DEK Expression in Breast Cancer Cells Leads to the Alternative Activation of Tumor Associated Macrophages.

Nicholas A Pease,Lisa M Privette Vinnedge,Susan E Waltz,Miranda S Shephard,Mathieu Sertorio

doi:10.3390/cancers12071936

Abstract

Breast cancer (BC) is the second leading cause of cancer deaths among women. DEK is a known oncoprotein that is highly expressed in over 60% of breast cancers and is an independent marker of poor prognosis. However, the molecular mechanisms by which DEK promotes tumor progression are poorly understood. To identify novel oncogenic functions of DEK, we performed RNA-Seq analysis on isogenic Dek-knockout and complemented murine BC cells. Gene ontology analyses identified gene sets associated with immune system regulation and cytokine-mediated signaling and differential cytokine and chemokine expression was confirmed across Dek-proficient versus Dek-deficient cells. By exposing murine bone marrow-derived macrophages (BMDM) to tumor cell conditioned media (TCM) to mimic a tumor microenvironment, we showed that Dek-expressing breast cancer cells produce a cytokine milieu, including up-regulated Tslp and Ccl5 and down-regulated Cxcl1, Il-6, and GM-CSF, that drives the M2 polarization of macrophages. We validated this finding in primary murine mammary tumors and show that Dek expression in vivo is also associated with increased expression of M2 macrophage markers in murine tumors. Using TCGA data, we verified that DEK expression in primary human breast cancers correlates with the expression of several genes identified by RNA-Seq in our murine model and with M2 macrophage phenotypes. Together, our data demonstrate that by regulating the production of multiple secreted factors, DEK expression in BC cells creates a potentially immune suppressed tumor microenvironment, particularly by inducing M2 tumor associated macrophage (TAM) polarization.

Highlights

The prognosis of patients with breast cancer is strongly influenced by the non-cancer cells in the microenvironment
We subsequently generated multiple murine breast cancer cell lines on the FVBN genetic background that were deficient for DEK gene (Dek), re-expressed murine Dek with a retroviral construct to create an isogenic model system (Figure 1C–E) [51]
Given that one of the gene ontologies from the RNA-Seq data identified differentially expressed genes associated with myeloid leukocytes, we focused on how Dek expression within breast cancer cells may impact the polarization and function of tumor associated macrophages

Summary

Introduction

The prognosis of patients with breast cancer is strongly influenced by the non-cancer cells in the microenvironment. Clinical data reveal a negative correlation between tumor-associated macrophage (TAM) density and patient survival as well as response to therapy in all subtypes of breast cancer [5,6,7,8]. The activation of these macrophages dictates their function within the tumor microenvironment. M1 activation, which is largely seen as tumor-inhibiting, is characterized by enhanced phagocytosis function as well as nitric oxide, IL-6, IL-12, and TNF production [9]. M2 activation, which is considered to be a tumor-promoting state, is characterized by the production of arginase, IL-10, and specific membrane proteins like MRC1 and CD163 [9]

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Results

Discussion

Conclusion