Background: Immunotherapy has emerged as one of the most promising approaches for the treatment of cancer. Unfortunately, a large number of patients and common tumor types do not respond to existing immunotherapies. Tumor-associated macrophages (TAMs), which accumulate in many cancers and suppress anti-tumor immunity, likely contribute to this problem. Hypothesis and Objective: Based on encouraging preliminary data, we hypothesize that engagement of Dectin-2, a pattern recognition receptor that is highly expressed by TAMs in certain tumors, can reprogram TAMs into potent antigen-presenting cells capable of inducing immunity against a wide range of cancers. Our objective is to validate this hypothesis by analyzing the immunological and anti-tumor effects of natural and synthetic Dectin-2 agonists in mouse models of cancer.
Specific Aims :
Aim 1 : Analyze the factors that regulate Dectin-2 expression and the mechanisms by which Dectin-2 agonists reprogram TAMs and induce anti-tumor immunity.
Aim 2 : Assess the anti-tumor effects of natural Dectin-2 agonists, alone and in combination with other agents, on a range of aggressive cancers.
Aim 3 : Synthesize glycopeptide agonists of Dectin-2 and assess their anti-tumor activity alone and in combination with other agents.
Aim 4 : Construct tumor-targeted antibody-glycopeptide conjugates and evaluate their functional and therapeutic effects. Study Design and Methods: Since TAMs in some tumors express little or no Dectin-2, we will analyze the effects of natural Dectin-2 agonists on TAMs in the presence of GM-CSF, which induces Dectin-2 expression. The anti-tumor effects of the agonists will be studied in mouse models of pancreas, breast, colon, lung, and skin cancer with a spectrum of Dectin-2 expression, both as monotherapies and in combination with GM-CSF and other agents shown to enhance the efficacy of Dectin-2 agonists in our mouse models. Mass cytometry and recently developed informatics tools will be utilized to analyze the effects of Dectin-2 ligands on the anti- tumor immune response in multiple tissues. To generate more effective and clinically applicable therapies, a novel synthetic approach will be used to produce compositionally defined Dectin-2 ligands that are optimized for TAM activation. The most efficacious of these synthetic Dectin-2 ligands will be conjugated to tumor- targeted antibodies for purposes of enhanced tumor delivery and TAM-mediated tumor cell killing, and their safety and efficacy assessed. Expected Results and Impact: We expect these experiments to demonstrate that engaging Dectin-2 on TAMs induces immunity against a wide range of tumors, including tumors resistant to checkpoint blockade, and that Dectin-2 agonists used alone or in combination with other anti-tumor agents can induce durable tumor regression. The most promising of these agonists will be candidates for clinical development.

Public Health Relevance

Although therapies that stimulate the immune system can be effective for some patients with cancer, many patients and tumor types do not respond to existing immunotherapies. We discovered a new way to stimulate the immune system to attack and eliminate tumors by reprogramming immune cells known as tumor- associated macrophages, which accumulate in large numbers and typically suppress anti-tumor immune responses. In this project, we will use naturally occurring and chemically synthesized molecules to evaluate the anti-tumor effects of this approach in various tumor models, toward the goal of developing a new kind of cancer immunotherapy.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Cancer Immunopathology and Immunotherapy Study Section (CII)
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Salomon, Rachelle
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Stanford University
Schools of Medicine
United States
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