed cell death 1 ligand 1 in ovarian carcinoma

The programmed cell death 1/programmed cell death 1 ligand 1 pathway was successfully targeted in cancer immunotherapy. Elevated interleukin-17 (IL-17), which is known in autoimmune diseases, has recently been recognized in cancer patients. We investigated the role of IL-17 in the regulation of expression of programmed cell death 1 ligand 1 in ovarian cancer by evaluating changes in the number of IL-17-producing cluster of differentiation 4 helper T cells (Th17) and γδT cells (γδT17) in PBMC of 52 gynecological cancer patients (including 30 ovarian cancer patients) and 18 healthy controls. The occupancy ratio of Th17 and γδT17 was higher in ovarian cancer and endometrial cancer patients than in controls, determined by multi-color flow cytometry (Th17: P < 0.0001 and P = 0.0002, respectively; γδT17: P = 0.0020 and P = 0.0084, respectively). IL-17 mRNA level was elevated in PBMC of ovarian cancer patients (P = 0.0029), as measured by RT-PCR. The neutrophil-to-lymphocyte ratio, which is a prognostic biomarker of ovarian cancer, correlated with Th17 occupancy ratio in patients (P = 0.0068). We found that programmed cell death 1 ligand 1 expression and its associated factors (IL-6 and phospho-signal transducer and activator of transcription 3) were induced by IL-17 in an ovarian cancer cell line. These results suggest that increased Th17 counts and IL-17 level, which correlated with high neutrophil-to-lymphocyte ratio and programmed cell death 1 ligand 1 expression, are potential biomarkers for poor prognosis in ovarian cancer and likely indications for application of programmed cell death 1 ligand 1 pathway inhibitors.

Inhibition of the PD-1/PD-L1 signaling pathway enhances innate immune response of alveolar macrophages to mycobacterium tuberculosis in mice

BACKGROUND

Mycobacterium tuberculosis (TB) is a pathogen that consequently leads to TB infection, which remains a significant global health concern. Programmed death 1 (PD-1)/programmed death-ligand 1 (PD-L1) signaling pathway is critical for terminating immune responses. The present study aimed to elucidate the regulatory role of the PD-1/PD-L1 signaling pathway in alveolar macrophages against Mycobacterium TB in mice.

METHODS

Specific pathogen free mice were initially prepared for Mycobacterium TB model establishment. The alveolar macrophages of the successfully modeled rats were evaluated to determine the levels of PD-1, PD-L1, AKT, mTOR, TNF-α, NF-κB, IL-2, IL-4, IL-6, IL-10, IL-17, IL-17A, and IFN-γ. The surface makers of macrophages (CD11c, CD16, CD86, CD163, CD206, CX3CR-1 and CSF-1R), level of ROS, apoptosis and cell cycle, were all assessed.

RESULTS

Elevated levels of PD-1 and PD-L1, decreased levels of AKT and mTOR, along with elevated levels of TNF-α, NF-κB, IL-17, IL-2, IL-6, IL-17A and IFN-γ were identified in the alveolar macrophages infected with Mycobacterium TB, while an opposite trend was observed when PD-1/PD-L1 signaling pathway was inhibited. Additionally, elevated protein levels of CD11c, CD16 and CD86, as well as an increased rate of positive ROS and cell apoptosis, levels of Bax, and a diminished percentage of alveolar macrophages at the S and G2/M stages were detected in the event of Mycobacterium TB infection. A contrasting trend to the aforementioned findings was detected when the PD-1/PD-L1 signaling pathway was inhibited.

CONCLUSION

Taken together, these results suggested that inhibition of the PD-1/PD-L1 signaling pathway enhanced the innate immune response of alveolar macrophages to Mycobacterium TB in mice.

Screening of key genes associated with R‑CHOP immunochemotherapy and construction of a prognostic risk model in diffuse large B‑cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is a common subtype of non-Hodgkin lymphoma, which is curable in the majority of patients treated with rituximab plus cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP) immunochemotherapy. However, the therapeutic mechanism of R-CHOP has not been elucidated. The GSE32918 and GSE57611 datasets were retrieved from The Gene Expression Omnibus database. The differentially expressed genes (DEGs) associated with R-CHOP therapy were identified using limma. Combined with prognostic information in GSE32918, DEGs found to be significantly associated with prognosis were selected using univariate Cox regression analysis and a risk prediction model was constructed. Based on this model, the samples in the training set (GSE32918) were divided into high and low risk score groups according to the median risk score. A total of 801 DEGs were identified between the R-CHOP treated DLBCL and primary DLBCL samples, from this 116 prognosis-associated genes were selected. Using Cox proportional hazards model, an optimal combination of 12 genes [including calcium/calmodulin dependent protein kinase I (CAMK1), hippocalcin like 4 (HPCAL4) and ephrin A5 (EFNA5)] was selected, and the sample risk score prediction model was constructed and validated. The DEGs between high risk score and low risk score groups were significantly enriched in functions associated with ‘response to DNA damage stimulus’, and pathways including ‘cytokine-cytokine receptor interaction’ and ‘cell cycle’. The optimal combination of the 12 genes, including CAMK1, HPCAL4 and EFNA5, was found to be useful in predicting the prognosis of patients with DLBCL after R-CHOP treatment. Therefore, these genes may be affected by R-CHOP in DLBCL.

Novel Human Bispecific Aptamer-Antibody Conjugates for Efficient Cancer Cell Killing

Monoclonal antibodies have been approved by the Food and Drug Administration for the treatment of various human cancers. More recently, oligonucleotide aptamers have risen increasing attention for cancer therapy thanks to their low size (efficient tumor penetration) and lack of immunogenicity, even though the short half-life and lack of effector functions still hinder their clinical applications. Here, we demonstrate, for the first time, that two novel bispecific conjugates, consisting of an anti-epidermal growth factor receptor (EGFR) aptamer linked either with an anti-epidermal growth factor receptor 2 (ErbB2) compact antibody or with an immunomodulatory (anti-PD-L1) antibody, were easily and rapidly obtained. These novel aptamer-antibody conjugates retain the targeting ability of both the parental moieties and acquire a more potent cancer cell killing activity by combining their inhibitory properties. Furthermore, the conjugation of the anti-EGFR aptamer with the immunomodulatory antibody allowed for the efficient redirection and activation of T cells against cancer cells, thus dramatically enhancing the cytotoxicity of the two conjugated partners. We think that these bispecific antibody-aptamer conjugates could have optimal biological features for therapeutic applications, such as increased specificity for tumor cells expressing both targets and improved pharmacokinetic and pharmacodynamic properties due to the combined advantages of the aptamer and antibody.

Thyroid hormone-induced expression of inflammatory cytokines interfere with resveratrol-induced anti-proliferation of oral cancer cells

Thyroid hormone, L-thyroxine (T₄), induces inflammatory genes expressions and promotes cancer growth. It also induces expression of the checkpoint programmed death-ligand 1 (PD-L1), which plays a vital role in cancer progression. On the other hand, resveratrol inhibits inflammatory genes expressions. Moreover, resveratrol increases nuclear inducible cyclooxygenase (COX)-2 accumulation, complexes with p53, and induces p53-dependent anti-proliferation. In this study, we investigated the effect of T₄ on resveratrol-induced anti-proliferation in oral cancer. T₄ increased the expression and cytoplasmic accumulation of PD-L1. Increased expressions of pro-inflammatory genes, interleukin (IL)-1β and transforming growth factor (TGF)-β1, were shown to stimulate PD-L1 expression. T₄ stimulated pro-inflammatory and proliferative genes expressions, and oral cancer cells proliferation. In contrast, resveratrol inhibited those genes and activated anti-proliferative genes. T₄ retained resveratrol-induced COX-2 in cytoplasm and prevented COX-2 nuclear accumulation when resveratrol treated cancer cells. A specific signal transducer and activator of transcription 3 (STAT3) inhibitor, S31-201, blocked T₄-induced inhibition and restored resveratrol-induced nuclear COX-2 accumulation. By inhibiting the T₄-activated STAT3 signal transduction axis with S31-201, resveratrol was able to sequentially reestablish COX-2/p53-dependent gene expressions and anti-proliferation. These findings provide a novel understanding of the inhibitory effects of T₄ on resveratrol-induced anticancer properties via the sequential expression of PD-L1 and inflammatory genes.

18F-FDG PET metabolic-to-morphological volume ratio predicts PD-L1 tumour expression and response to PD-1 blockade in non-small-cell lung cancer

PURPOSE

Anti-PD-1/PD-L1 blockade can restore tumour-specific T-cell immunity and is an emerging therapy in non-small-cell lung cancer (NSCLC). We investigated the correlation between ¹⁸F-FDG PET/CT-based markers and tumour tissue expression of PD-L1, necrosis and clinical outcome in patients receiving checkpoint inhibitor treatment.

METHODS

PD-Li expression in biopsy or resection specimens from 49 patients with confirmed NSCLC was investigated by immunohistochemistry. Maximum standardized uptake value (SUVmax), mean SUV (SUVmean), metabolic tumour volume (MTV) and total lesion glycolysis (TLG) were obtained from ¹⁸F-FDG PET/CT images. The ratio of metabolic to morphological lesion volumes (MMVR) and its association with PD-L1 expression in each lesion were calculated. The associations between histologically reported necrosis and ¹⁸F-FDG PET imaging patterns and radiological outcome (evaluated by iRECIST) following anti-PD-1/PD-L1 therapy were also analysed. In 14 patients, the association between necrosis and MMVR and tumour immune contexture were analysed by multiple immunofluorescent (IF) staining for CD8, PD-1, granzyme B (GrzB) and NFATC2.

RESULTS

In total, 25 adenocarcinomas and 24 squamous cell carcinomas were analysed. All tumours showed metabolic ¹⁸F-FDG PET uptake. MMVR was correlated inversely with PD-L1 expression in tumour cells. Furthermore, PD-L1 expression and low MMVR were significantly correlated with clinical benefit. Necrosis was correlated negatively with MMVR. Multiplex IF staining showed a greater frequency of activated CD8⁺ cells in necrotic tumours than in nonnecrotic tumours in both stromal and epithelial tumour compartments.

CONCLUSION

This study introduces MMVR as a new imaging biomarker and its ability to noninvasively capture increased PD-L1 tumour expression and predict clinical benefit from checkpoint blockade in NSCLC should be further evaluated.

PD-L1 instead of PD-1 status is associated with the clinical features in human primary prostate tumors

Immunotherapy targeting programmed cell death protein 1 (PD-1)/programmed cell death-ligand 1 (PD-L1) has shown efficacy in a variety of solid tumors. However, prostate cancer has often been a non-responder to anti-PD-1/PD-L1 therapies. The objective of this study was to determine PD-1 and PD-L1 expression status and its correlation with clinical features of the patients. A total of 279 patients who underwent radical prostatectomy for prostate cancer were included in this study. PD-1 and PD-L1 expression in primary prostate tumors was detected using immunohistochemical staining. Analyses were made between PD-1/PD-L1 status and patients' age, ethnicity, body mass index (BMI), diabetes mellitus, tumor stage, lymph node metastasis, prostate-specific antigen (PSA), Gleason score, grade group, and survival. We found that 6.5 (standard deviation 14.3; range 0-161.6) tumor-infiltrating lymphocytes per high power field were positive for PD-1 staining and 50/279 (17.9%) tumors were positive for PD-L1 staining. PD-L1-positive tumors had significantly more PD-1-positive lymphocytes than PD-L1-negative tumors. The number of PD-1-positive lymphocytes was not correlated with any clinical features except that patients with diabetes had significantly less PD-1-positive lymphocytes than patients without diabetes. In contrast, more PD-L1-positive tumors were found in older patients (≥ 65 years), obese patients (BMI ≥ 30), and patients with advanced tumor stage, lymph node metastasis, and high Gleason score. Neither PD-1 nor PD-L1 status was correlated with ethnicity, PSA, or survival. Our findings suggest that PD-L1 instead of PD-1 status is associated with the clinical features in human primary prostate tumors.