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Expression data from cultured mouse bone-marrow monocytes.

ABSTRACT: Retinoic acid signaling regulates monocyte differentiation into dendritic cells or macrophages. We used microarrays to uncover gene expression changes associated with retinoic acid exposure in mouse monocytes. The immunosuppressive tumor microenvironment (TME) is a major barrier to immunotherapy. Within solid tumors, why monocytes preferentially differentiate into immunosuppressive tumor associated macrophages (TAMs) but not immunostimulatory dendritic cells (DCs) remains unclear. Using multiple murine sarcoma models, we found that the TME induced retinoic acid (RA) production by tumor cells, which polarized intratumoral monocyte differentiation towards TAMs and away from DCs via suppression of DC-promoting transcription factor Irf4. Genetic inhibition of RA production by tumor cells or pharmacologic inhibition of RA signaling within TME increased stimulatory monocyte-derived cells, enhanced T cell-dependent anti-tumor immunity and demonstrated striking synergy with immune checkpoint blockade. Further, RA responsive gene signature in human monocytes correlated with an immunosuppressive TME in multiple human tumors. RA has been long considered as an anti-cancer agent, but our work demonstrates its tumorigenic capability via myeloid-mediated immune suppression and provides proof of concept for targeting this pathway for tumor immunotherapy.

ORGANISM(S): Mus musculus

PROVIDER: GSE144609 | GEO | 2020/05/01

REPOSITORIES: GEO

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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.

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Expression data from cultured mouse bone-marrow monocytes.

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