Abstract 5208: Monocyte-produced Chitinase-3-like 1 is a driver of metastatic behavior in prostate cancer patients
Authors: Cavassani Karen A. , Meza Rebecca J. , Habiel David M. , Chen Jie-Fu , Montes Alexander , Tripathi Manisha , Martins Gislaine A. , Crother Timothy R. , You Sungyong , Hogaboam Cory M. , Bhowmick Neil , Posadas Edwin M. 
Published: August 2018

Abstract
Purpose: The identification, functional status, distribution, and interactions of immune cells in prostate cancer (PCa) patients have yet to be fully characterized. Understanding these details could provide key insights as to how promising current and developing immunotherapies might be directed toward PCa. Recruited myeloid cells are known to promote cancer initiation, malignant progression, metastasis, and resistance to therapy in the tumor niche. In the present study, we tested the hypothesis that circulating blood monocytes from advanced PCa patients exhibit a protumor phenotype and directly influence the tumor microenvironment in response to tumor-derived signals.
Experimental Design: Monocytes from metastatic (PCa-M) and nonmetastatic (PCa-N) patient blood samples were isolated, cultured, and conditioned media (CM) was obtained. To evaluate the role of monocytes in metastatic behaviors of PCa cells, in vitro invasion (via Matrigel) and motility assays (Incucyte® Live Cell Analysis System) were performed using monocyte-CM. To identify the candidate PCa-M monocyte-secreted protein(s) that might be implicated in tumor progression, we analyzed the CM using Proteome Profiler Analysis (R&D). Data were validated using ELISA and qPCR.
Results: Herein, we report that CM from circulating monocytes in patients with PCa/mCRPC (metastatic castration-resistant PCa) increased motility and invasion of epithelial PCa cells in vitro. Proteome Profiler Analysis revealed that monocyte-derived CM from metastatic PCa/mCRPC patients presented high levels of Chitinase-3-like 1 (CHI3L1, YKL-40) when compared with PCa-N patients and healthy-control individuals (HC). The only described receptor for CHI3L1, interleukin-13 receptor α2 (IL-13Rα2), was significantly upregulated in the human metastatic prostate cancer cell line, ARCaPM. Accordingly, we observed that the activation of IL-13Rα2 from PCa-M CM increased the invasiveness of ARCaPM cells, and siRNA directed against this receptor significantly reduced invasiveness of these cells in the presence of CM from PCa-M patients.
Conclusions: Thus, we show that circulating monocytes from metastatic PCa/mCRPC patients exert a tumor-promoting role via the secretion of CHI3L1, and CHI3L1 demands further exploration as a possible therapeutic target in advanced PCa.
Citation Format: Karen A. Cavassani, Rebecca J. Meza, David M. Habiel, Jie-Fu Chen, Alexander Montes, Manisha Tripathi, Gislaine A. Martins, Timothy R. Crother, Sungyong You, Cory M. Hogaboam, Neil Bhowmick, Edwin M. Posadas. Monocyte-produced Chitinase-3-like 1 is a driver of metastatic behavior in prostate cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5208.