Abstract 4517: Tumor-associated macrophages are reprogrammed by pancreatic ductal adenocarcinoma cells through tumor-induced DNA methylation on metabolic genes
Authors: Pan Xingyi , Zhang Mengwen , Fujiwara Kenji , Jurcak Noelle R. , Muth Stephen , Zheng Lei 
Published: August 2019

Abstract
Metabolism is shifted toward glycolysis with increased glucose uptake in anti-tumor M1 macrophages, and toward oxidative phosphorylation with significant decreased glucose uptake in pro-tumor M2 macrophages in Pancreatic ductal adenocarcinoma (PDA). Current study aims to investigate the mechanism by which tumor cells reprogram tumor associated macrophages metabolically and functionally. Using mouse bone marrow derived macrophages and human macrophages derived from peripheral blood mononuclear cells for contact and non-contact co-culture experiments with PDA tumor cells, we showed PDA tumor cells, through direct cell-cell contact confirmed by Lucifer yellow dye-coupling assay, induced DNA methylation and downregulation of a panel of glucose metabolism and oxidative phosphorylation genes selectively in M1 but not M2 macrophages by methylation specific PCR, methylation microarray analysis and qPCR, RNA-seq analysis. Glucose-response genes such as IL10 were subsequently activated. Through IL10 and its receptor IL-10R on tumor cells, macrophages enhanced the in vitro migration of tumor cells in trans-well migration assay verified by shRNA knockdown of IL10 and IL10R respectively. Exogenous infusion of both M1 and M2 macrophages promoted PDA metastasis in orthotopic mouse model after resident macrophage depletion, although pretreating with DNA demethylating agent Decitabine prevented M1, but not M2 macrophages in promoting metastasis, suggesting M1 macrophages were reprogrammed metabolically and functionally by tumor cells to become pro-cancerous. To interrogate the mechanism that regulates the tumor-induced DNA methylation in macrophages, we first examined chromatin remodeling complex Polycomb Repressive Complex 2 (PRC2), with its major component enhancer of zeste homolog 2 (EZH2) previously shown to recruit DNA methyltransferases to specific chromatin regions for epigenetic gene regulation. We found EZH2 protein was most significantly increased in M1 macrophages while Ser21 phosphorylated EZH2 (pSer21-EZH2) remained constant, indicating a decreased percentage of pSer21-EZH2/EZH2 in M1 macrophages co-cultured with tumor cells. Further identification of potential F-box containing ubiquitin ligases that interact with pSer21-EZH2 by Co-immunoprecipitation suggested EZH2 may be stabilized in M1 macrophages by tumor cells through inhibiting the ubiquitin-dependent proteolysis of pSer21-EZH2 in a phosphorylation dependent manner. This study thus far reveals a novel mechanism that reprograms M1 macrophages phenotypically into M2-like macrophages and functionally into pro-cancerous macrophages. Identification of cell surface receptors that mediate the direct tumor-macrophage contact are actively being sought, which will lead to the development of therapeutic blockades to reverse the macrophage reprogramming.
Citation Format: Xingyi Pan, Mengwen Zhang, Kenji Fujiwara, Noelle R. Jurcak, Stephen Muth, Lei Zheng. Tumor-associated macrophages are reprogrammed by pancreatic ductal adenocarcinoma cells through tumor-induced DNA methylation on metabolic genes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4517.