Interferon-γ-induced PD-L1 surface expression on human oral squamous carcinoma via PKD2 signal pathway

Surveilling the Potential for Precision Medicine-driven PD-1/PD-L1-targeted Therapy in HNSCC

Immunotherapy is becoming an accepted treatment modality for many patients with cancer and is now approved for use in platinum-refractory recurrent or metastatic head and neck squamous cell carcinoma (HNSCC). Despite these successes, a minority of patients with HNSCC receiving immunotherapy respond to treatment, and few undergo a complete response. Thus, there is a critical need to identify mechanisms regulating immune checkpoints in HNSCC such that one can predict who will benefit, and so novel combination strategies can be developed for non-responders. Here, we review the immunotherapy and molecular genetics literature to describe what is known about immune checkpoints in common genetic subsets of HNSCC. We highlight several highly recurrent genetic lesions that may serve as biomarkers or targets for combination immunotherapy in HNSCC.

Targeting immune checkpoints in malignant glioma

Malignant glioma is the most common and a highly aggressive cancer in the central nervous system (CNS). Cancer immunotherapy, strategies to boost the body's anti-cancer immune responses instead of directly targeting tumor cells, recently achieved great success in treating several human solid tumors. Although once considered "immune privileged" and devoid of normal immunological functions, CNS is now considered a promising target for cancer immunotherapy, featuring the recent progresses in neurobiology and neuroimmunology and a highly immunosuppressive state in malignant glioma. In this review, we focus on immune checkpoint inhibitors, specifically, antagonizing monoclonal antibodies for programmed cell death protein-1 (PD-1), cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), and indoleamine 2,3-dioxygenase (IDO). We discuss advances in the working mechanisms of these immune checkpoint molecules, their status in malignant glioma, and current preclinical and clinical trials targeting these molecules in malignant glioma.

Image Analysis-based Assessment of PD-L1 and Tumor-Associated Immune Cells Density Supports Distinct Intratumoral Microenvironment Groups in Non-small Cell Lung Carcinoma Patients

PURPOSE

We investigated the correlation between immunohistochemical PD-L1 expression and tumor-associated immune cells (TAICs) density in non-small cell lung carcinoma (NSCLC) and correlated them with clinicopathologic variables.

EXPERIMENTAL DESIGN

Tumor tissue specimens from 254 stage I-III NSCLCs [146 adenocarcinomas; 108 squamous cell carcinomas (SCCs)] were examined. PD-L1 expression in malignant cells and macrophages and the density of TAICs expressing CD3, CD4, CD8, CD57, granzyme B, CD45RO, PD-1, FOXP3, and CD68 were evaluated using immunohistochemistry and image analysis.

RESULTS

Malignant cells PD-L1 H-score > 5 was detected in 23% of adenocarcinomas and 31% of SCCs, and no significant differences were detected comparing both histologies; the median H-score in macrophages was significantly higher in SCC than in adenocarcinoma (P < 0.001). In adenocarcinoma, high malignant cells PD-L1 expression and high TAIC density correlated with solid histology, smoking history, and airflow limitation. Multivariate analysis demonstrated that high CD57-positive cell density correlated with better recurrence-free survival (RFS; P = 0.0236; HR, 0.457) and overall survival (OS; P = 0.0261; HR, 0.481) rates for SCC. High CD68-positive cell density in intratumoral compartment correlated with better RFS (P = 0.0436; HR, 0.553) for adenocarcinoma. The combination of low CD4/CD8/C68-positive cell density and PD-L1 H-score >5 in malignant cells identified small subset of adenocarcinomas with worse outcomes (RFS: P = 0.036; HR, 4.299; OS: P = 0.00034; HR, 5.632).

CONCLUSIONS

We detected different PD-L1 expression and TAIC density patterns in NSCLC. Distinct groups of tumor microenvironment correlated with NSCLC clinicopathologic features, including outcome. Clin Cancer Res; 22(24); 6278-89. ©2016 AACR.

5-Fluorouracil upregulates cell surface B7-H1 (PD-L1) expression in gastrointestinal cancers

Background

Resistance to chemotherapy is a major obstacle in the effective treatment of cancer patients. B7-homolog 1, also known as programmed death ligand-1 (PD-L1), is an immunoregulatory protein that is overexpressed in several human cancers. Interaction of B7-H1 with programmed death 1 (PD-1) prevents T-cell activation and proliferation, sequestering the T-cell receptor from the cell membrane, inducing T-cell apoptosis, thereby leading to cancer immunoresistance. B7-H1 upregulation contributes to chemoresistance in several types of cancer, but little is known with respect to changes associated with 5-fluorouracil (5-FU) or gastrointestinal cancers.

Methods

HCT 116 p53^+/+, HCT 116 p53^−/− colorectal cancer (CRC) and OE33 esophageal adenocarcinoma (EAC) cells were treated with increasing doses of 5-FU (0.5 uM, 5 uM, 50 uM, 500 uM) or interferon gamma (IFN-γ, 10 ng/mL) in culture for 24 h and B7-H1 expression was quantified using flow cytometry and western blot analysis. We also evaluated B7-H1 expression, by immunohistochemistry, in tissue collected prior to and following neoadjuvant therapy in 10 EAC patients.

Results

B7-H1 expression in human HCT 116 p53^+/+ and HCT 116 p53^−/− CRC cells lines, while low at baseline, can be induced by treatment with 5-FU. OE33 baseline B7-H1 expression exceeded CRC cell maximal expression and could be further increased in a dose dependent manner following 5-FU treatment in the absence of immune cells. We further demonstrate tumor B7-H1 expression in esophageal adenocarcinoma patient-derived pre-treatment biopsies. While B7-H1 expression was not enhanced in post-treatment esophagectomy specimens, this may be due to the limits of immunohistochemical quantification.

Conclusions

B7-H1/PD-L1 expression can be increased following treatment with 5-FU in gastrointestinal cancer cell lines, suggesting alternative mechanisms to classic immune-mediated upregulation. This suggests that combining 5-FU treatment with PD-1/B7-H1 blockade may improve treatment in patients with gastrointestinal adenocarcinoma.

Overcoming barriers to effective immunotherapy: MDSCs, TAMs, and Tregs as mediators of the immunosuppressive microenvironment in head and neck cancer

A significant subset of head and neck cancers display a T-cell inflamed phenotype, suggesting that patients with these tumors should respond to therapeutic approaches aimed at strengthening anti-tumor immune responses. A major barrier to the development of an effective anti-tumor immune response, at baseline or in response to immunotherapy, is the development of an immunosuppressive tumor microenvironment. Several well described mechanisms of effector immune cell suppression in the head and neck cancer microenvironment are discussed here, along with updates on current trials designed to translate what we have learned from pre-clinical and correlative clinical studies into improved responses in patients with head and neck cancer following immune activating therapies.

miR-424(322) reverses chemoresistance via T-cell immune response activation by blocking the PD-L1 immune checkpoint

Immune checkpoint blockade of the inhibitory immune receptors PD-L1, PD-1 and CTLA-4 has emerged as a successful treatment strategy for several advanced cancers. Here we demonstrate that miR-424(322) regulates the PD-L1/PD-1 and CD80/CTLA-4 pathways in chemoresistant ovarian cancer. miR-424(322) is inversely correlated with PD-L1, PD-1, CD80 and CTLA-4 expression. High levels of miR-424(322) in the tumours are positively correlated with the progression-free survival of ovarian cancer patients. Mechanistic investigations demonstrated that miR-424(322) inhibited PD-L1 and CD80 expression through direct binding to the 3'-untranslated region. Restoration of miR-424(322) expression reverses chemoresistance, which is accompanied by blockage of the PD-L1 immune checkpoint. The synergistic effect of chemotherapy and immunotherapy is associated with the proliferation of functional cytotoxic CD8+ T cells and the inhibition of myeloid-derived suppressive cells and regulatory T cells. Collectively, our data suggest a biological and functional interaction between PD-L1 and chemoresistance through the microRNA regulatory cascade.

A primer on tumour immunology and prostate cancer immunotherapy

No abstract

Expression of programmed death 1 ligand 1 on periodontal tissue cells as a possible protective feedback mechanism against periodontal tissue destruction

Programmed death 1 ligand 1 (PD-L1) is a negative co-stimulatory molecule in immune responses. Previous reports have indicated that inflammatory cytokines can upregulate the expression of PD-L1 in tumor cells, which in turn suppresses host immune responses. Periodontitis is characterized by persistent inflammation of the periodontium, which is initiated by infection with oral bacteria and results in damage to cells and the matrices of the periodontal connective tissues. In the present study, the expression and function of PD-L1 in periodontal tissue destruction were examined. Periodontal ligament cells (PDLCs) were stimulated by inflammatory cytokines and periodontal pathogens. The expression and function of PD-L1 on the surface of PDLCs was investigated using flow cytometry in vitro. Periodontal disease was induced by the injection of Porphyromonas gingivalis in mouse models. The expression levels of PD-L1 in the periodontal tissues of the mice were analyzed using flow cytometry and immunohistochemistry. PD-L1 was inducibly expressed on the PDLCs by the inflammatory cytokines and periodontal pathogens. The inflammation-induced expression of PD-L1 was shown to cause the apoptosis of activated T lymphocytes and improve the survival of PDLCs. Furthermore, in the mouse model of experimental periodontitis, the expression of PD-L1 in severe cases of periodontitis was significantly lower, compared with that in mild cases. By contrast, no significant differences were observed between the healthy control and severe periodontitis groups. The results of the present study showed that the expression of PD-L1 may inhibit the destruction of periodontal tissues, indicating the involvement of a possible protective feedback mechanism against periodontal infection.

Imaging, Biodistribution, and Dosimetry of Radionuclide-Labeled PD-L1 Antibody in an Immunocompetent Mouse Model of Breast Cancer

The programmed cell death ligand 1 (PD-L1) participates in an immune checkpoint system involved in preventing autoimmunity. PD-L1 is expressed on tumor cells, tumor-associated macrophages, and other cells in the tumor microenvironment. Anti-PD-L1 antibodies are active against a variety of cancers, and combined anti-PD-L1 therapy with external beam radiotherapy has been shown to increase therapeutic efficacy. PD-L1 expression status is an important indicator of prognosis and therapy responsiveness, but methods to precisely capture the dynamics of PD-L1 expression in the tumor microenvironment are still limited. In this study, we developed a murine anti-PD-L1 antibody conjugated to the radionuclide Indium-111 ((111)In) for imaging and biodistribution studies in an immune-intact mouse model of breast cancer. The distribution of (111)In-DTPA-anti-PD-L1 in tumors as well as the spleen, liver, thymus, heart, and lungs peaked 72 hours after injection. Coinjection of labeled and 100-fold unlabeled antibody significantly reduced spleen uptake at 24 hours, indicating that an excess of unlabeled antibody effectively blocked PD-L1 sites in the spleen, thus shifting the concentration of (111)In-DTPA-anti-PD-L1 into the blood stream and potentially increasing tumor uptake. Clearance of (111)In-DTPA-anti-PD-L1 from all organs occurred at 144 hours. Moreover, dosimetry calculations revealed that radionuclide-labeled anti-PD-L1 antibody yielded tolerable projected marrow doses, further supporting its use for radiopharmaceutical therapy. Taken together, these studies demonstrate the feasibility of using anti-PD-L1 antibody for radionuclide imaging and radioimmunotherapy and highlight a new opportunity to optimize and monitor the efficacy of immune checkpoint inhibition therapy.

The increase of circulating PD-L1-expressing CD68(+) macrophage in ovarian cancer

Tumor-associated macrophages (TAMs) have been characterized as a critical population of immunosuppressive cells in a variety of tumor types. PD-L1 (also termed B7-H1) has been described to exert co-inhibitory and immune regulatory functions. Here, in ovarian cancer, PD-L1 is selectively overexpressed on some TAM compared that of benign ovarian disease. When expanding the data in peripheral blood, the proportion of PD-L1(+)CD68(+) cell among CD68(+) cells and the intensity of PD-L1 staining on CD68(+) cell in healthy group were similar to that observed in ovarian cyst group; instead, these two measures were significantly higher in ovarian cancer group, thereafter related to TNM stage. Interestingly, intracellular levels of IL-10, IL-6, TNF-α, and IFN-γ in PD-L1(+)CD68(+) macrophage were higher than those in PD-L1(-)CD68(+) macrophage, especially IL-6 expression. Based on the PD-L1 receptor PD-1 expression on tumor-infiltrating cytotoxic cells, our data supported that expression of PD-L1 on TAM promoted apoptosis of T cells via interaction with PD-1 on CD8(+)T cells. Taken together, these results suggested that PD-L1-expressing macrophage represents a novel suppressor cell population in ovarian cancer, which contributes immune escape of ovarian cancer.

Programmed death-1 & its ligands: promising targets for cancer immunotherapy

Novel strategies for cancer treatment involving blockade of immune inhibitors have shown significant progress toward understanding the molecular mechanism of tumor immune evasion. The preclinical findings and clinical responses associated with programmed death-1 (PD-1) and PD-ligand pathway blockade seem promising, making these targets highly sought for cancer immunotherapy. In fact, the anti-PD-1 antibodies, pembrolizumab and nivolumab, were recently approved by the US FDA for the treatment of unresectable and metastatic melanoma resistant to anticytotoxic T-lymphocyte antigen-4 antibody (ipilimumab) and BRAF inhibitor. Here, we discuss strategies of combining PD-1/PD-ligand interaction inhibitors with other immune checkpoint modulators and standard-of-care therapy to break immune tolerance and induce a potent antitumor activity, which is currently a research area of key scientific pursuit.

Harnessing the PD-1 pathway in renal cell carcinoma: current evidence and future directions

Programmed cell death-1 (PD-1) is a recognized immune checkpoint. It is frequently upregulated on the T cells that infiltrate tumors, providing an inhibitory signal, which may facilitate immune escape. Blocking antibodies have been developed to interrupt the interaction of PD-1 with its ligands PD-L1/PD-L2, with the goal of increasing the host antitumor immune response. Initial results have been encouraging, with durable responses in both treatment-naive and pretreated patients, along with an acceptable toxicity profile. This tolerability makes PD-1 blockade an excellent potential partner for combination strategies with the approved targeted agents, such as tyrosine kinase inhibitors (TKIs) and anti-vascular endothelial growth factor (anti-VEGF) antibodies, as well as other investigational immune checkpoint inhibitors or agonist antibodies that may costimulate an immune response. PD-L1 expression on tumor cells and tumor-infiltrating immune cells is also being evaluated as a predictive biomarker of response to treatment. This review summarizes the biological basis, preclinical studies, ongoing trials, and future challenges associated with targeting the PD-1 pathway in renal cell carcinoma.

Emerging drugs for head and neck cancer

INTRODUCTION

Despite improvements in treatment, survival rates of head and neck squamous cell carcinoma (HNSCC) are stagnant. The existing chemotherapeutic agents are non-selective and associated with toxicities. Combinations of the only the US FDA-approved epidermal growth factor receptor (EGFR)-targeted agent, cetuximab, with chemotherapy or radiation improves overall survival. However, the response rates to cetuximab are modest. Thus, there is an urgent need for new agents that can be safely integrated into current treatment regimens to improve outcome.

AREAS COVERED

Current EGFR-targeted drugs under clinical development include mAbs and tyrosine kinase inhibitors. The modest efficacy of these drugs implicates intrinsic or acquired resistance. Novel molecular agents inhibiting alternative targets to overcome anti-EGFR resistance in HNSCC are under investigation. Gene therapy and immunotherapy are also promising strategies to improve efficacy and reduce toxicity.

EXPERT OPINION

To date, only six drugs have been FDA-approved for the treatment of head and neck cancer. Cetuximab is the only approved molecular targeting agent for HNSCC and despite ubiquitous expression of EGFR in HNSCC tumors, clinical responses are limited. Genetic and epigenetic characterization of HNSCC tumors, coupled with improved preclinical models, should facilitate the development of more effective drugs.

CD4(+) T-Helper Type 1 Cytokines and Trastuzumab Facilitate CD8(+) T-cell Targeting of HER2/neu-Expressing Cancers

Vaccination strategies incorporating the immunodominant HLA-A2-restricted HER2/neu-derived peptide 369-377 (HER2369-377) are increasingly utilized in HER2/neu-expressing cancer patients. The failure of postvaccination HER2369-377-specific CD8(+) T cells to recognize HLA-A2(pos)HER2/neu-expressing cells in vitro, however, has been attributed to impaired MHC class I/HLA-A2 presentation observed in HER2/neu-overexpressing tumors. We reconcile this controversy by demonstrating that HER2369-377 is directly recognized by high functional-avidity HER2369-377-specific CD8(+) T cells-either genetically modified to express a novel HER2369-377 TCR or sensitized using HER2369-377-pulsed type 1-polarized dendritic cells (DC1)-on class I-abundant HER2(low), but not class I-deficient HER2(high), cancer cells. Importantly, a critical cooperation between CD4(+) T-helper type-1 (Th1) cytokines IFNγ/TNFα and HER2/neu-targeted antibody trastuzumab is necessary to restore class I expression in HER2(high) cancers, thereby facilitating recognition and lysis of these cells by HER2369-377-specific CD8(+) T cells. Concomitant induction of PD-L1 on HER2/neu-expressing cells by IFNγ/TNF and trastuzumab, however, has minimal impact on DC1-sensitized HER2369-377-CD8(+) T-cell-mediated cytotoxicity. Although activation of EGFR and HER3 signaling significantly abrogates IFNγ/TNFα and trastuzumab-induced class I restoration, EGFR/HER3 receptor blockade rescues class I expression and ensuing HER2369-377-CD8(+) cytotoxicity of HER2/neu-expressing cells. Thus, combinations of CD4(+) Th1 immune interventions and multivalent targeting of HER family members may be required for optimal anti-HER2/neu CD8(+) T-cell-directed immunotherapy.

Interferon-γ-induced activation of JAK1 and JAK2 suppresses tumor cell susceptibility to NK cells through upregulation of PD-L1 expression

Inhibition of JAK1 or JAK2 in human tumor cells was previously shown to increase susceptibility of these cells to NK cell lysis. In the present study, we examined the cellular mechanisms that mediate this effect in hematopoietic tumor cell lines and primary tumor cells. Incubation of tumor cells with supernatant from activated NK cells or interferon-gamma (IFNγ)-induced activation of pSTAT1 and increased expression of PD-L1 without altering expression of other activating or inhibitory NK cell ligands. These functional effects were blocked by chemical JAK inhibition or shRNAs targeting JAK1, JAK2 or STAT1. Inhibition of IFNγ signaling also prevented the upregulation of PD-L1 and blocking PD-L1 resulted in increased tumor lysis by NK cells. These results show that NK cell activation and secretion of IFNγ results in activation of JAK1, JAK2 and STAT1 in tumor cells, resulting in rapid up-regulation of PD-L1 expression. Increased expression of PD-L1 results in increased resistance to NK cell lysis. Blockade of JAK pathway activation prevents increased PD-L1 expression resulting in increased susceptibility of tumor cells to NK cell activity. These observations suggest that JAK pathway inhibitors as well as PD-1 and PD-L1 antibodies may work synergistically with other immune therapies by preventing IFN-induced inhibition of NK cell-mediated tumor cell lysis.

T lymphocyte-derived TNF and IFN-γ repress HFE expression in cancer cells

The immune system and tumors are closely intertwined initially upon tumor development. During this period, tumors evolve to promote self-survival through immune escape, including by targeting crucial components involved in the presentation of antigens to the immune system in order to avoid recognition. Accordingly, components involved in MHC I presentation of tumor antigens are often mutated and down-regulated targets in tumors. On the other hand, the immune system has been shown to influence tumors through production of immunosuppressive cytokines, recruitment and polarization of cells favoring or impeding tumor escape or through production of anti-tumor cytokines promoting tumor rejection. We previously discovered that the hemochromatosis protein HFE, a negative regulator of iron absorption, dampens classical MHC I antigen presentation. In this study, we evaluated the impact of activated T lymphocytes purified from peripheral blood mononuclear cells (PBMC) on HFE expression in tumor cell lines. We co-cultured tumor cell lines from melanoma, lung, and kidney cancers with anti-CD3-activated PBMC and established that HFE expression is increased in tumor cell lines compared to healthy tissues, whilst being down-regulated significantly upon exposure to activated PBMC. HFE down-regulation was mediated by both CD4 and CD8 T lymphocytes, through production of soluble mediators, namely TNF and IFN-γ. These results suggest that the immune system may modulate tumor HFE expression in inflammatory conditions in order to regulate MHC I antigen presentation and promote tumor clearance.

Clinicopathological analysis of PD-L1 and PD-L2 expression in pulmonary squamous cell carcinoma: Comparison with tumor-infiltrating T cells and the status of oncogenic drivers

PURPOSE

Programmed cell death-1 (PD-1)/programmed cell death-ligand-1 (PD-L1) pathway-targeted immunotherapy has beneficial therapeutic effects in pulmonary squamous cell carcinoma (SqCC) patients. However, the expression patterns of PD-1 and PD-1 ligands (PD-Ls) in pulmonary SqCC remain unclear. Moreover, the association between the PD-1/PD-Ls pathway and the status of oncogenic drivers in pulmonary SqCC is unknown.

METHODS

PD-L1 and PD-L2 expression in tumor cells and the numbers of PD-1(+) and CD8(+) tumor-infiltrating lymphocytes (TILs) were examined in 331 resected SqCC tumors along with matched lymph node metastases from 77 cases using immunohistochemistry. EGFR and FGFR1 and MET expression and genetic status were also examined.

RESULTS

PD-L1 and PD-L2 expression was detected in 26.9% and 23.9% of the pulmonary SqCC samples, respectively. PD-L1 and PD-L2 expression was maintained or increased in the metastatic lymph node tumors in 81.1% and 93.5% of the 77 cases, respectively. The numbers of PD-1(+) and CD8(+) TILs were significantly positively correlated (P<0.001). Cases displaying high PD-L1 expression exhibited consistently high CD8(+) T cell infiltration (P<0.001), even in subgroup analyses according to age, smoking status, tumor size, lymph node metastasis, stage, and the EGFR, MET and FGFR1 status. Moreover, MET expression in the tumors was significantly correlated with high PD-L2 expression and increased PD-1(+) TILs (P=0.001 for both). Increased numbers of CD8(+) or PD-1(+) TILs were significantly associated with prolonged disease-free survival of these patients, whereas PD-L1 and PD-L2 expression had no significant prognostic implications.

CONCLUSION

PD-L1 and PD-L2 expression in pulmonary SqCC is associated with an increased number of CD8(+) TILs and increased MET expression, which might provide therapeutic insight into targeting the PD-1/PD-Ls pathway in pulmonary SqCC.

Intrinsic and extrinsic control of expression of the immunoregulatory molecule PD-L1 in epithelial cells and squamous cell carcinoma

Recent clinical results for PD-1 blockade therapy have demonstrated durable tumor control with minimal immune-related adverse effects. PD-L1 is induced in non-lymphoid tissue cells and tumor cells, in addition to tissue-recruiting immune cells, under inflammatory conditions triggered by several cytokines, especially IFN-γ, and exogenous stimuli delivered by pathogen-associated molecular patterns. Receptor-mediated signaling molecules that affect the cell cycle, proliferation, apoptosis, and survival (including NF-κB, MAPK, PI3K, mTOR, and JAK/STAT) are involved in PD-L1 induction. PD-L1 expression in tumor cells is also triggered by the signals described above, but in some instances, intrinsic cell alteration associated with carcinogenesis contributes to PD-L1 induction. The tumor suppressor genes PTEN and Lkb1 and epithelial-mesenchymal transition-related molecules are also involved in the regulation of PD-L1 expression. Notably, squamous cell carcinoma of the head and neck (SCCHN) often exhibits both host immunosuppression and cytogenetic alternations of tumor cells. Precise understanding of how PD-L1 expression is controlled will allow the development of effective approaches to PD-1 blockade therapy for patients with SCCHN.

PD-1 blockade in renal cell carcinoma: to equilibrium and beyond

The past several years have witnessed a resurgence of interest in cancer immunotherapy. The development of blocking antibodies against the inhibitory programmed death-1 (PD-1) pathway represents a clinical breakthrough in the treatment of solid tumors such as melanoma, and these agents show great promise in renal cell carcinoma (RCC). The early data have been surprising in that they demonstrate that blockade of a single immune checkpoint can elicit objective responses in patients with RCC, despite the recognized complexity of the immunosuppressive tumor microenvironment. Reinvigorating the patient's own immune cells to reactivate and to target the tumor has the potential advantages of more selective killing and thus decreased toxicity. In addition, checkpoint blockade immunotherapy has the advantage of inducing a memory response that is unattainable with our current cytotoxic and targeted therapies. This Crossroads overview will highlight the emerging investigation of PD-1 blockade in RCC and how this T cell-targeted strategy may thwart the tumor's escape mechanisms and shift the immune system/tumor balance back to a state of equilibrium and even to tumor elimination.

Blockade of the PD-1 pathway enhances the efficacy of adoptive cell therapy against cancer

The blockade of the PD-1 pathway can increase the production of interferon γ by tumor-specific T cells located within or in the proximity of the malignant lesion, thereby increasing the chemokine-dependent trafficking of immune effector cells. This can boost the efficacy of adoptive T-cell therapy to achieve superior antitumor responses.

CSF1/CSF1R blockade reprograms tumor-infiltrating macrophages and improves response to T-cell checkpoint immunotherapy in pancreatic cancer models

Cancer immunotherapy generally offers limited clinical benefit without coordinated strategies to mitigate the immunosuppressive nature of the tumor microenvironment. Critical drivers of immune escape in the tumor microenvironment include tumor-associated macrophages and myeloid-derived suppressor cells, which not only mediate immune suppression, but also promote metastatic dissemination and impart resistance to cytotoxic therapies. Thus, strategies to ablate the effects of these myeloid cell populations may offer great therapeutic potential. In this report, we demonstrate in a mouse model of pancreatic ductal adenocarcinoma (PDAC) that inhibiting signaling by the myeloid growth factor receptor CSF1R can functionally reprogram macrophage responses that enhance antigen presentation and productive antitumor T-cell responses. Investigations of this response revealed that CSF1R blockade also upregulated T-cell checkpoint molecules, including PDL1 and CTLA4, thereby restraining beneficial therapeutic effects. We found that PD1 and CTLA4 antagonists showed limited efficacy as single agents to restrain PDAC growth, but that combining these agents with CSF1R blockade potently elicited tumor regressions, even in larger established tumors. Taken together, our findings provide a rationale to reprogram immunosuppressive myeloid cell populations in the tumor microenvironment under conditions that can significantly empower the therapeutic effects of checkpoint-based immunotherapeutics.

Radiation-induced modulation of costimulatory and coinhibitory T-cell signaling molecules on human prostate carcinoma cells promotes productive antitumor immune interactions

We sought to determine if single-dose external beam radiation therapy (EBRT) could modulate the expression signature of T-cell costimulatory and coinhibitory molecules in human prostate cancer (PCa) cell lines in vitro. We investigated the functional impact of irradiated PCa cells with a modulated costimulatory profile on responder T-cell activity. We used three PCa cell lines (DU145, PC3, and LNCaP) and two epithelial cell lines from noncancerous prostate and lung tissue. After 72 hours of EBRT, surface expression of four immunostimulatory molecules (CD70, CD275/ICOSL, CD134L/OX40L, and CD137L/41BBL) and two immunosuppressive markers (CTLA-4/CD152 and PD-L1/CD274) were evaluated by flow cytometry. We evaluated the impact of several radiation doses and the longevity of modulated expression. We examined the functional impact of radiation-induced modulation of cancer cells by cytotoxic T cells (CTL) cytotoxicity and ELISPOT assay for interferon-gamma (IFN-γ) production. Last, we evaluated whether IFN-γ-induced PD-L1 expression could be reversed by EBRT. After 10 Gy EBRT, expression of OX40L and 41BBL increased in all three PCa cell lines; expression of CD70 and ICOSL increased in PC3 cells. Conversely, a decrease in PD-L1 expression in DU145 and PC3 cells was detectable up to 144 hours after EBRT. No PD-L1 was detected in LNCaP. Epithelial cells from normal prostate were not modulated by radiation. CTL cytolytic activity and IFN-γ production were enhanced by interaction with irradiated PCa cells. Finally, EBRT failed to prevent IFN-γ-induced upregulation of PD-L1. We demonstrate that a single dose of EBRT increased surface expression of costimulatory molecules and decreased the expression of coinhibitory molecules in human PCa cell lines. Changes in irradiated tumor cells led to functional enhancement of T-cell activity, despite EBRT failing to reduce IFN-γ-induced expression of PD-L1. These data suggest that combining radiotherapy with T-cell stimulating immunotherapy may be an attractive strategy for cancer treatment.

Immune alterations and immunotherapy prospects in head and neck cancer

INTRODUCTION

Several literature sources have suggested that subjects with head and neck squamous cell carcinoma (HNSCC) display significant abnormalities of immunocompetent cells and cytokine secretion. Serious side effects and only a limited success with traditional therapies in HNSCC dictate the need for newer therapies.

AREAS COVERED

This article comprehensively reviews the immune system alterations in HNSCC and the rationale behind various experimental immunotherapies, aiming at keeping this disease under control. Relevant publications were identified through the PubMed database search. The ongoing clinical trials regarding experimental immunotherapy agents in HNSCC were accessed at www.clinicaltrials.gov . The obtained information was thoroughly analyzed and systematized.

EXPERT OPINION

Important and severe immune defects including T-cell dysfunction, cytokine alterations and antigen presentation defects are present in patients with HNSCC. In addition, tumor microenvironment was shown to play a critical role in the HNSCC progression. These discoveries have triggered a growing interest in immunotherapy as a potential treatment strategy for HNSCC. Effective immunotherapy could avoid the toxic side effects plaguing the current management of HNSCC. It is also hoped that immunotherapy will have long-lasting effects due to induction of immunologic memory. Promising directions include nonspecific immune stimulation, targeting specific HNSCC tumor antigens and therapeutic vaccines among others. These new agents may expand the existing therapy options for HNSCC in future.

Inflammation promotes oral squamous carcinoma immune evasion via induced programmed death ligand-1 surface expression

The association between inflammation and cancer provides a new target for tumor biotherapy. The inflammatory cells and molecules within the tumor microenvironment have decisive dual roles in antitumor immunity and immune evasion. In the present study, phytohemagglutinin (PHA) was used to stimulate peripheral blood mononuclear cells (PBMCs) to simulate the tumor inflammatory microenvironment. The effect of immune cells and inflammatory cytokines on the surface expression of programmed cell death-1 ligand 1 (PD-L1) and tumor immune evasion was investigated using flow cytometry (FCM) and an in vivo xenotransplantation model. Based on the data, PHA-activated, but not resting, immune cells were able to promote the surface expression of PD-L1 in Tca8113 oral squamous carcinoma cells via the secretion of inflammatory cytokines, but not by cell-cell contact. The majority of the inflammatory cytokines had no significant effect on the proliferation, cell cycle progression and apoptosis of the Tca8113 cells, although they each induced the expression of PD-L1 in a dose-dependent manner. In total, 99% of the Tca8113 cells expressed PD-L1 following treatment with the supernatant of PHA-stimulated PBMCs. The PHA-supernatant pretreated Tca8113 cells unusually induced Tca8113 antigen-specific CD8⁺ T cell apoptosis in vitro and the evasion of antigen-specific T cell attraction in a nude mouse tumor-bearing model. These results indicate a new mechanism for the promotion of tumor immune evasion by the tumor inflammatory microenvironment

The PD-1/PD-L1 axis contributes to T-cell dysfunction in chronic lymphocytic leukemia

Chronic lymphocytic leukemia is marked by profound defects in T-cell function. Programmed death-1 is a receptor involved in tumor-mediated immunosuppression through binding of the PD-L1 ligand. Multiparametric flow cytometry and immunohistochemistry were used to study PD-1/PD-L1 expression. Functional assays were used to determine the involvement of the PD-1/PD-L1 axis in T-cell responses. PD-1 expression by CD4(+) and CD8(+) T lymphocytes was significantly higher in 117 chronic lymphocytic leukemia patients than in 33 donors of a comparable age. CD4(+) and CD8(+) T lymphocytes from chronic lymphocytic leukemia patients displayed increased numbers of effector memory and terminally differentiated cells, respectively, when compared to controls. The number of effector memory CD4(+) and terminally differentiated CD8(+) lymphocytes positively associated with a more advanced stage of disease, treatment requirements and unfavorable genomic aberrations. Furthermore, leukemic lymphocytes expressed higher levels of PD-L1 than circulating B lymphocytes from normal donors. PD-1 and PD-L1 surface expression spiked in proliferating T and B lymphocytes, suggesting that this interaction works efficiently in activated environments. Within chronic lymphocytic leukemia proliferation centers in the lymph node, CD4(+)/PD-1(+) T lymphocytes were found to be in close contact with PD-L1(+) chronic lymphocytic leukemia cells. Lastly, functional experiments using recombinant soluble PD-L1 and blocking antibodies indicated that this axis contributes to the inhibition of IFN-γ production by CD8(+) T cells. These observations suggest that pharmacological manipulation of the PD-1/PD-L1 axis may contribute to restoring T-cell functions in the chronic lymphocytic leukemia microenvironment.

An in vivo immunotherapy screen of costimulatory molecules identifies Fc-OX40L as a potent reagent for the treatment of established murine gliomas

PURPOSE

We tested the combination of a tumor lysate vaccine with a panel of costimulatory molecules to identify an immunotherapeutic approach capable of curing established murine gliomas.

EXPERIMENTAL DESIGN

Glioma-bearing mice were primed with a tumor lysate vaccine, followed by systemic administration of the following costimulatory ligands: OX40L, CD80, 4-1BBL, and GITRL, which were fused to the Fc portion of human immunoglobulin. Lymphocytes and mRNA were purified from the brain tumor site for immune monitoring studies. Numerous variations of the vaccine and Fc-OX40L regimen were tested alone or in combination with temozolomide.

RESULTS

Lysate vaccinations combined with Fc-OX40L led to the best overall survival, yielding cure rates of 50% to 100% depending on the timing, regimen, and combination with temozolomide. Cured mice that were rechallenged with glioma cells rejected the challenge, showing immunologic memory. Lymphocytes isolated from the draining lymph nodes of vaccine/Fc-OX40L-treated mice had superior tumoricidal function relative to all other groups. Vaccine/Fc-OX40L-treated mice exhibited a significant increase in proliferation of brain-infiltrating CD4 and CD8 T cells, as indicated by Ki67 staining. Fc-OX40L had single-agent activity in transplanted and spontaneous glioma models, and the pattern of inflammatory gene expression in the tumor predicted the degree of therapeutic response.

CONCLUSIONS

These data show that Fc-OX40L has unique and potent activity against experimental gliomas and warrants further testing.