Androgen-Regulated Expression of Arginase 1, Arginase 2 and Interleukin-8 in Human Prostate Cancer

Philippe O Gannon,Jessica Godin-Ethier,Mona Alam Fahmy,Fred Saad,Réjean Lapointe,Nathalie Delvoye,Benjamin Péant,Alexis O Poisson,Matthew Hassler,Meghan Aversa,Anne-Marie Mes-Masson,Chad Creighton

doi:10.1371/journal.pone.0012107

Philippe O Gannon, Jessica Godin-Ethier + Show 10 more

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https://doi.org/10.1371/journal.pone.0012107

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Abstract

BackgroundProstate cancer (PCa) is the most frequently diagnosed cancer in North American men. Androgen-deprivation therapy (ADT) accentuates the infiltration of immune cells within the prostate. However, the immunosuppressive pathways regulated by androgens in PCa are not well characterized. Arginase 2 (ARG2) expression by PCa cells leads to a reduced activation of tumor-specific T cells. Our hypothesis was that androgens could regulate the expression of ARG2 by PCa cells.Methodology/Principal FindingsIn this report, we demonstrate that both ARG1 and ARG2 are expressed by hormone-sensitive (HS) and hormone-refractory (HR) PCa cell lines, with the LNCaP cells having the highest arginase activity. In prostate tissue samples, ARG2 was more expressed in normal and non-malignant prostatic tissues compared to tumor tissues. Following androgen stimulation of LNCaP cells with 10 nM R1881, both ARG1 and ARG2 were overexpressed. The regulation of arginase expression following androgen stimulation was dependent on the androgen receptor (AR), as a siRNA treatment targeting the AR inhibited both ARG1 and ARG2 overexpression. This observation was correlated in vivo in patients by immunohistochemistry. Patients treated by ADT prior to surgery had lower ARG2 expression in both non-malignant and malignant tissues. Furthermore, ARG1 and ARG2 were enzymatically active and their decreased expression by siRNA resulted in reduced overall arginase activity and l-arginine metabolism. The decreased ARG1 and ARG2 expression also translated with diminished LNCaP cells cell growth and increased PBMC activation following exposure to LNCaP cells conditioned media. Finally, we found that interleukin-8 (IL-8) was also upregulated following androgen stimulation and that it directly increased the expression of ARG1 and ARG2 in the absence of androgens.Conclusion/SignificanceOur data provides the first detailed in vitro and in vivo account of an androgen-regulated immunosuppressive pathway in human PCa through the expression of ARG1, ARG2 and IL-8.

Highlights

Prostate cancer (PCa) is the most frequently diagnosed cancer and third leading cause of cancer related deaths for North American men [1]
Gene expression analyses by Quantitative real-time PCR (qPCR) demonstrated that ARG1 mRNA was more abundant in the 22Rv1 cell line (Figure 1A), while ARG1 protein was slightly more expressed by the two HR PCa cell lines (Du145 and PC3) than in the LNCaP cells (Figure 1B, bottom panel)
Low Arginase 2 (ARG2) mRNA expression was detected in the two HR cell lines DU145 and PC3 compared to the two HS PCa cell lines

Summary

Introduction

Prostate cancer (PCa) is the most frequently diagnosed cancer and third leading cause of cancer related deaths for North American men [1]. The most common treatment modality for men with an advanced stage or recurrent PCa is androgen-deprivation therapy (ADT). Within one to five years following ADT initiation, most patients develop hormone refractory PCa (HRPC), whose treatment remains palliative [4]. New treatment modalities, such as immunotherapy, attempt to tackle these later stages of PCa. current immunotherapies against PCa have resulted in limited success in the clinical settings. Our hypothesis was that androgens could regulate the expression of ARG2 by PCa cells

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