Regulation and impact of tumor-specific CD4+ T cells in cancer and immunotherapy

CD4+ T cells are crucial in generating and sustaining immune responses. They orchestrate and fine-tune mammalian innate and adaptive immunity through cell-based interactions and the release of cytokines. The role of these cells in contributing to the efficacy of antitumor immunity and immunotherapy has just started to be uncovered. Yet, many aspects of the CD4+ T cell response are still unclear, including the differentiation pathways controlling such cells during cancer progression, the external signals that program them, and how the combination of these factors direct ensuing immune responses or immune-restorative therapies. In this review, we focus on recent advances in understanding CD4+ T cell regulation during cancer progression and the importance of CD4+ T cells in immunotherapies.

IL-2 produced by HBV-specific T cells as a biomarker of viral control and predictor of response to PD-1 therapy across clinical phases of chronic hepatitis B

BACKGROUND

There are no immunological biomarkers that predict control of chronic hepatitis B (CHB). The lack of immune biomarkers raises concerns for therapies targeting PD-1/PD-L1 because they have the potential for immune-related adverse events. Defining specific immune functions associated with control of HBV replication could identify patients likely to respond to anti-PD-1/PD-L1 therapies and achieve a durable functional cure.

METHODS

We enrolled immunotolerant, HBeAg+ immune-active (IA+), HBeAg- immune-active (IA-), inactive carriers, and functionally cured patients to test ex vivo PD-1 blockade on HBV-specific T cell functionality. Peripheral blood mononuclear cells were stimulated with overlapping peptides covering HBV proteins +/-α-PD-1 blockade. Functional T cells were measured using a 2-color FluoroSpot assay for interferon-γ and IL-2. Ex vivo functional restoration was compared to the interferon response capacity assay, which predicts overall survival in cancer patients receiving checkpoint inhibitors.

RESULTS

Ex vivo interferon-γ+ responses did not differ across clinical phases. IL-2+ responses were significantly higher in patients with better viral control and preferentially restored with PD-1 blockade. Inactive carrier patients displayed the greatest increase in IL-2 production, which was dominated by CD4 T cell and response to the HBcAg. The interferon response capacity assay significantly correlated with the degree of HBV-specific T cell restoration.

CONCLUSIONS

IL-2 production was associated with better HBV control and superior to interferon-γ as a marker of T cell restoration following ex vivo PD-1 blockade. Our study suggests that responsiveness to ex vivo PD-1 blockade, or the interferon response capacity assay, may support stratification for α-PD-1 therapies.

Molecular, metabolic, and functional CD4 T cell paralysis in the lymph node impedes tumor control

CD4 T cells are central effectors of anti-cancer immunity and immunotherapy, yet the regulation of CD4 tumor-specific T (TTS) cells is unclear. We demonstrate that CD4 TTS cells are quickly primed and begin to divide following tumor initiation. However, unlike CD8 TTS cells or exhaustion programming, CD4 TTS cell proliferation is rapidly frozen in place by a functional interplay of regulatory T cells and CTLA4. Together these mechanisms paralyze CD4 TTS cell differentiation, redirecting metabolic circuits, and reducing their accumulation in the tumor. The paralyzed state is actively maintained throughout cancer progression and CD4 TTS cells rapidly resume proliferation and functional differentiation when the suppressive constraints are alleviated. Overcoming their paralysis established long-term tumor control, demonstrating the importance of rapidly crippling CD4 TTS cells for tumor progression and their potential restoration as therapeutic targets.

Molecular, metabolic and functional CD4 T cell paralysis impedes tumor control

CD4 T cells are important effectors of anti-tumor immunity, yet the regulation of CD4 tumor-specific T (T TS ) cells during cancer development is still unclear. We demonstrate that CD4 T TS cells are initially primed in the tumor draining lymph node and begin to divide following tumor initiation. Distinct from CD8 T TS cells and previously defined exhaustion programs, CD4 T TS cell proliferation is rapidly frozen in place and differentiation stunted by a functional interplay of T regulatory cells and both intrinsic and extrinsic CTLA4 signaling. Together these mechanisms paralyze CD4 T TS cell differentiation, redirecting metabolic and cytokine production circuits, and reducing CD4 T TS cell accumulation in the tumor. Paralysis is actively maintained throughout cancer progression and CD4 T TS cells rapidly resume proliferation and functional differentiation when both suppressive reactions are alleviated. Strikingly, Treg depletion alone reciprocally induced CD4 T TS cells to themselves become tumor-specific Tregs, whereas CTLA4 blockade alone failed to promote T helper differentiation. Overcoming their paralysis established long-term tumor control, demonstrating a novel immune evasion mechanism that specifically cripples CD4 T TS cells to favor tumor progression.

The transcription factor IRF2 drives interferon-mediated CD8+ T cell exhaustion to restrict anti-tumor immunity

Type I and II interferons (IFNs) stimulate pro-inflammatory programs that are critical for immune activation, but also induce immune-suppressive feedback circuits that impede control of cancer growth. Here, we sought to determine how these opposing programs are differentially induced. We demonstrated that the transcription factor interferon regulatory factor 2 (IRF2) was expressed by many immune cells in the tumor in response to sustained IFN signaling. CD8+ T cell-specific deletion of IRF2 prevented acquisition of the T cell exhaustion program within the tumor and instead enabled sustained effector functions that promoted long-term tumor control and increased responsiveness to immune checkpoint and adoptive cell therapies. The long-term tumor control by IRF2-deficient CD8+ T cells required continuous integration of both IFN-I and IFN-II signals. Thus, IRF2 is a foundational feedback molecule that redirects IFN signals to suppress T cell responses and represents a potential target to enhance cancer control.

Biomarker opportunities in the treatment of cancer-related depression

Depression comorbid with cancer is common and associated with a host of negative health outcomes. The inflammatory basis of depression is a growing area of research in cancer, focused on how stressors transduce into inflammation and contribute to the emergence of depression. In this review, we synthesize inflammatory biomarker associations with both depression and the currently available pharmacotherapies and psychotherapies in cancer, underscoring the need for expanding research on anti-inflammatory agents with antidepressant effects. Modulation of inflammatory neuroimmune pathways can slow tumor progression and reduce metastases. Biomarkers associated with depression in cancer may help with diagnosis and treatment monitoring, as well as inform research on novel drug targets to potentially improve cancer survival.

Mass cytometry immunostaining protocol for multiplexing clinical samples

This is a cytometry by time-of-flight (CyTOF) staining protocol for hematopoietic-derived cells, that leverages live-cell barcoding using receptor-type tyrosine-protein phosphatase C (CD45) antibodies conjugated to metal isotopes in combination with DNA-based palladium barcoding to multiplex up to 40 samples. In this protocol, DNA-based barcoding is performed before surface and intracellular immunostaining, which reduces the batch effects that result from day-to-day variations in staining and instrument sensitivity. This protocol also reduces antibody consumption and eliminates the need for repeated instrument adjustment.

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Mass cytometry immunostaining for 40+ samples to reduce batch-to-batch variation

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Barcoding samples before immunostaining ensures consistency across all samples

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Reduction in antibody volume consumption and data acquisition time

Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

Pre-encoded responsiveness to type I interferon in the peripheral immune system defines outcome of PD1 blockade therapy

Type I interferons (IFN-Is) are central regulators of anti-tumor immunity and responses to immunotherapy, but they also drive the feedback inhibition underlying therapeutic resistance. In the present study, we developed a mass cytometry approach to quantify IFN-I-stimulated protein expression across immune cells and used multi-omics to uncover pre-therapy cellular states encoding responsiveness to inflammation. Analyzing peripheral blood cells from multiple cancer types revealed that differential responsiveness to IFN-Is before anti-programmed cell death protein 1 (PD1) treatment was highly predictive of long-term survival after therapy. Unexpectedly, IFN-I hyporesponsiveness efficiently predicted long-term survival, whereas high responsiveness to IFN-I was strongly associated with treatment failure and diminished survival time. Peripheral IFN-I responsive states were not associated with tumor inflammation, identifying a disconnect between systemic immune potential and 'cold' or 'hot' tumor states. Mechanistically, IFN-I responsiveness was epigenetically imprinted before therapy, poising cells for differential inflammatory responses and dysfunctional T cell effector programs. Thus, we identify physiological cell states with clinical importance that can predict success and long-term survival of PD1-blocking immunotherapy.

Peripheral CD4 T cell resistance to type I interferon defines outcome of PD1 blockade therapy in human cancer

Type I interferons (IFN-Is) are paradoxically associated with both the success and failure of immune checkpoint blockade (ICB), with increased inflammation in the tumor associated with better response. To understand how IFN-Is modulate the immune response to ICB, we developed a mass cytometry approach to quantify pro- and anti-inflammatory features of IFN-I responsiveness at the single cell level. Using high dimensional analysis we show that the inflammatory responses that are beneficial in the peripheral blood are the opposite of what is considered beneficial in the tumor, thus identifying a functional disconnect between the peripheral and tumor immune compartments. We demonstrate that an initial resistance to IFN-I by CD4 T effector (Teff) cells in the peripheral blood is strongly associated to long-term benefit of anti-PD1 therapy in patients with melanoma, head and neck and lung cancers. By contrast, a strong IFN-I response correlates with progression and low survival probability. Upregulation of PDL1 by IFN-I did not relate to response, however patients with myeloid cells that initially reacted to IFN-I with higher IDO1 induction survived longer after anti-PD1. Single-cell RNA-sequencing stratified based on response to IFN-I identified transcriptional programs associated with therapy response, providing mechanistic insight into the peripheral cell states prior to therapy conducive to anti-PD1 success. Thus, contrary to a benefit of an initially inflamed tumor environment, an initially restrained CD4 Teff inflammatory response to IFN-I averts therapy failure and enables tumor control. This IFN-I response potential is a promising new biomarker for prediction of which patients will benefit most from anti-PD1 therapy.

Supported by Canadian Institutes of Health Research (CIHR) Foundation Grant FDN148386, the Canadian Cancer Society (CCSRI) Innovation Award No. 706230, the National Institutes of Health (NIH) grant AI085043, The Terry Fox New Frontiers Grant the Scotiabank Research Chair to D.G.B, the Princess Margaret Hold’em for Life Cancer Research Fellowship (G. M. B).

DC1s shield Tpex cells to bolster PD-1 blockade

Responsiveness to PD-1 blockade depends on a cell subset known as Tpex cells, but how these cells are sustained is less understood. In this issue of Immunity, Dähling et al. show how dendritic cells form a niche for Tpex preservation.

Translational randomized phase II trial of cabozantinib in combination with nivolumab in advanced, recurrent, or metastatic endometrial cancer

BACKGROUND

Combining immunotherapy and antiangiogenic agents is a promising treatment strategy in endometrial cancer. To date, no biomarkers for response have been identified and data on post-immunotherapy progression are lacking. We explored the combination of a checkpoint inhibitor (nivolumab) and an antiangiogenic agent (cabozantinib) in immunotherapy-naïve endometrial cancer and in patients whose disease progressed on previous immunotherapy with baseline biopsy for immune profiling.

PATIENTS AND METHODS

In this phase II trial (ClinicalTrials.gov NCT03367741, registered December 11, 2017), women with recurrent endometrial cancer were randomized 2:1 to nivolumab with cabozantinib (Arm A) or nivolumab alone (Arm B). The primary endpoint was Response Evaluation Criteria in Solid Tumors-defined progression-free survival (PFS). Patients with carcinosarcoma or prior immune checkpoint inhibitor received combination treatment (Arm C). Baseline biopsy and serial peripheral blood mononuclear cell (PBMC) samples were analyzed and associations between patient outcome and immune data from cytometry by time of flight (CyTOF) and PBMCs were explored.

RESULTS

Median PFS was 5.3 (90% CI 3.5 to 9.2) months in Arm A (n=36) and 1.9 (90% CI 1.6 to 3.4) months in Arm B (n=18) (HR=0.59, 90% CI 0.35 to 0.98; log-rank p=0.09, meeting the prespecified statistical significance criteria). The most common treatment-related adverse events in Arm A were diarrhea (50%) and elevated liver enzymes (aspartate aminotransferase 47%, alanine aminotransferase 42%). In-depth baseline CyTOF analysis across treatment arms (n=40) identified 35 immune-cell subsets. Among immunotherapy-pretreated patients in Arm C, non-progressors had significantly higher proportions of activated tissue-resident (CD103+CD69+) ɣδ T cells than progressors (adjusted p=0.009).

CONCLUSIONS

Adding cabozantinib to nivolumab significantly improved outcomes in heavily pretreated endometrial cancer. A subgroup of immunotherapy-pretreated patients identified by baseline immune profile and potentially benefiting from combination with antiangiogenics requires further investigation.

Tryptophan-derived microbial metabolites activate the aryl hydrocarbon receptor in tumor-associated macrophages to suppress anti-tumor immunity

The aryl hydrocarbon receptor (AhR) is a sensor of products of tryptophan metabolism and a potent modulator of immunity. Here, we examined the impact of AhR in tumor-associated macrophage (TAM) function in pancreatic ductal adenocarcinoma (PDAC). TAMs exhibited high AhR activity and Ahr-deficient macrophages developed an inflammatory phenotype. Deletion of Ahr in myeloid cells or pharmacologic inhibition of AhR reduced PDAC growth, improved efficacy of immune checkpoint blockade, and increased intra-tumoral frequencies of IFNγ⁺CD8⁺ T cells. Macrophage tryptophan metabolism was not required for this effect. Rather, macrophage AhR activity was dependent on Lactobacillus metabolization of dietary tryptophan to indoles. Removal of dietary tryptophan reduced TAM AhR activity and promoted intra-tumoral accumulation of TNFα⁺IFNγ⁺CD8⁺ T cells; provision of dietary indoles blocked this effect. In patients with PDAC, high AHR expression associated with rapid disease progression and mortality, as well as with an immune-suppressive TAM phenotype, suggesting conservation of this regulatory axis in human disease.

Dynamic CD4+ T cell heterogeneity defines subset-specific suppression and PD-L1-blockade-driven functional restoration in chronic infection

Inhibiting PD-1:PD-L1 signaling has transformed therapeutic immune restoration. CD4+ T cells sustain immunity in chronic infections and cancer, yet little is known about how PD-1 signaling modulates CD4+ helper T (TH) cell responses or the ability to restore CD4+ TH-mediated immunity by checkpoint blockade. We demonstrate that PD-1:PD-L1 specifically suppressed CD4+ TH1 cell amplification, prevents CD4+ TH1 cytokine production and abolishes CD4+ cytotoxic killing capacity during chronic infection in mice. Inhibiting PD-L1 rapidly restored these functions, while simultaneously amplifying and activating TH1-like T regulatory cells, demonstrating a system-wide CD4-TH1 recalibration. This effect coincided with decreased T cell antigen receptor signaling, and re-directed type I interferon (IFN) signaling networks towards dominant IFN-γ-mediated responses. Mechanistically, PD-L1 blockade specifically targeted defined populations with pre-established, but actively suppressed proliferative potential, with limited impact on minimally cycling TCF-1+ follicular helper T cells, despite high PD-1 expression. Thus, CD4+ T cells require unique differentiation and functional states to be targets of PD-L1-directed suppression and therapeutic restoration.

Pan-cancer analysis of longitudinal metastatic tumors reveals genomic alterations and immune landscape dynamics associated with pembrolizumab sensitivity

Serial circulating tumor DNA (ctDNA) monitoring is emerging as a non-invasive strategy to predict and monitor immune checkpoint blockade (ICB) therapeutic efficacy across cancer types. Yet, limited data exist to show the relationship between ctDNA dynamics and tumor genome and immune microenvironment in patients receiving ICB. Here, we present an in-depth analysis of clinical, whole-exome, transcriptome, and ctDNA profiles of 73 patients with advanced solid tumors, across 30 cancer types, from a phase II basket clinical trial of pembrolizumab (NCT02644369) and report changes in genomic and immune landscapes (primary outcomes). Patients stratified by ctDNA and tumor burden dynamics correspond with survival and clinical benefit. High mutation burden, high expression of immune signatures, and mutations in BRCA2 are associated with pembrolizumab molecular sensitivity, while abundant copy-number alterations and B2M loss-of-heterozygosity corresponded with resistance. Upon treatment, induction of genes expressed by T cell, B cell, and myeloid cell populations are consistent with sensitivity and resistance. We identified the upregulated expression of PLA2G2D, an immune-regulating phospholipase, as a potential biomarker of adaptive resistance to ICB. Together, these findings provide insights into the diversity of immunogenomic mechanisms that underpin pembrolizumab outcomes.

Prevention of CD8 T Cell Deletion during Chronic Viral Infection

During chronic viral infections, CD8 T cells rapidly lose antiviral and immune-stimulatory functions in a sustained program termed exhaustion. In addition to this loss of function, CD8 T cells with the highest affinity for viral antigen can be physically deleted. Consequently, treatments designed to restore function to exhausted cells and control chronic viral replication are limited from the onset by the decreased breadth of the antiviral T cell response. Yet, it remains unclear why certain populations of CD8 T cells are deleted while others are preserved in an exhausted state. We report that CD8 T cell deletion during chronic viral infection can be prevented by therapeutically lowering viral replication early after infection. The initial resistance to deletion enabled long-term maintenance of antiviral cytolytic activity of the otherwise deleted high-affinity CD8 T cells. In combination with decreased virus titers, CD4 T cell help and prolonged interactions with costimulatory molecules B7-1/B7-2 were required to prevent CD8 T cell deletion. Thus, therapeutic strategies to decrease early virus replication could enhance virus-specific CD8 T cell diversity and function during chronic infection.

Uncovering the underlying immune perturbations that determine long-term severity of chronic virus and Mycobacterium tuberculosis coinfection

Chronic viral infections increase severity of Mycobacterium tuberculosis (Mtb) coinfection, yet how they alter the pulmonary microenvironment to foster coinfection and worsen disease severity is unclear. We developed a coinfection model in mice with chronic lymphocytic choriomeningitis virus and Mtb coinfection that recapitulated the central clinical manifestations of coinfection, including increased Mtb burden, extra-pulmonary dissemination and heightened mortality. These long-term disease consequences were not due to chronic virus-induced immunosuppression or exhaustion, but instead were determined by early alterations in immune surveillance of Mtb coinfection. Mechanistically, increased chronic virus induced TNFα production initially arrested pulmonary Mtb growth, impeding dendritic cell mediated antigen transportation to the lung-draining lymph nodes (LNs) and allowing bacterial sanctuary. The inhibited antigen arrival to LNs delayed CD4 T cell priming, allowing Mtb to replicate to higher set-points before T cell mediated control could be initiated. Once primed, Mtb-specific CD4 T cell differentiation skewed away from the Th1 responses associated with Mtb control, and instead toward Th17 differentiation. The elevated IL17 increased pulmonary neutrophil influx that decreased the long-term survival of coinfected mice. Therapeutically correcting the timing of CD4 T cell priming re-established CD4 Th1 over Th17 dominance, diminished pulmonary neutrophilia, and enabled enhanced Mtb control in the presence of chronic viral coinfection. Thus, Mtb co-opts TNFα from the chronic inflammatory environment to subvert immune-surveillance, avert early immune function and foster long-term coinfection.

A network of immune and microbial modifications underlies viral persistence in the gastrointestinal tract

Many pathogens subvert intestinal immunity to persist within the gastrointestinal tract (GIT); yet, the underlying mechanisms that enable sanctuary specifically in this reservoir are unclear. Using mass cytometry and network analysis, we demonstrate that chronic LCMV infection of the GIT leads to dysregulated microbial composition, a cascade of metabolic alterations, increased susceptibility to GI disease, and a system-wide recalibration of immune composition that defines viral persistence. Chronic infection led to outgrowth of activated Tbet–expressing T reg cell populations unique to the GIT and the rapid erosion of pathogen-specific CD8 tissue-resident memory T cells. Mechanistically, T reg cells and coinhibitory receptors maintained long-term viral sanctuary within the GIT, and their targeting reactivated T cells and eliminated this viral reservoir. Thus, our data provide a high-dimensional definition of the mechanisms of immune regulation that chronic viruses implement to exploit the unique microenvironment of the GIT and identify T reg cells as key modulators of viral persistence in the intestinal tract.

DNA hypomethylating agents increase activation and cytolytic activity of CD8+ T cells

We demonstrate that DNA hypomethylating agent (HMA) treatment can directly modulate the anti-tumor response and effector function of CD8⁺ T cells. In vivo HMA treatment promotes CD8⁺ T cell tumor infiltration and suppresses tumor growth via CD8⁺ T cell-dependent activity. Ex vivo, HMAs enhance primary human CD8⁺ T cell activation markers, effector cytokine production, and anti-tumor cytolytic activity. Epigenomic and transcriptomic profiling shows that HMAs vastly regulate T cell activation-related transcriptional networks, culminating with over-activation of NFATc1 short isoforms. Mechanistically, demethylation of an intragenic CpG island immediately downstream to the 3' UTR of the short isoform was associated with antisense transcription and alternative polyadenylation of NFATc1 short isoforms. High-dimensional single-cell mass cytometry analyses reveal a selective effect of HMAs on a subset of human CD8⁺ T cell subpopulations, increasing both the number and abundance of a granzyme B^high, perforin^high effector subpopulation. Overall, our findings support the use of HMAs as a therapeutic strategy to boost anti-tumor immune response.

Opposing Roles of Type I Interferons in Cancer Immunity

The immune system is tasked with identifying malignant cells to eliminate or prevent cancer spread. This involves a complex orchestration of many immune cell types that together recognize different aspects of tumor transformation and growth. In response, tumors have developed mechanisms to circumvent immune attack. Type I interferons (IFN-Is) are a class of proinflammatory cytokines produced in response to viruses and other environmental stressors. IFN-Is are also emerging as essential drivers of antitumor immunity, potently stimulating the ability of immune cells to eliminate tumor cells. However, a more complicated role for IFN-Is has arisen, as prolonged stimulation can promote feedback inhibitory mechanisms that contribute to immune exhaustion and other deleterious effects that directly or indirectly permit cancer cells to escape immune clearance. We review the fundamental and opposing functions of IFN-Is that modulate tumor growth and impact immune function and ultimately how these functions can be harnessed for the design of new cancer therapies.

GCN2 drives macrophage and MDSC function and immunosuppression in the tumor microenvironment

General control nonderepressible 2 (GCN2) is an environmental sensor controlling transcription and translation in response to nutrient availability. Although GCN2 is a putative therapeutic target for immuno-oncology, its role in shaping the immune response to tumors is poorly understood. Here, we used mass cytometry, transcriptomics, and transcription factor-binding analysis to determine the functional impact of GCN2 on the myeloid phenotype and immune responses in melanoma. We found that myeloid-lineage deletion of GCN2 drives a shift in the phenotype of tumor-associated macrophages and myeloid-derived suppressor cells (MDSCs) that promotes antitumor immunity. Time-of-flight mass cytometry (CyTOF) and single-cell RNA sequencing showed that this was due to changes in the immune microenvironment with increased proinflammatory activation of macrophages and MDSCs and interferon-γ expression in intratumoral CD8⁺ T cells. Mechanistically, GCN2 altered myeloid function by promoting increased translation of the transcription factor CREB-2/ATF4, which was required for maturation and polarization of macrophages and MDSCs in both mice and humans, whereas targeting Atf4 by small interfering RNA knockdown reduced tumor growth. Last, analysis of patients with cutaneous melanoma showed that GCN2-dependent transcriptional signatures correlated with macrophage polarization, T cell infiltrates, and overall survival. Thus, these data reveal a previously unknown dependence of tumors on myeloid GCN2 signals for protection from immune attack.

Chronic virus infection drives CD8 T cell-mediated thymic destruction and impaired negative selection

Chronic infection provokes alterations in inflammatory and suppressive pathways that potentially affect the function and integrity of multiple tissues, impacting both ongoing immune control and restorative immune therapies. Here we demonstrate that chronic lymphocytic choriomeningitis virus infection rapidly triggers severe thymic depletion, mediated by CD8 T cell-intrinsic type I interferon (IFN) and signal transducer and activator of transcription 2 (Stat2) signaling. Occurring temporal to T cell exhaustion, thymic cellularity reconstituted despite ongoing viral replication, with a rapid secondary thymic depletion following immune restoration by anti-programmed death-ligand 1 (PDL1) blockade. Therapeutic hematopoietic stem cell transplant (HSCT) during chronic infection generated new antiviral CD8 T cells, despite sustained virus replication in the thymus, indicating an impairment in negative selection. Consequently, low amounts of high-affinity self-reactive T cells also escaped the thymus following HSCT during chronic infection. Thus, by altering the stringency and partially impairing negative selection, the host generates new virus-specific T cells to replenish the fight against the chronic infection, but also has the potentially dangerous effect of enabling the escape of self-reactive T cells.

Validation of CyTOF Against Flow Cytometry for Immunological Studies and Monitoring of Human Cancer Clinical Trials

Flow cytometry is a widely applied approach for exploratory immune profiling and biomarker discovery in cancer and other diseases. However, flow cytometry is limited by the number of parameters that can be simultaneously analyzed, severely restricting its utility. Recently, the advent of mass cytometry (CyTOF) has enabled high dimensional and unbiased examination of the immune system, allowing simultaneous interrogation of a large number of parameters. This is important for deep interrogation of immune responses and particularly when sample sizes are limited (such as in tumors). Our goal was to compare the accuracy and reproducibility of CyTOF against flow cytometry as a reliable analytic tool for human PBMC and tumor tissues for cancer clinical trials. We developed a 40+ parameter CyTOF panel and demonstrate that compared to flow cytometry, CyTOF yields analogous quantification of cell lineages in conjunction with markers of cell differentiation, function, activation, and exhaustion for use with fresh and viably frozen PBMC or tumor tissues. Further, we provide a protocol that enables reliable quantification by CyTOF down to low numbers of input human cells, an approach that is particularly important when cell numbers are limiting. Thus, we validate CyTOF as an accurate approach to perform high dimensional analysis in human tumor tissue and to utilize low cell numbers for subsequent immunologic studies and cancer clinical trials.

CCR4 expression on host T cells is a driver for alloreactive responses and lung rejection

Despite current immunosuppressive strategies, long-term lung transplant outcomes remain poor due to rapid allogenic responses. Using a stringent mouse model of allo-airway transplantation, we identify the CCR4-ligand axis as a central node driving secondary lymphoid tissue homing and activation of the allogeneic T cells that prevent long-term allograft survival. CCR4 deficiency on transplant recipient T cells diminishes allograft injury and when combined with CTLA4-Ig leads to an unprecedented long-term lung allograft accommodation. Thus, we identify CCR4-ligand interactions as a central mechanism driving allogeneic transplant rejection and suggest it as a potential target to enhance long-term lung transplant survival.

High dimensional analysis of the GI tract as a long-term reservoir for chronic viral infection

Chronic viruses such as HIV and hepatitis are a major health concern worldwide. As an organ constantly exposed to the external environment, the gastrointestinal tract (GIT) must constantly balance suppressive and inflammatory immunity, making it an ideal organ for virus persistence. Yet despite its importance, chronic virus infection of the GIT and its ramifications towards host immunity remains poorly understood. We recently discovered that the GIT is a long-term reservoir for chronic lymphocytic choriomeningitis virus (LCMV); persisting well after virus is cleared from the blood and other peripheral tissues.

To identify host and microbial alterations that facilitate chronic GIT infection we performed high dimensional CyTOF analysis, 16s rRNA-seq and next generation sequencing. Primary infection induced acute CD4 T cell ablation and chronic infection promoted Treg outgrowth, which was associated with viral persistence. Interestingly, chronic infection led to acute GI pathology and dysbiosis, with long-term infection enhancing susceptibility to IBD. Transcriptional signatures indicated enhanced type I interferon induced inflammation and metabolic changes associated with immune exhaustion. Interestingly, upstream regulators of GIT immunity were shared in chronic LCMV, HIV and SIV, indicating the induction of conserved pathways across multiple viral infections. Finally, we demonstrate the efficacy of immunotherapeutic targets and cell depletions to control the long-lived chronic GIT reservoir. Ultimately our studies define molecular, cellular and microbial impacts of chronic virus infection to alter GI function and identify potential immunotherapeutic strategies to control virus in this long-lived reservoir.

An interim report on the investigator-initiated phase 2 study of pembrolizumab immunological response evaluation (INSPIRE)

Background

Immune checkpoint inhibitors (ICIs) demonstrate unprecedented efficacy in multiple malignancies; however, the mechanisms of sensitivity and resistance are poorly understood and predictive biomarkers are scarce. INSPIRE is a phase 2 basket study to evaluate the genomic and immune landscapes of peripheral blood and tumors following pembrolizumab treatment.

Methods

Patients with incurable, locally advanced or metastatic solid tumors that have progressed on standard therapy, or for whom no standard therapy exists or standard therapy was not deemed appropriate, received 200 mg pembrolizumab intravenously every three weeks. Blood and tissue samples were collected at baseline, during treatment, and at progression. One core biopsy was used for immunohistochemistry and the remaining cores were pooled and divided for genomic and immune analyses. Univariable analysis of clinical, genomic, and immunophenotyping parameters was conducted to evaluate associations with treatment response in this exploratory analysis.

Results

Eighty patients were enrolled from March 21, 2016 to June 1, 2017, and 129 tumor and 382 blood samples were collected. Immune biomarkers were significantly different between the blood and tissue. T cell PD-1 was blocked (≥98%) in the blood of all patients by the third week of treatment. In the tumor, 5/11 (45%) and 11/14 (79%) patients had T cell surface PD-1 occupance at weeks six and nine, respectively. The proportion of genome copy number alterations and abundance of intratumoral 4-1BB+ PD-1+ CD8 T cells at baseline (P < 0.05), and fold-expansion of intratumoral CD8 T cells from baseline to cycle 2–3 (P < 0.05) were associated with treatment response.

Conclusion

This study provides technical feasibility data for correlative studies. Tissue biopsies provide distinct data from the blood and may predict response to pembrolizumab.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0541-0) contains supplementary material, which is available to authorized users.

Recirculating Intestinal IgA-Producing Cells Regulate Neuroinflammation via IL-10

Plasma cells (PC) are found in the CNS of multiple sclerosis (MS) patients, yet their source and role in MS remains unclear. We find that some PC in the CNS of mice with experimental autoimmune encephalomyelitis (EAE) originate in the gut and produce immunoglobulin A (IgA). Moreover, we show that IgA⁺ PC are dramatically reduced in the gut during EAE, and likewise, a reduction in IgA-bound fecal bacteria is seen in MS patients during disease relapse. Removal of plasmablast (PB) plus PC resulted in exacerbated EAE that was normalized by the introduction of gut-derived IgA⁺ PC. Furthermore, mice with an over-abundance of IgA⁺ PB and/or PC were specifically resistant to the effector stage of EAE, and expression of interleukin (IL)-10 by PB plus PC was necessary and sufficient to confer resistance. Our data show that IgA⁺ PB and/or PC mobilized from the gut play an unexpected role in suppressing neuroinflammation.

CD8+ T Cell Priming in Established Chronic Viral Infection Preferentially Directs Differentiation of Memory-like Cells for Sustained Immunity

CD8⁺ T cell exhaustion impedes control of chronic viral infection; yet how new T cell responses are mounted during chronic infection is unclear. Unlike T cells primed at the onset of infection that rapidly differentiate into effectors and exhaust, we demonstrate that virus-specific CD8⁺ T cells primed after establishment of chronic LCMV infection preferentially generate memory-like transcription factor TCF1⁺ cells that were transcriptionally and proteomically distinct, less exhausted, and more responsive to immunotherapy. Mechanistically, adaptations of antigen-presenting cells and diminished T cell signaling intensity promoted differentiation of the memory-like subset at the expense of rapid effector cell differentiation, which was now highly dependent on IL-21-mediated CD4⁺ T cell help for its functional generation. Chronic viral infection similarly redirected de novo differentiation of tumor-specific CD8⁺ T cells, ultimately preventing cancer control. Thus, targeting these T cell stimulatory pathways could enable strategies to control chronic infection, tumors, and enhance immunotherapeutic efficacy.

CRACR2A-Mediated TCR Signaling Promotes Local Effector Th1 and Th17 Responses

Ca²⁺ release-activated Ca²⁺ channel regulator 2A (CRACR2A) is expressed abundantly in T cells and acts as a signal transmitter between TCR stimulation and activation of the Ca²⁺/NFAT and JNK/AP1 pathways. CRACR2A has been linked to human diseases in numerous genome-wide association studies and was shown to be one of the most sensitive targets of the widely used statin drugs. However, the physiological role of CRACR2A in T cell functions remains unknown. In this study, using transgenic mice for tissue-specific deletion, we show that CRACR2A promotes Th1 responses and effector function of Th17 cells. CRACR2A was abundantly expressed in Th1 and Th17 cells. In vitro, deficiency of CRACR2A decreased Th1 differentiation under nonpolarizing conditions, whereas the presence of polarizing cytokines compensated this defect. Transcript analysis showed that weakened TCR signaling by deficiency of CRACR2A failed to promote Th1 transcriptional program. In vivo, conditional deletion of CRACR2A in T cells alleviated Th1 responses to acute lymphocytic choriomeningitis virus infection and imparted resistance to experimental autoimmune encephalomyelitis. Analysis of CNS from experimental autoimmune encephalomyelitis-induced mice showed impaired effector functions of both Th1 and Th17 cell types, which correlated with decreased pathogenicity. Collectively, our findings demonstrate the requirement of CRACR2A-mediated TCR signaling in Th1 responses as well as pathogenic conversion of Th17 cells, which occurs at the site of inflammation.

Diagnostic accuracy of a prototype rapid chlamydia and gonorrhoea recombinase polymerase amplification assay: a multicentre cross-sectional preclinical evaluation

Objectives

Rapid and accurate sexually transmitted infection diagnosis can reduce onward transmission and improve treatment efficacy. We evaluated the accuracy of a 15-minute run-time recombinase polymerase amplification–based prototype point-of-care test (TwistDx) for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG).

Methods

Prospective, multicentre study of symptomatic and asymptomatic patients attending three English sexual health clinics. Research samples provided were additional self-collected vulvovaginal swab (SCVS) (female participants) and first-catch urine (FCU) aliquot (female and male participants). Samples were processed blind to the comparator (routine clinic CT/NG nucleic acid amplification test (NAAT)) results. Discrepancies were resolved using Cepheid CT/NG GeneXpert.

Results

Both recombinase polymerase amplification and routine clinic NAAT results were available for 392 male and 395 female participants. CT positivity was 8.9% (35/392) (male FCU), 7.3% (29/395) (female FCU) and 7.1% (28/395) (SCVS). Corresponding NG positivity was 3.1% (12/392), 0.8% (3/395) and 0.8% (3/395). Specificity and positive predictive values were 100% for all sample types and both organisms, except male CT FCU (99.7% specificity (95% confidence interval (CI) 98.4–100.0; 356/357), 97.1% positive predictive value (95% CI 84.7–99.9; 33/34)). For CT, sensitivity was ≥94.3% for FCU and SCVS. CT sensitivity for female FCU was higher (100%; 95% CI, 88.1–100; 29/29) than for SCVS (96.4%; 95% CI, 81.7–99.9; 27/28). NG sensitivity and negative predictive values were 100% in FCU (male and female).

Conclusions

This prototype test has excellent performance characteristics, comparable to currently used NAATs, and fulfils several World Health Organization ASSURED criteria. Its rapidity without loss of performance suggests that once further developed and commercialized, this test could positively affect clinical practice and public health.

Priming of CD8 T cells in established chronic viral infection directs a distinct differentiation and functional program for long-term immunity

CD8 T cell exhaustion impedes control of chronic virus infection, yet how CD8 T cell fate decisions and function are instilled and progressively controlled throughout infection is unclear. We demonstrate that in contrast to T cells primed at the onset of persistent viral infection, CD8 T cells primed after the chronic infection is established preferentially generate into memory-like cells that resist contraction, are less exhausted and have heightened responsiveness to immunotherapy. Mechanistically, viral persistence down-regulates APC activation machinery, decreasing T cell intrinsic TCR and CD28 signaling upon priming. The lower signal intensity provides the required threshold for activation and proliferation, but alters transcriptional programming and cellular differentiation to enable long-term retention of antiviral functions despite high levels of virus replication. In the absence of strong antigenic signaling, IL-21 acquires the ability to induce functional effectors, while preserving the memory-like reservoir. Analogous mechanisms also govern differentiation of anti-tumor CD8 T cells in the tumor microenvironment during chronic viral infection, undermining tumor control. Thus, dynamic changes in signal intensity and IL-21 usage during chronic infection function as fate-assigning rheostats to resist exhaustion and program long-term immunity.

Overcoming CD4 Th1 Cell Fate Restrictions to Sustain Antiviral CD8 T Cells and Control Persistent Virus Infection

Viral persistence specifically inhibits CD4 Th1 responses and promotes Tfh immunity, but the mechanisms that suppress Th1 cells and the disease consequences of their loss are unclear. Here, we demonstrate that the loss of CD4 Th1 cells specifically leads to progressive CD8 T cell decline and dysfunction during viral persistence. Therapeutically reconstituting CD4 Th1 cells restored CD4 T cell polyfunctionality, enhanced antiviral CD8 T cell numbers and function, and enabled viral control. Mechanistically, combined interaction of PD-L1 and IL-10 by suppressive dendritic cell subsets inhibited new CD4 Th1 cells in both acute and persistent virus infection, demonstrating an unrecognized suppressive function for PD-L1 in virus infection. Thus, the loss of CD4 Th1 cells is a key event leading to progressive CD8 T cell demise during viral persistence with important implications for restoring antiviral CD8 T cell immunity to control persistent viral infection.

A CD103+ Conventional Dendritic Cell Surveillance System Prevents Development of Overt Heart Failure during Subclinical Viral Myocarditis

Innate and adaptive immune cells modulate heart failure pathogenesis during viral myocarditis, yet their identities and functions remain poorly defined. We utilized a combination of genetic fate mapping, parabiotic, transcriptional, and functional analyses and demonstrated that the heart contained two major conventional dendritic cell (cDC) subsets, CD103⁺ and CD11b⁺, which differentially relied on local proliferation and precursor recruitment to maintain their tissue residency. Following viral infection of the myocardium, cDCs accumulated in the heart coincident with monocyte infiltration and loss of resident reparative embryonic-derived cardiac macrophages. cDC depletion abrogated antigen-specific CD8⁺ T cell proliferative expansion, transforming subclinical cardiac injury to overt heart failure. These effects were mediated by CD103⁺ cDCs, which are dependent on the transcription factor BATF3 for their development. Collectively, our findings identified resident cardiac cDC subsets, defined their origins, and revealed an essential role for CD103⁺ cDCs in antigen-specific T cell responses during subclinical viral myocarditis.

Purging Exhausted Virus-Specific CD8 T Cell Phenotypes by Somatic Cell Reprogramming

Cytotoxic T cells are critical in controlling virus infections. However, continuous antigen stimulation and negative regulatory factors cause CD8 T cells to enter a dysfunctional state (T cell exhaustion), resulting in viral persistence. We hypothesized that the exhausted T cell state could be molecularly rejuvenated using a somatic cell reprogramming technology, which is technically able to convert any types of cells to induced pluripotent stem cells (iPSCs), to regenerate functional T cells capable of purging chronic infection. We generated a new mouse line (B6/129^OKSM) in which every somatic cell contains four doxycycline-inducible reprogramming genes (Oct4, Klf4, Sox2, and c-Myc: OKSM), and infected them with lymphocytic choriomeningitis virus (LCMV) clone 13 to establish chronic infection. Exhausted LCMV-specific T cells isolated by flow sorting were successfully reprogrammed ex vivo into iPSCs in the presence of doxycycline. Upon injection into blastocysts and subsequent transfer into foster females, the reprogrammed cells differentiated into functional naive T cells that maintained their original antigen specificity. These results provide proof of concept that somatic cell reprogramming of exhausted T cells into iPSCs can erase imprints of their previous exhausted state and in turn regenerate functional virus-specific T cells.

Type I Interferon in Chronic Virus Infection and Cancer

Type I interferons (IFN-Is) are emerging as key drivers of inflammation and immunosuppression in chronic infection. Control of these infections requires IFN-I signaling; however, prolonged IFN-I signaling can lead to immune dysfunction. IFN-Is are also emerging as double-edged swords in cancer, providing necessary inflammatory signals, while initiating feedback suppression in both immune and cancer cells. Here, we review the proinflammatory and suppressive mechanisms potentiated by IFN-Is during chronic virus infections and discuss the similar, newly emerging dichotomy in cancer. We then discuss how this understanding is leading to new therapeutic concepts and immunotherapy combinations. We propose that, by modulating the immune response at its foundation, it may be possible to widely reshape immunity to control these chronic diseases.

Targeting type I interferon-mediated activation restores immune function in chronic HIV infection

Chronic immune activation, immunosuppression, and T cell exhaustion are hallmarks of HIV infection, yet the mechanisms driving these processes are unclear. Chronic activation can be a driving force in immune exhaustion, and type I interferons (IFN-I) are emerging as critical components underlying ongoing activation in HIV infection. Here, we have tested the effect of blocking IFN-I signaling on T cell responses and virus replication in a murine model of chronic HIV infection. Using HIV-infected humanized mice, we demonstrated that in vivo blockade of IFN-I signaling during chronic HIV infection diminished HIV-driven immune activation, decreased T cell exhaustion marker expression, restored HIV-specific CD8 T cell function, and led to decreased viral replication. Antiretroviral therapy (ART) in combination with IFN-I blockade accelerated viral suppression, further decreased viral loads, and reduced the persistently infected HIV reservoir compared with ART treatment alone. Our data suggest that blocking IFN-I signaling in conjunction with ART treatment can restore immune function and may reduce viral reservoirs during chronic HIV infection, providing validation for IFN-I blockade as a potential therapy for HIV infection.

Overcoming CD4 T helper cell fate restrictions to enhance CD8 T cell and B cell immunity to control persistent LCMV infection

Persistent viral infection inhibits CD4 Th1 responses, resulting in loss of the CD8 T cell helping Th1 subset and accumulation of B cell helping Tfh cells. Yet, the mechanisms that inhibit CD4 Th1 differentiation and the repercussions of loss of Th1 cells on viral control are unclear. Herein, we demonstrate that the dual upregulation of PD-L1 and IL-10 by chronic type I interferon (IFN-I) signaling during persistent infection suppresses CD4 Th1 priming. Therapeutic blockade of IL-10R and PD-L1 could restore the differentiation of new CD4 Th1 cells, highlighting a new function for PD-L1 to co-inhibit CD4 Th1 priming and identifying a new combinatorial suppressive mechanism during persistent infection. However, CD4 Th1 cells generated by blocking IFN-I signaling in vivo could not be sustained, giving way to a Tfh based response and predominant help to B cells. In vitro polarized virus-specific CD4 Th1 cells also converted towards Tfh cells, however maintained a population of Th1 cells that could enhance exhausted CD8 T cell responses and promote augmented viral clearance. Interestingly, virus-specific CD4 Th17 and Treg cells were also redirected towards Tfh as persistent infection progressed. Thus, our studies have important implications for stability of de novo activated and immunotherapeutic T cells and demonstrate that the redirection away from Th1 responses is a mechanism of immunosuppression to limit the control of persistent viral infection.

Type I and Type II Interferon Coordinately Regulate Suppressive Dendritic Cell Fate and Function during Viral Persistence

Persistent viral infections are simultaneously associated with chronic inflammation and highly potent immunosuppressive programs mediated by IL-10 and PDL1 that attenuate antiviral T cell responses. Inhibiting these suppressive signals enhances T cell function to control persistent infection; yet, the underlying signals and mechanisms that program immunosuppressive cell fates and functions are not well understood. Herein, we use lymphocytic choriomeningitis virus infection (LCMV) to demonstrate that the induction and functional programming of immunosuppressive dendritic cells (DCs) during viral persistence are separable mechanisms programmed by factors primarily considered pro-inflammatory. IFNγ first induces the de novo development of naive monocytes into DCs with immunosuppressive potential. Type I interferon (IFN-I) then directly targets these newly generated DCs to program their potent T cell immunosuppressive functions while simultaneously inhibiting conventional DCs with T cell stimulating capacity. These mechanisms of monocyte conversion are constant throughout persistent infection, establishing a system to continuously interpret and shape the immunologic environment. MyD88 signaling was required for the differentiation of suppressive DCs, whereas inhibition of stimulatory DCs was dependent on MAVS signaling, demonstrating a bifurcation in the pathogen recognition pathways that promote distinct elements of IFN-I mediated immunosuppression. Further, a similar suppressive DC origin and differentiation was also observed in Mycobacterium tuberculosis infection, HIV infection and cancer. Ultimately, targeting the underlying mechanisms that induce immunosuppression could simultaneously prevent multiple suppressive signals to further restore T cell function and control persistent infections.

Persistent virus infections induce host derived immunosuppressive factors that attenuate the immune response and prevent control of infection. Although the mechanisms of T cell exhaustion are being defined, we know surprisingly little about the underlying mechanisms that induce the immunosuppressive state and the origin and functional programming of the cells that deliver these signals to the T cells. We recently demonstrated that type I interferon (IFN-I) signaling was responsible for many of the immune dysfunctions associated with persistent virus infection and in particular the induced expression of the suppressive factors IL-10 and PDL1 by dendritic cells (DCs). Yet, mechanistically how IFN-I signaling specifically generates and programs cells to become immunosuppressive is still unknown. Herein, we define the underlying mechanisms of IFN-I mediated immunosuppression and establish that the induction of factors and the generation of the DCs that express them are separable events integrally reliant on additional inflammatory factors. Further, we demonstrate a similar derivation of the suppressive DCs that emerge in other diseases associated with prolonged inflammation and immunosuppression, specifically in HIV infection, Mycobacterium tuberculosis, and cancer, indicating a conserved origin of immunosuppression and suggesting that targeting the pathways that underlie expression of immunosuppressive cells and factors could be beneficial to treat multiple chronic diseases.

Limiting Cholesterol Biosynthetic Flux Spontaneously Engages Type I IFN Signaling

Cellular lipid requirements are achieved through a combination of biosynthesis and import programs. Using isotope tracer analysis, we show that type I interferon (IFN) signaling shifts the balance of these programs by decreasing synthesis and increasing import of cholesterol and long chain fatty acids. Genetically enforcing this metabolic shift in macrophages is sufficient to render mice resistant to viral challenge, demonstrating the importance of reprogramming the balance of these two metabolic pathways in vivo. Unexpectedly, mechanistic studies reveal that limiting flux through the cholesterol biosynthetic pathway spontaneously engages a type I IFN response in a STING-dependent manner. The upregulation of type I IFNs was traced to a decrease in the pool size of synthesized cholesterol and could be inhibited by replenishing cells with free cholesterol. Taken together, these studies delineate a metabolic-inflammatory circuit that links perturbations in cholesterol biosynthesis with activation of innate immunity.

Abstract CT329: Phase I study of the PI3Kβ/δ inhibitor AZD8186 in patients with advanced castration resistant prostate cancer, triple negative breast cancer, squamous non-small cell lung cancer or PTEN deficient solid tumors: update from dose-finding

Background: A frequent mechanism of dysregulation of the PI3K/AKT/mTOR pathway, commonly altered in cancer, is loss of function of the tumour suppressor PTEN, leading to increased PI3K signalling, particularly through the PI3Kβ isoform. AZD8186 is a potent and selective inhibitor of PI3Kβ/δ with significant activity in PTEN-deficient preclinical models. We report the dose-finding portion of the study, assessing the safety/tolerability of an intermittent dosing schedule of AZD8186.

Trial design and eligibility criteria: AZD8186 tablets were administered twice daily 5 days on treatment, 2 days off (5/2 schedule) in 3 week cycles. Escalating doses of AZD8186 were evaluated in cohorts of 3-6 evaluable patients treated until confirmed disease progression, unacceptable toxicity, or withdrawal of consent. A safety review committee reviewed all available safety data and dose limiting toxicities (DLTs) prior to each dose modification. The dose/schedule finding, safety and activity will be updated at time of presentation. Adult patients were recruited with tumor types known to be PTEN deficient or to have prevalent PTEN loss, such as castration-resistant prostate cancer (CRPC), triple negative breast cancer, squamous non-small cell lung cancer or, that had relapsed and/or were refractory to suitable therapies.

Results: As of 25 Oct, 32 patients have received treatment (30 mg n = 7, 60 mg n = 6, 120 mg n = 5; 240 mg n = 6, 360 mg n = 6; 300 mg n = 2). Pharmacokinetic parameters show that systemic exposures to parent drug and its major active metabolite increased in a dose proportional manner and exceeded preclinical exposures that have demonstrated robust anti-tumour activity in PTEN deficient xenograft models. DLTs of maculopapular rash (CTCAE Grade 3) were observed at 360 mg (in 2/6 patients) and at 300 mg (2/2 patients). Additional AEs occurring in &gt;10% of patients included diarrhea, nausea, vomiting, fatigue, rash, decreased appetite and QTc prolongation. AEs of ≥ grade 3 included: rash, hypophosphatemia, hypokalemia, diarrhea elevated aspartate transaminase and 1st degree atrioventricular block; there were no grade 5 events. Overall, 11 patients remained on study for at least 60 days; one CRPC patient remained on study for more than 160 days with minor PSA response, symptomatic improvement and stable disease by CT and bone scan.

Conclusions: AZD8186 is a potent oral inhibitor of PI3Kβ/δ, with potential for treatment of PTEN-deficient tumors. Investigation of the safety/tolerability of the 5/2 schedule is continuing. This agent may hold potential for treatment of PTEN deficient tumors.

Citation Format: Lillian L. Siu, Johann De Bono, Kari B. Wisinski, Celestia S. Higano, Natalie Cook, Maria Jose De Miguel Luken, Rajiv Kumar, Joshua Lang, Gurkamal S. Chatta, Sara M. Tolaney, Stefan M. Symeonides, Gilmour Morrison, Patrick D. Mitchell, David G. Brooks, Geoffrey I. Shapiro. Phase I study of the PI3Kβ/δ inhibitor AZD8186 in patients with advanced castration resistant prostate cancer, triple negative breast cancer, squamous non-small cell lung cancer or PTEN deficient solid tumors: update from dose-finding. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT329. doi:10.1158/1538-7445.AM2015-CT329

LKB1 inhibition of NF-κB in B cells prevents T follicular helper cell differentiation and germinal center formation

T-cell-dependent antigenic stimulation drives the differentiation of B cells into antibody-secreting plasma cells and memory B cells, but how B cells regulate this process is unclear. We show that LKB1 expression in B cells maintains B-cell quiescence and prevents the premature formation of germinal centers (GCs). Lkb1-deficient B cells (BKO) undergo spontaneous B-cell activation and secretion of multiple inflammatory cytokines, which leads to splenomegaly caused by an unexpected expansion of T cells. Within this cytokine response, increased IL-6 production results from heightened activation of NF-κB, which is suppressed by active LKB1. Secreted IL-6 drives T-cell activation and IL-21 production, promoting T follicular helper (TFH ) cell differentiation and expansion to support a ~100-fold increase in steady-state GC B cells. Blockade of IL-6 secretion by BKO B cells inhibits IL-21 expression, a known inducer of TFH -cell differentiation and expansion. Together, these data reveal cell intrinsic and surprising cell extrinsic roles for LKB1 in B cells that control TFH -cell differentiation and GC formation, and place LKB1 as a central regulator of T-cell-dependent humoral immunity.

New insights into type I interferon and the immunopathogenesis of persistent viral infections

Most viruses generate potent T cell responses that rapidly control infection. However, certain viruses can subvert the immune response to establish persistent infections. The inability to clear virus induces an immunosuppressive program leading to the sustained expression of many immunoregulatory molecules that down-regulate T cell responses. Further, viral persistence is associated with multiple immune dysfunctions including lymphoid disorganization, defective antigen presentation, aberrant B cell responses and hypergammaglobulinemia. Although best known for its antiviral activity, recent data has highlighted the role of type I IFN (IFN-I) signaling as a central mediator of immunosuppression during viral persistence. It is also becoming increasingly apparent that many of the immune dysfunctions during persistent virus infection can be attributed directly or indirectly to the effects of chronic IFN-I signaling. This review explores the increasingly complex role of IFN-I in the regulation of immunity against persistently replicating virus infections and examines current and potential uses of IFN-I and blockade of IFN-I signaling to dampen chronic inflammation and activation in the clinic.

Suppression of Fcγ-receptor-mediated antibody effector function during persistent viral infection

Understanding how viruses subvert host immunity and persist is essential for developing strategies to eliminate infection. T cell exhaustion during chronic viral infection is well described, but effects on antibody-mediated effector activity are unclear. Herein, we show that increased amounts of immune complexes generated in mice persistently infected with lymphocytic choriomeningitis virus (LCMV) suppressed multiple Fcγ-receptor (FcγR) functions. The high amounts of immune complexes suppressed antibody-mediated cell depletion, therapeutic antibody-killing of LCMV infected cells and human CD20-expressing tumors, as well as reduced immune complex-mediated cross-presentation to T cells. Suppression of FcγR activity was not due to inhibitory FcγRs or high concentrations of free antibody, and proper FcγR functions were restored when persistently infected mice specifically lacked immune complexes. Thus, we identify a mechanism of immunosuppression during viral persistence with implications for understanding effective antibody activity aimed at pathogen control.

Discovery of novel drugs for promising targets

BACKGROUND

Once a promising drug target is identified, the steps to actually discover and optimize a drug are diverse and challenging.

OBJECTIVE

The goal of this study was to provide a road map to navigate drug discovery.

METHODS

Review general steps for drug discovery and provide illustrating references.

RESULTS

A number of approaches are available to enhance and accelerate target identification and validation. Consideration of a variety of potential mechanisms of action of potential drugs can guide discovery efforts. The hit to lead stage may involve techniques such as high-throughput screening, fragment-based screening, and structure-based design, with informatics playing an ever-increasing role. Biologically relevant screening models are discussed, including cell lines, 3-dimensional culture, and in vivo screening. The process of enabling human studies for an investigational drug is also discussed.

CONCLUSIONS

Drug discovery is a complex process that has significantly evolved in recent years.

Networking at the level of host immunity: immune cell interactions during persistent viral infections

Persistent viral infections are the result of a series of connected events that culminate in diminished immunity and the inability to eliminate infection. By building our understanding of how distinct components of the immune system function both individually and collectively in productive versus abortive responses, new potential therapeutic targets can be developed to overcome immune dysfunction and thus fight persistent infections. Using lymphocytic choriomeningitis virus (LCMV) as a model of a persistent virus infection and drawing parallels to persistent human viral infections such as human immunodeficiency virus (HIV) and hepatitis C virus (HCV), we describe the cellular relationships and interactions that determine the outcome of initial infection and highlight immune targets for therapeutic intervention to prevent or treat persistent infections. Ultimately, these findings will further our understanding of the immunologic basis of persistent viral infection and likely lead to strategies to treat human viral infections.

Decoding the complexity of type I interferon to treat persistent viral infections

Type I interferons (IFN-I) are a broad family of cytokines that are central to the innate immune response. These proteins have long been appreciated for the critical roles they play in restraining viral infections and shaping antiviral immune responses. However, in recent years there has been increased awareness of the immunosuppressive actions of these proteins as well. Although there are many current therapeutic applications to manipulate IFN-I pathways, we have limited understanding of the mechanisms by which these therapies are actually functioning. In this review, we highlight the diversity and temporal impact of IFN-I signaling, discuss the current therapeutic uses of IFN-I, and explore the strategy of blocking IFN-I to alleviate immune dysfunction in persistent virus infections.

Final results of the phase I trial of niraparib (MK4827), a poly(ADP)ribose polymerase (PARP) inhibitor incorporating proof of concept biomarker studies and expansion cohorts involving BRCA1/2 mutation carriers, sporadic ovarian, and castration resistant prostate cancer (CRPC)

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Background: Niraparib(N) is an oral, potent PARP1/2 inhibitor that induces synthetic lethality in BRCA1/2 deficient tumors. PARP is also implicated in transcription regulated by the androgen receptor (AR) and rearranged ETS genes; key targets in CRPC. Methods: Dose-escalation was enriched for BRCA1/2mutation carriers (BRCA-MCs). Two MTD expansion cohorts were undertaken in patients (pts) with sporadic high grade serous ovarian cancer (HGSOC) and CRPC. In CRPC pts, archival tissue and circulating tumor cells (CTC) were analyzed for PTEN deletion and ETS gene rearrangements. Results: 100 pts [ovary (49), CRPC (23), breast (12) others (16)], received N at 10 dose levels: 30mg to 400mg daily (od), continuously. Grade (G) 4 thrombocytopenia was dose limiting at 400mg od; MTD was established at 300mg od. Drug-related toxicities were G1-2 reversible anemia (48%), fatigue (42%), nausea (42%), thrombocytopenia (35%), anorexia (27%), neutropenia (24%), constipation (23%), and vomiting (20%). PKs were dose proportional with a mean elimination t1/2of 40 hours. Peripheral blood mononuclear cells had >50% PARP inhibition from 80 mg od. gH2AX foci formation, a marker of DNA damage, was seen in CTCs. Antitumor activity occurred from 60mg od with RECIST and/or CA125 partial responses (PR) in 9/20 (45%) BRCA-MC ovarian cancer pts and 2/4 (50%) BRCA-MC breast cancer pts. Platinum-sensitive vs resistant BRCA-MC HGSOC response rate was 60% vs 33% with median time for responding pts of 429 and 340 days, respectively. In sporadic HGSOC, there were 2/3 PRs in platinum-sensitive pts, and 3/20 PRs plus 4/20 stable disease (SD) >16 weeks in platinum resistant pts. In CRPC, symptomatic benefit and SD >6 months (median 9 months) was seen in 9/21 (43%) pts treated at MTD. CTC declines of >30% (median 80%; range 36%-92%) were observed in 7/10 (70%) pts with evaluable CTC counts (≥5 cells/ 7.5mL blood). Conclusions: Niraparib was well tolerated and has promising antitumor activity in BRCA-MCs, sporadic HGSOC and CRPC. Clinical trial information: NCT0074902.