Inflammatory ER stress responses dictate the immunopathogenic progression of systemic candidiasis

Recognition of pathogen-associated molecular patterns can trigger the inositol-requiring enzyme 1 α (IRE1α) arm of the endoplasmic reticulum (ER) stress response in innate immune cells. This process maintains ER homeostasis and also coordinates diverse immunomodulatory programs during bacterial and viral infections. However, the role of innate IRE1α signaling in response to fungal pathogens remains elusive. Here, we report that systemic infection with the human opportunistic fungal pathogen Candida albicans induced proinflammatory IRE1α hyperactivation in myeloid cells that led to fatal kidney immunopathology. Mechanistically, simultaneous activation of the TLR/IL-1R adaptor protein MyD88 and the C-type lectin receptor dectin-1 by C. albicans induced NADPH oxidase-driven generation of ROS, which caused ER stress and IRE1α-dependent overexpression of key inflammatory mediators such as IL-1β, IL-6, chemokine (C-C motif) ligand 5 (CCL5), prostaglandin E2 (PGE2), and TNF-α. Selective ablation of IRE1α in leukocytes, or treatment with an IRE1α pharmacological inhibitor, mitigated kidney inflammation and prolonged the survival of mice with systemic C. albicans infection. Therefore, controlling IRE1α hyperactivation may be useful for impeding the immunopathogenic progression of disseminated candidiasis.

Decoding endoplasmic reticulum stress signals in cancer cells and antitumor immunity

The tumor microenvironment (TME) provokes endoplasmic reticulum (ER) stress in malignant cells and infiltrating immune populations. Sensing and responding to ER stress is coordinated by the unfolded protein response (UPR), an integrated signaling pathway governed by three ER stress sensors: activating transcription factor (ATF6), inositol-requiring enzyme 1α (IRE1α), and protein kinase R (PKR)-like ER kinase (PERK). Persistent UPR activation modulates malignant progression, tumor growth, metastasis, and protective antitumor immunity. Hence, therapies targeting ER stress signaling can be harnessed to elicit direct tumor killing and concomitant anticancer immunity. We highlight recent findings on the role of the ER stress responses in onco-immunology, with an emphasis on genetic vulnerabilities that render tumors highly sensitive to therapeutic UPR modulation.

Tumor-Derived Lysophosphatidic Acid Blunts Protective Type I Interferon Responses in Ovarian Cancer

Lysophosphatidic acid (LPA) is a bioactive lipid enriched in the tumor microenvironment of immunosuppressive malignancies such as ovarian cancer. Although LPA enhances the tumorigenic attributes of cancer cells, the immunomodulatory activity of this phospholipid messenger remains largely unexplored. Here, we report that LPA operates as a negative regulator of type I interferon (IFN) responses in ovarian cancer. Ablation of the LPA-generating enzyme autotaxin (ATX) in ovarian cancer cells reprogrammed the tumor immune microenvironment, extended host survival, and improved the effects of therapies that elicit protective responses driven by type I IFN. Mechanistically, LPA sensing by dendritic cells triggered PGE2 biosynthesis that suppressed type I IFN signaling via autocrine EP4 engagement. Moreover, we identified an LPA-controlled, immune-derived gene signature associated with poor responses to combined PARP inhibition and PD-1 blockade in patients with ovarian cancer. Controlling LPA production or sensing in tumors may therefore be useful to improve cancer immunotherapies that rely on robust induction of type I IFN.

SIGNIFICANCE

This study uncovers that ATX-LPA is a central immunosuppressive pathway in the ovarian tumor microenvironment. Ablating this axis sensitizes ovarian cancer hosts to various immunotherapies by unleashing protective type I IFN responses. Understanding the immunoregulatory programs induced by LPA could lead to new biomarkers predicting resistance to immunotherapy in patients with cancer. See related commentary by Conejo-Garcia and Curiel, p. 1841. This article is highlighted in the In This Issue feature, p. 1825.

Optineurin Guards IFNγ Signaling in Cancer Cells

In this issue, Du and colleagues uncover that optineurin functions as a key regulator of IFNγ receptor (IFNGR1) stability in malignant cells. Loss of optineurin in colorectal cancer cells causes IFNGR1 degradation, leading to impaired IFNγ signaling, decreased MHC-I expression, and enhanced ability to evade adaptive immune control.See related article by Du et al., p. 1826.

Transcriptional Signature Derived from Murine Tumor-Associated Macrophages Correlates with Poor Outcome in Breast Cancer Patients

Tumor-associated macrophages (TAMs) are frequently the most abundant immune cells in cancers and are associated with poor survival. Here, we generated TAM molecular signatures from K14cre;Cdh1^flox/flox;Trp53^flox/flox (KEP) and MMTV-NeuT (NeuT) transgenic mice that resemble human invasive lobular carcinoma (ILC) and HER2⁺ tumors, respectively. Determination of TAM-specific signatures requires comparison with healthy mammary tissue macrophages to avoid overestimation of gene expression differences. TAMs from the two models feature a distinct transcriptomic profile, suggesting that the cancer subtype dictates their phenotype. The KEP-derived signature reliably correlates with poor overall survival in ILC but not in triple-negative breast cancer patients, indicating that translation of murine TAM signatures to patients is cancer subtype dependent. Collectively, we show that a transgenic mouse tumor model can yield a TAM signature relevant for human breast cancer outcome prognosis and provide a generalizable strategy for determining and applying immune cell signatures provided the murine model reflects the human disease.

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Murine TAM signatures prognosticate outcomes in corresponding cancer patients

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TAM signatures are robust when they are compared with healthy tissue macrophages

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TAM transcriptome is dictated by tissue and tumor subtype-related signals

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Murine TAM signatures can be translated only when a suitable model is chosen

Therapeutic targeting of macrophages enhances chemotherapy efficacy by unleashing type I interferon response

Recent studies have revealed a role for macrophages and neutrophils in limiting chemotherapy efficacy; however, the mechanisms underlying the therapeutic benefit of myeloid-targeting agents in combination with chemotherapy are incompletely understood. Here, we show that targeting tumour-associated macrophages by colony-stimulating factor-1 receptor (CSF-1R) blockade in the K14cre;Cdh1^F/F;Trp53^F/F transgenic mouse model for breast cancer stimulates intratumoural type I interferon (IFN) signalling, which enhances the anticancer efficacy of platinum-based chemotherapeutics. Notably, anti-CSF-1R treatment also increased intratumoural expression of type I IFN-stimulated genes in patients with cancer, confirming that CSF-1R blockade is a powerful strategy to trigger an intratumoural type I IFN response. By inducing an inflamed, type I IFN-enriched tumour microenvironment and by further targeting immunosuppressive neutrophils during cisplatin therapy, antitumour immunity was activated in this poorly immunogenic breast cancer mouse model. These data illustrate the importance of breaching multiple layers of immunosuppression during cytotoxic therapy to successfully engage antitumour immunity in breast cancer.

Purification of Immune Cell Populations from Freshly Isolated Murine Tumors and Organs by Consecutive Magnetic Cell Sorting and Multi-parameter Flow Cytometry-Based Sorting

It is well established that tumors evolve together with nonmalignant cells, such as fibroblasts, endothelial cells, and immune cells. These cells constantly entangle and interact with each other creating the tumor microenvironment. Immune cells can exert both tumor-promoting and tumor-protective functions. Detailed phenotypic and functional characterization of intra-tumoral immune cell subsets has become increasingly important in the field of cancer biology and cancer immunology. In this chapter, we describe a method for isolation of viable and pure immune cell subsets from freshly isolated murine solid tumors and organs. First, we describe a protocol for the generation of single-cell suspensions from tumors and organs using mechanical and enzymatic strategies. In addition, we describe how immune cell subsets can be purified by consecutive magnetic cell sorting and multi-parameter flow cytometry-based cell sorting.

Mammary tumor-derived CCL2 enhances pro-metastatic systemic inflammation through upregulation of IL1β in tumor-associated macrophages

Patients with primary solid malignancies frequently exhibit signs of systemic inflammation. Notably, elevated levels of neutrophils and their associated soluble mediators are regularly observed in cancer patients, and correlate with reduced survival and increased metastasis formation. Recently, we demonstrated a mechanistic link between mammary tumor-induced IL17-producing γδ T cells, systemic expansion of immunosuppressive neutrophils and metastasis formation in a genetically engineered mouse model for invasive breast cancer. How tumors orchestrate this systemic inflammatory cascade to facilitate dissemination remains unclear. Here we show that activation of this cascade relies on CCL2-mediated induction of IL1β in tumor-associated macrophages. In line with these findings, expression of CCL2 positively correlates with IL1Β and macrophage markers in human breast tumors. We demonstrate that blockade of CCL2 in mammary tumor-bearing mice results in reduced IL17 production by γδ T cells, decreased neutrophil expansion and enhanced CD8⁺ T cell activity. These results highlight a new role for CCL2 in facilitating the breast cancer-induced pro-metastatic systemic inflammatory γδ T cell – IL17 – neutrophil axis.

Abstract IA04: Cancer-associated systemic inflammation facilitates breast cancer metastasis

Over 90% of breast cancer deaths are due to complications as a consequence of metastasis formation. Despite its devastating effects, metastatic disease is still poorly understood. Accumulating evidence indicates that cells and mediators of the immune system influence metastasis formation. In our lab, we use preclinical mouse models for metastatic breast cancer to dissect the impact of the immune system on the different steps of the metastatic cascade. Neutrophils make up a significant proportion of the inflammatory infiltrate in many tumors and their systemic accumulation in cancer patients has been associated with metastasis formation. Also in our recently developed spontaneous breast cancer metastasis mouse model that accurately mimics each step of the metastatic cascade in humans, metastasis formation is accompanied by pronounced systemic accumulation of neutrophils. Antibody-mediated depletion of neutrophils did not affect primary breast cancer outgrowth, but profoundly decreased spontaneous metastasis formation in lungs and lymph nodes. Using biological and genetic approaches, we have uncovered a novel mammary tumor-induced systemic communication network between gamma delta T cells and neutrophils that is critical for breast cancer metastasis. Our data indicate that targeting this novel cancer cell-initiated systemic inflammatory cascade represents a viable strategy to inhibit metastatic disease.

Citation Format: Seth B. Coffelt, Kelly Kersten, Max Wellenstein, Chris W. Doornebal, Camilla Salvagno, Kim Vrijland, Cheei-Sing Hau, Jos Jonkers, Karin E. de Visser. Cancer-associated systemic inflammation facilitates breast cancer metastasis. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr IA04.

Exploiting the Immunomodulatory Properties of Chemotherapeutic Drugs to Improve the Success of Cancer Immunotherapy

Cancer immunotherapy is gaining momentum in the clinic. The current challenge is to understand why a proportion of cancer patients do not respond to cancer immunotherapy, and how this can be translated into the rational design of combinatorial cancer immunotherapy strategies aimed at maximizing success of immunotherapy. Here, we discuss how tumors orchestrate an immunosuppressive microenvironment, which contributes to their escape from immune attack. Relieving the immunosuppressive networks in cancer patients is an attractive strategy to extend the clinical success of cancer immunotherapy. Since the clinical availability of drugs specifically targeting immunosuppressive cells or mediators is still limited, an alternative strategy is to use conventional chemotherapy drugs with immunomodulatory properties to improve cancer immunotherapy. We summarize the preclinical and clinical studies that illustrate how the anti-tumor T cell response can be enhanced by chemotherapy-induced relief of immunosuppressive networks. Treatment strategies aimed at combining chemotherapy-induced relief of immunosuppression and T cell-boosting checkpoint inhibitors provide an attractive and clinically feasible approach to overcome intrinsic and acquired resistance to cancer immunotherapy, and to extend the clinical success of cancer immunotherapy.

Abstract IA07: Cancer-associated inflammation facilitates metastatic breast cancer and counteracts chemoresponsiveness

Over 90% of breast cancer deaths are due to complications as a consequence of metastasis formation. Much progress has been made in understanding primary breast cancer formation; however, metastatic disease is still largely unexplored, poorly understood and incurable. Clearly, there is an urgent need for novel therapies with efficacious anti-metastatic activity. The different steps of the metastatic cascade are largely regulated by reciprocal interactions between cancer cells and their microenvironment. Accumulating evidence indicates that cells and mediators of the immune system can facilitate metastasis formation. To mechanistically study how immune cells and their mediators modulate breast cancer metastasis, we have recently developed a mouse model of spontaneous breast cancer metastasis that mimics the clinical course of metastatic disease in humans. The basis is the K14cre;EcadF/F;p53F/F transgenic mouse that develops breast cancer resembling human invasive lobular carcinoma. We orthotopically transplant invasive lobular carcinoma fragments from these mice into mammary glands of wild-type syngeneic mice. Once primary tumors are established, we mimic the clinical setting and perform a mastectomy. Following surgery, the mice develop clinically overt metastases in lymph nodes, lungs, liver and other distant organs. This novel mouse model of breast cancer metastasis accurately mimics each step of the metastatic cascade in humans. It provides a unique tool to further explore the biology of metastatic breast cancer with the aim to contribute to the development of more effective treatment strategies.

Neutrophils make up a significant proportion of the inflammatory infiltrate in many tumors and their accumulation in breast cancer patients has been associated with metastasis formation. Also in our spontaneous breast cancer metastasis mouse model, metastasis formation is accompanied by a very pronounced accumulation of neutrophils in circulation and distant organs. Antibody-mediated depletion of neutrophils did not affect primary breast cancer outgrowth, but did result in a profound decrease in lung and lymph node metastasis. Using biological and genomic approaches, we have uncovered a novel communication network between gamma delta T cells and neutrophils that is critical for breast cancer metastasis. We are currently dissecting the mechanisms by which neutrophils facilitate breast cancer metastasis formation.

Besides regulating metastatic disease, the immune system also modulates responsiveness of cancer to conventional forms of therapy. Using the K14cre;EcdF/F;p53F/F mouse mammary tumor model, we study the ability of the immune system to influence the anti-cancer efficacy of chemotherapy. We have observed that it is very important to optimally match chemotherapeutic drugs with immunomodulatory compounds. In addition, combining chemotherapy with an immunomodulatory drug can trigger a rewiring of the inflammatory tumor microenvironment resulting in immune-dependent therapy resistance. Taken together, through mechanistic understanding of the crosstalk between the immune system and cancer, we aim to contribute to the design of novel immunomodulatory strategies to fight metastatic breast cancer and to increase the efficacy of conventional anti-cancer therapies.

(Supported by the Dutch Cancer Society grant 2011-5004, NWO/VIDI 91796307, AICR 11-0677 and FP7 MCA-ITN 317445)

Citation Format: Seth B. Coffelt, Chris W. Doornebal, Metamia Ciampricotti, Camilla Salvagno, Kelly Kersten, Kim Vrijland, Cheei-Sing Hau, Jos Jonkers, Karin E. De Visser. Cancer-associated inflammation facilitates metastatic breast cancer and counteracts chemoresponsiveness. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr IA07. doi:10.1158/1538-7445.CHTME14-IA07

Therapeutic benefit of lentiviral-mediated neonatal intracerebral gene therapy in a mouse model of globoid cell leukodystrophy

Globoid cell leukodystrophy (GLD) is an inherited lysosomal storage disease caused by β-galactocerebrosidase (GALC) deficiency. Gene therapy (GT) should provide rapid, extensive and lifetime GALC supply in central nervous system (CNS) tissues to prevent or halt irreversible neurologic progression. Here we used a lentiviral vector (LV) to transfer a functional GALC gene in the brain of Twitcher mice, a severe GLD model. A single injection of LV.GALC in the external capsule of Twitcher neonates resulted in robust transduction of neural cells with minimal and transient activation of inflammatory and immune response. Importantly, we documented a proficient transduction of proliferating and post-mitotic oligodendroglia, a relevant target cell type in GLD. GALC activity (30–50% of physiological levels) was restored in the whole CNS of treated mice as early as 8 days post-injection. The early and stable enzymatic supply ensured partial clearance of storage and reduction of psychosine levels, translating in amelioration of histopathology and enhanced lifespan. At 6 months post-injection in non-affected mice, LV genome persisted exclusively in the injected region, where transduced cells overexpressed GALC. Integration site analysis in transduced brain tissues showed no aberrant clonal expansion and preferential targeting of neural-specific genes. This study establishes neonatal LV-mediated intracerebral GT as a rapid, effective and safe therapeutic intervention to correct CNS pathology in GLD and provides a strong rationale for its application in this and similar leukodystrophies, alone or in combination with therapies targeting the somatic pathology, with the final aim of providing an effective and timely treatment of these global disorders.

Competitive antagonism by phenylglycine derivatives at type I metabotropic glutamate receptors

The metabotropic glutamate receptors (mGluRs) form a family of G-protein-coupled receptors which consists of at least seven members termed mGluR1-mGluR7. These members are classified into subfamilies according to their sequence similarities, signal transduction mechanisms and agonist selectivities. mGluR1 and mGluR5 are coupled to the phosphoinositide hydrolysis/Ca2+ signal transduction and efficiently respond to quisqualate. In this study, we have stably expressed mGluR1 in Chinese hamster ovary cells on which the activation of the phosphoinositide signal transduction pathway was evaluated by means of two methods and their degree of correspondence was analyzed. These two methods involve the Li(+)-dependent accumulation of [3H]inositol-labeled inositol phosphates or the [3H]cytidine-labeled phospholiponucleotide cytidine diphospho (CDP)- diacylglycerol (DAG). The correlation between the two measures was found to be generally uniform for the different agonists evaluated. However, the levels of CDP-DAG were found to be consistently higher. Furthermore, quisqualate showed a differential activity on the two methods behaving as a partial agonist and as a full agonist on the inositol phosphate and the CDP-DAG responses, respectively. On the same cells the activity of a series of carboxyphenylglycines recently described as possible new tools for investigating the role of mGluRs has been evaluated. Three phenylglycine derivatives were tested and found to be competitive antagonists at this mGluR subtype. They inhibited both the phosphoinositide signal transduction pathway and the release of intracellular Ca2+ induced by quisqualate the most potent agonist at mGluR1. The pharmacological nature of these compounds and their relative potencies in antagonizing mGluR1 activation are described.