Sphingosine Kinase-1 Is Central to Androgen-Regulated Prostate Cancer Growth and Survival Audrey Dayon1,2, Leyre Brizuela1,2, Claire Martin1,2, Catherine Mazerolles1,4, Nelly Pirot2, Nicolas Doumerc2,3, Leonor Nogueira5, Muriel Golzio1,2, Justin Teissie´ 1,2, Guy Serre5, Pascal Rischmann1,2,3, Bernard Malavaud1,2,3, Olivier Cuvillier1,2,3* 1 CNRS, Institut de Pharmacologie et de Biologie Structurale, Toulouse, France, 2 Universite´ de Toulouse, UPS, IPBS, Toulouse, France, 3 CHU Toulouse, H oˆpital Rangueil, Service d’Urologie et de Transplantation Re´nale, Toulouse, France, 4 CHU Toulouse, H oˆpital Rangueil, Laboratoire Anatomie Pathologique et Histologie-Cytologie, Toulouse, France, 5 CHU Toulouse, H oˆpital Purpan, Laboratoire de Biologie Cellulaire et Cytologie, Toulouse, France Abstract Background: Sphingosine kinase-1 (SphK1) is an oncogenic lipid kinase notably involved in response to anticancer therapies in prostate cancer. Androgens regulate prostate cancer cell proliferation, and androgen deprivation therapy is the standard of care in the management of patients with advanced disease. Here, we explored the role of SphK1 in the regulation of androgen-dependent prostate cancer cell growth and survival. Methodology/Principal Findings: Short-term androgen removal induced a rapid and transient SphK1 inhibition associated with a reduced cell growth in vitro and in vivo, an event that was not observed in the hormono-insensitive PC-3 cells. Supporting the critical role of SphK1 inhibition in the rapid effect of androgen depletion, its overexpression could impair the cell growth decrease. Similarly, the addition of dihydrotestosterone (DHT) to androgen-deprived LNCaP cells re-established cell proliferation, through an androgen receptor/PI3K/Akt dependent stimulation of SphK1, and inhibition of SphK1 could markedly impede the effects of DHT. Conversely, long-term removal of androgen support in LNCaP and C4-2B cells resulted in a progressive increase in SphK1 expression and activity throughout the progression to androgen-independence state, which was characterized by the acquisition of a neuroendocrine (NE)-like cell phenotype. Importantly, inhibition of the PI3K/ Akt pathway—by negatively impacting SphK1 activity—could prevent NE differentiation in both cell models, an event that could be mimicked by SphK1 inhibitors. Fascinatingly, the reversability of the NE phenotype by exposure to normal medium was linked with a pronounced inhibition of SphK1 activity. Conclusions/Significance: We report the first evidence that androgen deprivation induces a differential effect on SphK1 activity in hormone-sensitive prostate cancer cell models. These results also suggest that SphK1 activation upon chronic androgen deprivation may serve as a compensatory mechanism allowing prostate cancer cells to survive in androgen- depleted environment, giving support to its inhibition as a potential therapeutic strategy to delay/prevent the transition to androgen-independent prostate cancer. Citation: Dayon A, Brizuela L, Martin C, Mazerolles C, Pirot N, et al. (2009) Sphingosine Kinase-1 Is Central to Androgen-Regulated Prostate Cancer Growth and Survival. PLoS ONE 4(11): e8048. doi:10.1371/journal.pone.0008048 Editor: Joseph Alan Bauer, Bauer Research Foundation, United States of America Received July 23, 2009; Accepted November 2, 2009; Published November 26, 2009 Copyright: 2009 Dayon et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by Inserm, CNRS, Fondation pour la Recherche Me´dicale, Association pour la Recherche sur les Tumeurs de la Prostate, and Institut National du Cancer (to OC). AD is recipient of the Ministe`re de l’Enseignement Supe´rieur et de la Recherche and La Ligue Nationale Contre le Cancer. CM is recipient of the Ministe`re de l’Enseignement Supe´rieur et de la Recherche. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: olivier.cuvillier@ipbs.fr Introduction Prostate cancer is the most frequent malignancy accounting for 25% of all newly diagnosed cancers in men and is the second leading cause of death from cancer [1]. Primary treatment with surgery or radiation therapy in patients with organ-confined prostate cancer demonstrates overall 10-year survival rates of over 75% [2,3]. In spite of that, it is estimated that approximatively 15% of the patients present locally advanced or metastatic disease, and about 40% of patients will relapse after local therapy [4]. Prostate cancer cell proliferation is regulated by androgens and androgen deprivation therapy (ADT) is the standard of care in the management of patients with advanced disease. ADT is initially effective, reducing both prostate size and prostate-specific antigen (PSA) levels, but ultimately all patients become resistant to hormonal manipulation [4]. ADT induces changes in prostate cancer biology promoting its progression to the androgen- refractory state or hormone-refractory prostate cancer (HRPC) phenotype, with an associated life expectancy of only 15 to 20 months. It is not clear how prostate cancer cells make the transition from androgen-dependent to androgen-independent status after ADT. Among the multiple mechanisms involved in circumventing the effects of androgen ablation, the activation of the phosphatidylinositol-3-kinase/Akt (PI3K/Akt) signaling has been described as a central pathway [5,6,7,8,9]. Importantly, clinical studies have confirmed the importance of Akt activation in PLoS ONE | www.plosone.org 1 November 2009 | Volume 4 | Issue 11 | e8048