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MyD88/IL-1R axis sustains immunosuppressive function of TAMs by regulating PD-1 expression in melanoma

ABSTRACT: Macrophages are critical mediators of tissue homeostasis, cell proliferation, angiogenesis and tumor metastasis. The presence of TAMs is generally associated with tumor-promoting immunosuppressive function in solid tumors. These macrophages are widely acknowledged as one of the central suppressive populations within tumors, blocking effective T-cell responses. In the present study, we examined the transcriptional landscape of adaptor molecules downstream of TLRs in human cancers and found that higher expression of MYD88 is very well correlated with the tumor progression. In addition, we also found that mouse MyD88 but not TRIF, is essential for tumor progression and angiogenesis in melanoma. Interestingly, MyD88 is critical to maintain the immunosuppressive phenotype of TAMs in the tumors. Moreover, we found that interleukin-1 receptor (IL-1R)-Myd88 axis regulates programmed cell death (PD)-1 expression on TAMs by promoting the recruitment of phospho-NF-κB p65 to the CR-C region of the Pdcd1 promoter. Using myeloid-cell specific MyD88 mutant mice, we also showed that MyD88 expression in myeloid cells alone is sufficient to drive the melanoma progression. Thus, IL-1R/MyD88 axis maintains the immunosuppressive function of tumor-tissue macrophages to promote tumor growth by regulating PD-1/PD-L1 expression

ORGANISM(S): Mus musculus

PROVIDER: GSE137046 | GEO | 2021/03/26

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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MyD88/IL-1R axis sustains immunosuppressive function of TAMs by regulating PD-1 expression in melanoma

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