Authors:
Bianca Cioni, Judy van Beijnum, Monique Melis, Johan van Burgsteden, Mauro Muraro, Erik Hooijberg, Dennis Peters, Ingrid Hofland, Yoni Lubeck, Jeroen de Jong, Joyce Sanders, Judith Vivié, Henk van der Poel, Jan Paul de Boer, Arjan Griffioen, Wilbert Zwart, Andries Bergman
 
 
Affiliations:
The Netherlands Cancer Institute, Cancer Center Amsterdam, Hubrecht Institute - KNAW and University Medical Center Utrecht, Eindhoven University of Technology
 
 
 Abstract Body:
 "The Androgen Receptor (AR) is the master regulator of Prostate Cancer (PCa) development, and inhibition of AR signaling is the most effective PCa treatment. AR is expressed in PCa cells and also in the PCa-associated stroma, including infiltrating macrophages. As AR is the main drug target in PCa treatment, cells in the microenvironment are affected by therapy as well. Macrophages play a decisive role in PCa initiation and progression. However, the role of AR in these cells remains largely unexplored.
 
 This study aims to elucidate the functional impact of AR signaling in macrophages, and the downstream consequences thereof on PCa tumor cell behavior.
 
 PCa cell migration and invasion were increased when cultured in conditioned medium of THP-1 macrophage cells stimulated with the synthetic androgen R1881, which was blocked by the anti-androgen RD162. Chromatin Immunoprecipitation, followed by massive parallel sequencing (ChIP-seq) for AR showed increased DNA binding sites upon testosterone stimulation in the macrophages. Ingenuity Pathway Analysis (IPA) revealed the triggering receptor expressed on myeloid cells 1 (TREM-1) signaling pathway as the most-dominant biological process regulated by AR in these cells. Macrophage TREM-1 functioned in trans to drive PCa cell migration and invasion, as both were reduced when cultured in conditioned medium of THP-1 cells with blocked TREM-1 activity. However, how does TREM-1 signaling influence PCa migration? AR-dependent TREM-1 associated chemokines (CCL2, CCL3, CCL7, CXCL8 and CCL13) were upregulated in macrophage THP-1 cells upon R1881 stimulation. Blocking these chemokines decreased migration of PCa cells when cultured in THP-1 conditioned medium. In addition, AR signaling polarized M1 anti-tumor macrophages into M2 like pro-tumor or Tumor Associated Macrophages (TAMs), and the fraction of TAMs in the PCa-associated stroma was lower in patients treated with anti-androgen therapy. 
 
 These data illustrate that activation of AR-mediated TREM-1 signaling in macrophages promotes PCa cell migration and invasion, via increased expression and secretion of chemokines. 
 
 AR activates TREM-1 signaling in macrophages which promotes chemokine-mediated PCa migration. As the observed PCa cell migration is blocked by inhibiting AR in macrophages, our results provide a new microenvironment-centered mechanism of action of AR inhibition in PCa treatment. In addition, our data position TREM-1 blockade as an attractive novel therapeutic target in the treatment of PCa patients."
 
 
 Funding Acknowledgments:
 Netherlands Cancer Institute
 
 
 Corresponding Author Email:
 a.zaalberg@nki.nl
 
 
 Conflict of Interest:
 Nothing to Disclose

Androgen Receptor Signalling in Macrophages Promotes TREM-1-mediated Prostate Cancer Cell Line Migration and Invasion