Abstract S4-05: Expression of the DEK oncogene promotes M2 polarization and iron recycling in tumor associated macrophages

Abstract

Abstract The chromatin-remodeling DEK oncogene is highly expressed in over 60% of breast cancers, regardless of sub-type. DEK over-expression correlates with poor clinical outcome, including decreased survival and chemotherapy resistance. Previously, using human breast cancer cell lines and the MMTV-Ron mouse breast cancer model, we have demonstrated that DEK expression promotes proliferation and metastasis and supports the breast cancer stem cell population. These functions were due, in part, through upregulated Wnt ligand expression and β-catenin activation, leading to paracrine and autocrine effects promoting tumorigenesis. To investigate additional drivers of DEK-induced tumorigenesis, we performed RNA-Sequencing on control and DEK over-expressing immortalized MCF10A cells. Gene ontology analysis identified several immune signaling processes. This is in alignment with the well-characterized role of DEK expression in the promotion of inflammatory diseases. We investigated the immune cell infiltration of tumors from MMTV-Ron/Dek+/+ and MMTV-Ron/Dek-/- mice. Interestingly, we discovered that Dek-expressing tumors demonstrated decreased tumor associated macrophage (TAM) infiltration, where TAMs were largely limited to the periphery. Furthermore, these TAMs demonstrated an iron-recycling phenotype (M2 polarization), whereas TAMs from Dek-knockout tumors retained iron (M1 polarization). M1 macrophages are typically associated with inflammatory responses whereas M2 macrophages have been linked to tissue remodeling, angiogenesis, and tumor promotion. To investigate this further, we compared Dek+/+ and Dek-/- bone marrow-derived macrophages (BMDM) and found no inherent difference in polarization. However, BMDM demonstrated different gene expression profiles when cultured in conditioned media from Dek-expressing murine breast cancer cell lines compared to isogenic Dek-/- cells. BMDM exposed to conditioned media from Dek-expressing cancer cells demonstrated the same iron recycling phenotype observed in vivo, likely caused by increased expression of ferroportin, as well as increased expression of M2 markers CXCR4, VEGF, and an elevated ARG1hi/NOSlo population. We thus used a combination of genetic models and small molecule inhibitors to identify the mechanism of M2 polarization of BMDM exposed to Dek-expressing cancer cells. NRF2 transcription activity was eliminated as a possible mechanism for ferroportin regulation. However, small molecule inhibitors and gene expression analyses implicated secreted Wnt ligands and S100A8/A9 alarmins from the cancer cells, and downstream C/EBP transcriptional activity in the macrophages, as possible mechanisms of Dek-induced M2 polarization. Combined, this suggests that the poor clinical outcome of high DEK expressing breast cancers may be due to not only cell intrinsic factors, but also cell extrinsic factors, such as the tumor-promoting M2 polarization of tumor associated macrophages. Citation Format: Privette Vinnedge LM, Pease NA, Cheek J. Expression of the DEK oncogene promotes M2 polarization and iron recycling in tumor associated macrophages [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr S4-05.