B7-H1 Overexpression Regulates Epithelial–Mesenchymal Transition and Accelerates Carcinogenesis in Skin

Platelet PD-L1 inhibits storage-induced apoptosis by sustaining activation of the AKT signalling pathway

Platelet apoptosis is irreversible under current storage conditions in blood banks. Studies have shown that programmed cell death ligand 1 (PD-L1) in tumour cells is required for neoplastic progression, tumour recurrence and metastasis by regulating apoptosis. However, whether PD-L1 is involved in storage-induced apoptosis in platelets remains poorly understood. In this study, we explored whether PD-L1 on platelets participated in the regulation of storage-induced apoptosis under blood bank conditions, as well as the underlying mechanism. Several apoptotic events in platelets from humans and PD-L1-knockout mice during storage under blood bank conditions were measured. The mechanism by which storage-induced apoptosis was regulated by platelet-intrinsic PD-L1 signalling was further investigated. Our results showed that PD-L1 in platelets progressively decreased. There was a strong negative correlation between platelet PD-L1 expression and the phosphatidylserine (PS) externalization rate and cleaved caspase-3 level and a positive correlation with anti-apoptosis protein Bcl-xl. Ex vivo, PD-L1-/- platelets stored at 22 °C showed rapid apoptosis via an intrinsic mitochondria-dependent pathway over time. Likewise, inhibiting PD-L1 signalling with BMS-1166 accelerated apoptosis by intrinsic mitochondria-dependent pathway. Coimmunoprecipitation analysis revealed that PD-L1 could bind AKT in platelets, and the binding capacity of both showed a progressive decrease with time. Finally, the decrease in PD-L1 expression levels during storage could be attributed to a complex process of progressive secretion. Therefore, platelet PD-L1 inhibits storage-induced apoptosis by sustaining activation of the AKT signalling pathway, which is expected to become a target for alleviating platelet storage lesions (PSLs) under current blood bank conditions.

A comprehensive exploration of twist1 to identify a biomarker for tumor immunity and prognosis in pan-cancer

Twist1 has been identified as a critical gene in tumor, but current study of this gene remains limitative. This study aims to investigate its roles and potential mechanisms across pan-cancer. The study used various databases and computational techniques to analyze twist's RNA expression, clinical data, gene mutations, tumor stemness, tumor microenvironment, immune regulation. Furthermore, the experimental method of fluorescence staining was carried out to identify twist1 expression in various tumor masses. After analyzing the protein-protein interaction of TWIST, enrichment analysis and predictive potential drugs were performed, and molecular docking was conducted to validate. We found that twist1 expression was significantly higher in various types of cancer and associated with tumor stage, grade, and poor prognosis in multiple cancers. Differential expression of twist1 was linked to gene mutation, RNA modifications, and tumor stemness. Additionally, twist1 expression was positively associated with tumor immunoregulation and immune checkpoint. Salinomycin, klugline, isocephaelince, manassantin B, and pimonidazole are predictive potential drugs targeting TWIST1. This study revealed that twist1 plays an important role in tumor, and might be a curial marker in tumor diagnose and prognosis. The study also highlighted twist1 as a promising therapeutic target for cancer treatment and provided a foundation for future research.

Immune checkpoints between epithelial-mesenchymal transition and autophagy: A conflicting triangle

Inhibitory immune checkpoint (ICP) molecules are pivotal in inhibiting innate and acquired antitumor immune responses, a mechanism frequently exploited by cancer cells to evade host immunity. These evasion strategies contribute to the complexity of cancer progression and therapeutic resistance. For this reason, ICP molecules have become targets for antitumor drugs, particularly monoclonal antibodies, collectively referred to as immune checkpoint inhibitors (ICI), that counteract such cancer-associated immune suppression and restore antitumor immune responses. Over the last decade, however, it has become clear that tumor cell-associated ICPs can also induce tumor cell-intrinsic effects, in particular epithelial-mesenchymal transition (EMT) and macroautophagy (hereafter autophagy). Both of these processes have profound implications for cancer metastasis and drug responsiveness. This article reviews the positive or negative cross-talk that tumor cell-associated ICPs undergo with autophagy and EMT. We discuss that tumor cell-associated ICPs are upregulated in response to the same stimuli that induce EMT. Moreover, ICPs themselves, when overexpressed, become an EMT-inducing stimulus. As regards the cross-talk with autophagy, ICPs have been shown to either stimulate or inhibit autophagy, while autophagy itself can either up- or downregulate the expression of ICPs. This dynamic equilibrium also extends to the autophagy-apoptosis axis, further emphasizing the complexities of cellular responses. Eventually, we delve into the intricate balance between autophagy and apoptosis, elucidating its role in the broader interplay of cellular dynamics influenced by ICPs. In the final part of this article, we speculate about the driving forces underlying the contradictory outcomes of the reciprocal, inhibitory, or stimulatory effects between ICPs, EMT, and autophagy. A conclusive identification of these driving forces may allow to achieve improved antitumor effects when using combinations of ICIs and compounds acting on EMT and/or autophagy. Prospectively, this may translate into increased and/or broadened therapeutic efficacy compared to what is currently achieved with ICI-based clinical protocols.

Inhibition of UV-Induced Stress Signaling and Inflammatory Responses in SKH-1 Mouse Skin by Topical Small-Molecule PD-L1 Blockade

The immune checkpoint ligand PD-L1 has emerged as a molecular target for skin cancer therapy and might also hold promise for preventive intervention targeting solar UV light-induced skin damage. In this study, we have explored the role of PD-L1 in acute keratinocytic photodamage testing the effects of small-molecule pharmacological inhibition. Epidermal PD-L1 upregulation in response to chronic photodamage was established using immunohistochemical and proteomic analyses of a human skin cohort, consistent with earlier observations that PD-L1 is upregulated in cutaneous squamous cell carcinoma. Topical application of the small-molecule PD-L1 inhibitor BMS-202 significantly attenuated UV-induced activator protein-1 transcriptional activity in SKH-1 bioluminescent reporter mouse skin, also confirmed in human HaCaT reporter keratinocytes. RT-qPCR analysis revealed that BMS-202 antagonized UV induction of inflammatory gene expression. Likewise, UV-induced cleavage of procaspase-3, a hallmark of acute skin photodamage, was attenuated by topical BMS-202. NanoString nCounter transcriptomic analysis confirmed downregulation of cutaneous innate immunity- and inflammation-related responses, together with upregulation of immune response pathway gene expression. Further mechanistic analysis confirmed that BMS-202 antagonizes UV-induced PD-L1 expression both at the mRNA and protein levels in SKH-1 epidermis. These data suggest that topical pharmacological PD-L1 antagonism using BMS-202 shows promise for skin protection against photodamage.

Prevalence and prognostic role of PD-L1 in patients with gynecological cancers: A systematic review and meta-analysis

OBJECTIVE

Our study aims to evaluate programmed cell death ligand-1 (PD-L1) expression and its prognostic significance in cervical cancer (CC), endometrial cancer (EC) and ovarian cancer (OC).

METHODS

Several electronic databases were searched. Fixed effects models or random effects models were employed to calculate the pooled prevalence of PD-L1 positivity and pooled hazard ratios (HRs) as appropriate. Heterogeneity and publication bias were also assessed.

RESULTS

The pooled prevalence of PD-L1 positivity was 58.1%, 33.8% and 37.5% for CC, EC and OC patients, respectively. There were significant differences in the pooled estimates after stratification by PD-L1-positive assessment criteria and antibody clones. PD-L1 positivity was associated with worse OS in CC and EC patients and poorer progression-free survival (PFS) in CC patients.

CONCLUSIONS

The prevalence of PD-L1-positive expression was considerably high in CC and modestly high in EC and OC patients. PD-L1 expression has the potential to be a prognostic biomarker for predicting the clinical outcomes of patients with CC and EC but not OC.

MET Receptor Tyrosine Kinase Inhibition Reduces Interferon-Gamma (IFN-γ)-Stimulated PD-L1 Expression through the STAT3 Pathway in Melanoma Cells

Melanoma is the leading cause of death from cutaneous malignancy. While targeted therapy and immunotherapy with checkpoint inhibitors have significantly decreased the mortality rate of this disease, advanced melanoma remains a therapeutic challenge. Here, we confirmed that interferon-gamma (IFN-γ)-induced PD-L1 expression in melanoma cell lines. This increased expression was down-regulated by the reduction in phosphorylated STAT3 signaling via MET tyrosine kinase inhibitor treatment. Furthermore, immunoprecipitation and confocal immunofluorescence microscopy analysis reveals MET and PD-L1 protein-protein interaction and colocalization on the cell surface membrane of melanoma cells. Together, these findings demonstrate that the IFN-γ-induced PD-L1 expression in melanoma cells is negatively regulated by MET inhibition through the JAK/STAT3 signaling pathway and establish the colocalization and interaction between an RTK and a checkpoint protein in melanoma cells.

PD-1/PD-L1 blockade inhibits epithelial-mesenchymal transition and improves chemotherapeutic response in breast cancer

Therapies targeting the PD-1/PD-L1 axis have recently been implemented for triple negative breast cancer (TNBC) management with limited efficacy, indicating that this axis may promote tumor growth by means other than immune suppression. Because PD-L1 overexpression causes resistance to the chemotherapeutic response in many cancers, here we explored the tumor promoting role of the PD-1/PD-L1 axis in breast cancer. We observed that the downregulation of PD-L1 by specific siRNA and pharmacological inhibitor significantly suppressed tumor cell proliferation, invasion and migration thereby enhancing T cell-mediated cell killing in vitro. We also showed that inhibiting PD-L1 improves cytotoxic sensitivity to chemotherapy in TNBC cells. Our in vivo results confirmed that combining a PD-L1 inhibitor with chemotherapy could significantly reduce tumor progression by inhibiting epithelial-mesenchymal transition. Overall, our results proved that PD-L1 contributes to the transformation and progression of breast cancer cells and that its intervention is a promising therapeutic strategy against breast cancer.

Review: PD-L1 as an emerging target in the treatment and prevention of keratinocytic skin cancer

Recent advances in the understanding and targeting of immune checkpoints have led to great progress in immune therapies against many forms of cancer. While many types of immune checkpoints are currently targeted in the clinic, this review will focus on recent research implicating the programmed cell death protein 1/programmed death-ligand 1 (PD-1/PD-L1) axis as an emerging focus for the treatment of keratinocytic tumors. PD-L1 is of particular interest in nonmelanoma skin cancer (NMSC), as it is not only upregulated in these tumors but is stimulated by environmental ultraviolet exposure. This response may also make PD-L1 an excellent target for photochemoprevention using topically applied small molecule inhibitors. Here, we summarize recent investigations on PD-L1 expression and clinically relevant immune checkpoint inhibitor treatment in cutaneous squamous cell carcinoma, basal cell carcinoma, and head and neck squamous cell carcinoma, as well as small molecule agents targeting PD-L1 that may be useful for clinical development aiming at treatment or prevention of NMSC.

Programmed Cell Death Protein 1 Axis Inhibition in Viral Infections: Clinical Data and Therapeutic Opportunities

A vital function of the immune system is the modulation of an evolving immune response. It is responsible for guarding against a wide variety of pathogens as well as the establishment of memory responses to some future hostile encounters. Simultaneously, it maintains self-tolerance and minimizes collateral tissue damage at sites of inflammation. In recent years, the regulation of T-cell responses to foreign or self-protein antigens and maintenance of balance between T-cell subsets have been linked to a distinct class of cell surface and extracellular components, the immune checkpoint molecules. The fact that both cancer and viral infections exploit similar, if not the same, immune checkpoint molecules to escape the host immune response highlights the need to study the impact of immune checkpoint blockade on viral infections. More importantly, the process through which immune checkpoint blockade completely changed the way we approach cancer could be the key to decipher the potential role of immunotherapy in the therapeutic algorithm of viral infections. This review focuses on the effect of programmed cell death protein 1/programmed death-ligand 1 blockade on the outcome of viral infections in cancer patients as well as the potential benefit from the incorporation of immune checkpoint inhibitors (ICIs) in treatment of viral infections.

PD-L1 regulates cell proliferation and apoptosis in acute myeloid leukemia by activating PI3K-AKT signaling pathway

As immune checkpoint inhibitors (ICIs) continue to advance, more evidence has emerged that anti-PD-1/PD-L1 immunotherapy is an effective treatment against cancers. Known as the programmed death ligand-1 (PD-L1), this co-inhibitory ligand contributes to T cell exhaustion by interacting with programmed death-1 (PD-1) receptor. However, cancer-intrinsic signaling pathways of the PD-L1 molecule are not well elucidated. Therefore, the present study aimed to evaluate the regulatory network of PD-L1 and lay the basis of successful use of anti-PD-L1 immunotherapy in acute myeloid leukemia (AML). Data for AML patients were extracted from TCGA and GTEx databases. The downstream signaling pathways of PD-L1 were identified via Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. The key PD-L1 related genes were selected by weighted gene co-expression network analysis (WGCNA), MCC algorithm and Molecular Complex Detection (MCODE). The CCK-8 assay was used to assess cell proliferation. Flow cytometry was used to determine cell apoptosis and cell cycle. Western blotting was used to identify the expression of the PI3K-AKT signaling pathway. PD-L1 was shown to be elevated in AML patients when compared with the control group, and high PD-L1 expression was associated with poor overall survival rate. The ECM-receptor interaction, as well as the PI3K-AKT signaling pathway, were important PD-L1 downstream pathways. All three analyses found eight genes (ITGA2B, ITGB3, COL6A5, COL6A6, PF4, NMU, AGTR1, F2RL3) to be significantly associated with PD-L1. Knockdown of PD-L1 inhibited AML cell proliferation, induced cell apoptosis and G2/M cell cycle arrest. Importantly, PD-L1 knockdown reduced the expression of PI3K and p-AKT, but PD-L1 overexpression increased their expression. The current study elucidates the main regulatory network and downstream targets of PD-L1 in AML, assisting in the understanding of the underlying mechanism of anti-PD-1/PD-L1 immunotherapy and paving the way for clinical application of ICIs in AML.

LINC00244 suppresses cell growth and metastasis in hepatocellular carcinoma by downregulating programmed cell death ligand 1

The role of programmed cell death ligand 1 (PD-L1) in suppressing antitumor immune responses has been widely reported, and recent studies showed that PD-L1 also plays an important role in epithelial-mesenchymal transition (EMT), determination of tumor cell phenotypes, metastasis, and drug resistance. Long non-coding RNAs (lncRNAs) are involved in a variety of epigenetic regulatory processes. The tumorigenesis and development of most cancers cannot be studied separately from their regulation by lncRNAs. To explore the epigenetic regulation of PD-L1, we identified an lncRNA, LINC00244, which reduced PD-L1 expression and predicted good clinical outcomes in hepatocellular carcinoma (HCC). LINC00244 inhibited the proliferation, invasion, and metastasis of HCC by downregulating PD-L1 expression. In addition, low LINC00244 expression activated epithelial-mesenchymal transition (EMT) pathways and facilitated the rapid growth and metastasis of HCC cells. Thus, LINC00244 is a potential therapeutic target for HCC.

Clinical significance of tumoral PD-L1 expression in Wilms tumors

BACKGROUND

Although cure rate for Wilms tumor (WT) is high recent years, there is still small fraction of patients suffering from tumor relapse or metastases. It is urgent to identify more valuable biomarkers associated with disease progression. Previous studies have shown that PD-L1 was abnormally expressed in various type of cancers and acted as predictor for poor prognosis for those cancers. PD-1/PD-L1 inhibitors have achieved great success in various malignancies with correlation between PD-L1 expression and responses. We conducted this retrospective study to better understand the role of PD-L1 in WT development.

OBJECTIVE

The aim of this study was to evaluate the expression rate of tumoral PD-L1 in WT and investigate the association of PD-L1 with tumor invasion and metastasis.

STUDY DESIGN

Seventy-seven patients with WT, including 20 cases of primary WTs with corresponding resected invasive/lymph node metastatic tumors were enrolled in the research. Immunohistochemistry was used to examine tumoral PD-L1 expression. Kaplan-Meier analysis with regard to the relationship between the expression of tumoral PD-L1 and follow-up information was performed.

RESULTS

Positive expression rate of tumoral PD-L1 was 28.6% in primary WT tissues, while 35% in associated invasive/metastatic ones. The tumoral PD-L1 expression in primary WTs were correlated with late stage and unfavorable histology (P = 0.007; P = 0.002). The expression rate of tumoral PD-L1 was higher in the progression group than that without distant metastasis or relapse (P = 0.038). The expression rate of PD-L1 between primary WTs and matched invasive/metastatic tissues was concordant (P = 0.435). Tumoral PD-L1 expression was associated with disease-free survival (DFS) and overall survival (OS) (P = 0.02; P = 0.03). Tumor PD-L1 expression was associated with DFS and OS in univariable analyses but not in multivariable Cox regression, adjusting for histology and tumor stage.

DISCUSSION

We found that PD-L1 expression was associated with the late-stage of WT and unfavorable histology, which were tightly associated with disease relapse and progression, predicting poor prognosis. The subsequent survival analysis also showed that PD-L1 expression was linked to both shorter DFS and OS. After adjustment for WT stage and histology, PD-L1 expression was no longer an independent predictor of DFS/OS. The value of PD-L1 as predictor for prognosis and potential therapeutic target in WT still need to be validated in large cohort in future.

CONCLUSION

Although PD-L1 expression correlated with established prognostic factors in our dataset, its value as a prognostic marker and therapeutic target, if any, remains to be shown in future.

Metformin inhibits human non-small cell lung cancer by regulating AMPK-CEBPB-PDL1 signaling pathway

Metformin has been found to have inhibitory effects on a variety of tumors. However, its effects on non-small cell lung cancer (NSCLC) remain unclear. We demonstrated that metformin could inhibit the proliferation of A549 and H1299 cells. RNA transcriptome sequencing revealed that PDL1 was significantly downregulated in both cell types following treatment with metformin (P < 0.001). Jaspar analysis and chromatin immunoprecipitation showed that CEBPB could directly bind the promoter region of PDL1. Western blotting showed that protein expression of the isoforms CEBPB-LAP*, CEBPB-LAP, and CEBPB-LIP was significantly upregulated and the LIP/LAP ratio was increased. Gene chip analysis showed that PDL1 was significantly upregulated in A549-CEBPB-LAP cells and significantly downregulated in A549-CEBPB-LIP cells (P < 0.05) compared with CEBPB-NC cells. Dual-luciferase reporter gene assay showed that CEBPB-LAP overexpression could promote transcription of PDL1 and CEBPB-LIP overexpression could inhibit the process. Functional assays showed that the changes in CEBPB isoforms affected the function of NSCLC cells. Western blotting showed that metformin could regulate the function of NSCLC cells via AMPK-CEBPB-PDL1 signaling. Animal experiments showed that tumor growth was significantly inhibited by metformin, and atezolizumab and metformin had a synergistic effect on tumor growth. A total of 1247 patients were retrospectively analyzed, including 166 and 1081 patients in metformin and control groups, respectively. The positive rate of PDL1 was lower than that of the control group (HR = 0.338, 95% CI = 0.235-0.487; P < 0.001). In conclusion, metformin inhibited the proliferation of NSCLC cells and played an anti-tumor role in an AMPK-CEBPB-PDL1 signaling-dependent manner.

The Epithelial-Mesenchymal Transition Influences the Resistance of Oral Squamous Cell Carcinoma to Monoclonal Antibodies via Its Effect on Energy Homeostasis and the Tumor Microenvironment

Oral squamous cell carcinoma (OSCC) is a major type of cancer that accounts for over 90% of all oral cancer cases. Recently developed evidence-based therapeutic regimens for OSCC based on monoclonal antibodies (mAbs), such as cetuximab, pembrolizumab, and nivolumab, have attracted considerable attention worldwide due to their high specificity, low toxicity, and low rates of intolerance. However, the efficacy of those three mAbs remains poor because of the low rate of responders and acquired resistance within a short period of time. The epithelial-mesenchymal transition (EMT) process is fundamental for OSCC growth and metastasis and is also responsible for the poor response to mAbs. During EMT, cancer cells consume abundant energy substrates and create an immunosuppressive tumor microenvironment to support their growth and evade T cells. In this review, we provide an overview of the complex roles of major substrates and signaling pathways involved in the development of therapeutic resistance in OSCC. In addition, we summarize potential therapeutic strategies that may help overcome this resistance. This review aims to help oral oncologists and researchers aiming to manage OSCC and establish new treatment modalities.

Programmed Death Ligand 2 Gene Polymorphisms Are Associated With Lung Adenocarcinoma Risk in Female Never-Smokers

Objectives

Lung cancer in never-smokers is a distinct disease associated with a different genomic landscape, pathogenesis, risk factors, and immune checkpoint inhibitor responses compared to those observed in smokers. This study aimed to identify novel single nucleotide polymorphisms (SNPs) of programmed death-1 (encoded by PDCD1) and its ligands, programmed death ligand 1 (CD274) and 2 (PDCD1LG2), associated with lung cancer risk in never-smoking women.

Materials and Methods

During September 2002 and July 2012, we enrolled never-smoking female patients with lung adenocarcinoma (LUAD) (n=1153) and healthy women (n=1022) from six tertiary hospitals in Taiwan. SNP data were obtained and analyzed from the genome-wide association study dataset and through an imputation method. The expression quantitative trait loci (eQTL) analysis was performed in both tumor and non-tumor tissues for the correlation between genetic expression and identified SNPs.

Results

A total of 12 PDCD1LG2 SNPs related to LUAD risk were identified in never-smoking women, including rs2381282, rs4742103, rs4237162, rs4742104, rs12237624, rs78096119, rs6476988, rs7857315, rs10975178, rs7854413, rs56001683, and rs7858319. Among them, six tagged PDCD1LG2 SNPs rs2381282, rs4742103, rs4237162, rs4742104, rs78096119, and rs56001683 were significantly associated with LUAD risk. Specifically, two PDCD1LG2 SNPs, rs12237624 and rs78096119, were associated with previous pulmonary tuberculosis infection in relation to LUAD susceptibility. Through an eQTL assay, we found that rs2381282 (p < 0.001), rs12237624 (p = 0.019), and rs78096119 (p = 0.019) were associated with the expression levels of programed death ligand 2.

Conclusions

Novel SNPs of programed death ligand 2 associated with lung adenocarcinoma risk were identified. Among them, two SNPs were associated with pulmonary tuberculosis infection in relation to lung adenocarcinoma susceptibility. These SNPs may help to stratify high-risk populations of never-smokers during lung cancer screening.

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

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

Analysis of immune subtypes across the epithelial-mesenchymal plasticity spectrum

Epithelial-mesenchymal plasticity plays a critical role in many solid tumor types as a mediator of metastatic dissemination and treatment resistance. In addition, there is also a growing appreciation that the epithelial/mesenchymal status of a tumor plays a role in immune evasion and immune suppression. A deeper understanding of the immunological features of different tumor types has been facilitated by the availability of large gene expression datasets and the development of methods to deconvolute bulk RNA-Seq data. These resources have generated powerful new ways of characterizing tumors, including classification of immune subtypes based on differential expression of immunological genes. In the present work, we combine scoring algorithms to quantify epithelial-mesenchymal plasticity with immune subtype analysis to understand the relationship between epithelial plasticity and immune subtype across cancers. We find heterogeneity of epithelial-mesenchymal transition (EMT) status both within and between cancer types, with greater heterogeneity in the expression of EMT-related factors than of MET-related factors. We also find that specific immune subtypes have associated EMT scores and differential expression of immune checkpoint markers.

CMTM4 regulates epithelial-mesenchymal transition and PD-L1 expression in head and neck squamous cell carcinoma

The epithelial-mesenchymal transition (EMT) is a pivotal step involved in cancer recurrence and metastasis. In addition, the activation of the EMT program can induce a cancer stem cell (CSC)-like phenotype and programmed death-ligand 1 (PD-L1) expression in head and neck squamous cell carcinoma (HNSCC). The CMTM family has reported as an important regulator in this process. Here, we investigated the role of CMTM4 in HNSCC. We indicated that CMTM4 was overexpressed in human and mouse HNSCC samples and in HNSCC cell lines by immunohistochemistry and Western blot. A high expression level of CMTM4 was correlated with advanced lymph node metastasis and a negative prognosis. CMTM4-knockdown by small interfering RNA downregulated the EMT process and inhibited the migration and invasion abilities of tumor cells. Moreover, knockdown of CMTM4 decreased CSC-associated markers via the protein kinase B pathway. Notably, CMTM4-knockdown inhibited the expression of interferon-γ induced PD-L1 in HNSCC cells. A positive correlation was found between CMTM4 expression and CD8⁺ and PD-1⁺ cell density in the stroma. Our findings indicated that CMTM4 may play an important role in regulating EMT/CSC phenotypes and PD-L1 expression. This study may reinforce the interest in CMTM4 as a potential target for the prognosis and treatment of HNSCC.

Discovery of Pyrrole-imidazole Polyamides as PD-L1 Expression Inhibitors and Their Anticancer Activity via Immune and Nonimmune Pathways

In recent years, PD-1 immune checkpoint inhibitors based on monoclonal antibodies have revolutionized cancer therapy, but there still exist unresolved issues, such as the high cost, the relatively low response rates, and so on, compared with small-molecule drugs. Herein a type of pyrrole-imidazole (Py-Im) polyamide as a small-molecule DNA binder was designed and synthesized, which could competitively bind to the same double-stranded DNA stretch in the PD-L1 promoter region as the STAT3 binding site and thus downregulate PD-L1 expression. It was demonstrated that the Py-Im polyamides directly caused apoptosis in tumor cells and retarded cell migration in the absence of T cells through inhibiting the Akt/caspase-3 pathway. Also, in a coculture system, they enhanced the T-cell-mediated killing of tumor cells by the reversal of immune escape. Because such polyamides induced antitumor effects via both immune and nonimmune pathways, they could be further developed as promising PD-L1 gene-targeting antitumor drugs.

Programmed death ligand-1 regulates angiogenesis and metastasis by participating in the c-JUN/VEGFR2 signaling axis in ovarian cancer

Background

Although programmed cell death‐ligand 1 (PD‐L1) plays a well‐known function in immune checkpoint response by interacting with programmed cell death‐1 (PD‐1), the cell‐intrinsic role of PD‐L1 in tumors is still unclear. Here, we explored the molecular regulatory mechanism of PD‐L1 in the progression and metastasis of ovarian cancer.

Methods

Immunohistochemistry of benign tissues and ovarian cancer samples was performed, followed by migration, invasion, and angiogenesis assays in PD‐L1‐knockdown ovarian cancer cells. Immunoprecipitation, mass spectrometry, and chromatin immunoprecipitation were conducted along with zebrafish and mouse experiments to explore the specific functions and mechanisms of PD‐L1 in ovarian cancer.

Results

Our results showed that PD‐L1 induced angiogenesis, which further promoted cell migration and invasion in vitro and in vivo of ovarian cancer. Mechanistically, PD‐L1 was identified to directly interact with vascular endothelial growth factor receptor‐2 (VEGFR2) and then activated the FAK/AKT pathway, which further induced angiogenesis and tumor progression, leading to poor prognosis of ovarian cancer patients. Meanwhile, PD‐L1 was found to be regulated by the oncogenic transcription factor c‐JUN at the transcriptional level, which enhanced the expression of PD‐L1 in ovarian cancer. Furthermore, we demonstrated that PD‐L1 inhibitor durvalumab, combined with the antiangiogenic drug, apatinib, could enhance the effect of anti‐angiogenesis and the inhibition of cell migration and invasion.

Conclusion

Our results demonstrated that PD‐L1 promoted the angiogenesis and metastasis of ovarian cancer by participating in the c‐JUN/VEGFR2 signaling axis, suggesting that the combination of PD‐L1 inhibitor and antiangiogenic drugs may be considered as a potential therapeutic approach for ovarian cancer patients.

PD-L1 tumor-intrinsic signaling and its therapeutic implication in triple-negative breast cancer

Although the immune checkpoint role of programmed death ligand 1 (PD-L1) has been established and targeted in cancer immunotherapy, the tumor-intrinsic role of PD-L1 is less appreciated in tumor biology and therapeutics development, partly because of the incomplete mechanistic understanding. Here we demonstrate a potentially novel mechanism by which PD-L1 promotes the epithelial-mesenchymal transition (EMT) in triple-negative breast cancer (TNBC) cells by suppressing the destruction of the EMT transcription factor Snail. PD-L1 directly binds to and inhibits the tyrosine phosphatase PTP1B, thus preserving p38-MAPK activity that phosphorylates and inhibits glycogen synthase kinase 3β (GSK3β). Via this mechanism, PD-L1 prevents the GSK3β-mediated phosphorylation, ubiquitination, and degradation of Snail and consequently promotes the EMT and metastatic potential of TNBC. Significantly, PD-L1 antibodies that confine the tumor-intrinsic PD-L1/Snail pathway restricted TNBC progression in immunodeficient mice. More importantly, targeting both tumor-intrinsic and tumor-extrinsic functions of PD-L1 showed strong synergistic tumor suppression effect in an immunocompetent TNBC mouse model. Our findings support that PD-L1 intrinsically facilitates TNBC progression by promoting the EMT, and this potentially novel PD-L1 signaling pathway could be targeted for better clinical management of PD-L1–overexpressing TNBCs.

Increased PD-L1 Expression in Human Skin Acutely and Chronically Exposed to UV Irradiation

Overexpression of PD-L1 (CD274) on tumor cells may represent a hallmark of immune evasion, and overexpression has been documented in several tumors including cutaneous squamous cell carcinoma (cSCC). While PD-L1/PD-1 activity in the skin has been primarily described in inflammatory models, our goal was to examine PD-L1 expression in human keratinocytes exposed to UV irradiation. We assessed PD-L1 expression in human sun-protected (SP) and sun-damaged (SD) skin, actinic keratosis (AK), and cSCC using IHC and protein microarray. Both methods found low baseline levels of PD-L1 in SP and SD skin and significantly increased expression in cSCC. Next, we examined PD-L1 expression in acute models of UV exposure. In human SP skin exposed to 2-3 MED of UV (n = 20), epidermal PD-L1 was induced in 70% of subjects after 24 h (P = 0.0001). SKH-1 mice exposed to acute UV also showed significant epidermal PD-L1 induction at 16, 24 and 48 h. A time- and dose-dependent induction of PD-L1 was confirmed in cultured human keratinocytes after UV, which was markedly reduced in the presence of MEK/ERK, JNK or STAT3 inhibitors. These findings suggest that UV induces upregulation of PD-L1 through established, pharmacologically targetable stress-signaling pathways in keratinocytes.

Triptolide suppresses oral cancer cell PD-L1 expression in the interferon-γ-modulated microenvironment in vitro, in vivo, and in clinical patients

Biological and prognostic roles of programmed death ligand 1 (PD-L1) remain unclear in oral squamous cell carcinoma (OSCC). Moreover, the pivotal role of tumor microenvironmental interferon-gamma (IFN-γ) in host responses to malignant cells, oral cancer growth, and PD-L1 expression has not been adequately studied. Thus, PD-L1 expression in 130 OSCC samples was analyzed using immunohistochemistry, which was found significantly overexpressed at the tumor site (P <  .01). We further analyzed the effects of IFN-γ on OSCC cell proliferation using enzyme-linked immunosorbent assays and found that IFN-γ drives PD-L1 expression in OSCC cells in a dose-dependent manner. Triptolide (TPL), a bioactive compound isolated from Tripterygium wilfordii, exhibits anti-inflammatory and antitumor activities. To investigate whether the antitumor effect of TPL involves the suppression of PD-L1 expression, we treated OSCC cells in vitro and a patient-derived tumor xenograft (PDTX) model with TPL. TPL suppressed PD-L1 expression in the PDTX model, inhibiting tumor growth, and in OSCC cells in an IFN-γ-modulated microenvironment. We concluded that TPL inhibits tumor growth in oral cancer and downregulates PD-L1 expression in oral cancer cells in vitro. Our results provide evidence for the clinical development of PD-L1-targeted therapy for OSCC.

Inhibition to Epithelial-Mesenchymal Transition and Metastatic Potential In Colorectal Cancer Cell By Combination of Traditional Chinese Medicine Formulation Jiedu Sangen Decoction and PD-L1 Inhibitor

BACKGROUND

Jiedu Sangen Decoction (JSD), a traditional Chinese medicine formula, has been widely applied in the treatment of gastrointestinal cancer, especially in colorectal cancer. Our study mainly aimed to assess the combined efficacy of Jiedu Sangen aqueous extract (JSAE) and a PD-L1 inhibitor (PI) in colon cancer cells migration and invasion, along with epithelial-mesenchymal transition, and then provide deep insights into the potential mechanism.

METHODS

We explored the inhibitory effects on invasion and metastasis and the reverse effect on EMT process in CT-26 colon cancer cell via Transwell migration assay, Matrigel invasion assay and confocal laser scanning microscopy. Furthermore, regulation in expression of EMT-related proteins and molecular biomarkers and underlying signal pathway proteins were detected through Western blotting and IHC.

RESULTS

The combination of JSD and PD-L1 inhibitor could inhibit migration, invasive ability and EMT of CT-26 cells in a concentration-dependent manner. Meanwhile, JSD combined with PD-L1 inhibitor could also remarkably reverse EMT and metastasis in vivo. In addition, the protein expression of N-cadherin, Slug, Snail, Vimentin was down-regulated along with E-cadherin s up-regulation with the combination of JSD and PD-L1 inhibitor, while that of PI3K/AKT was notably down-regulated.

CONCLUSIONS

These findings indicated that JSAE and a PD-L1 inhibitor could drastically inhibit the migration and invasion of colorectal cancer by reversing EMT through the PI3K/AKT signaling pathway.

VEGFR2 Promotes Metastasis and PD-L2 Expression of Human Osteosarcoma Cells by Activating the STAT3 and RhoA-ROCK-LIMK2 Pathways

The survival rate of osteosarcoma, the most prevalent primary bone tumor, has not been effectively improved in the last 30 years. Hence, new treatments and drugs are urgently needed. Antiangiogenic therapy and immunotherapy have good antitumor effects in many kinds of tumors. It is hypothesized that there may be a synergistic effect between immune checkpoint inhibitors and antiangiogenic therapy. Nevertheless, its potential mechanism is still unclear. Vascular endothelial growth factor receptor-2 (VEGFR2) expression was detected by immunohistochemistry in 18 paired osteosarcoma tissues. Moreover, we investigated the effects of apatinib treatment and VEGFR2 knockdown on osteosarcoma as well as the relevant underlying mechanism. Immunohistochemistry assays showed that, compared with that in primary osteosarcoma, VEGFR2 expression was higher in lung metastases. VEGFR2 was positively correlated with PD-L2 expression in osteosarcoma lung metastasis. Transwell assays indicated that VEGFR2 inhibition reduced osteosarcoma cell metastatic abilities in vitro. We also demonstrated that VEGFR2 inhibition downregulated the STAT3 and RhoA-ROCK-LIMK2 pathways, thereby attenuating migration and invasion. Additionally, VEGFR2 inhibition targeted STAT3, through which it reduced PD-L2 expression in osteosarcoma cells. VEGFR2 inhibition markedly attenuated osteosarcoma lung metastatic ability in vivo. In this study, we presented the pro-metastatic functional mechanism of VEGFR2 in osteosarcoma. VEGFR2 inhibition exhibits antitumor effects through antiangiogenic effects and inhibition of immune escape, which possibly provides potential clinical treatment for metastatic osteosarcoma.

Prognostic Significance of PD-L1 Expression and Its Tumor-Intrinsic Functions in Hypopharyngeal Squamous Cell Carcinoma

Purpose

The expression of programmed death-ligand 1 (PD-L1) is common in various solid human cancers and it is an important therapeutic target. However, the expression pattern, clinical significance and potential mechanism of PD-L1 in hypopharyngeal squamous cell carcinoma (HSCC) are still lacking.

Methods

PD-L1 expression in HSCC tumor tissues and paired adjacent hypopharyngeal mucosal tissues was detected using immunohistochemistry assay, and the clinical significance of PD-L1 in HSCC was characterized. In vitro assays including cell viability assays, migration assays, invasion assays as well as Western blot assays were performed to illuminate the biological functions and underlying molecular mechanisms of PD-L1 in HSCC development.

Results

PD-L1 expression was detected in HSCC samples but we found no positive expression in matched normal hypopharyngeal mucosal tissues. The levels of PD-L1 expression were significantly correlated with advanced clinical progression and poor patient survival. Multivariable analysis of Cox model showed that PD-L1 expression was an independent predictor for the prognosis of HSCC patients. Functional experiments showed that the ectopic expression of PD-L1 markedly influenced the proliferation, migration and invasion of FaDu cells in vitro. Mechanistically, investigations demonstrated that PD-L1 could promote the epithelial–mesenchymal transition of FaDu cells. Meanwhile, PD-L1 knockdown inhibited, while PD-L1 overexpression activated the Akt-mTOR signaling pathway in FaDu cells. The EMT induced by PD-L1 overexpression could be reversed by the Akt inhibitor.

Conclusion

In summary, the expression of PD-L1 can act as a significant biomarker for the adverse clinicopathological features and poor prognosis of patients with HSCC. PD-L1 can promote the proliferation, migration and invasion of FaDu cells and consequently enhance the aggressiveness. Moreover, PD-L1 induces EMT through AKT-mTOR signaling pathway. These suggest that PD-L1 has important tumor-intrinsic functions independent of its immunopathogenic effects.

The role of genetic polymorphism within PD-L1 gene in cancer. Review

The maintenance of homeostasis of the immune system depends on the balance between excitatory and inhibitory signals. Programmed death ligand (PD-L1) is a molecule which downregulates the immune system targeting the programmed death receptor 1 (PD-1). Under physiological conditions, the receptor is constitutively expressed in lymphocytes. The PD-L1 / PD-1 pathway plays a key role in completing the immune response in the right way, preventing excessive stimulation of the cells of the immune system, protecting the organism against autoimmunity. Under pathological conditions PD-L1 expression may take place in tumor cells. Binding of PD-1 to its ligand on tumor cells suppresses T lymphocytes through a negative feedback. This mechanism allows abnormal cells to avoid destruction by the host immune system. The expression of PD-L1 in tumors has been described in many histological types of cancer: melanoma, lung cancer, breast and ovarian, pancreatic and esophagus adenocarcinoma, kidney tumors and bladder cancers as well as in hematopoietic malignancies. Many studies report a significant effect of PD-L1 polymorphisms on clinical parameters of patients. Studies of PD-L1 polymorphisms showed their influence on the stage of cancer, effectiveness of chemotherapy and prognosis after tumor resection. Further analysis of the polymorphisms may result in development of effective therapies that restore anti-tumor immunity. Inhibition of PD-L1 / PD-1 is one of the most promising immunotherapies for various types of cancer. This work was intended to present information about the impact of PD-L1 gene expression and polymorphisms on the clinical parameters of patients with cancer.

Interactive Effects of PD-L1 Expression in Tumor and Immune Cells on Prognosis of Esophageal Squamous Cell Carcinoma: A One-Center Retrospective Cohort Study

Purpose

The present study aimed to investigate the prognostic effect of PD-L1 expressing in tumor and immune cells among patients with esophageal squamous cell carcinoma.

Patients and Methods

We performed a retrospective cohort study by consecutively recruiting 142 patients. The clinicopathological features and PD-L1 expression on tumor and immune cells were independently evaluated by two pathologists.

Results

The median expression rate of PD-L1 was 5% and 30% in tumor and immune cells, respectively. Patients with higher expression of PD-L1 in tumor cells had shorter disease-free and overall survival, and the HRs were 1.52 for relapse (95% CI: 0.88, 2.60) and 1.48 for death (95% CI: 0.82, 2.69). There was no significant association between the PD-L1 expression in immune cells and survival. However, among the patients with PD-L1 expression rate ≤30% in immune cells, the high expression rate of PD-L1 in tumor cells was significantly associated with the relapse and death, with HRs of 2.51 (95% CI: 1.25, 5.06) and 3.51 (95% CI: 1.57, 7.85), respectively. Among patients with PD-L1 expression rate >30% in immune cells, the PD-L1 expression in tumor cells did not show any association with the disease-free and overall survival.

Conclusion

Our study demonstrates that the integration of PD-L1 expression in tumor and immune cells could be used to predict the relapse and survival among patients with esophageal squamous cell carcinoma.

Functions of Immune Checkpoint Molecules Beyond Immune Evasion

Immune checkpoint molecules, including inhibitory and stimulatory immune checkpoint molecules, are defined as ligand-receptor pairs that exert inhibitory or stimulatory effects on immune responses. Most of the immune checkpoint molecules that have been described so far are expressed on cells of the adaptive immune system, particularly on T cells, and of the innate immune system. They are crucial for maintaining the self-tolerance and modulating the length and magnitude of immune responses of effectors in different tissues to minimize the tissue damage. More and more evidences have shown that inhibitory or stimulatory immune checkpoint molecules are expressed on a sizeable fraction of tumor types. Although the main function of tumor cell-associated immune checkpoint molecules is considered to mediate the immune evasion, it has been reported that the immune checkpoint molecules expressed on tumor cells also play important roles in the maintenance of many malignant behaviors, including self-renewal, epithelial-mesenchymal transition, metastasis, drug resistance, anti-apoptosis, angiogenesis, or enhanced energy metabolisms. In this section, we mainly focus on delineating the roles of the tumor cell-associated immune checkpoint molecules beyond immune evasion, such as PD-L1, PD-1, B7-H3, B7-H4, LILRB1, LILRB2, TIM3, CD47, CD137, and CD70.

Epithelial-Mesenchymal Transition in Skin Cancers: A Review

Epithelial-mesenchymal transition (EMT) is involved in physiologic processes such as embryogenesis and wound healing. A similar mechanism occurs in some tumors where cells leave the epithelial layer and gain mesenchymal particularities in order to easily migrate to other tissues. This process can explain the invasiveness and aggressiveness of these tumors which metastasize, by losing the epithelial phenotype (loss of E-cadherin, desmoplakin, and laminin-1) and acquiring mesenchymal markers (N-cadherin). Complex changes and interactions happen between the tumor cells and the microenvironment involving different pathways, transcription factors, altered expression of adhesion molecules, reorganization of cytoskeletal proteins, production of ECM-degrading enzymes, and changes in specific microRNAs. The purpose of this review is to determine particularities of the EMT process in the most common malignant cutaneous tumors (squamous cell carcinoma, basal cell carcinoma, and melanoma) which still have an increasingly high incidence. More studies are required on this topic in order to establish clear correlations. High costs related to skin cancer therapies in general as well as high impact on patients' quality of life demand finding new, reliable prognostic and therapeutic markers with significant public health impact.

Communication between EMT and PD-L1 signaling: New insights into tumor immune evasion

Immune checkpoint blockage has been considered a breakthrough in cancer treatment, achieving encouraging anti-tumor effects in some advanced solid malignancies. However, low response rate and therapeutic resistance represent significant challenges in this field. In addition to its typical role in embryonic development and tissue fibrosis, epithelial-mesenchymal transition (EMT) plays a pivotal role in tumor immunosuppression and immune evasion. Previous studies revealed that EMT is associated with activation of different immune checkpoint molecules, including PD-L1. EMT-induced immune escape promotes cancer progression and may also provide a platform for discovery of novel therapeutic approaches and predictive biomarkers for checkpoint inhibitor therapeutic response. Here, we summarize recent findings focused on EMT-induced immune suppression and evasion in the tumor microenvironment (TME). EMT transcription factors (EMT-TFs), immune cells, cell plasticity and their regulatory role in the immune response are thoroughly reviewed. Bidirectional regulation between EMT and PD-L1 signaling is discussed in terms of cancer immune escape and possible combined therapies. Additionally, we investigated the value of preclinical or clinical trials using EMT targeted therapy combined with PD-L1 inhibitors. This review may help to further understand the role of EMT and PD-L1 signaling in cancer immune evasion. Meanwhile, additional molecular mechanistic studies and clinical trials are urgently needed.

PD-L1 Acts as a Promising Immune Marker to Predict the Response to Neoadjuvant Chemotherapy in Breast Cancer Patients

BACKGROUND

Programmed death ligand 1 (PD-L1) is a negative immune stimulatory molecule that plays a key role in tumor immune escape. We analyzed the clinical value of PD-L1-positive expression in predicting the outcome of breast cancer patients and to establish its role as new biomarker to guide precise treatment.

PATIENTS AND METHODS

PubMed and Embase were searched for all original English-language articles published before January 30, 2019; all articles reported the predictive and prognostic implications of PD-L1⁺ in breast cancer. Data were analyzed by Stata SE 12 software.

RESULTS

The PD-L1⁺ rate varied from 19.7% to 77.6% in breast cancer patients. Specifically, patients with estrogen receptor-positive, progesterone receptor-positive, luminal A, luminal B, and HER2⁺ disease subtypes had lower PD-L1 expression, while the PD-L1⁺ percentages did not follow any trend in patients with Ki-67⁺, normal-like, HER2 overexpression, and basal-like subtype. In addition, PD-L1⁺ was observed to be associated with significantly improved pathologic complete response to neoadjuvant chemotherapy (odds ratio = 2.01; 95% confidence interval, 1.35-3.01; P < .05). Using PD-L1⁺ to predict pathologic response showed obvious accuracy. However, PD-L1⁺ did not show significant association with risk of higher recurrence or metastasis, or higher death risk (hazard ratio = 0.91, P = .655; hazard ratio = 1.00, P = .995).

CONCLUSION

PD-L1⁺ is a promising immune parameter with the potential to predict response to neoadjuvant chemotherapy, but it cannot indicate a higher risk of death, recurrence, or metastasis.

Intersection of the p63 and NF-κB pathways in epithelial homeostasis and disease

Overexpression of ΔNp63α, a member of the p53/p63/p73 family of transcription factors, is a molecular attribute of human squamous cancers of the head and neck, lung and skin. The TP63 gene plays important roles in epidermal morphogenesis and homeostasis, regulating diverse biological processes including epidermal fate decisions and keratinocyte proliferation and survival. When overexpressed experimentally in primary mouse keratinocytes, ΔNp63α maintains a basal cell phenotype including the loss of normal calcium-mediated growth arrest, at least in part through the activation and enhanced nuclear accumulation of the c-rel subunit of NF-κB (Nuclear Factor-kappa B). Initially identified for its role in the immune system and hematopoietic cancers, c-Rel has increasingly been associated with solid tumors and other pathologies. ΔNp63α and c-Rel have been shown to be associated in the nuclei of ΔNp63α overexpressing human squamous carcinoma cells. Together, these transcription factors cooperate in the transcription of genes regulating intrinsic keratinocyte functions, as well as the elaboration of factors that influence the tumor microenvironment (TME). This review provides an overview of the roles of ΔNp63α and c-Rel in normal epidermal homeostasis and elaborates on how these pathways may intersect in pathological conditions such as cancer and the associated TME.

Chronic nicotine exposure affects programmed death-ligand 1 expression and sensitivity to epidermal growth factor receptor-tyrosine kinase inhibitor in lung cancer

Background

Smoking histories are independently associated with poor response to epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC) patients with activating EGFR mutations. The aim of the present study was to determine the effect of nicotine exposure on programmed death-ligand 1 (PD-L1) expression in EGFR mutant lung cancer cells.

Methods

Human lung adenocarcinoma PC9 cells were exposed to 1 µM nicotine for 3 months designated as PC9/N, and cells were stimulated with gefitinib (0, 0.1, or 1 µM) for 48 hrs. Cell viability by the MTT assay and morphological changes by immunofluorescence staining were assessed. The protein expression of EGFR, mTOR, AKT, α1-nicotine acetylcholine receptor (nAchR) and PD-L1 were measured by Western blot. Gene expression of α1-nAchR and PD-L1 were examined by RT-PCR. Intratumoral levels of PD-L1 expression were compared according to the burden of smoking dosage in 54 EGFR mutant lung cancer patients.

Results

Cellular growth was inhibited by treatment with gefitinib, and PC9 cells were significantly more sensitive to gefitinib than PC9/N cells. Pleomorphic appearance with atypical nuclei and to be detached and shrunken with condensed nuclei in PC9 than PC9/N cells. The gene expression level of α1-nAchR and PD-L1 gene were higher in PC9/N cells compared to those in PC9 cells after treatment with gefitinib. Phosphorylation levels of EGFR, mTOR, AKT and PD-L1 level were decreased by gefitinib in PC9/N cells, which was to a lesser extent than that in PC9 cells. In tumors, heavy smokers (≥30 PY) showed 28.5% of ≥50% PD-L1 tumor proportion score (TPS) while light smoker and never smokers had 12.5% and 9.7% of ≥50% PD-L1 TPS, respectively. However, there was no statistical significance (P value =0.628).

Conclusions

Chronic nicotine exposure could increase PD-L1 expression related to intrinsic resistance to EGFR-TKI in NSCLC patients harboring activating EGFR mutation. Considering the clinical importance of inevitable EGFR resistance, further studies regarding the role of anti-PD-1/PD-L1 treatment are needed, especially in EGFR mutant smokers.

PROGRAMMED CELL DEATH-LIGAND 1 OVEREXPRESSION IN THYROID CANCER

OBJECTIVE

Programmed cell death-ligand 1 (PD-L1) expression on tumor tissue has been associated with favorable response to anti-programmed cell death-receptor 1/PD-L1 therapy in many human cancers. Studies have reported that PD-L1 is also expressed in thyroid cancer. The objective of this paper is to introduce the potential predictive and therapeutic values of PD-L1 in thyroid cancer.

METHODS

A literature search was conducted in the PubMed database using the terms "PD-L1," "B7-H1," and "thyroid cancer." PD-L1 positivity was determined by immunohistochemical assay.

RESULTS

The frequency of PD-L1 positivity in different studies ranged from 6.1 to 82.5% in papillary thyroid cancer (PTC) patients and 22.2 to 81.2% in anaplastic thyroid cancer (ATC) patients. PD-L1 positivity rate was higher in ATC than in PTC within the same studies, and its expression intensity was significantly higher in tumor tissue than in the corresponding nontumor thyroid tissues. Moreover, PD-L1 expression was positively associated with the aggressiveness and recurrence of thyroid cancers and negatively associated with the differentiation status and outcomes. PD-L1 checkpoint pathway blockade may emerge as a promising therapeutic target in the treatment of thyroid cancers.

CONCLUSION

PD-L1 is a potential biomarker to predict the recurrence and prognosis of thyroid cancers. It is also a novel immunotherapy target for optimizing the management landscape of radioiodine-refractory and ATCs.

ABBREVIATIONS

ATC = anaplastic thyroid cancer; DTC = differentiated thyroid cancer; IHC = immunohistochemical; OS = overall survival; PD-1 = programmed cell death-receptor 1; PD-L1 = programmed cell death-ligand 1; PD-L2 = programmed cell death-ligand 2; PTC = papillary thyroid cancer; TNM = tumor-node-metastasis; Treg = regulatory T cell.

IFN-γ Promotes Epithelial-Mesenchymal Transition and the Expression of PD-L1 in Pancreatic Cancer

BACKGROUND

Tumor immune reactions not only provide host defense but also accelerate tumor immune escape and phenotype switching. Here, we examined the association of programmed cell death ligand 1 (PD-L1) expression with epithelial-mesenchymal transition (EMT)-associated markers in pancreatic ductal adenocarcinoma (PDA) within the context of the tumor microenvironment.

MATERIALS AND METHODS

PDA samples from 36 patients were analyzed for PD-L1, vimentin, E-cadherin, and Snail expressions and for PDA cell and immune cell infiltration. PD-L1 expression and EMT in PDA cell lines under conditions of altering interferon gamma (IFN-γ) signals were also assessed.

RESULTS

Immunohistochemistry revealed a significant correlation between vimentin and PD-L1 expression, whereas double staining showed them to be simultaneously expressed by PDA cells. Positive vimentin expression was associated with the infiltration of a lower number of CD8⁺ T cells and a higher number of FoxP3⁺ cells and poor patient prognosis (P = 0.03). PDA tumor cells promoted PD-L1 expression and EMT under the presence of IFN-γ, which was inhibited by the signal transducer and activator of transcription (STAT)1 small interfering RNA.

CONCLUSIONS

Strong correlations were observed between PD-L1 expression, EMT, and the immunosuppressive tumor microenvironment. Targeting STAT1 combined with PD-1/PD-L1 immunotherapy may improve outcomes for patients with PDA.

Osteosarcoma cell intrinsic PD-L2 signals promote invasion and metastasis via the RhoA-ROCK-LIMK2 and autophagy pathways

Known as co-stimulatory molecule, programmed death ligand-2 (PD-L2) contributes to T-cell exhaustion by interaction with programmed death-1 (PD-1) receptor, but its tumor cell-intrinsic signal effects have been little investigated. PD-L2 expression was detected by immunohistochemistry in 18 pairs of primary osteosarcoma tissues and matching lung metastasis tissues. We also investigated the effects of PD-L2 knockdown on osteosarcoma both in vitro and in vivo. In our study, PD-L2 expression was elevated in lung metastases compared with primary osteosarcoma according to an immunohistochemistry assay. Wound-healing and transwell assays revealed that PD-L2 knockdown  leaded to inhibition of migration and invasion of human osteosarcoma cells in vitro. Mechanistically, we demonstrated that PD-L2 knockdown attenuated migration and invasion by inactivating RhoA-ROCK-LIMK2 signaling, suppressing epithelial–mesenchymal transition (EMT), and inhibiting autophagy by decreasing beclin-1 expression. In support of these observations, beclin-1 knockdown also inhibited activation of the RhoA-ROCK-LIMK2 pathway, leading to autophagy inhibition-induced blockade of migration and invasion. Depletion of PD-L2 in KHOS cells markedly weakens pulmonary metastatic potential in vivo by orthotopic transplantation of nude mice. Our study reveals a pro-metastatic functional mechanism for PD-L2 in osteosarcoma. Furthermore, we demonstrate a regulatory role for PD-L2 on autophagy, as well as a relationship between autophagy and metastasis in osteosarcoma, which may represent a potential therapeutic target for osteosarcoma.

PD‑L1 promotes head and neck squamous cell carcinoma cell growth through mTOR signaling

Programmed death-ligand 1 (PD-L1), an immune co-stimulatory molecule, is expressed on various cancer cells and the surface of immune cells. Its overexpression on tumor cells suppresses the immune response to promote tumor cell immune escape. The present study demonstrated that PD-L1 was critical in head and neck squamous cell carcinoma (HNSCC) carcinogenesis. Immunohistochemical analysis of HNSCC tissue microarrays revealed that PD-L1 was overexpressed in tumor tissue, and its expression increased as tumor malignancy progressed (from grade I to IV). Subsequently, the expression of PD-L1 was knocked down or overexpressed in the HNSCC cell lines Cal-27 and Fadu. It was demonstrated that PD-L1 significantly induced HNSCC cell proliferation and colony forming ability. Cell proliferation was also promoted in Cal-27 cell xenograft BALB/c nude mice. In addition, it was determined by western blotting that the PD-L1-mediated increase in HNSCC cell proliferation may have been associated with the activation of mammalian target of rapamycin (mTOR) signaling pathway. Furthermore, mTOR inhibitor (rapamycin) prevented the increase in proliferation. Based on these results, it was concluded that PD-L1 promoted cell proliferation of HNSCC cells through mTOR signaling, and blocking PD-L1 may be conducive in HNSCC therapy.

Programmed death ligand 1 promotes lymph node metastasis and glucose metabolism in cervical cancer by activating integrin β4/SNAI1/SIRT3 signaling pathway

Although PD-L1 has been shown to play a well-characterized role in inhibiting antitumor immunity via engagement of its receptor PD-1 in T lymphocytes, little is known about the tumor cell-intrinsic function of PD-L1 and its association with prognosis. Here, we investigate this issue and dissect the molecular mechanisms underlying the role of PD-L1 in glucose metabolism, proliferation, migration, and invasion in human cervical cancer cells. As a result, we found that PD-L1 overexpression in cervical cancer cells increases glucose metabolism and metastasis-related behaviors. Mechanistically, PD-L1 bound directly to integrin β4 (ITGB4), activating the AKT/GSK3β signaling pathway and consequently inducing the expression of the transcriptional repressor SNAI1. SNAIL in turn influenced the expression of genes involved in the epithelial-to-mesenchymal transition and regulated glucose metabolism by inhibiting SIRT3 promoter activity. High expression of PD-L1 and ITGB4 in human cervical carcinomas was significantly associated with lymph node metastasis and poor prognosis. Finally, ¹⁸F-fluorodeoxyglucose microPET/CT and bioluminescence imaging analyses of cervical xenograft tumors in mice revealed that PD-L1 overexpression markedly increases tumor glucose uptake and promotes lymph node metastasis. Together, these results demonstrate that PD-L1 can promote the growth and metastasis of cervical cancer by activating the ITGB4/SNAI1/SIRT3 signaling pathway, and also suggest the possibility of targeting PD-L1 and its downstream effectors as a potential approach for interfering with cervical cancer growth and metastasis.

PD-1 axis expression in musculoskeletal tumors and antitumor effect of nivolumab in osteosarcoma model of humanized mouse

Background

Immune checkpoint inhibitors have led to a breakthrough in solid tumor immunotherapy, but related studies on musculoskeletal tumors are few, especially for PD-L2.

Methods

We examined expression of three molecular effectors of the PD-1 axis in 234 patients with musculoskeletal tumors, including osteosarcoma, chondrosarcoma, synovial sarcoma, and giant cell tumor. Survival analyses and potential mechanisms were investigated in osteosarcoma per the Gene Expression Omnibus (GEO) and immunohistochemistry analyses. In vivo, humanized mice were used to evaluate the effect of nivolumab on osteosarcoma.

Results

PD-L1, PD-L2, and PD-1 expression levels were significantly different between the histologic types of the musculoskeletal tumors. For osteosarcoma, PD-L1 was negatively correlated with prognosis, while PD-1 had a negative correlation tendency with overall survival (OS). Meanwhile, PD-L2 had a positive correlation trend with OS. Nivolumab inhibited osteosarcoma metastasis in humanized mice by increasing CD4+ and CD8+ lymphocytes and the cytolytic activity of CD8 lymphocytes in the lung but did not affect primary osteosarcoma growth.

Conclusion

We systematically detected the expression patterns of PD-L1, PD-L2, and PD-1 in musculoskeletal tumors for the first time and demonstrated the prognostic roles and underlying mechanisms of PD-1 axis in osteosarcoma. Furthermore, PD-1 blockade could effectively control osteosarcoma pulmonary metastasis in vivo. Therefore, the PD-1 axis may be a potential immunotherapeutic target for metastatic osteosarcoma.

Electronic supplementary material

The online version of this article (10.1186/s13045-018-0560-1) contains supplementary material, which is available to authorized users.

B7-Homolog 4 Promotes Epithelial-Mesenchymal Transition and Invasion of Bladder Cancer Cells via Activation of Nuclear Factor-κB

B7-homolog 4 (B7-H4), a member of the B7 family of costimulatory molecules, has been reported to be upregulated in urothelial cell carcinoma. This study was conducted to explore the biological role of B7-H4 in the aggressiveness of bladder cancer and the associated molecular mechanism. We found that the mRNA and protein levels of B7-H4 were significantly greater in bladder cancer cell lines than in SV-HUC-1 (normal human urothelial cells). Overexpression of B7-H4 significantly promoted bladder cancer cell migration and invasion, whereas knockdown of B7-H4 exerted an opposite effect. However, the growth of bladder cancer cells was not altered by B7-H4 overexpression or knockdown. Overexpression of B7-H4 promoted epithelial–mesenchymal transition (EMT), as evidenced by decreased E-cadherin and increased vimentin expression. The EMT inducers Twist1 and Snail were upregulated by B7-H4 overexpression and downregulated by B7-H4 silencing. Mechanistically, overexpression of B7-H4 induced the activation of NF-κB signaling. Pharmacological inhibition of NF-κB partially prevented B7-H4-mediated bladder cancer cell invasion. Taken together, B7-H4/NF-κB signaling is involved in the EMT and invasion of bladder cancer cells and represents a new candidate target for the treatment of bladder cancer.

Programmed death-ligand 1 overexpression is a prognostic marker for aggressive papillary thyroid cancer and its variants

Programmed death-ligand 1(PD-L1) expression on tumor cells is emerging as a potential predictive biomarker in anti-PD-L1 directed cancer immunotherapy. We analyzed PD-L1 expression in papillary thyroid carcinoma (PTC) and its variants and determined its prognostic potential to predict clinical outcome in these patients. This study was conducted at an academic oncology hospital which is a prime referral centre for thyroid diseases. Immunohistochemical subcellular localization (IHC) analyses of PD-L1 protein was retrospectively performed on 251 archived formalin fixed and paraffin embedded (FFPE) surgical tissues (66 benign thyroid nodules and 185 PTCs) using a rabbit monoclonal anti-PD-L1 antibody (E1L3N, Cell Signaling Technology) and detected using VECTASTAIN rapid protocol with diaminobenzidine (DAB) as the chromogen. The clinical-pathological factors and disease outcome over 190 months were assessed; immunohistochemical subcellular localization of PD-L1 was correlated with disease free survival (DFS) using Kaplan Meier survival and Cox multivariate regression analysis. Increased PD-L1 immunostaining was predominantly localized in cytoplasm and occasionally in plasma membrane of tumor cells. Among all combined stages of PTC, patients with increased PD-L1 membrane or cytoplasmic positivity had significantly shorter median DFS (36 months and 49 months respectively) as compared to those with PD-L1 negative tumors (DFS, both 186 months with p < 0.001 and p < 0.01 respectively). Comparison of PD-L1⁺ and PD-L1⁻ patients with matched staging showed increased cytoplasmic positivity in all four stages of PTC that correlated with a greater risk of recurrence and a poor prognosis, but increased membrane positivity significantly correlated with a greater risk of metastasis or death only in Stage IV patients. In conclusion, PD-L1 positive expression in PTC correlates with a greater risk of recurrence and shortened disease free survival supporting its potential application as a prognostic marker for PTC.

PD-L1 expression is associated with epithelial-mesenchymal transition in head and neck squamous cell carcinoma

Virus-associated malignancies and sarcomatoid cancers correlate with high PD-L1 expression, however, underlying mechanisms remain controversial. We evaluated the correlation between PD-L1 expression and epithelial-mesenchymal transition (EMT) in head and neck squamous cell carcinomas (HNSCC). Tumor tissues from 50 patients with HNSCC were evaluated for PD-L1 by immunohistochemistry, which showed 32 (64.0%) were PD-L1 positive (PD-L1+). Interestingly, PD-L1 expression was significantly associated with EMT (P = 0.010), as assessed by low E-cadherin and high vimentin expression. The overall survival of PD-L1+ patients with EMT features was significantly worse than those without EMT features (P = 0.007). In an independent validation cohort (N = 91), as well as in HNSCC cases of The Cancer Genome Atlas (TCGA) and the Cancer Cell Line Encyclopedia, high PD-L1 expression was also associated with the high probability of an EMT signature, referred from the GEO dataset, GSE4824. Survival analysis confirmed PD-L1+/EMT+ patients had a poorer prognosis than PD-L1+/EMT- patients in the TCGA cohort. PD-L1 positivity can thus be divided into two categories according to the absence or presence of EMT. PD-L1 expression is also independently associated with EMT features in HNSCC.

PD-L1

Programmed death ligand 1 (PD-L1) is the principal ligand of programmed death 1 (PD-1), a coinhibitory receptor that can be constitutively expressed or induced in myeloid, lymphoid, normal epithelial cells and in cancer. Under physiological conditions, the PD-1/PD-L1 interaction is essential in the development of immune tolerance preventing excessive immune cell activity that can lead to tissue destruction and autoimmunity. PD-L1 expression is an immune evasion mechanism exploited by various malignancies and is generally associated with poorer prognosis. PD-L1 expression is also suggested as a predictive biomarker of response to anti-PD-1/PD-L1 therapies; however, contradictory evidence exists as to its role across histotypes. Over the years, anti-PD-1/PD-L1 agents have gained momentum as novel anticancer therapeutics, by inducing durable tumour regression in numerous malignancies including metastatic lung cancer, melanoma and many others. In this review, we discuss the immunobiology of PD-L1, with a particular focus on its clinical significance in malignancy.

Tumor cell-associated immune checkpoint molecules - Drivers of malignancy and stemness

Inhibitory or stimulatory immune checkpoint molecules are expressed on a sizeable fraction of tumor cells in different tumor types. It was thought that the main function of tumor cell-associated immune checkpoint molecules would be the modulation (down- or upregulation) of antitumor immune responses. In recent years, however, it has become clear that the expression of immune checkpoint molecules on tumor cells has important consequences on the biology of the tumor cells themselves. In particular, a causal relationship between the expression of these molecules and the acquisition of malignant traits has been demonstrated. Thus, immune checkpoint molecules have been shown to promote the epithelial-mesenchymal transition of tumor cells, the acquisition of tumor-initiating potential and resistance to apoptosis and antitumor drugs, as well as the propensity to disseminate and metastasize. Herein, we review this evidence, with a main focus on PD-L1, the most intensively investigated tumor cell-associated immune checkpoint molecule and for which most information is available. Then, we discuss more concisely other tumor cell-associated immune checkpoint molecules that have also been shown to induce the acquisition of malignant traits, such as PD-1, B7-H3, B7-H4, Tim-3, CD70, CD28, CD137, CD40 and CD47. Open questions in this field as well as some therapeutic approaches that can be derived from this knowledge, are also addressed.

The tissue distribution and significance of B7-H4 in laryngeal carcinoma

The costimulatory signals CD28 and B7 have been shown to control tumor invasion and metastasis by regulating T cell activation, whereas the distribution characteristics of B7-associated proteins in laryngeal carcinoma (LC) tissue are still unclear. Here, the expression of members of the B7 superfamily, including B7-H1 (PD-L1), B7-DC (PD-L2) and B7-H4, in fifty-two LC samples was determined by immunohistochemistry, and the relationship between B7-H4 and epithelial-mesenchymal transition (EMT)-associated markers was further assessed by immunofluorescence double staining. Furthermore, the human LC cell lines, Hep-2 and TU212 cells, were further transfected to overexpress B7-H4, and cell invasion and metastasis were analyzed. The results showed that B7-H1, B7-DC and B7-H4 were expressed in the tumor cells, and their expression was restricted to the cell membrane and the cytoplasm. The positive rates of these molecules in the tumor tissues were 57.7% (30/52), 32.7% (17/52) and 34.6% (18/52), respectively. Interestingly, double immunofluorescence staining showed that B7-H4 is coexpression with EMT-related markers, including p-Smad2/3, Snail and Vimentin, in carcinoma cells. Moreover, overexpression of B7-H4 in Hep-2 cells promotes the expression of pSmad2/3 and Snail by activating AKT-STAT3 signaling. Transwell and wound-healing assays demonstrated that B7-H4 enhanced both Hep-2 and TU212 cell invasion and metastasis. Our results suggest that B7-H4 transmits feedback signaling to tumor cells and promotes invasion and metastasis by promoting EMT progression. Therefore, blocking B7-H4 signaling might be a novel treatment strategy for LC.

Programmed death-ligand 1 expression at tumor invasive front is associated with epithelial-mesenchymal transition and poor prognosis in esophageal squamous cell carcinoma

Programmed death‐ligand 1 (PD‐L1) plays a crucial role in the host immune system in cancer progression. The gene promoter region of PD‐L1 also contains a binding site for ZEB1, a transcription factor related to epithelial‐mesenchymal transition (EMT). The purpose of this study was to clarify the relationship between PD‐L1 and EMT and its clinical importance in esophageal squamous cell carcinoma (ESCC). PD‐L1 and ZEB1 expression at the tumor invasive front was examined by immunohistochemistry in resected specimens from 90 patients with ESCC who underwent surgery without preoperative therapy, and their expression and clinicopathological factors were compared. ZEB1 and PD‐L1 expression was determined in TE8 cells, which demonstrate the EMT phenotype, following ZEB1 knockdown by siZEB1. TE5, TE6 and TE11 cells with non‐EMT phenotype were also used for studies of TGF‐β1‐dependent EMT induction and ZEB1 and PD‐L1 expression. In cases of high PD‐L1 expression at the invasive front, significantly greater depth of tumor invasion, EMT, and less CD8⁺ lymphocyte infiltration were observed. High PD‐L1 expression was also associated with worse overall and relapse‐free survival. A correlation was observed between PD‐L1 and ZEB1 expression. In TE8 cells, siZEB1 suppressed PD‐L1 and promoted E‐cadherin mRNA and protein expression. TGF‐β1 induced EMT and surface expression of PD‐L1 in TE5, TE6 and TE11 cell lines. PD‐L1 expression at the ESCC invasive front was related to ZEB1 expression, EMT and poor prognosis. We suggest that a cooperative mechanism bridging between tumor immune avoidance and EMT contributes to tumor malignancy in ESCC.