Abstract 2836: Expression of the DEK oncogene in breast cancer cells promotes M2 polarization of tumor associated macrophages

Breast cancer is the second leading cause of cancer deaths among women. DEK is a known oncoprotein found to be highly expressed in more than 60% breast cancers and is found to be an independent marker of poor prognosis. However, the molecular mechanisms by which DEK promotes tumor progression are poorly understood. To elucidate the oncogenic functions of DEK, we performed RNA-seq analysis on isogenic Dek-knockout and complemented murine breast cancer cells, which indicated dysregulation of immune signaling. Among the target genes identified and confirmed was an upregulation of thymic stromal lymphopoietin (TSLP) in Dek expressing murine breast cancer cells. TSLP was previously shown by Han et al to amplify the alternative (M2) activation of macrophages. M2-like macrophages are tumor promoting, they recycle iron for cell growth and encourage tissue remodeling and repair activities like angiogenesis. To test the immune modulating functions of Dek-expressing breast cancer cells, we treated bone marrow derived macrophages (BMDM) with tumor cell conditioned media. We found that in vitro, Dek expressing cancer cells induced an M2-like polarization of macrophages, as determined by the expression of M2-associated genes, enhanced migration, and iron recycling phenotypes, which was accompanied by inhibited ERK1/2 signaling. We found this phenotypic trend to be true in vivo, as well. In sectioned mammary tumors from MMTV-RontgDek+/+ and MMTV-RontgDek−/− mice, we see lower levels of iron staining in Dek+/+ tumors than in Dek−/− tumors using Prussian blue staining that co-localized with F4/80 macrophage marker staining. This suggested that Dek expression in the tumors induced an iron recycling, M2-like phenotype in tumor associated macrophages. Furthermore, we observed increased TSLP expression and angiogenesis, as determined by CD31 staining, in Dek-expressing tumors in vivo. These findings suggest that tumor Dek expression may promote breast cancer progression by inducing M2-like macrophage polarization in a murine breast cancer model. Citation Format: Miranda Shephard, Nicholas Pease, Lisa M. Privette Vinnedge. Expression of the DEK oncogene in breast cancer cells promotes M2 polarization of tumor associated macrophages [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2836.