Constitutive PD-L1 Expression Research Articles

Integrin αvβ6 mediates the immune escape through regulation of PD-L1 and serves as a novel marker for immunotherapy of colon carcinoma.

The immune escape of colon cancer and its role in the response to immunotherapies such as PD-1/PD-L1 checkpoint inhibitors have long been of great interest. The positive outcomes of immunotherapy are limited by the immunosuppressive nature of the tumor microenvironment. Integrin αvβ6, which can regulate the progression of colon cancer, was recently reported to be involved in the immune suppression of colon cancer. In the present study, we explored the correlation between αvβ6 and PD-L1 expression by immunohistochemistry of colon cancer tissues. Then, the regulation of PD-L1 signaling by αvβ6 in colon cancer cells was demonstrated. We constructed an in vivo model and performed immunophenotyping experiments to analyze further the regulation of the immune response by αvβ6. The role of αvβ6 in the response to anti-PD-1 therapy in colon cancer was also verified. αvβ6-positive tissues exhibited increased PD-L1 expression. Inhibition of αvβ6 not only downregulated constitutive PD-L1 expression but also decreased IFN-γ-induced PD-L1 expression. In addition, αvβ6-induced PD-L1 expression was suppressed by the ERK inhibitor PD98059, and knockdown of the β6-ERK2 binding site had the equivalent effect. αvβ6 decreased CD8+ T cell infiltration and granzyme B expression in CD8+ T cells in colon cancer patients. Furthermore, mice engrafted with αvβ6-expressing colon cancer cells exhibited an unsatisfactory response to anti-PD-1 therapy, and anti-PD-1-induced increases in CD4+ and CD8+ T cell infiltration could be inhibited by αvβ6. These results indicate that αvβ6 mediates immune escape in colon cancer by upregulating PD-L1 through the ERK/MAPK pathway. Moreover, αvβ6 could serve as a marker for the efficacy of anti-PD-1 therapy in colon cancer.

ICOSLG-associated immunological landscape and diagnostic value in oral squamous cell carcinoma: a prospective cohort study.

Background: We previously reported that stroma cells regulate constitutive and inductive PD-L1 (B7-H1) expression and immune escape of oral squamous cell carcinoma. ICOSLG (B7-H2), belongs to the B7 protein family, also participates in regulating T cells activation for tissue homeostasis via binding to ICOS and inducing ICOS+ T cell differentiation as well as stimulate B-cell activation, while it appears to be abnormally expressed during carcinogenesis. Clarifying its heterogeneous clinical expression pattern and its immune landscape is a prerequisite for the maximum response rate of ICOSLG-based immunotherapy in a specific population. Methods: This retrospective study included OSCC tissue samples (n = 105) to analyze the spatial distribution of ICOSLG. Preoperative peripheral blood samples (n = 104) and independent tissue samples (n = 10) of OSCC were collected to analyze the changes of immunocytes (T cells, B cells, NK cells and macrophages) according to ICOSLG level in different cellular contents. Results: ICOSLG is ubiquitous in tumor cells (TCs), cancer-associated fibroblasts (CAFs) and tumor infiltrating lymphocytes (TILs). Patients with high ICOSLGTCs or TILs showed high TNM stage and lymph node metastasis, which predicted a decreased overall or metastasis-free survival. This sub-cohort was featured with diminished CD4+ T cells and increased Foxp3+ cells in invasive Frontier in situ, and increased absolute numbers of CD3+CD4+ and CD8+ T cells in peripheral blood. ICOSLG also positively correlated with other immune checkpoint molecules (PD-L1, CSF1R, CTLA4, IDO1, IL10, PD1). Conclusion: Tumor cell-derived ICOSLG could be an efficient marker of OSCC patient stratification for precision immunotherapy.

CLINICOPATHOLOGICAL CHARACTERISTICS OF INVASIVE BREAST CARCINOMA ON PDL-1 IMMUNOHISTOCHEMICAL EXPRESSION IN H. ADAM MALIK HOSPITAL MEDAN

Abstract
 Background: Immune biologic markers that can predict clinical response to anti-PD-1/PD-L1 therapy are needed to identify and validate tumor immunotherapy studies. High PD-L1 expression is associated with increased clinical response in patients with various types of cancer treated with inhibitors of the PD-1/PD-L1 pathway. The researcher wanted to see the clinicopathological characteristics of invasive breast carcinoma according to the immunohistochemical expression of PD-L1.
 Methods: This study is a descriptive study with a cross-sectional, retrospective approach by looking at secondary data from the medical records of the Department of Surgery, Oncology Division, Haji Adam Malik Hospital from January 1, 2019, to December 31, 2021.
 Results: Immunohistochemical expression of PD-L1 was positive in 76.6% of invasive breast carcinomas and negative in 23.3% of invasive breast carcinomas. Immunohistochemical expression of PD-L1 was positive in non-specific IBCs that predominated in every molecular subgroup of breast carcinoma.
 Discussion: Tumours can show positive or negative PD-L1 expression through several biological processes with different functional significance, namely the genetic mechanism of constitutive or oncogene-induced PD-L1 expression, PD-L1 expression induced in T cells, and absence of PD-L1 expression. Due to the absence of T cells and genetic events that block the expression of PD-L1 despite T cell infiltration.

IL-33/ST2 signaling promotes constitutive and inductive PD-L1 expression and immune escape in oral squamous cell carcinoma.

Loss-of-function of PD-L1 induces therapy resistance of anti-PD-1/L1 therapy, and the complex regulatory mechanisms are not completely understood. We previously reported that stroma-derived interleukin-33 (IL-33) promoted the progression of oral squamous cell carcinoma (OSCC). We here focused on the immune-regulation role of IL-33 and its receptor ST2 signaling in PD-L1-positive OSCC patients. Activated T cells in in situ and peripheral blood were analyzed by IL-33/ST3 expression. Knockdown or overexpression of ST2 combined with IL-33/IFN-γ stimulation were performed to determine PD-L1 expression and PD-L1-dependent immune escape in OSCC/human T cells co-culture system, and OSCC orthotopic model based on humanized mouse with immune reconstitution and C57BL/6 mice models. High IL-33/ST2 correlated with less activated T cells infiltration in situ and peripheral blood. Knockdown of ST2 down-regulated constitutive PD-L1 expression, whereas ST2 also promoted IL-33-induced PD-L1 Mechanistically, IL-33/ST2 activated JAK2/STAT3 pathway to directly promoted PD-L1 expression, and also activated MyD88/NF-κB signaling to up-regulate IFN-γ receptor (IFN-γR), which indirectly strengthen IFN-γ-induced PD-L1. Furthermore, ST2 is required for PD-L1-mediated immune tolerance in vitro and in vivo. ST2high OSCC patients have more PD-L1 and IFN-γR level in situ. IL-33/ST2 signaling enhanced PD-L1-mediated immune escape, ST2high OSCC patients might benefit from anti-PD-1/L1 therapy.

Lung cancer in never smokers: Tumor immunology and challenges for immunotherapy.

Lung cancer is the second most common and the most lethal malignancy worldwide. It is estimated that lung cancer in never smokers (LCINS) accounts for 10-25% of cases, and its incidence is increasing according to recent data, although the reasons remain unclear. If considered alone, LCINS is the 7th most common cause of cancer death. These tumors occur more commonly in younger patients and females. LCINS tend to have a better prognosis, possibly due to a higher chance of bearing an actionable driver mutation, making them amenable to targeted therapy. Notwithstanding, these tumors respond poorly to immune checkpoint inhibitors (ICI). There are several putative explanations for the poor response to immunotherapy: low immunogenicity due to low tumor mutation burden and hence low MANA (mutation-associated neo-antigen) load, constitutive PD-L1 expression in response to driver mutated protein signaling, high expression of immunosuppressive factors by tumors cells (like CD39 and TGF-beta), non-permissive immune TME (tumor microenvironment), abnormal metabolism of amino acids and glucose, and impaired TLS (Tertiary Lymphoid Structures) organization. Finally, there is an increasing concern of offering ICI as first line therapy to these patients owing to several reports of severe toxicity when TKIs (tyrosine kinase inhibitors) are administered sequentially after ICI. Understanding the biology behind the immune response against these tumors is crucial to the development of better therapeutic strategies.

Abstract 576: Shark VNAR single domain-based CAR T cells targeting PD-L1 for cancer therapy

Abstract Background: Chimeric antigen receptor (CAR)-T therapy shows great potency against hematological malignancies, whereas it is difficult to transfer CAR T into solid tumors due to lack of appropriate antigenic targets and immunosuppressive tumor microenvironment. Checkpoint molecule PD-L1 is widely overexpressed on multiple tumor types, and PD-1/PD-L1 interaction is a primary mediator of immunosuppression in the TME. Here, we generated anti-PD-L1-specific shark single domain VNAR-based CAR T cell strategy and explored its anti-tumor efficacy in xenograft mouse models. Methods: We isolated anti-PD-L1 single domain antibodies from semi-synthetic shark VNAR phage display libraries. The binding of isolated VNARs was validated by ELISA, flow cytometry, and Octet. A peptide library based on human PD-L1 was synthesized to predict the epitope of select VNARs. Anti-tumor efficacy of CAR T cells was determined via cell luciferase-based cell assay as well as xenograft mouse models. Two tumor models, MDA-MB-231 (triple-negative breast cancer) and Hep3B (hepatocellular carcinoma or HCC) were used in the present study. Glypican-3 (GPC3) is a tumor-specific target in the Hep3B model. Results: We identified three anti-PD-L1 phage binders, B2, A11, and F5 from our shark phage libraries. All three binders showed cross-activity to human, mouse, and canine antigens, whereas only B2 functionally blocked the interaction of human PD-1 to PD-L1. Moreover, CAR (B2) T cells specifically lysed both MDA-MB-231 and Hep3B tumor cells by targeting constitutive and inducible expression of PD-L1. Importantly, the combination of anti-GPC3 CAR (hYP7) T cells with CAR (B2) T cells regress Hep3B tumors synergistically in mice. Conclusions: PD-L1-targeted shark VNAR single domain-based CAR T cell therapy is a novel strategy to treat breast cancer and liver cancer. This work provides a rationale for a potential use of anti-PD-L1 CAR T cells as a monotherapy or combination with a tumor-specific therapy in clinical studies for solid tumors. Citation Format: Dan Li, Hejiao English, Jessica Hong, Tianyuzhou Liang, Glenn Merlino, Chi-Ping Day, Mitchell Ho. Shark VNAR single domain-based CAR T cells targeting PD-L1 for cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 576.

Evaluation of cancer immunotherapy using mini-tumor chips.

Rationale: Predicting tumor responses to adjuvant therapies can potentially help guide treatment decisions and improve patient survival. Currently, tumor pathology, histology, and molecular profiles are being integrated into personalized profiles to guide therapeutic decisions. However, it remains a grand challenge to evaluate tumor responses to immunotherapy for personalized medicine.Methods: We present a microfluidics-based mini-tumor chip approach to predict tumor responses to cancer immunotherapy in a preclinical model. By uniformly infusing dissociated tumor cells into isolated microfluidic well-arrays, 960 mini-tumors could be uniformly generated on-chip, with each well representing the ex vivo tumor niche that preserves the original tumor cell composition and dynamic cell-cell interactions and autocrine/paracrine cytokines.Results: By incorporating time-lapse live-cell imaging, our mini-tumor chip allows the investigation of dynamic immune-tumor interactions as well as their responses to cancer immunotherapy (e.g., anti-PD1 treatment) in parallel within 36 hours. Additionally, by establishing orthotopic breast tumor models with constitutive differential PD-L1 expression levels, we showed that the on-chip interrogation of the primary tumor's responses to anti-PD1 as early as 10 days post tumor inoculation could predict the in vivo tumors' responses to anti-PD1 at the endpoint of day 24. We also demonstrated the application of this mini-tumor chip to interrogate on-chip responses of primary tumor cells isolated from primary human breast and renal tumor tissues.Conclusions: Our approach provides a simple, quick-turnaround solution to measure tumor responses to cancer immunotherapy.

Structure–activity relationship and biological evaluation of 12 N-substituted aloperine derivatives as PD-L1 down-regulatory agents through proteasome pathway

Twenty-nine 12 N-substituted aloperine derivatives were synthesized and screened for suppression on PD-L1 expression in H460 cells, as a continuation of our work. Systematic structural modifications led to the identification of compound 6b as the most active PD-L1 modulator. Compound 6b could significantly down-regulate both constitutive and inductive PD-L1 expression in NSCLC cells, and successively enhance the cytotoxicity of co-cultured T cells against tumor cells at the concentration of 20 μM. Also, it exhibited a moderate in vivo anticancer efficacy against Lewis tumor xenograft with a stable PK and safety profile. The mechanism study indicated that 6b mediated the degradation of PD-L1 through a proteasome pathway, rather than a lysosome route. These results provided the powerful information for cancer immunotherapy of aloperine derivatives with unique endocyclic skeleton by targeting PD-L1 to activate immune cells to kill cancer cells.

Super-enhancer receives signals from the extracellular matrix to induce PD-L1-mediated immune evasion via integrin/BRAF/TAK1/ERK/ETV4 signaling.

Objective:PD-L1 and PD-L2 expression levels determine immune evasion and the therapeutic efficacy of immune checkpoint blockade. The factors that drive inducible PD-L1 expression have been extensively studied, but mechanisms that result in constitutive PD-L1 expression in cancer cells are largely unknown.Methods:DNA elements were deleted in cells by CRISPR/Cas9-mediated knockout. Protein function was inhibited by chemical inhibitors. Protein levels were examined by Western blot, mRNA levels were examined by real-time RT-PCR, and surface protein expression was determined by cellular immunofluorescence and flow cytometry. Immune evasion was examined by in vitro T cell-mediated killing.Results:We determined the core regions (chr9: 5, 496, 378–5, 499, 663) of a previously identified PD-L1L2-super-enhancer (SE). Through systematic analysis, we found that the E26 transformation-specific (ETS) variant transcription factor (ETV4) bound to this core DNA region but not to DNA surrounding PD-L1L2SE. Genetic knockout of ETV4 dramatically reduced the expressions of both PD-L1 and PD-L2. ETV4 transcription was dependent on ERK activation, and BRAF/TAK1-induced ERK activation was dependent on extracellular signaling from αvβ3 integrin, which profoundly affected ETV4 transcription and PD-L1/L2 expression. Genetic silencing or pharmacological inhibition of components of the PD-L1L2-SE-associated pathway rendered cancer cells susceptible to T cell-mediated killing.Conclusions:We identified a pathway originating from the extracellular matrix that signaled via integrin/BRAF/TAK1/ERK/ETV4 to PD-L1L2-SE to induce PD-L1-mediated immune evasion. These results provided new insights into PD-L1L2-SE activation and pathways associated with immune checkpoint regulation in cancer.

GATA2 Regulates Constitutive PD-L1 and PD-L2 Expression in Brain Tumors

Encouraging clinical results using immune checkpoint therapies to target the PD-1 axis in a variety of cancer types have paved the way for new immune therapy trials in brain tumor patients. However, the molecular mechanisms that regulate expression of the PD-1 pathway ligands, PD-L1 and PD-L2, remain poorly understood. To address this, we explored the cell-intrinsic mechanisms of constitutive PD-L1 and PD-L2 expression in brain tumors. PD-L1 and PD-L2 expression was assessed by flow cytometry and qRT-PCR in brain tumor cell lines and patient tumor-derived brain tumor-initiating cells (BTICs). Immunologic effects of PD-L2 overexpression were evaluated by IFN-γ ELISPOT. CD274 and PDCD1LG2 cis-regulatory regions were cloned from genomic DNA and assessed in full or by mutating and/or deleting regulatory elements by luciferase assays. Correlations between clinical responses and PD-L1 and PD-L2 expression status were evaluated in TCGA datasets in LGG and GBM patients. We found that a subset of brain tumor cell lines and BTICs expressed high constitutive levels of PD-L1 and PD-L2 and that PD-L2 overexpression inhibited neoantigen specific T cell IFN-γ production. Characterization of novel cis-regulatory regions in CD274 and PDCD1LG2 lead us to identify that GATA2 is sufficient to drive PD-L1 and PD-L2 expression and is necessary for PD-L2 expression. Importantly, in TCGA datasets, PD-L2 correlated with worse clinical outcomes in glioma patients.. By perturbing GATA2 biology, targeted therapies may be useful to decrease inhibitory effects of PD-L2 in the microenvironment.

Mechanisms regulating PD-L1 expression on tumor and immune cells

BackgroundThe PD-1/PD-L1 checkpoint is a central mediator of immunosuppression in the tumor immune microenvironment (TME) and is primarily associated with IFN-g signaling. To characterize other factors regulating PD-L1 expression on tumor and/or immune cells, we investigated TME-resident cytokines and the role of transcription factors in constitutive and cytokine-induced PD-L1 expression.MethodsThirty-four cultured human tumor lines [18 melanomas (MEL), 12 renal cell carcinomas (RCC), 3 squamous cell carcinomas of the head and neck (SCCHN), and 1 non-small-cell lung carcinoma (NSCLC)] and peripheral blood monocytes (Monos) were treated with cytokines that we detected in the PD-L1+ TME by gene expression profiling, including IFN-g, IL-1a, IL-10, IL-27 and IL-32g. PD-L1 cell surface protein expression was detected by flow cytometry, and mRNA by quantitative real-time PCR. Total and phosphorylated STAT1, STAT3, and p65 proteins were detected by Western blotting, and the genes encoding these proteins were knocked down with siRNAs. Additionally, the proximal promoter region of PDL1 (CD274) was sequenced in 33 cultured tumors.ResultsPD-L1 was constitutively expressed on 1/17 cultured MELs, 8/11 RCCs, 3/3 SCCHNs, and on Monos. Brief IFN-g exposure rapidly induced PD-L1 on all tumor cell lines and Monos regardless of constitutive PD-L1 expression. PD-L1 mRNA levels were associated with protein expression, which was diminished by exposure to transcriptional inhibitors. siRNA knockdown of STAT1 but not STAT3 reduced IFN-g- and IL-27-induced PD-L1 protein expression on tumor cells. In contrast, STAT3 knockdown in Monos reduced IL-10-induced PD-L1 protein expression, and p65 knockdown in tumor cells reduced IL-1a-induced PD-L1 expression. Notably, constitutive PD-L1 expression was not affected by knocking down STAT1, STAT3, or p65. Differential effects of IFN-g, IL-1a, and IL-27 on individual tumor cell lines were not due to PDL1 promoter polymorphisms.ConclusionsMultiple cytokines found in an immune-reactive TME may induce PD-L1 expression on tumor and/or immune cells through distinct signaling mechanisms. Factors driving constitutive PD-L1 expression were not identified in this study. Understanding complex mechanisms underlying PD-L1 display in the TME may allow treatment approaches mitigating expression of this immunosuppressive ligand, to enhance the impact of PD-1 blockade.

αvβ3-integrin regulates PD-L1 expression and is involved in cancer immune evasion

Tumors utilize a number of effective strategies, including the programmed death 1/PD ligand 1 (PD-1/PD-L1) axis, to evade immune-mediated control of their growth. PD-L1 expression is mainly induced by IFN receptor signaling or constitutively induced. Integrins are an abundantly expressed class of proteins which play multiple deleterious roles in cancer and exert proangiogenic and prosurvival activities. We asked whether αvβ3-integrin positively regulates PD-L1 expression and the anticancer immune response. We report that αvβ3-integrin regulated constitutive and IFN-induced PD-L1 expression in human and murine cancerous and noncancerous cells. αvβ3-integrin targeted STAT1 through its signaling C tail. The implantation of β3-integrin-depleted tumor cells led to a dramatic decrease in the growth of primary tumors, which exhibited reduced PD-L1 expression and became immunologically hot, with increased IFNγ content and CD8+ cell infiltration. In addition, the implantation of β3-integrin-depleted tumors elicited an abscopal immunotherapeutic effect measured as protection from the challenge tumor and durable splenocyte and serum reactivity to B16 cell antigens. These modifications to the immunosuppressive microenvironment primed cells for checkpoint (CP) blockade. When combined with anti-PD-1, β3-integrin depletion led to durable therapy and elicited an abscopal immunotherapeutic effect. We conclude that in addition to its previously known roles, αvβ3-integrin serves as a critical component of the cancer immune evasion strategy and can be an effective immunotherapy target.

JAK2/PD-L1/PD-L2 (9p24.1) amplifications in renal cell carcinomas with sarcomatoid transformation: implications for clinical management

Amplifications of JAK2, PD-L1, and PD-L2 at 9p24.1 lead to constitutive expression of PD-L1. This, coupled with JAK2-activation dependent upregulation of PD-L1 and adaptive/induced expression leads to higher tumor PD-L1 expression and immune evasion. Renal tumors were therefore evaluated for 9p24.1 amplifications. A combination of next generation sequencing-based copy number analysis, fluorescence in situ hybridization for JAK2/INSL6 and PD-L1/PD-L2 and immunohistochemistry for phospho-STAT3 (downstream target of JAK2), PD-L1, PD-L2, and PD-1 was performed. In this study we interrogated a “Discovery” cohort of 593 renal tumors, a “Validation” cohort of 398 high-grade renal tumors, The Cancer Genome Atlas (879 cases) and other public datasets (846 cases). 9p24.1 amplifications were significantly enriched in renal tumors with sarcomatoid transformation (5.95%, 15/252) when compared to all histologic subtypes in the combined “Discovery”, “Validation” and public datasets (16/2636, 0.6%, p < 0.00001). Specifically, 9p24.1 amplifications amongst sarcomatoid tumors in public datasets, the “Discovery” and “Validation” cohorts were 7.7% (6/92), 15.1% (5/33), and 3.1% (4/127), respectively. Herein, we describe 13 cases and amplification status for these was characterized using next generation sequencing (n = 9) and/or fluorescence in situ hybridization (n = 10). Correlation with PD-L1 immunohistochemistry (n = 10) revealed constitutive expression (mean H-score: 222/300, n = 10). Analysis of outcomes based on PD-L1 expression in tumor cells performed on 282 cases (“Validation” cohort) did not reveal a significant prognostic effect and was likely reflective of advanced disease. A high incidence of constitutive PD-L1 expression in tumor cells in the “Validation” cohort (H-Score ≥250/300) was noted amongst 83 rhabdoid (6%) and 127 sarcomatoid renal tumors (7.1%). This suggests additional mechanisms of constitutive expression other than amplification events. Importantly, two patients with 9p24.1-amplified sarcomatoid renal tumors showed significant response to immunotherapy. In summary, a subset of renal tumors with sarcomatoid transformation exhibits constitutive PD-L1 overexpression and these patients should be evaluated for enhanced response to immunotherapy.

Inhibitory Effect of Anoectochilus formosanus Extract on Hyperglycemia-Related PD-L1 Expression and Cancer Proliferation.

Traditional herb medicine, golden thread (Anoectochilus formosanus Hayata) has been used to treat various diseases. Hyperglycemia induces generation of reactive oxygen species (ROS) and enhancement of oxidative stress which are risk factors for cancer progression and metastasis. In this study, we evaluated hypoglycemic effect of A. formosanus extracts (AFEs) in an inducible hyperglycemia animal model and its capacity of free-radical scavenging to establish hyperglycemia-related carcinogenesis. AFE reduced blood glucose in hyperglycemic mice while there was no change in control group. The incremental area under blood glucose response curve was decreased significantly in hyperglycemic mice treated with AFE in a dose-dependent manner. AFE and metformin at the same administrated dose of 50 mg/kg showed similar effect on intraperitoneal glucose tolerance test in hyperglycemic mice. Free-radical scavenger capacity of AFE was concentration dependent and 200 μg/ml of AFE was able to reduce more than 41% of the free radical. Treatment of cancer cells with AFE inhibited constitutive PD-L1 expression and its protein accumulation. It also induced expression of pro-apoptotic genes but inhibited proliferative and metastatic genes. In addition, it induced anti-proliferation in cancer cells. The results suggested that AFE not only reduced blood glucose concentration as metformin but also showed its potential use in cancer immune chemoprevention/therapy via hypoglycemic effect, ROS scavenging and PD-L1 suppression.

PD-L1 expression in inflammatory myofibroblastic tumors

AbstractInflammatory myofibroblastic tumor is a rare mesenchymal tumor occurring at many anatomic sites, with a predilection for children and young adults. Often indolent, they can be locally aggressive and can metastasize, resulting in significant morbidity and mortality. Therapeutic options are often limited. The identification of underlying kinase mutations has allowed the use of targeted therapy in a subset of patients. Unfortunately, not all tumors harbor mutations and resistance to tyrosine kinase inhibitor therapy is a potential problem. We hypothesized that these tumors may be amenable to PD-L1 therapy given the immune nature of the tumor. PD-L1 expression in inflammatory myofibroblastic tumors has not yet been defined. The purpose of this study was to explore PD-L1 expression in inflammatory myofibroblastic tumors, as adaptive PD-L1 expression is known to enrich for response to anti-PD-1/PD-L1 therapies. Expression of PD-L1 (clone SP142) was assessed in 35 specimens from 28 patients. Positivity was defined as membranous expression in ≥5% of cells and evaluated separately in tumor and immune cells. Adaptive vs. constitutive patterns of tumor cell PD-L1 expression were assessed. PD-L1 status was correlated with clinicopathologic features. CD8+ T cell infiltrates were quantified by digital image analysis. ALK status was assessed by immunohistochemistry and/or FISH. Twenty-four (69%) tumors had PD-L1(+) tumor cells and 28 (80%) showed PD-L1(+) immune cells. Most recurrent and metastatic tumors (80%) and ALK(−) tumors (88%) were PD-L1(+). Adaptive PD-L1 expression was present in 23 (96%) of PD-L1(+) tumors, which also showed a three–four fold increase in CD8+ T cell infiltration relative to PD-L1(−) tumors. Constitutive PD-L1 expression was associated with larger tumor size (p = 0.002). Inflammatory myofibroblastic tumors show frequent constitutive and adaptive PD-L1 expression, the latter of which is thought to be predictive of response to anti-PD-1. These data support further investigation into PD-1/PD-L1 blockade in this tumor type.

Abstract 4693: Characterization of the tumor immune microenvironment in head and neck squamous cell carcinoma (SCCHN)

Abstract Approximately 20% of advanced SCCHNs respond to anti-PD-(L)1. We aimed to inform rational combination therapy development, which might have greater efficacy, by understanding the potential immune effects of the oncogenic human papillomavirus (HPV) in SCCHN, and by characterizing potentially targetable immune checkpoints in the tumor microenvironment (TME). Immunohistochemistry (IHC) was performed on archival SCCHN specimens from 27 treatment-naive patients. HPV testing with p16 IHC was confirmed by HPV genotyping. IHC for PD-L1 assessed percentage of positive tumor cells, and whether PD-L1 was expressed in an adaptive or constitutive pattern (i.e., PD-L1+ tumor cells juxtaposed to TILs or in the absence of TILs, respectively). PD-L1 on infiltrating immune cells was scored separately. IHC for CD3, CD4, CD8, CD20, CD68, FoxP3, PD-1, PD-L2, LAG-3, TIM-3, GITR and IDO was quantified using Halo image analysis for density of positive cells. Among 27 SCCHN specimens, 14 were HPV(-) and 13 were HPV+ (one HPV58, 12 HPV16). In 19 of 27 specimens (70%), ≥5% of tumor cells had PD-L1 cell surface expression by IHC, including 9 HPV+ and 10 HPV(-) cases. Among 23 tumors expressing any level of PD-L1 (≥1% tumor cells+), 12 displayed an adaptive PD-L1 expression pattern, 5 a constitutive pattern, and 6 were mixed. All tumors were infiltrated by immune cells (ICs). Notably, 26 of 27 specimens (96%) contained PD-L1+ immune cells (range 5-80% of ICs expressing PD-L1). The proportion of PD-L1+ ICs exceeded PD-L1+ tumor cells in 21/26 (81%) cases. Neither the proportion of PD-L1+ tumor cells nor infiltrating immune cells correlated with tumor viral status. When compared to HPV(-) tumors, HPV+ tumors contained significantly higher densities of CD3+, CD4+, CD8+, CD20+, and PD-1+ cells (p&amp;lt;0.02); there was a trend towards an increased density of FoxP3+ cells in HPV+ tumors. However, when comparing specimens in which tumor cells were PD-L1+ vs. (-), none of these markers were differentially expressed. This may reflect heterogeneous mechanisms driving constitutive vs. adaptive PD-L1 expression patterns in SCCHN. In addition to finding abundant IDO expression in these specimens (&amp;gt;500 IDO+ cells/mm2 in 17/27 specimens), IDO was expressed by tumor cells as well as ICs in 12/27 (44%) cases (range 5-95% tumor cells+). In summary, we found that both HPV+ and (-) SCCHNs abundantly express PD-L1 on tumor and/or stromal cells, although HPV+ tumors are more heavily infiltrated by ICs. Multiple other immune checkpoints are expressed in these tumors, providing options for therapeutic co-targeting. Tumor DNA sequencing is in progress to explore the genetic basis for constitutive vs. adaptive PD-L1 expression. These studies are expected to provide a comprehensive portrait of the SCCHN TME, with implications for future immunotherapy development. Funded by the Bristol-Myers Squibb International Immuno-Oncology Network and NCI R01 CA142779 Citation Format: Farah Succaria, Pia Kvistborg, Elizabeth L. Engle, Tracee L. McMiller, Elizabeth Thompson, Alan E. Berger, John Haanen, Suzanne L. Topalian, Janis M. Taube. Characterization of the tumor immune microenvironment in head and neck squamous cell carcinoma (SCCHN) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4693.

Marked Global DNA Hypomethylation Is Associated with Constitutive PD-L1 Expression in Melanoma

SummaryConstitutive expression of the immune checkpoint, PD-L1, inhibits anti-tumor immune responses in cancer, although the factors involved in PD-L1 regulation are poorly understood. Here we show that loss of global DNA methylation, particularly in intergenic regions and repeat elements, is associated with constitutive (PD-L1CON), versus inducible (PD-L1IND), PD-L1 expression in melanoma cell lines. We further show this is accompanied by transcriptomic up-regulation. De novo epigenetic regulators (e.g., DNMT3A) are strongly correlated with PD-L1 expression and methylome status. Accordingly, decitabine-mediated inhibition of global methylation in melanoma cells leads to increased PD-L1 expression. Moreover, viral mimicry and immune response genes are highly expressed in lymphocyte-negative plus PD-L1-positive melanomas, versus PD-L1-negative melanomas in The Cancer Genome Atlas (TCGA). In summary, using integrated genomic analysis we identified that global DNA methylation influences PD-L1 expression in melanoma, and hence melanoma's ability to evade anti-tumor immune responses. These results have implications for combining epigenetic therapy with immunotherapy.

Decitibine improve the efficiency of anti-PD-1 therapy via activating the response to IFN/PD-L1 signal of lung cancer cells.

IFN-γ-induced PD-L1 expression represents the existence of tumor-specific T cells, which predicts high-response rate to anti-PD-1/L1 therapy, but loss-of-function of IFN signals (e.g., JAK mutation) induces adaptive immune resistance in patients with low-response rate. Interferon regulatory factors (IRF) are frequently epigenetic silenced in carcinogenesis, while the role of methylation in anti-PD-1/L1 therapy remains unclear. We here investigated the methylation status of IFN-γ related genes IRF1/8 and IFN-α/β-related genes IRF3/7 in lung cancer tissues and found that only highly methylated IRF1 and 7 negatively correlated to cd274 (coding PD-L1) expression, similar to JAK mutation. Interestingly, decitibine (DAC) as methylation inhibitor could hypomethylate IRF1/7 to restore PD-L1 level. Meanwhile, IRF7 enhanced constitutive PD-L1 expression, which was independent of IFN-γ though directly promote transcription of PD-L1, leading to abrogating cytotoxic T lymphocytes (CTLs) generation which could be restored by anti-PD-L1 antibody, or siRNA-IRF7. The supplement of DAC to anti-PD-1 therapy in vivo improve the efficiency of anti-tumor with less methylated IRF1/7, more interferon-related genes expression (e.g., CXCL9) and IFN-γ/CD8+ T-cells infiltrations, suggesting that additional treatment of DAC could rescue the ability to response to IFN in lung cancer patients with anti-PD-1/L1 therapy resistance.

PD-L1 expression and the immune microenvironment in primary invasive lobular carcinomas of the breast

Tumor-infiltrating lymphocytes and immune checkpoint proteins such as PD-L1 are potential prognostic factors and therapeutic targets in breast cancer. Most studies characterizing the breast tumor immune microenvironment have focused on ductal carcinomas. Here we investigate the tumor microenvironment of primary invasive lobular carcinomas. Previously constructed tissue microarrays of 47 lobular carcinomas were labeled by immunohistochemistry for PD-L1, CD8, CD20, and FoxP3. The stromal immune infiltrate density was qualitatively scored as a percentage of tumor area: 1+ (<5%); 2+ (5–10%); 3+ (10–15%); or 4+ (>50%). The average immune cell subtype per high-power field was quantitatively scored. The percentage PD-L1 labeling on tumor-infiltrating lymphocytes was scored as none, focal (<5%), moderate (10–24%), or diffuse (50–100%). The percentage of membranous carcinoma cell PD-L1 labeling was also recorded, with <5% considered negative. All lobular carcinomas contained PD-L1+ tumor-infiltrating lymphocytes with the majority showing 1+ immune infiltrates with focal–moderate PD-L1 labeling. PD-L1 was expressed by tumor cells in 17% of lobular carcinomas. In contrast to ductal carcinomas, there was no correlation between the immune infiltrate density, the PD-L1 expression by lobular carcinoma cells, tumor grade, or the expression of estrogen receptor or human epidermal growth factor receptor-2. However, both the tumor-infiltrating lymphocyte density and the average CD8+ T-cell counts correlated with immune cell PD-L1 status (P=0.004 and 0.03, respectively). Similar to breast ductal carcinomas, PD-L1+ lobular breast carcinomas had higher numbers of PD-L1+ tumor-infiltrating lymphocytes (63%) than PD-L1− lobular carcinomas (23%; P=0.04). These data show that a subset of primary breast lobular carcinomas both express PD-L1 on tumor cells and contain PD-L1+ tumor-infiltrating lymphocytes, suggesting the possibility of both constitutive and adaptive PD-L1 expression. Together, these results support immunotherapy as a potential treatment for a subset of patients with primary invasive lobular breast carcinomas.

Beyond the Percentages of PD-L1-Positive Tumor Cells: Induced Versus Constitutive PD-L1 Expression in Primary and Metastatic Head and Neck Squamous Cell Carcinoma.

Anti-PD1 antibody has been approved for metastatic squamous cell carcinoma of the head and neck (SCCHN) and objective response rates of approximately 20% have been reported. Defining PD-L1 expression at ≥ 1% tumor cells as positive, PD-L1-positive tumors showed a higher response rate. However, it is unclear whether 1% is the optimal cutoff, and studies on lung cancer suggested 50% cutoff as a stronger predictive biomarker. 96 primary SCCHN from oropharynx and oral cavity and 34 corresponding metastatic lesions were typed for membranous PD-L1 expression. p16 immunohistochemistry was used as a surrogate marker for HPV status in SCCHN from the oropharynx. Fifty-two of 96 (54%) tumors were PD-L1-positive, 72% if PD-L1 expression in tumor-infiltrating immunocytes was also included as positive. Fifteen of 34 primary-metastasis tumor pairs differed in PD-L1 expression, and p16(+) cases more frequently showed PD-L1 expression in immunocytes than p16(-) cases (82 vs. 45%, p < 0.05). PD-L1-positive SCCHN showed two distinct patterns of expression. In the induced pattern of expression, PD-L1-positive tumor cells were limited to the periphery of tumor nests at the tumor-immunocyte interface, comprising < 5% of tumor cells, and were almost always associated with PD-L1-positive immunocytes. In contrast, tumors with constitutive PD-L1 expression had a higher percentage of positive tumor cells, often diffusely distributed throughout the tumor, and often were not accompanied by PD-L1-positive immunocytes. We propose that distinguishing these two biologically distinctive patterns of PD-L1 expression and typing metastatic instead of primary lesions might better predict immunotherapeutic response to anti-PD1/PD-L1 regimens beyond just the percentage of PD-L1-positive tumor cells.