Project description:Tumor-associated macrophages (TAMs) are key components of the tumor microenvironment (TME) which can either promote tumor progression (M2) or induce antitumor immunity (M1). The hypothesis of our study is that the expression of FOLR2 is associated with an M2-like macrophage profile. The main goal of this study is to compare the transcriptomic profile of FOLR2 positive and FOLR2 negative TAMs obtained from the ascites of C57BL/6 mice bearing ovarian ID8 intraperitoneal tumors. Abstract: The immunosuppressive tumor microenvironment (TME) represents a major barrier for effective immunotherapy. Tumor-associated macrophages (TAMs) are highly heterogeneous and plastic cell components of the TME which can either promote tumor progression (M2-like) or boost antitumor immunity (M1-like). Selective targeting of the pro-tumorigenic subset of TAMs represents an attractive therapeutic strategy. Here, we demonstrate that a subset of TAMs that expressing folate receptor β (FRβ) possess an immunosuppressive, tumor-promoting M2-like profile, while FRβ negative TAMs feature pro-inflammatory M1 macrophage properties. In syngeneic tumor mouse models, the administration of FRβ-targeted chimeric antigen receptor (CAR) T-cells mediated elimination of FRβ+ TAMs in the TME, which resulted in an enrichment of pro-inflammatory monocytes, an influx of endogenous tumor-specific CD8+ T-cells, delayed tumor progression, and prolonged survival. Preconditioning of the TME with FRβ-specific CAR T-cells also improved the effectiveness of tumor-directed anti-mesothelin CAR T-cells, while simultaneous co-administration of both CAR products did not. Thus, CAR T-cell-mediated depletion of immunosuppressive M2-like TAMs incites a pro-inflammatory TME that broadens endogenous antitumor immunity and limits tumor progression, highlighting the pro-tumor role of FRβ+ TAMs in the TME and the therapeutic implications of TAM-depleting agents as preparative adjuncts to conventional immunotherapies that directly target tumor antigens.

Project description:Neuroblastoma (NB) is considered an immunologically cold tumor and is usually less responsive to immune checkpoint blockade (ICB). Tumor-associated macrophages (TAMs) are highly infiltrated in NB tumors and promote immune escape and resistance to ICB. Hence therapeutic strategies targeting immunosuppressive TAMs can improve responses to ICB in NB. We recently discovered that spleen tyrosine kinase (Syk) reprograms TAMs toward an immunostimulatory phenotype and enhances T-cell responses in the lung adenocarcinoma model. Here we investigated if Syk is an immune-oncology target in NB and tested whether a novel immunotherapeutic approach utilizing Syk inhibitor together with radiation and ICB could provide a durable antitumor immune response in an MYCN amplified murine model of NB. Myeloid Syk KO mice and syngeneic MYCN-amplified cell lines were used to elucidate the effect of myeloid Syk on the NB tumor microenvironment (TME). In addition, the effect of Syk inhibitor, R788, on anti-tumor immunity alone or combination with anti-PDL1 mAb and radiation was also determined in murine NB models. The underlying mechanism of action of this novel therapeutic combination was also investigated. Herein, we report that Syk is a marker of NB -associated macrophages and plays a crucial role in promoting immunosuppression in the NB TME. We found that the blockade of Syk in NB-bearing mice markedly impairs tumor growth. This effect is facilitated by macrophages that become immunogenic in the absence of Syk, skewing the suppressive TME towards immunostimulation and activating anti-tumor immune responses. Moreover, combining FDA-approved Syk inhibitor, R788 (fostamatinib) along with anti-PDL1 mAb provides a synergistic effect leading to complete tumor regression and durable anti-tumor immunity in mice bearing small tumors (50 mm3) but not larger tumors (250 mm3). However, combining radiation to R788 and anti-PDL1 mAb prolongs the survival of mice bearing large NB9464 tumors.

Dataset Information

Expression data from tumor-infiltrating macrophages.

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