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Chromatin Regulator CHD1 Remodels the Immunosuppressive Tumor Microenvironment in PTEN-Deficient Prostate Cancer.

ABSTRACT: Genetic inactivation of PTEN is common in prostate cancer and correlates with poorer prognosis. We previously identified CHD1 as an essential gene in PTEN-deficient cancer cells. Here, we sought definitive in vivo genetic evidence for, and mechanistic understanding of, the essential role of CHD1 in PTEN-deficient prostate cancer. In Pten and Pten/Smad4 genetically engineered mouse models, prostate-specific deletion of Chd1 resulted in markedly delayed tumor progression and prolonged survival. Chd1 deletion was associated with profound tumor microenvironment (TME) remodeling characterized by reduced myeloid-derived suppressor cells (MDSC) and increased CD8⁺ T cells. Further analysis identified IL6 as a key transcriptional target of CHD1, which plays a major role in recruitment of immunosuppressive MDSCs. Given the prominent role of MDSCs in suppressing responsiveness to immune checkpoint inhibitors (ICI), our genetic and tumor biological findings support combined testing of anti-IL6 and ICI therapies, specifically in PTEN-deficient prostate cancer. SIGNIFICANCE: We demonstrate a critical role of CHD1 in MDSC recruitment and discover CHD1/IL6 as a major regulator of the immunosuppressive TME of PTEN-deficient prostate cancer. Pharmacologic inhibition of IL6 in combination with immune checkpoint blockade elicits robust antitumor responses in prostate cancer.This article is highlighted in the In This Issue feature, p. 1241.

SUBMITTER: Zhao D

PROVIDER: S-EPMC7483306 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Chromatin Regulator CHD1 Remodels the Immunosuppressive Tumor Microenvironment in PTEN-Deficient Prostate Cancer.

Zhao Di D Cai Li L Lu Xin X Liang Xin X Li Jiexi J Chen Peiwen P Ittmann Michael M Shang Xiaoying X Jiang Shan S Li Haoyan H Meng Chenling C Flores Ivonne I Song Jian H JH Horner James W JW Lan Zhengdao Z Wu Chang-Jiun CJ Li Jun J Chang Qing Q Chen Ko-Chien KC Wang Guocan G Deng Pingna P Spring Denise J DJ Wang Y Alan YA DePinho Ronald A RA

Cancer discovery 20200508 9

Genetic inactivation of PTEN is common in prostate cancer and correlates with poorer prognosis. We previously identified CHD1 as an essential gene in PTEN-deficient cancer cells. Here, we sought definitive in vivo genetic evidence for, and mechanistic understanding of, the essential role of CHD1 in PTEN-deficient prostate cancer. In Pten and Pten/Smad4 genetically engineered mouse models, prostate-specific deletion of Chd1 resulted in markedly del ...[more]

PMID: 32385075

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Project description:BackgroundThe molecular characteristics of prostate cancer (PCa) cells and the immunosuppressive bone tumor microenvironment (TME) contribute to the limitations of immune checkpoint therapy (ICT). Identifying subgroups of patients with PCa for ICT remains a challenge. Herein, we report that basic helix-loop-helix family member e22 (BHLHE22) is upregulated in bone metastatic PCa and drives an immunosuppressive bone TME.MethodsIn this study, the function of BHLHE22 in PCa bone metastases was clarified. We performed immunohistochemical (IHC) staining of primary and bone metastatic PCa samples, and assessed the ability to promote bone metastasis in vivo and in vitro. Then, the role of BHLHE22 in bone TME was determined by immunofluorescence (IF), flow cytometry, and bioinformatic analyses. RNA sequencing, cytokine array, western blotting, IF, IHC, and flow cytometry were used to identify the key mediators. Subsequently, the role of BHLHE22 in gene regulation was confirmed using luciferase reporter, chromatin immunoprecipitation assay, DNA pulldown, co-immunoprecipitation, and animal experiments. Xenograft bone metastasis mouse models were used to assess whether the strategy of immunosuppressive neutrophils and monocytes neutralization by targeting protein arginine methyltransferase 5 (PRMT5)/colony stimulating factor 2 (CSF2) could improve the efficacy of ICT. Animals were randomly assigned to treatment or control groups. Moreover, we performed IHC and correlation analyses to identify whether BHLHE22 could act as a potential biomarker for ICT combination therapies in bone metastatic PCa.ResultsTumorous BHLHE22 mediates the high expression of CSF2, resulting in the infiltration of immunosuppressive neutrophils and monocytes and a prolonged immunocompromised T-cell status. Mechanistically, BHLHE22 binds to the CSF2 promoter and recruits PRMT5, forming a transcriptional complex. PRMT5 epigenetically activates CSF2 expression. In a tumor-bearing mouse model, ICT resistance of Bhlhe22+ tumors could be overcome by inhibition of Csf2 and Prmt5.ConclusionsThese results reveal the immunosuppressive mechanism of tumorous BHLHE22 and provide a potential ICT combination therapy for patients with BHLHE22+ PCa.

Dataset Information

Chromatin Regulator CHD1 Remodels the Immunosuppressive Tumor Microenvironment in PTEN-Deficient Prostate Cancer.

Publications

Chromatin Regulator CHD1 Remodels the Immunosuppressive Tumor Microenvironment in PTEN-Deficient Prostate Cancer.

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