Abstract 3737: Targeting the YKL40 pathway inhibits monocyte-mediated cell migration of prostate cancer cells following radiotherapy treatment
Authors: Armstrong Chris W. , Wilson Melissa LaBonte , Redmond Kelly M. , Jain Suneil , Waugh David J. 
Published: August 2019

Introduction: Loss of the tumor suppressor PTEN is associated with relapse following radiotherapy (RT) in men with prostate cancer (PCa). We have previously shown that PTEN-deficient tumors display increased monocyte and macrophage infiltration. Co-culture models have confirmed that monocyte-derived paracrine signaling factors can significantly alter the radiation response of PCa cells. The aim of this study is to identify monocyte-derived cytokines that can be therapeutically targeted in combination with RT to reduce the occurrence of relapse in men with PTEN-deficient PCa.

Methods: Techniques employed included: cytokine arrays to detect radiation-induced proteins secreted from monocytes; IF and IHC on FFPE tumor sections; in vitro biological assays extending to RT-PCR, ELISA, immunoblotting and transwell migration assays; and analysis of relevant genes in the FASTMAN radiotherapy patient cohort.

Results: Cytokine array analysis of monocytes with and without prior ionizing radiation exposure identified several upregulated secreted proteins - the most abundant of which was YKL40 (CHI3L1). This was further potentiated in co-culture with PCa cell lines. Secretion of YKL40 was confirmed as being monocyte-derived by ELISA and this was further supported by IF co-staining of YKL40 with a monocyte marker (F4/80) in PTEN-deficient tumour sections. Exposure of PCa cell lines to conditioned media (CM) from irradiated monocytes increased cell migration - an effect that was also observed by direct addition of rhYKL40. Previous studies have reported the role of syndecan-integrin complexes in mediating YKL40 signal transduction. Immunoblotting confirmed expression of these receptors (Sdc1 and αvβ3) on PCa cell lines. Using siRNA to knockdown Sdc1 expression inhibited YKL40-induced activation of the FAK pathway and subsequently attenuated YKL40-induced cell migration. In addition, YKL40 was shown to increase expression of genes involved in both actin cytoskeleton rearrangement and epithelial-mesenchymal transition. Use of a FAK inhibitor (PF-573228) successfully prevented the induction of these genes and attenuated the capacity of YKL40 to drive cell migration. The clinical relevance of our observations is supported by high expression of YKL40-receptor and signaling mediators in prostate cancer biopsy tissue and its correlation to increased biochemical recurrence following RT treatment.

Conclusion: Use of a YKL40-pathway-targeted agent alongside radiotherapy may reduce disease recurrence in men with high-risk clinically-localized PTEN-deficient PCa by preventing radiation-induced cell migration and metastatic escape. Current and future experiments will aim to confirm this via a series of relevant in vivo studies.

Citation Format: Chris W. Armstrong, Melissa LaBonte Wilson, Kelly M. Redmond, Suneil Jain, David J. Waugh. Targeting the YKL40 pathway inhibits monocyte-mediated cell migration of prostate cancer cells following radiotherapy treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3737.