PT  - JOURNAL ARTICLE
AU  - Zoila A. Lopez-Bujanda
AU  - Michael C. Haffner
AU  - Matthew G. Chaimowitz
AU  - Nivedita Chowdhury
AU  - Nicholas J. Venturini
AU  - Aleksandar Obradovic
AU  - Corey S. Hansen
AU  - Joanna Jacków
AU  - Karen S. Sfanos
AU  - Charles J. Bieberich
AU  - Paula J. Hurley
AU  - Mark J. Selby
AU  - Alan J. Korman
AU  - Angela M. Christiano
AU  - Angelo M. De Marzo
AU  - Charles G. Drake
TI  - Castration-mediated IL-8 Promotes Myeloid Infiltration and Prostate Cancer Progression
AID  - 10.1101/651083
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 651083
4099  - http://biorxiv.org/content/early/2019/05/28/651083.short
4100  - http://biorxiv.org/content/early/2019/05/28/651083.full
AB  - Immunotherapy is a treatment for many types of cancer, primarily due to deep and durable clinical responses mediated by immune checkpoint blockade (ICB)1, 2. Prostate cancer is a notable exception in that it is generally unresponsive to ICB. The standard treatment for advanced prostate cancer is androgen-deprivation therapy (ADT), a form of castration (CTX). ADT is initially effective, but over time patients eventually develop castration-resistant prostate cancer (CRPC). Here, we focused on defining tumor-cell intrinsic factors that contribute to prostate cancer progression and resistance to immunotherapy. We analyzed cancer cells isolated from castration-sensitive and castration-resistant prostate tumors, and discovered that castration resulted in significant secretion of Interleukin-8 (IL-8) and it’s likely murine homolog Cxcl15. These chemokines drove subsequent intra-tumoral infiltration with polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), promoting tumor progression. PMN-MDSC infiltration was abrogated when IL-8 was deleted from prostate cancer epithelial cells using CRISPR/Cas9, or when PMN-MDSC migration was blocked with antibodies against the IL-8 receptor CXCR2. Blocking PMN-MDSC infiltration in combination with anti-CTLA-4 delayed the onset of castration resistance and increased the density of polyfunctional CD8 T cells in tumors. Taken together, our findings establish castration-mediated IL-8 secretion and subsequent PMN-MDSC infiltration as a key suppressive mechanism in the progression of prostate cancer. Targeting of the IL-8/CXCR2 axis around the time of ADT, in combination with ICB, represents a novel therapeutic approach to delay prostate cancer progression to advanced disease.