PD-L1 and PD-L2 are differentially regulated by Th1 and Th2 cells

Preclinical investigation of combined gene-mediated cytotoxic immunotherapy and immune checkpoint blockade in glioblastoma

Background

Combined immunotherapy approaches are promising cancer treatments. We evaluated anti-programmed cell death protein 1 (PD-1) treatment combined with gene-mediated cytotoxic immunotherapy (GMCI) performed by intratumoral injection of a prodrug metabolizing nonreplicating adenovirus (AdV-tk), providing in situ chemotherapy and immune stimulation.

Methods

The effects of GMCI on PD ligand 1 (PD-L1) expression in glioblastoma were investigated in vitro and in vivo. The efficacy of the combination was investigated in 2 syngeneic mouse glioblastoma models (GL261 and CT-2A). Immune infiltrates were analyzed by flow cytometry.

Results

GMCI upregulated PD-L1 expression in vitro and in vivo. Both GMCI and anti-PD-1 increased intratumoral T-cell infiltration. A higher percentage of long-term survivors was observed in mice treated with combined GMCI/anti-PD-1 relative to single treatments. Long-term survivors were protected from tumor rechallenge, demonstrating durable memory antitumor immunity. GMCI led to elevated interferon gamma positive T cells and a lower proportion of exhausted double positive PD1+TIM+CD8+ T cells. GMCI also increased PD-L1 levels on tumor cells and infiltrating macrophages/microglia. Our data suggest that anti-PD-1 treatment improves the effectiveness of GMCI by overcoming interferon-induced PD-L1-mediated inhibitory signals, and GMCI improves anti-PD-1 efficacy by increasing tumor-infiltrating T-cell activation.

Conclusions

Our data show that the GMCI/anti-PD-1 combination is well tolerated and effective in glioblastoma mouse models. These results support evaluation of this combination in glioblastoma patients.

Combination of Sunitinib and PD-L1 Blockade Enhances Anticancer Efficacy of TLR7/8 Agonist-Based Nanovaccine

Cancer vaccines composed of tumor-associated antigens (TAAs) and toll-like receptor (TLR) agonists have shown promising antitumor efficacy in preclinical studies by generating antigen-specific CD8 T cells, but translation of cancer vaccines to the clinic has been limited due to variables responses and development of resistance. The tumor microenvironment deploys various immune escape mechanisms that neutralize CD8 T cell-mediated tumor rejection. Therefore, we hypothesized that modulation of the tumor microenvironment can augment CD8 T cell activation and enhance therapeutic efficacy of cancer vaccines. To accomplish this, we aimed to eliminate immune suppressive cells and block their inhibitory signaling. Combination of the tyrosine kinase inhibitor (TKI) sunitinib with a nanoparticle-based cancer vaccine (nanovaccine) resulted in the reduction of immune-suppressive myeloid-derived suppressive cells (MDSCs) and regulatory T cells (Tregs). Blockade of programmed death-ligand 1 (PD-L1) using anti-PD-L1 antibody was used to reduce CD8 T cell exhaustion. Combination of nanovaccine+sunitinib+PD-L1 antibody treatment reduced PD-L1^high M2 macrophages and MDSCs and upregulated activation of CD8 T cells in the tumor. Nanovaccine+sunitinib+PD-L1 antibody treatment also stimulated antigen-specific CD8 T cell response, which led to improved therapeutic efficacy in MB49 and B16F10 murine tumor models. These results suggest that modulation of tumor microenvironment using sunitinib and PD-L1 blockade can significantly enhance the antitumor efficacy of cancer nanovaccine.

PD-1/PD-L1 Pathway Modulates Macrophage Susceptibility to Mycobacterium tuberculosis Specific CD8+ T cell Induced Death

CD8⁺T cells contribute to tuberculosis (TB) infection control by inducing death of infected macrophages. Mycobacterium tuberculosis (Mtb) infection is associated with increased PD-1/PD-L1 expression and alternative activation of macrophages. We aimed to study the role of PD-1 pathway and macrophage polarization on Mtb-specific CD8⁺T cell-induced macrophage death. We observed that both PD-L1 on CD14⁺ cells and PD-1 on CD8⁺T cells were highly expressed at the site of infection in pleurisy TB patients’ effusion samples (PEMC). Moreover, a significant increase in CD8⁺T cells’ Mtb-specific degranulation from TB-PEMC vs. TB-PBMC was observed, which correlated with PD-1 and PDL-1 expression. In an in vitro model, M1 macrophages were more susceptible to Mtb-specific CD8⁺T cells’ cytotoxicity compared to M2a macrophages and involved the transfer of cytolytic effector molecules from CD8⁺T lymphocytes to target cells. Additionally, PD-L1 blocking significantly increased the in vitro Ag-specific CD8⁺T cell cytotoxicity against IFN-γ-activated macrophages but had no effect over cytotoxicity on IL-4 or IL-10-activated macrophages. Interestingly, PD-L1 blocking enhanced Mtb-specific CD8⁺ T cell killing of CD14⁺ cells from human tuberculous pleural effusion samples. Our data indicate that PD-1/PD-L1 pathway modulates antigen-specific cytotoxicity against M1 targets in-vitro and encourage the exploration of checkpoint blockade as new adjuvant for TB therapies.

Helicobacter pylori Deregulates T and B Cell Signaling to Trigger Immune Evasion

Helicobacter pylori is a prevalent human pathogen that successfully establishes chronic infection, which leads to clinically significant gastric diseases including chronic gastritis, peptic ulcer disease (PUD), and gastric cancer (GC). H. pylori is able to produce a persistent infection due in large part to its ability to hijack the host immune response. The host adaptive immune response is activated to strategically and specifically attack pathogens and normally clears them from the infected host. Since B and T lymphocytes are central mediators of adaptive immunity, in this chapter we review their development and the fundamental mechanisms regulating their activation in order to understand how some of the normal processes are subverted by H. pylori. In this review, we place particular emphasis on the CD4⁺ T cell responses, their subtypes, and regulatory mechanisms because of the expanding literature in this area related to H. pylori. T lymphocyte differentiation and function are finely orchestrated through a series of cell-cell interactions, which include immune checkpoint receptors. Among the immune checkpoint receptor family, there are some with inhibitory properties that are exploited by tumor cells to facilitate their immune evasion. Gastric epithelial cells (GECs), which act as antigen-presenting cells (APCs) in the gastric mucosa, are induced by H. pylori to express immune checkpoint receptors known to sway T lymphocyte function and thus circumvent effective T effector lymphocyte responses. This chapter reviews these and other mechanisms used by H. pylori to interfere with host immunity in order to persist.

Trichloroethene metabolite dichloroacetyl chloride induces apoptosis and compromises phagocytosis in Kupffer Cells: Activation of inflammasome and MAPKs

Exposure to trichloroethene (TCE), an occupational and ubiquitous environmental contaminant, is associated with the development of several autoimmune diseases, including autoimmune hepatitis (AIH). However, mechanisms contributing to TCE-mediated AIH are not known. Earlier, we have shown that dichloroacetyl chloride (DCAC), one of the reactive metabolites of TCE with strong acylating capability, can elicit an autoimmune response at much lower dose than TCE in female MRL+/+ mice. Furthermore, Kupffer cells (KCs), the liver resident macrophages, are crucial for hepatic homeostasis, but can also participate in the immunopathogenesis of AIH. However, contribution of KCs in TCE-mediated AIH and the underlying mechanisms are not understood. We hypothesized that increased apoptosis and delayed clearance of apoptotic bodies, due to compromised KC function, will result in the breakdown of self-tolerance, autoimmunity, and ultimately AIH. Therefore, using an in vitro model of immortalized mouse KCs, we investigated the contribution of DCAC in TCE-mediated AIH. KCs were treated with different concentrations of DCAC and apoptosis was measured by Annexin V and PI staining. Also, the impact of DCAC on phagocytic potential of KCs was evaluated. Furthermore, markers of inflammasome (NLRP3 and caspase1) were analyzed by real-time PCR and Western blot analysis. DCAC treatment resulted in significantly increased early and late-stage apoptosis, accompanied with inflammasome activation (NLRP3 increases). DCAC treatment resulted in decreased phagocytic function of KCs in a dose-dependent manner, with reduced MFG-E8 levels (phagocytotic function). Furthermore, DCAC exposure led to induction of phos-ERK and phos-AKT signaling. These findings suggest that DCAC induces apoptosis and inflammasome activation, while compromising the phagocytic function of KCs. Our data support that increased apoptosis and impaired KC function by DCAC could be contributory to TCE-mediated AIH.

PD-1 and PD-L1 regulate cellular immunity in canine visceral leishmaniasis

PD-1 is a negative costimulator of chronic infectious diseases In this study, we investigated the expression of PD-1 and its ligands in the spleen of dogs with visceral leishmaniasis and lymphoproliferative response to soluble antigen, in lymph node cells in the presence or absence of antibodies blocking PD-1 and its ligands. Our results showed expression of PD-1 and its ligands is higher after L. infantum infection and in the spleen of infected dogs, PD-1 blockage was able to restore the antigen-dependent lymphoproliferative response and regulated production of the cytokines IL-4 and IL-10 and NO production. We concluded that L. infantum infection modulates PD-1 and its ligands expression in canine VL and that blockage of PD-1 restores the immune response. Thus, blockage of PD-1 is a target for therapeutic drug development.

Sex- and Development-Dependent Responses of Rat Microglia to Pro- and Anti-inflammatory Stimulation

Addressing potential sex differences in pre-clinical studies is crucial for developing therapeutic interventions. Although sex differences have been reported in epidemiological studies and from clinical experience, most pre-clinical studies of neuroinflammation use male rodents; however, sexual dimorphisms in microglia might affect the CNS inflammatory response. Developmental changes are also important and, in rodents, there is a critical period of sexual brain differentiation in the first 3 weeks after birth. We compared rat microglia from sex-segregated neonates (P1) and at about the time of weaning (P21). To study transitions from a basal homeostatic state (untreated), microglia were subjected to a pro-inflammatory (IFNγ + TNFα) or anti-inflammatory (IL-4) stimulus. Responses were compared by quantifying changes in nitric oxide production, migration, and expression of nearly 70 genes, including inflammatory mediators and receptors, inflammasome molecules, immune modulators, and genes that regulate microglial physiological functions. No sex differences were seen in transcriptional responses in either age group but the IL-4-evoked migration increase was larger in male cells at both ages. Protein changes for the hallmark molecules, NOS2, COX-2, PYK2 and CD206 correlated with mRNA changes. P1 and P21 microglia showed substantial differences, including expression of genes related to developmental roles. That is, P21 microglia had a more mature phenotype, with higher basal and stimulated levels of many inflammatory genes, while P1 cells had higher expression of phagocytosis-related molecules. Nevertheless, cells of both ages responded to IL-4 and IFNγ + TNFα. We examined the Kv1.3 potassium channel (a potential target for modulating neuroinflammation) and the Kir2.1 channel, which regulate several microglia functions. Kv1.3 mRNA (Kcna3) was higher at P21 under all conditions and male P21 cells had higher mRNA and Kv currents in response to IFNγ + TNFα. Overall, numerous transcriptional and functional responses of microglia changed during the first 3 weeks after birth but few sex-dependent changes were seen.

Role of the HDAC6/STAT3 pathway in regulating PD-L1 expression in osteosarcoma cell lines

Histone deacetylases (HDACs), initially described as histone modifiers, have more recently been verified to target various other proteins unrelated to the chromatin environment. On this basis, findings of the current study demonstrates that the pharmacological or genetic abrogation of HDAC6 in osteosarcoma cell lines down-regulates the expression of program death receptor ligand-1 (PD-L1), an important co-stimulatory molecule expressed in cancer cells, which activates the inhibitory regulatory pathway PD-1 in T cells. As shown by our results, the mechanism by which HDAC6 regulated PD-L1 expression was mediated by the transcription factor STAT3. In addition, we observed that selective HDAC6 inhibitors could inhibit tumor progression in vivo. Crucially, these results provide an essential pre-clinical rationale and justification for the necessity of further research on HDAC6 inhibitors as potential immuno-modulatory agents in osteosarcoma.

Loss of VGLL4 suppresses tumor PD-L1 expression and immune evasion

Targeting immune checkpoints, such as PD-L1 and its receptor PD-1, has opened a new avenue for treating cancers. Understanding the regulatory mechanism of PD-L1 and PD-1 will improve the clinical response rate and efficacy of PD-1/PD-L1 blockade in cancer patients and the development of combinatorial strategies. VGLL4 inhibits YAP-induced cell proliferation and tumorigenesis through competition with YAP for binding to TEADs. However, whether VGLL4 has a role in anti-tumor immunity is largely unknown. Here, we found that disruption of Vgll4 results in potent T cell-mediated tumor regression in murine syngeneic models. VGLL4 deficiency reduces PD-L1 expression in tumor cells. VGLL4 interacts with IRF2BP2 and promotes its protein stability through inhibiting proteasome-mediated protein degradation. Loss of IRF2BP2 results in persistent binding of IRF2, a transcriptional repressor, to PD-L1 promoter. In addition, YAP inhibits IFNγ-inducible PD-L1 expression partially through suppressing the expression of VGLL4 and IRF1 by YAP target gene miR-130a. Our study identifies VGLL4 as an important regulator of PD-L1 expression and highlights a central role of VGLL4 and YAP in the regulation of tumor immunity.

MERTK inhibition alters the PD-1 axis and promotes anti-leukemia immunity

MERTK is ectopically expressed and promotes survival in acute lymphoblastic leukemia (ALL) cells and is thus a potential therapeutic target. Here we demonstrate both direct therapeutic effects of MERTK inhibition on leukemia cells and induction of anti-leukemia immunity via suppression of the coinhibitory PD-1 axis. A MERTK-selective tyrosine kinase inhibitor, MRX-2843, mediated therapeutic anti-leukemia effects in immunocompromised mice bearing a MERTK-expressing human leukemia xenograft. In addition, inhibition of host MERTK by genetic deletion (Mertk-/- mice) or treatment with MRX-2843 significantly decreased tumor burden and prolonged survival in immune-competent mice inoculated with a MERTK-negative ALL, suggesting immune-mediated therapeutic activity. In this context, MERTK inhibition led to significant decreases in expression of the coinhibitory ligands PD-L1 and PD-L2 on CD11b+ monocytes/macrophages in the leukemia microenvironment. Furthermore, although T cells do not express MERTK, inhibition of MERTK indirectly decreased PD-1 expression on CD4+ and CD8+ T cells and decreased the incidence of splenic FOXP3+ Tregs at sites of leukemic infiltration, leading to increased T cell activation. These data demonstrate direct and immune-mediated therapeutic activities in response to MERTK inhibition in ALL models and provide validation of a translational agent targeting MERTK for modulation of tumor immunity.

SMAD4 promotes TGF-β-independent NK cell homeostasis and maturation and antitumor immunity

SMAD4 is the only common SMAD in TGF-β signaling that usually impedes immune cell activation in the tumor microenvironment. However, we demonstrated here that selective deletion of Smad4 in NK cells actually led to dramatically reduced tumor cell rejection and augmented tumor cell metastases, reduced murine CMV clearance, as well as impeded NK cell homeostasis and maturation. This was associated with a downregulation of granzyme B (Gzmb), Kit, and Prdm1 in Smad4-deficient NK cells. We further unveiled the mechanism by which SMAD4 promotes Gzmb expression. Gzmb was identified as a direct target of a transcriptional complex formed by SMAD4 and JUNB. A JUNB binding site distinct from that for SMAD4 in the proximal Gzmb promoter was required for transcriptional activation by the SMAD4-JUNB complex. In a Tgfbr2 and Smad4 NK cell-specific double-conditional KO model, SMAD4-mediated events were found to be independent of canonical TGF-β signaling. Our study identifies and mechanistically characterizes unusual functions and pathways for SMAD4 in governing innate immune responses to cancer and viral infection, as well as NK cell development.

Gene expression profile of peripheral blood mononuclear cells may contribute to the identification and immunological classification of breast cancer patients

BACKGROUND

It has been reported that the gene expression profile of peripheral blood mononuclear cells (PBMCs) exhibits a unique gene expression signature in several types of cancer. In this study, we aimed to explore the breast cancer patient-specific gene expression profile of PBMCs and discuss immunological insight on host antitumor immune responses.

METHODS

We comprehensively analyzed the gene expression of PBMCs by RNA sequencing in the breast cancer patients as compared to that of healthy volunteers (HVs). Pathway enrichment analysis was performed on MetaCore^tm to search the molecular pathways associated with the gene expression profile of PBMCs in cancer patients compared with HVs.

RESULTS

We found a significant unique gene expression signature, such as the Toll-like receptor (TLR) 3- and TLR4-induced Toll/interleukin-1 receptor domain-containing adapter molecule 1 (TICAM1)-specific signaling pathway in the breast cancer patients as compared to that of healthy volunteers. Distinctive immunological gene expression profiles also showed the possibility of classifying breast cancer patients into subgroups such as T-cell inhibitory and monocyte-activating groups independent of known phenotypes of breast cancer.

CONCLUSIONS

These preliminary findings suggest that evaluation of gene expression patterns of PBMCs might be both a less invasive diagnostic procedure and a useful way to reveal immunological insight of breast cancer, including biomarkers for cancer immunotherapy, such as immune checkpoint inhibitor therapy.

Differential regulation of PD-L1 expression by immune and tumor cells in NSCLC and the response to treatment with atezolizumab (anti-PD-L1)

Programmed death-ligand 1 (PD-L1) expression on tumor cells and tumor-infiltrating immune cells is regulated by distinct mechanisms and has nonredundant roles in regulating anticancer immunity, and PD-L1 on both cell types is important for predicting best response to atezolizumab in non-small cell lung cancer.

Programmed death-ligand 1 (PD-L1) expression on tumor cells (TCs) by immunohistochemistry is rapidly gaining importance as a diagnostic for the selection or stratification of patients with non-small cell lung cancer (NSCLC) most likely to respond to single-agent checkpoint inhibitors. However, at least two distinct patterns of PD-L1 expression have been observed with potential biological and clinical relevance in NSCLC: expression on TC or on tumor-infiltrating immune cells (ICs). We investigated the molecular and cellular characteristics associated with PD-L1 expression in these distinct cell compartments in 4,549 cases of NSCLC. PD-L1 expression on IC was more prevalent and likely reflected IFN-γ–induced adaptive regulation accompanied by increased tumor-infiltrating lymphocytes and effector T cells. High PD-L1 expression on TC, however, reflected an epigenetic dysregulation of the PD-L1 gene and was associated with a distinct histology described by poor immune infiltration, sclerotic/desmoplastic stroma, and mesenchymal molecular features. Importantly, durable clinical responses to atezolizumab (anti–PD-L1) were observed in patients with tumors expressing high PD-L1 levels on either TC alone [40% objective response rate (ORR)] or IC alone (22% ORR). Thus, PD-L1 expression on TC or IC can independently attenuate anticancer immunity and emphasizes the functional importance of IC in regulating the antitumor T cell response.

PDL1 is expressed in the islets of people with type 1 diabetes and is up-regulated by interferons-α and-γ via IRF1 induction

Background

Antibodies targeting PD-1 and its ligand PDL1 are used in cancer immunotherapy but may lead to autoimmune diseases, including type 1 diabetes (T1D). It remains unclear whether PDL1 is expressed in pancreatic islets of people with T1D and how is it regulated.

Methods

The expression of PDL1, IRF1, insulin and glucagon was evaluated in samples of T1D donors by immunofluorescence. Cytokine-induced PDL1 expression in the human beta cell line, EndoC-βH1, and in primary human pancreatic islets was determined by real-time RT-PCR, flow cytometry and Western blot. Specific and previously validated small interference RNAs were used to inhibit STAT1, STAT2, IRF1 and JAK1 signaling. Key results were validated using the JAK inhibitor Ruxolitinib.

Findings

PDL1 was present in insulin-positive cells from twelve T1D individuals (6 living and 6 deceased donors) but absent from insulin-deficient islets or from the islets of six non-diabetic controls. Interferons-α and -γ, but not interleukin-1β, induced PDL1 expression in vitro in human islet cells and EndoC-βH1 cells. Silencing of STAT1 or STAT2 individually did not prevent interferon-α-induced PDL1, while blocking of JAKs – a proposed therapeutic strategy for T1D – or IRF1 prevented PDL1 induction.

Interpretation

These findings indicate that PDL1 is expressed in beta cells from people with T1D, possibly to attenuate the autoimmune assault, and that it is induced by both type I and II interferons via IRF1.

[Physiopathological mechanisms of immune-related adverse events induced by anti-CTLA-4, anti-PD-1 and anti-PD-L1 antibodies in cancer treatment]

Recently, the emergence of anti-CTLA-4 and anti-PD-1/PD-L1 antibodies called immune check-point inhibitors (ICPI) has modified the landscape of anti-cancer treatments. These therapeutics are associated with immune related adverse events that affect many organs, most commonly skin, digestive tract, endocrine glands and lungs. This review summarizes the main physiopathological hypotheses on the mechanisms of these toxicities. In most cases, the T lymphocytes hyperactivation induced by ICPI generates a specific response directed against tumor antigens, leading to anti-tumor activity in tumor tissues but also side effects in normal tisues called "on-target". The CD8+ cytotoxic T lymphocytes-mediated cell lysis induces the release of neoantigens, tumor antigens and auto-antigens from normal tissues, respectively. This phenomenon called "epitope spreading" leads to diversification of the T cell repertoire and thus to reduced immune tolerance, which is exacerbated by inhibition of regulator T lymphocytes. Furthermore, the predominant activation of Th1 and Th17T lymphocytes mediated by ICPI induced an increased production of pro-inflammatory cytokines such as interferon-γ (IFNγ) and interleukine-17 (IL-17). These two mechanisms are responsible for the so called "off-target" toxicities. The roles of cross-reactivity with the intestinal microbiota, hypersensitivity and the specific effect of PD-L2 remain to be determined. Better knowledge of these mechanisms will improve patient care and help predict patients at risk of developing severe toxicities to ICPIs.

Immunomodulators targeting the PD-1/PD-L1 protein-protein interaction: From antibodies to small molecules

Cancer immunotherapy has made great strides in the recent decade, especially in the area of immune checkpoint blockade. The outstanding efficacy, prolonged durability of effect, and rapid assimilation of anti-PD-1 and anti-PD-L1 monoclonal antibodies in clinical practice have been nothing short of a medical breakthrough in the treatment of numerous malignancies. The major advantages of these therapeutic antibodies over their small molecule counterparts have been their high binding affinity and target specificity. However, antibodies do have their flaws including immune-related toxicities, inadequate pharmacokinetics and tumor penetration, and high cost burden to manufacturers and consumers. These limitations hinder broader clinical applications of the antibodies and have heightened interests in developing the alternative small molecule platform that includes peptidomimetics and peptides to target the PD-1/PD-L1 immune checkpoint system. The progress on these small molecule alternatives has been relatively slow compared to that of the antibodies. Fortunately, recent structural studies of the interactions among PD-1, PD-L1, and their respective antibodies have revealed key hotspots on PD-1 and PD-L1 that may facilitate drug discovery efforts for small molecule immunotherapeutics. This review is intended to discuss key concepts in immuno-oncology, describe the successes and shortcomings of PD-1/PD-L1 antibody-based therapies, and to highlight the recent development of small molecule inhibitors of the PD-1/PD-L1 protein-protein interaction.

Proteomic Profiling of Native Unpassaged and Culture-Expanded Mesenchymal Stromal Cells (MSC)

Human culture-expanded mesenchymal stromal cells (MSC) are being considered for multiple therapeutic applications because of their regenerative and anti-inflammatory properties. Although a large number of MSC can be propagated from a small initial sample, several lines of evidence indicate that MSC lose their immunosuppressive and regenerative potency aftaer multiple passages. In this report, we use the FACSCAP Lyoplate proteomic analysis system to detect changes in cell surface protein expression of CD45^- /CD31^- /CD34^- /CD73⁺ /CD105⁺ stromal cells in unpassaged bone marrow (BM) and through 10 serial culture passages. We provide for the first time a detailed characterization of native unpassaged BM MSC (0.08% of BM mononuclear cells) as well as the changes that occur during the initial expansion. Adipogenic and osteogenic differentiative potential was determined though the serial passages and correlated with immunophenotypic changes and senescence. Among the most prominent were striking decreases in Fas ligand, CD98, CD205, and CD106, accompanied by a gain in the expression of CD49c, CD63, CD98, and class 1 and class 2 major histocompatibility complex (MHC) molecules. Other molecules that are down-modulated with later passage include CD24, CD54, CD59, CD243/P-glycoprotein, and CD273/PD-L2. Early senescence, as defined by the loss of replicative capacity occurring with the loss of differentiative capacity, increase in CDKN2A p16, and increased time to confluence, was accompanied by loss of the motility-associated metalloproteinase CD10 and the proliferation-associated transferrin receptor CD71. Among the strongest statistical associations were loss of MAC-inhibitory protein/CD59, loss of ICAM-1/CD54, and increase in CDKN2A as a function of increasing passage, as well as increased CD10 expression with adipogenic and osteogenic capacities. The data provide a clear set of markers that can be used to assess MSC quality. We suggest that clinically relevant numbers of highly functional low passage MSC can be manufactured starting with large quantities of BM, which are readily available from cadaveric organ donors.

Cancer Immunotherapy in Diffuse Large B-Cell Lymphoma

Remarkable progress has been made in the field of cancer immunotherapy in the past few years. Immunotherapy has become a standard treatment option for patients with various cancers, including melanoma, lymphoma, and carcinomas of the lungs, kidneys, bladder, and head and neck. Promising immunotherapy approaches, such as chimeric antigen receptor (CAR) T cell therapy and therapeutic blockade of immune checkpoints, in particular cytotoxic T lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 pathway (PD-1/PD-L1), have boosted the development of new therapeutic regimens for patients with cancer. Immunotherapeutic strategies for diffuse large B-cell lymphoma (DLBCL) include monoclonal anti-CD20 antibody (rituximab), monoclonal anti-PD-1 antibodies (nivolumab and pembrolizumab), monoclonal anti-PD-L1 antibodies (avelumab, durvalumab, and atezolizumab) and chimeric antigen receptor (CAR) T cell therapy. In this review, we outline the latest highlights and progress in using immunotherapy to treat patients with DLBCL, with a focus on the therapeutic blockade of PD-1/PD-L1 and CAR T cell therapy in DLBCL. We also discuss current clinical trials of PD-1/PD-L1 and CAR T cell therapy and review the challenges and opportunities of using immunotherapy for the treatment of DLBCL.

Valproic acid attenuates immunosuppressive function of myeloid-derived suppressor cells

Immune checkpoint blockade (ICB) is a promising novel therapy for multiple cancer types; however, most patients show limited or no clinical response. Accumulating evidence indicates that myeloid-derived suppressor cells (MDSCs) are a major factor responsible for immunosuppression in patients with cancer. Therefore, identifying effective therapies that deplete or modulate MDSCs is essential. In this study, we focus on the anticonvulsant drug valproic acid (VPA), which has additional activities including anticancer and immunoregulation by inhibition of histone deacetylases. We showed that VPA decreased the proportion of polymorphonuclear (PMN)-MDSCs in vitro and showed for the first time that VPA greatly attenuated the immunosuppressive function of MDSCs in a dose-dependent manner. Moreover, we demonstrated that in vitro differentiated VPA-conditioned MDSCs exhibited impaired ability to stimulate tumor progression in vivo. We also showed the possible involvement of several mechanisms in the VPA-induced attenuation of the immunosuppressive function of MDSCs, including the interleukin-4 receptor-α (IL-4Rα)/arginase axis, programmed cell death 1 ligand 1 (PD-L1) and toll-like receptor 4 (TLR4) signaling pathways, and retinoblastoma 1 (Rb1) derepression. This research highlights the potential of combining VPA with ICB in cancer treatment.

Fundamental Mechanisms of Immune Checkpoint Blockade Therapy

Immune checkpoint blockade is able to induce durable responses across multiple types of cancer, which has enabled the oncology community to begin to envision potentially curative therapeutic approaches. However, the remarkable responses to immunotherapies are currently limited to a minority of patients and indications, highlighting the need for more effective and novel approaches. Indeed, an extraordinary amount of preclinical and clinical investigation is exploring the therapeutic potential of negative and positive costimulatory molecules. Insights into the underlying biological mechanisms and functions of these molecules have, however, lagged significantly behind. Such understanding will be essential for the rational design of next-generation immunotherapies. Here, we review the current state of our understanding of T-cell costimulatory mechanisms and checkpoint blockade, primarily of CTLA4 and PD-1, and highlight conceptual gaps in knowledge.Significance: This review provides an overview of immune checkpoint blockade therapy from a basic biology and immunologic perspective for the cancer research community. Cancer Discov; 8(9); 1069-86. ©2018 AACR.

Prognostic role of pretreatment circulating MDSCs in patients with solid malignancies: A meta-analysis of 40 studies

Myeloid-derived suppressor cells (MDSCs) have been shown to contribute to tumor progression, mainly through immune suppression. Inverse correlations have been observed between MDSC levels and patient survival for various malignancies. The purpose of this meta-analysis was to evaluate the prognostic value of pretreatment circulating MDSCs. We searched MEDLINE and EMBASE from their inceptions to September 2017 to identify relevant articles. Using a fixed or random effects model, pooled hazard ratios (HRs) were estimated for overall survival (OS) and combined disease-free survival, progression-free survival, and recurrence-free survival (DFS/PFS/RFS). A total of 40 studies comprising 2721 were included. For solid tumors, high levels of pretreatment circulating MDSCs were significantly associated with worse OS (HR = 1.796, 95% CI = 1.587-2.032) and DFS/PFS/RFS (HR = 2.459, 95% CI = 2.018-2.997). Breast cancer showed the largest association between high MDSC levels and worse OS (pooled HR = 3.053). Elevated MDSCs were also associated with worse OS for mixed-stage tumors (pooled HR = 1.659) and advanced-stage tumors (pooled HR = 2.337). Furthermore, both monocytic-MDSCs (M-MDSCs) and granulocytic or polymorphonuclear (PMN-MDSCs) showed negative associations with survival outcomes. Overall, high levels of pretreatment circulating MDSCs negatively influenced survival in most cancers. Pretreatment circulating MDSCs should be taken into account to further improve prognostic evaluation and develop novel therapeutic strategies.

Keeping Tumors in Check: A Mechanistic Review of Clinical Response and Resistance to Immune Checkpoint Blockade in Cancer

Immune checkpoints are a diverse set of inhibitory signals to the immune system that play a functional role in adaptive immune response and self-tolerance. Dysregulation of these pathways is a vital mechanism in the avoidance of immune destruction by tumor cells. Immune checkpoint blockade (ICB) refers to targeted strategies to disrupt the tumor co-opted immune suppression to enhance anti-tumor immunity. Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death 1 (PD-1) are two immune checkpoints that have the widest range of antibody-based therapies. These therapies have gone from promising approaches to Food and Drug Administration-approved first- and second-line agents for a number of immunogenic cancers. The burgeoning investigations of ICB efficacy in blood and solid cancers have underscored the importance of identifying the predictors of response and resistance to ICB. Identification of response correlates is made complicated by the observations of mixed reactions, or different responses in multiple lesions from the same patient, and delayed responses that can occur over a year after the induction therapy. Factors that can influence response and resistance in ICB can illuminate underlying molecular mechanisms of immune activation and suppression. These same response predictors can guide the identification of patients who would benefit from ICB, reduce off-target immune-relate adverse events, and facilitate the use of combinatorial therapies to increase efficacy. Here we review the underlying principles of immune checkpoint therapy and results of single-agent ICB clinical trials, and summarize the predictors of response and resistance.

Macrophage Activation and Functions during Helminth Infection: Recent Advances from the Laboratory Mouse

Macrophages are highly plastic innate immune cells that adopt an important diversity of phenotypes in response to environmental cues. Helminth infections induce strong type 2 cell-mediated immune responses, characterized among other things by production of high levels of interleukin- (IL-) 4 and IL-13. Alternative activation of macrophages by IL-4 in vitro was described as an opposite phenotype of classically activated macrophages, but the in vivo reality is much more complex. Their exact activation state as well as the role of these cells and associated molecules in type 2 immune responses remains to be fully understood. We can take advantage of a variety of helminth models available, each of which have their own feature including life cycle, site of infection, or pathological mechanisms influencing macrophage biology. Here, we reviewed the recent advances from the laboratory mouse about macrophage origin, polarization, activation, and effector functions during parasitic helminth infection.

Under-Evaluated or Unassessed Pathogenic Pathways in Autoimmune Hepatitis and Implications for Future Management

Autoimmune hepatitis is a consequence of perturbations in homeostatic mechanisms that maintain self-tolerance but are incompletely understood. The goals of this review are to describe key pathogenic pathways that have been under-evaluated or unassessed in autoimmune hepatitis, describe insights that may shape future therapies, and encourage investigational efforts. The T cell immunoglobulin mucin proteins constitute a family that modulates immune tolerance by limiting the survival of immune effector cells, clearing apoptotic bodies, and expanding the population of granulocytic myeloid-derived suppressor cells. Galectins influence immune cell migration, activation, proliferation, and survival, and T cell exhaustion can be induced and exploited as a possible management strategy. The programmed cell death-1 protein and its ligands comprise an antigen-independent inhibitory axis that can limit the performance of activated T cells by altering their metabolism, and epigenetic changes can silence pro-inflammatory genes or de-repress anti-inflammatory genes that affect disease severity. Changes in the intestinal microbiota and permeability of the intestinal mucosal barrier can be causative or consequential events that affect the occurrence and phenotype of immune-mediated disease, and they may help explain the female propensity for autoimmune hepatitis. Perturbations within these homeostatic mechanisms have been implicated in experimental models and limited clinical experiences, and they have been favorably manipulated by monoclonal antibodies, recombinant molecules, pharmacological agents or dietary supplements. In conclusion, pathogenic mechanisms that have been implicated in other systemic immune-mediated and liver diseases but under-evaluated or unassessed in autoimmune hepatitis warrant consideration and rigorous evaluation.

Clinical relevance of PD-L1 and PD-L2 overexpression in patients with esophageal squamous cell carcinoma

Background

Even with the advance of diagnosis and the treatment, the 5-year survival rate for esophageal cancer patients is still poor. The checkpoint protein inhibition provides another choice to improve the survival. The expression of the programmed death ligand-1 (PD-L1) was reported but the clinical relevance remained inconsistent in esophageal cancer. Besides, there were few references about the other ligand, programed death ligand-2 (PD-L2). In this study, we evaluated the expressions of PD-L1 and PD-L2 in patients with esophageal squamous cell carcinoma (ESCC) and assessed their clinical relevance.

Methods

From 1996 to 2011, 150 patients undergone complete surgical resection for ESCC were enrolled. Clinical data were recorded. Expression of PD-L1 and PD-L2 on cytoplasm in paraffin embedded tumor samples were analyzed by immunohistochemistry staining and scored with a semi-quantitative method.

Results

Of the patients, 96 (64.0%) patients had PD-L1 overexpression and 63 (42.0%) had PD-L2 overexpression. There was a correlation between the expression of PD-L1 and PD-L2 (P<0.001). Patients without overexpression of PD-L1, pathological T1-2 and N0 status, pathological stage I-II and no post-operative adjuvant treatment had a better disease free survival (DFS). In multivariate analysis, PD-L1 expression and pathological stage were the independent prognostic factors for DFS. The expression of PD-L2 did not influence the DFS. Although not statistically significant, patients without overexpression of PD-L1 and PD-L2 seem to have a better overall survival (OS).

Conclusions

The overexpression of PD-L1 on cytoplasm, not PD-L2, is an independent prognostic factor for DFS in patients with ESCC undergone esophagectomy. However, there is a trend which suggested that patients without overexpression of PD-L1 and PD-L2 had a better OS.

Interferon Signaling Is Frequently Downregulated in Melanoma

Immune checkpoint inhibitors that block the programmed cell death protein 1/PD-L1 pathway have significantly improved the survival of patients with advanced melanoma. Immunotherapies are only effective in 15–40% of melanoma patients and resistance is associated with defects in antigen presentation and interferon signaling pathways. In this study, we examined interferon-γ (IFNγ) responses in a large panel of immune checkpoint inhibitor-naïve melanoma cells with defined genetic drivers; BRAF-mutant (n = 11), NRAS-mutant (n = 10), BRAF/NRAS wild type (n = 10), and GNAQ/GNA11-mutant uveal melanomas (UVMs) (n = 8). Cell surface expression of established IFNγ downstream targets PD-L1, PD-L2, HLA-A, -B, and -C, HLA-DR, and nerve growth factor receptor (NGFR) were analyzed by flow cytometry. Basal cellular expression levels of HLA-A, -B, -C, HLA-DR, NGFR, and PD-L2 predicted the levels of IFNγ-stimulation, whereas PD-L1 induction was independent of basal expression levels. Only 13/39 (33%) of the melanoma cell lines tested responded to IFNγ with potent induction of all targets, indicating that downregulation of IFNγ signaling is common in melanoma. In addition, we identified two well-recognized mechanisms of immunotherapy resistance, the loss of β-2-microglobulin and interferon gamma receptor 1 expression. We also examined the influence of melanoma driver oncogenes on IFNγ signaling and our data suggest that UVM have diminished capacity to respond to IFNγ, with lower induced expression of several targets, consistent with the disappointing response of UVM to immunotherapies. Our results demonstrate that melanoma responses to IFNγ are heterogeneous, frequently downregulated in immune checkpoint inhibitor-naïve melanoma and potentially predictive of response to immunotherapy.

MET-Oncogenic and JAK2-Inactivating Alterations Are Independent Factors That Affect Regulation of PD-L1 Expression in Lung Cancer

Purpose: The blockade of immune checkpoints such as PD-L1 and PD-1 is being exploited therapeutically in several types of malignancies. Here, we aimed to understand the contribution of the genetics of lung cancer to the ability of tumor cells to escape immunosurveillance checkpoints.Experimental Design: More than 150 primary non-small cell lung cancers, including pulmonary sarcomatoid carcinomas, were tested for levels of the HLA-I complex, PD-L1, tumor-infiltrating CD8⁺ lymphocytes, and alterations in main lung cancer genes. Correlations were validated in cancer cell lines using appropriate treatments to activate or inhibit selected pathways. We also performed RNA sequencing to assess changes in gene expression after these treatments.Results:MET-oncogenic activation tended to associate with positive PD-L1 immunostaining, whereas STK11 mutations were correlated with negative immunostaining. In MET-altered cancer cells, MET triggered a transcriptional increase of PD-L1 that was independent of the IFNγ-mediated JAK/STAT pathway. The activation of MET also upregulated other immunosuppressive genes (PDCD1LG2 and SOCS1) and transcripts involved in angiogenesis (VEGFA and NRP1) and in cell proliferation. We also report recurrent inactivating mutations in JAK2 that co-occur with alterations in MET and STK11, which prevented the induction of immunoresponse-related genes following treatment with IFNγ.Conclusions: We show that MET activation promotes the expression of several negative checkpoint regulators of the immunoresponse, including PD-L1. In addition, we report inactivation of JAK2 in lung cancer cells that prevented the response to IFNγ. These alterations are likely to facilitate tumor growth by enabling immune tolerance and may affect the response to immune checkpoint inhibitors. Clin Cancer Res; 24(18); 4579-87. ©2018 AACR.

Toxoplasma Chinese 1 Strain of WH3Δrop16I/III /gra15II Genetic Background Contributes to Abnormal Pregnant Outcomes in Murine Model

Toxoplasma gondii infection evokes a strong Th1-type response with interleukin (IL)-12 and interferon (IFN)-γ secretion. Recent studies suggest that the infection of pregnant mice with T. gondii may lead to adverse pregnancy results caused by subversion of physiological immune tolerance at maternofetal interface rather than direct invasion of the parasite. Genotype-associated dense granule protein GRA15II tends to induce classically activated macrophage (M1) differentiation and subsequently activating NK, Th1, and Th17 cells whereas rhoptry protein ROP16I/III drives macrophages to alternatively activated macrophage (M2) polarization and elicits Th2 immune response. Unlike the archetypal strains of types I, II, and III, type Chinese 1 strains possess both GRA15II and ROP16I/III, suggesting a distinct pathogenesis of Toxoplasma-involved adverse pregnancies. We constructed T. gondii type Chinese 1 strain of WH3Δrop16 based on CRISPR/Cas9 technology to explore the ROP16I/III-deficient/GRA15II-dominant parasites in induction of trophoblast apoptosis in vitro and abnormal pregnant outcomes of mice in vivo. Our study showed that Toxoplasma WH3Δrop16 remarkably induced apoptosis of trophoblasts. C57BL/6 pregnant mice injected with the tachyzoites of WH3Δrop16 presented increased absorptivity of fetuses in comparison with the mice infected with WH3 wild type (WH3 WT) parasites although no remarkable difference of virulence to mice was seen between the two strains. Additionally, the mice inoculated with WH3Δrop16 tachyzoites exhibited a notable expression of both IL-17A and IFN-γ, while the percentage of CD4+CD25+FoxP3 [T regulatory cells (Tregs)] were diminished in splenocytes and placenta tissues compared to those infected with WH3 WT parasites. Accordingly, expressions of IL-4, IL-10, and transforming growth factor beta 1, the pivotal cytokines of Th2 and Tregs response, were significantly dampened whereas IFN-γ and IL-12 expressions were upregulated in WH3Δrop16-infected mice, which gave rise to more prominent outcomes of abnormal pregnancies. Our results indicated that the WH3Δrop16 parasites with gra15II background of T. gondii type Chinese 1 strains may cause miscarriage and stillbirth due to subversion of the maternal immune tolerance and system immunity of the animals and the GRA15II effector contributes to the process of adverse pregnant consequences.

Emerging therapeutic biomarkers of autoimmune hepatitis and their impact on current and future management

Autoimmune hepatitis lacks a quantifiable biomarker that is close to its pathogenic mechanisms and that accurately reflects inflammatory activity, correlates with treatment response, and ensures inactive disease before treatment withdrawal. Areas covered: Micro-ribonucleic acids, programmed death-1 protein and its ligands, macrophage migration inhibitory factor, soluble CD163, B cell activating factor, and metabolite patterns in blood were considered the leading candidates as therapeutic biomarkers after search of PubMed from August 1981 to August 2017 using the search words 'biomarkers of autoimmune hepatitis'. Expert commentary: Each of the candidate biomarkers is close to the putative pathogenic mechanisms of autoimmune hepatitis, and each has attributes that support its potential role as a surrogate marker of inflammatory activity that can be monitored during treatment. Future studies must demonstrate the superiority of each biomarker to conventional indices of inflammatory activity and validate their correlation with treatment response and outcome. A reliable therapeutic biomarker would facilitate the individualization of current management algorithms, ensure that pathogenic mechanisms were disrupted or eliminated prior to treatment withdrawal, and reduce the frequency of relapse or unnecessary protracted therapy. The biomarker might also prove to be a target of next-generation therapies.

IFNAR1 Controls Autocrine Type I IFN Regulation of PD-L1 Expression in Myeloid-Derived Suppressor Cells

Tumor cells respond to IFN-γ of activated T cells to upregulate programmed death-ligand 1 (PD-L1) in the tumor microenvironment as an adaptive immune resistance mechanism. Tumor cells also express oncogene-driven PD-L1. PD-L1 is also expressed on myeloid-derived suppressor cells (MDSCs). It is known that both type I and II IFNs upregulate PD-L1 expression in MDSCs. However, the molecular mechanism underlying PD-L1 expression in MDSCs is still largely unknown. We report in this article that MDSCs exhibit constitutive STAT1 phosphorylation in vitro without exogenous IFNs, indicating a constitutive active JAK-STAT signaling pathway in mouse MDSCs in vitro. Furthermore, IFN-α and IFN-β but not IFN-γ are endogenously expressed in the MDSC cell line in vitro and in tumor-induced MDSCs in vivo. Neutralizing type I IFN or inhibiting the JAK-STAT signaling pathway significantly decreased constitutive PD-L1 expression in MDSCs in vitro. However, neither IFN-α expression level nor IFN-β expression level is correlated with PD-L1 expression level in MDSCs; instead, the level of IFN receptor type I (IFNAR1) is correlated with PD-L1 expression levels in MDSCs. Consequently, knocking out IFNAR1 in mice diminished PD-L1 expression in tumor-induced MDSCs. Therefore, we determined that 1) PD-L1 expression in MDSCs is activated by type I IFN through an autocrine manner and 2) the expression level of PD-L1 is controlled at least in part by the IFNAR1 level on MDSCs. Our data indicate that MDSCs may maintain their PD-L1 expression via autocrine type I IFN to exert their suppressive activity in the absence of IFN-γ from the suppressed T cells in the tumor microenvironment.

Trastuzumab upregulates PD-L1 as a potential mechanism of trastuzumab resistance through engagement of immune effector cells and stimulation of IFNγ secretion

Here, we report that treatment of syngeneic mouse tumors transduced to overexpress human epidermal growth factor receptor-2 (HER2) with the anti-human HER2 antibody trastuzumab upregulated the level of programmed death-ligand 1 (PD-L1), an important negative regulator of T-cell response, in a transgenic mouse model immune-tolerant to human HER2. We further found that trastuzumab alone had no detectable effect on the level of PD-L1 expression in monocultures of HER2-overexpressing human breast cancer cells but upregulated PD-L1 in the same panel of HER2-overexpressing breast cancer cells when they were co-cultured with human peripheral blood mononuclear cells, and the upregulation of PD-L1 could be blocked by an IFNγ-neutralizing antibody. Inhibition of HER2 intrinsic signaling via HER2 expression knockdown or kinase inhibition had variable and cell-context-specific effects on downregulating the PD-L1 level. Analysis of The Cancer Genome Atlas database showed no direct correlation between HER2 and PD-L1 at the messenger RNA level. Trastuzumab-mediated upregulation of PD-L1 through engagement of immune effector cells may function as a potential mechanism of trastuzumab resistance. Our data justify further investigation of the value of adding anti-PD-1 or anti-PD-L1 therapy to trastuzumab-based treatment.

Dual inhibition of STAT1 and STAT3 activation downregulates expression of PD-L1 in human breast cancer cells

OBJECTIVES

Breast cancer is the most commonly diagnosed cancer, and it is a leading cause of cancer-related deaths in females worldwide. Triple-negative breast cancer (TNBC) constitutes 15% of breast cancer and shows distinct metastasis profiles with poor prognosis. Strong PD-L1 expression has been observed in some tumors, supporting their escape from immune surveillance. Targeting PD-L1 could be a promising therapeutic approach in breast cancer patients. We investigated potential molecular mechanisms for constitutive expression of PD-L1 by inhibiting upstream STAT1 and STAT3 signals.

METHODS

PD-L1 expression in three breast cancer cell lines was measured using quantitative PCR and western blotting. Activation of STAT1 and STAT3 was blocked using pharmacological inhibitors and siRNA. The mechanism underlying the constitutive expression of PD-L1 was investigated using ChIP and co-immunoprecipitation assays.

RESULTS

We found that individual inhibition of STAT1 and STAT3 activation partially downregulated PD-L1, while combined inhibition completely downregulated PD-L1 expression. Moreover, our results suggest that pSTAT1-pSTAT3 dimerize in cytosol and translocate to the nucleus, where they bind to PD-L1 promoter and induce PD-L1 expression.

CONCLUSION

These findings provide a rationale for combined targeting of STAT1 and STAT3 for the development of immune-based cancer therapies for down regulation of PD-L1 expression.

CXCL9/10/11, a regulator of PD-L1 expression in gastric cancer

Background

Programmed death-ligand 1 (PD-L1) is an immunosuppressor that plays an important role in cancer treatments. Although majority of the studies demonstrated that PD-L1 expression was regulated by cellular intrinsic and extrinsic controls, and IFN-γ was a key molecule of extrinsic control, other studies imply that other cytokines play important roles in PD-L1 expression. In this study, we investigated the regulation of PD-L1 by chemokine signaling pathway in gastric cancer (GC) cells.

Methods

Bioinformatics was used to explore the PD-L1-related genes in GC and propose a hypothesis. PD-L1 and CXCR3 expression were detected by western blot in SGC7901 and MKN74 cell lines. Meanwhile, PD-L1 and CXCR3 expressions were immunohistochemically assessed for their relevance. Moreover, PD-L1, pSTAT3 and pAkt were detected after treatment with CXCL9/10/11. Furthermore,PD-L1, pSTAT3 and pAkt were evaluated after blocking chemokine signaling in SGC7901 cells.

Results

Based on online database analysis, CXCL9/10/11-CXCR3 is proposed to upregulate PD-L1 expression by activating the STAT and PI3K-Akt pathways. This hypothesis was confirmed by in vitro and vivo experiments. CXCR3 and PD-L1 were expressed in GC cell lines and tissues, and the expression of CXCR3 and PD-L1 was positively related. PD-L1 was upregulated after treatment with CXCL9/10/11, accompanied by activation of STAT3 and Akt. After blocking chemokine signaling, upregulation of PD-L1 and activation of STAT3 and Akt were diminished.

Conclusions

CXCL9/10/11-CXCR3 upregulated the expression of PD-L1 by activating the STAT and PI3K-Akt signaling pathways in GC cells. There was a significant positive correlation between the expression of PD-L1 and CXCR3 in gastric cancer patient tissues.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4384-8) contains supplementary material, which is available to authorized users.

BRCA1/2 and TP53 mutation status associates with PD-1 and PD-L1 expression in ovarian cancer

Checkpoint molecules such as programmed cell death protein-1 (PD-1) and its ligand PD-L1 are critically required for tumor immune escape. The objective of this study was to investigate tumoral PD-1 and PD-L1 mRNA-expression in a cohort of ovarian cancer (OC) patients in relation to tumor mutations. We analyzed mRNA expression of PD-1, PD-L1 and IFNG by quantitative real-time PCR in tissue of 170 patients with low grade-serous (LGSOC), high-grade serous (HGSOC), endometrioid and clear cell OC compared to 28 non-diseased tissues (ovaries and fallopian tubes) in relation to tumor protein 53 (TP53) and breast cancer gene 1/2 (BRCA1/2) mutation status. TP53-mutated OC strongly expressed PD-L1 compared to TP53 wild-type OC (p = 0.028) and BRCA1/2-mutated OC increasingly expressed PD-1 (p = 0.024) and PD-L1 (p = 0.012) compared to BRCA1/2 wild-type OC. For the first time in human, we noted a strong correlation between tumoral IFNG and PD-1 or PD-L1 mRNA-expression, respectively (p < 0.001). OC tissue increasingly expressed PD-1 compared to healthy controls (vs. ovaries: p < 0.001; vs. tubes: p = 0.018). PD-1 and PD-L1 mRNA-expression increased with higher tumor grade (p = 0.008 and p = 0.027, respectively) and younger age (< median age, p = 0.001). Finally, in the major subgroup of our cohort, FIGO stage III/IV HGSOC, high PD-1 and PD-L1 mRNA-expression was associated with reduced progression-free (p = 0.024) and overall survival (p = 0.049) but only in the univariate analysis. Our study suggests that in OC PD-1/PD-L1 mRNA-expression is controlled by IFNγ and affected by TP53 and BRCA1/2 mutations. We suggest that these mutations might serve as potential predictive factors that guide anti-PD1/PD-L1 immunotherapy.

BRCA1/2 and TP53 mutation status associates with PD-1 and PD-L1 expression in ovarian cancer

Checkpoint molecules such as programmed cell death protein-1 (PD-1) and its ligand PD-L1 are critically required for tumor immune escape. The objective of this study was to investigate tumoral PD-1 and PD-L1 mRNA-expression in a cohort of ovarian cancer (OC) patients in relation to tumor mutations. We analyzed mRNA expression of PD-1, PD-L1 and IFNG by quantitative real-time PCR in tissue of 170 patients with low grade-serous (LGSOC), high-grade serous (HGSOC), endometrioid and clear cell OC compared to 28 non-diseased tissues (ovaries and fallopian tubes) in relation to tumor protein 53 (TP53) and breast cancer gene 1/2 (BRCA1/2) mutation status. TP53-mutated OC strongly expressed PD-L1 compared to TP53 wild-type OC (p = 0.028) and BRCA1/2-mutated OC increasingly expressed PD-1 (p = 0.024) and PD-L1 (p = 0.012) compared to BRCA1/2 wild-type OC. For the first time in human, we noted a strong correlation between tumoral IFNG and PD-1 or PD-L1 mRNA-expression, respectively (p < 0.001). OC tissue increasingly expressed PD-1 compared to healthy controls (vs. ovaries: p < 0.001; vs. tubes: p = 0.018). PD-1 and PD-L1 mRNA-expression increased with higher tumor grade (p = 0.008 and p = 0.027, respectively) and younger age (< median age, p = 0.001). Finally, in the major subgroup of our cohort, FIGO stage III/IV HGSOC, high PD-1 and PD-L1 mRNA-expression was associated with reduced progression-free (p = 0.024) and overall survival (p = 0.049) but only in the univariate analysis. Our study suggests that in OC PD-1/PD-L1 mRNA-expression is controlled by IFNγ and affected by TP53 and BRCA1/2 mutations. We suggest that these mutations might serve as potential predictive factors that guide anti-PD1/PD-L1 immunotherapy.

Oncofetal gene SALL4 reactivation by hepatitis B virus counteracts miR-200c in PD-L1-induced T cell exhaustion

A chronic viral or tumor microenvironment can push T cells to exhaustion by promoting coinhibitory ligand expression. However, how host factors control coinhibitory ligand expression and whether viral infection breaks this control during tumor progress is unknown. Here we show a close negative correlation between SALL4 or PD-L1 and miR-200c in tumors from 98 patients with HBV-related hepatocellular carcinoma. SALL4 or PD-L1 expression correlates negatively with miR-200c expression, and patients with lower levels of SALL4 or PD-L1 and higher miR-200c survive longer. Moreover, over-expression of miR-200c antagonizes HBV-mediated PD-L1 expression by targeting 3'-UTR of CD274 (encoding PD-L1) directly, and reverses antiviral CD8⁺ T cell exhaustion. MiR-200c transcription is inhibited by oncofetal protein SALL4, which is re-expressed through HBV-induced STAT3 activation in adulthood. We propose that an HBV-pSTAT3-SALL4-miR-200c axis regulates PD-L1. Therapeutic strategies to influence this axis might reverse virus-induced immune exhaustion.

Intrinsic and Extrinsic Regulation of PD-L2 Expression in Oncogene-Driven Non-Small Cell Lung Cancer

INTRODUCTION

The interaction of programmed cell death ligand 2 (PD-L2) with programmed cell death 1 is implicated in tumor immune escape. The regulation of PD-L2 expression in tumor cells has remained unclear, however. We here examined intrinsic and extrinsic regulation of PD-L2 expression in NSCLC.

METHODS

PD-L2 expression was evaluated by reverse transcription and real-time polymerase chain reaction analysis and by flow cytometry.

RESULTS

BEAS-2B cells stably expressing an activated mutant form of EGFR or the echinoderm microtubule associated protein like 4 (EML4)-ALK receptor tyrosine kinase fusion oncoprotein manifested increased expression of PD-L2 at both the mRNA and protein levels. Furthermore, treatment of NSCLC cell lines that harbor such driver oncogenes with corresponding EGFR or ALK tyrosine kinase inhibitors or depletion of EGFR or ALK by small interfering RNA transfection suppressed expression of PD-L2, demonstrating that activating EGFR mutations or echinoderm microtubule associated protein like 4 gene (EML4)-ALK receptor tyrosine kinase gene (ALK) fusion intrinsically induce PD-L2 expression. We also found that interferon gamma (IFN-γ) extrinsically induced expression of PD-L2 through signal transducer and activator of transcription 1 signaling in NSCLC cells. Oncogene-driven expression of PD-L2 in NSCLC cells was inhibited by knockdown of the transcription factors signal transducer and activator of transcription 3 (STAT3) or c-FOS. IFN-γ also activated STAT3 and c-FOS, suggesting that these proteins may also contribute to the extrinsic induction of PD-L2 expression.

CONCLUSIONS

Expression of PD-L2 is induced intrinsically by activating EGFR mutations or EML4-ALK fusion and extrinsically by IFN-γ, with STAT3 and c-FOS possibly contributing to both intrinsic and extrinsic pathways. Our results thus provide insight into the complexity of tumor immune escape in NSCLC.

Cancer-associated oxidoreductase ERO1-α promotes immune escape through up-regulation of PD-L1 in human breast cancer

Many human cancers have been reported to have enhanced expression of the immune checkpoint molecule programmed death-ligand 1 (PD-L1), which binds to programmed cell death-1 (PD-1) expressed on immune cells. PD-L1/PD-1 plays a role in inhibition of antitumor immunity by inducing T cell apoptosis and tolerance. Thus, it is crucial to elucidate mechanisms of PD-L1 expression on cancer cells. ERO1-α is an oxidase located in the endoplasmic reticulum. It is overexpressed in a variety of tumor types and it plays a role in disulfide bond formation in collaboration with PDI. Here, we investigated the influence of ERO1-α on expression of PD-L1 and immune escape. We demonstrated that ERO1-α augmented the expression of PD-L1 via facilitation of oxidative protein folding within PD-L1. In addition, we showed that overexpression of ERO1-α increased HIF-1α protein expression, resulting in an increase of PD-L1 mRNA as well as protein. In clinical cases, we observed that the expression of ERO1-α in triple negative breast cancer was related to the expression of PD-L1. Moreover, apoptosis of Jurkat leukemia T cells, which express PD-1, induced by tumor PD-L1 was inhibited when ERO1-α was depleted. The results suggest that targeting ERO1-α in tumor cells can be a novel approach for cancer immunotherapy. Therefore, the role of ERO1-α in tumor-mediated immunosuppression should be further explored.

Regulation and Function of the PD-L1 Checkpoint

Expression of programmed death-ligand 1 (PD-L1) is frequently observed in human cancers. Binding of PD-L1 to its receptor PD-1 on activated T cells inhibits anti-tumor immunity by counteracting T cell-activating signals. Antibody-based PD-1-PD-L1 inhibitors can induce durable tumor remissions in patients with diverse advanced cancers, and thus expression of PD-L1 on tumor cells and other cells in the tumor microenviroment is of major clinical relevance. Here we review the roles of the PD-1-PD-L1 axis in cancer, focusing on recent findings on the mechanisms that regulate PD-L1 expression at the transcriptional, posttranscriptional, and protein level. We place this knowledge in the context of observations in the clinic and discuss how it may inform the design of more precise and effective cancer immune checkpoint therapies.

Targeting Macrophages in Cancer: From Bench to Bedside

Macrophages are a major component of the tumor microenvironment and orchestrate various aspects of immunity. Within tumors, macrophages can reversibly alter their endotype in response to environmental cues, including hypoxia and stimuli derived from other immune cells, as well as the extracellular matrix. Depending on their activation status, macrophages can exert dual influences on tumorigenesis by either antagonizing the cytotoxic activity immune cells or by enhancing antitumor responses. In most solid cancers, increased infiltration with tumor-associated macrophages (TAMs) has long been associated with poor patient prognosis, highlighting their value as potential diagnostic and prognostic biomarkers in cancer. A number of macrophage-centered approaches to anticancer therapy have been investigated, and include strategies to block their tumor-promoting activities or exploit their antitumor effector functions. Integrating therapeutic strategies to target TAMs to complement conventional therapies has yielded promising results in preclinical trials and warrants further investigation to determine its translational benefit in human cancer patients. In this review, we discuss the molecular mechanisms underlying the pro-tumorigenic programming of macrophages and provide a comprehensive update of macrophage-targeted therapies for the treatment of solid cancers.

Characteristics of Infection Immunity Regulated by Toxoplasma gondii to Maintain Chronic Infection in the Brain

To examine the immune environment of chronic Toxoplasma gondii infection in the brain, the characteristics of infection-immunity (premunition) in infection with T. gondii strain ME49 were investigated for 12 weeks postinfection (PI). The results showed that neuronal cell death, microglia infiltration and activation, inflammatory and anti-inflammatory cytokine expression, Stat1 phosphorylation, and microglia activation and inflammatory gene transcripts related to M1 polarization in the brain were increased during the acute infection (AI) stage (within 6 weeks PI), suggesting that innate and cellular inflammatory response activation and neurodegeneration contributed to excessive inflammatory responses. However, these immune responses decreased during the chronic infection (CI) stage (over 6 weeks PI) with reductions in phosphorylated STAT1 (pSTAT1) and eosinophilic neurons. Notably, increases were observed in transcripts of T-cell exhaustion markers (TIM3, LAG3, KLRG1, etc.), suppressor of cytokines signaling 1 protein (SOCS1), inhibitory checkpoint molecules (PD-1 and PD-L1), and Arg1 from the AI stage (3 weeks PI), implying active immune intervention under the immune environment of M1 polarization of microglia and increases in inflammatory cytokine levels. However, when BV-2 microglia were stimulated with T. gondii lysate antigens (strain RH or ME49) in vitro, nitrite production increased and urea production decreased. Furthermore, when BV-2 cells were infected by T. gondii tachyzoites (strain RH or ME49) in vitro, nitric oxide synthase and COX-2 levels decreased, whereas Arg1 levels significantly increased. Moreover, Arg1 expression was higher in ME49 infection than in RH infection, whereas nitrite production was lower in ME49 infection than in RH infection. Accordingly, these results strongly suggest that immune triggering of T. gondii antigens induces M1 polarization and activation of microglia as well as increase NO production, whereas T. gondii infection induces the inhibition of harmful inflammatory responses, even with M1 polarization and activation of microglia and Th1 inflammatory responses, suggesting a host–parasite relationship through immune regulation during CI. This is a characteristic of infection immunity in infection with T. gondii in the central nervous system, and SOCS1, a negative regulator of toxoplasmic encephalitis, may play a role in the increase in Arg1 levels to suppress NO production.

Ribosome biogenesis in cancer: new players and therapeutic avenues

The ribosome is a complex molecular machine composed of numerous distinct proteins and nucleic acids and is responsible for protein synthesis in every living cell. Ribosome biogenesis is one of the most multifaceted and energy- demanding processes in biology, involving a large number of assembly and maturation factors, the functions of which are orchestrated by multiple cellular inputs, including mitogenic signals and nutrient availability. Although causal associations between inherited mutations affecting ribosome biogenesis and elevated cancer risk have been established over the past decade, mechanistic data have emerged suggesting a broader role for dysregulated ribosome biogenesis in the development and progression of most spontaneous cancers. In this Opinion article, we highlight the most recent findings that provide new insights into the molecular basis of ribosome biogenesis in cancer and offer our perspective on how these observations present opportunities for the design of new targeted cancer treatments.

YAP regulates PD-L1 expression in human NSCLC cells

Programmed death-ligand 1 (PD-L1) is a membrane protein on tumor cells that binds to the PD-1 receptor expressed on immune cells, leading to the immune escape of tumor cells. Yes-associated protein (YAP) is a main effector of the Hippo/YAP signaling pathway, which plays important roles in cancer development. Here we show that YAP regulates PD-L1 expression in human non-small cell lung cancer (NSCLC) cells. First, we investigated YAP and PD-L1 expression at the protein level in 142 NSCLC samples and 15 normal lung samples. In tumor tissue, immunohistochemistry showed positive staining for YAP and PD-L1, which correlated significantly (n = 142, r = 0.514, P < 0.001). Second, in cell lines that express high levels of PD-L1 (H460, SKLU-1, and H1299), the ratio of p-YAP/YAP was lower and GTIIC reporter activity of the Hippo pathway was higher than those in three cell lines expressing low levels of PD-L1 (A549, H2030, and PC9) (P < 0.05). Third, in the same three cell lines, inhibition of YAP by two small interfering RNAs (siRNAs) decreased the mRNA and protein level of PD-L1 (P < 0.05). Fourth, forced overexpression of the YAP gene rescued the PD-L1 mRNA and protein level after siRNA knockdown targeting 3′UTR of the endogenous YAP gene. Finally, chromatin immunoprecipitation (ChIP) assays using a YAP-specific monoclonal antibody resulted in the precipitation of PD-L1 enhancer region encompassing two putative TEAD binding sites. Our results indicate that YAP regulates the transcription of PD-L1 in NSCLC.

Interleukin-22 attenuates double-stranded RNA-induced upregulation of PD-L1 in airway epithelial cells via a STAT3-dependent mechanism

Double-stranded RNA derived from viruses induces host immune responses. PD-L1, also known as B7-H1, is an immune-checkpoint molecule associated with the escape of viruses from host immune systems, which plays a role in the persistence of viral infection, resulting in exacerbations of underlying diseases such as asthma and chronic obstructive pulmonary disease. Interleukin (IL)-22 is produced from various immune cells and has protective properties on mucosal tissue. The binding of IL-22 to IL-22 receptor induces STAT3 activation. We investigated the effect of IL-22 on the expression in airway epithelial cells in vitro and in mouse lungs in vivo after the stimulation with an analog of viral double-stranded RNA, polyinosinic-polycytidylic acid (poly I:C). Stimulation with poly I:C upregulated PD-L1 expression on BEAS-2B cells. This upregulation of PD-L1 was attenuated by IL-22 administration. STAT3 phosphorylation was induced by IL-22 and poly I:C. Treatment of cells with STAT3 siRNA abolished the effect of IL-22 on the poly I:C-induced upregulation of PD-L1. This upregulation of PD-L1 was also attenuated by IL-11, a cytokine inducing STAT3 phosphorylation, in BEAS-2B cells. In mouse lung cells in vivo, IL-22 suppressed poly I:C-induced upregulation of PD-L1. These results suggest that IL-22 attenuates virus-induced upregulation of PD-L1 in airway epithelial cells via a STAT3-dependent mechanism.

Immune checkpoint inhibitors in advanced non-small cell lung cancer

The emergence of immune checkpoint inhibitors for the treatment of cancer has led to major changes to the therapeutic landscape of lung cancer. Improvements in overall survival relative to standard chemotherapy have been observed in the first-line and second-line therapy settings for patients with advanced non-small cell lung cancer (NSCLC) who are treated with immune checkpoint inhibitors. Consequently, every patient with advanced-stage NSCLC is now a candidate for immune checkpoint inhibitor therapy. However, it is clear that the benefit from therapy is not universal, and identification of biomarkers to select therapy has assumed importance. In addition to programmed cell death receptor ligand 1 expression, both tissue-based and blood-based markers are under evaluation to select patients. In an era of increasing costs of care and potential for toxicities related to immune checkpoint inhibition, proper patient selection is critical to the optimal use of this new class of agents. In addition, development of novel combination approaches has also emerged as an important way to improve the efficacy of immune checkpoint inhibition. Studies in earlier stages of NSCLC are already underway with the hope of improving the cure rate. In this article, the authors review the current landscape of immune checkpoint inhibitors in the treatment of advanced NSCLC. Cancer 2018;124:248-61. © 2017 American Cancer Society.

Intratumoural PD-L1 expression is associated with worse survival of patients with Epstein-Barr virus-associated gastric cancer

BACKGROUND

This study investigated the clinical relevance and prognostic impact of the overall expression of programmed cell death protein ligand-1 (PD-L1) and programmed cell death protein ligand-2 (PD-L2), in patients with Epstein-Barr virus-associated gastric cancer (EBVaGC).

METHODS

After reviewing 1318 consecutive cases of surgically resected or endoscopic submucosal dissected gastric cancers, the expression status of PD-L1 and PD-L2 in 120 patients with EBVaGC identified by EBV-encoded RNA in situ hybridisation was retrospectively analysed using immunohistochemistry (IHC). For each IHC marker, positivity was separately in intraepithelial tumour cells (iTu-) and immune cells in the tumour stroma area (str-).

RESULTS

Among 116 eligible patients, 57 (49.1%) and 66 patients (56.9%) were determined as iTu-PD-L1-positive and str-PD-L1-positive, respectively, whereas 23 (21.6%) and 45 patients (38.8%) were determined as iTu-PD-L2 positive and str-PD-L2 positive, respectively. Intraepithelial tumour cell PD-L1 positivity was found to be significantly associated with lymph node (LN) metastasis (P=0.012) and a poor disease-free survival (DFS) (P=0.032), yet not overall survival (P=0.482). In a multivariate analysis, iTu-PD-L1 positivity was independently associated with a poor DFS (P=0.006, hazard ratio=12.085). In contrast, str-PD-L2-positivity was related to a lower T category (P=0.003), absence of LN metastasis (P=0.032) and perineural invasion (P=0.028). Intraepithelial tumour cell and str-PD-L2 positivity showed a trend towards an improved DFS, although not significant (P=0.060 and P=0.073, respectively).

CONCLUSIONS

Intraepithelial tumour cells PD-L1 expression can be used to predict a poor outcome in patients with EBVaGC and can represent a rational approach for PD-1/PD-L pathway-targeted immunotherapy.