Implication of NPM1 phosphorylation and preclinical evaluation of the nucleoprotein antagonist N6L in prostate cancer

// Damien Destouches 1, 2, 3 , Maha Sader 1, 3 , Stephane Terry 4 , Charles Marchand 1, 2 , Pascale Maille 1, 2, 5 , Pascale Soyeux 1, 2 , Gilles Carpentier 1, 3 , Fannie Semprez 1, 2 , Jocelyn Ceraline 7 , Yves Allory 1, 2, 5 , Jose Courty 1, 3 , Alexandre De La Taille 1, 2, 6 , Francis Vacherot 1, 2 1 Universite Paris-Est, UPEC, Creteil, F-94000, France 2 INSERM, U955, Equipe 7, Creteil, F-94000, France 3 CNRS, ERL 9215, Laboratoire de Recherche sur la Croissance Cellulaire, la Reparation et la Regeneration Tissulaires (CRRET), Creteil, F-94000, France 4 INSERM, U1186, Gustave Roussy Cancer Campus, Villejuif, F-94805, France 5 AP-HP, Hopital H. Mondor – A. Chenevier, Departement de Pathologie, Creteil, F-94000, France 6 AP-HP, Hopital H. Mondor – A. Chenevier, Departement d’Urologie, Creteil, F-94000, France 7 INSERM, U1113, Federation de Medecine Translationnelle de Strasbourg (FMTS), Universite de Strasbourg, Strasbourg, F-67000, France Correspondence to: Damien Destouches, email: damien.destouches@u-pec.fr Keywords: prostate cancer, NPM1, phosphorylated NPM1, N6L, androgen receptor Received: September 29, 2015      Accepted: February 29, 2016      Published: March 14, 2016 ABSTRACT Despite the advent of several new treatment options over the past years, advanced/metastatic prostate carcinoma (PCa) still remains incurable, which justifies the search for novel targets and therapeutic molecules. Nucleophosmin (NPM1) is a shuttling nucleoprotein involved in tumor growth and its targeting could be a potential approach for cancer therapy. We previously demonstrated that the multivalent pseudopeptide N6L binds to NPM1 potently affecting in vitro and in vivo tumor cell growth of various tumor types as well as angiogenesis. Furthermore, NPM1 binds to androgen receptor (AR) and modulate its activity. In this study, we first investigated the implication of the NPM1 and its Thr199 and Thr234/237 phosphorylated forms in PCa. We showed that phosphorylated forms of NPM1 interact with androgen receptor (AR) in nucleoplasm. N6L treatment of prostate tumor cells led to inhibition of NPM1 phosphorylation in conjunction with inhibition of AR activity. We also found that total and phosphorylated NPM1 were overexpressed in castration-resistant PCa. Assessment of the potential therapeutic role of N6L in PCa indicated that N6L inhibited tumor growth both in vitro and in vivo when used either alone or in combination with the standard-of-care first- (hormonotherapy) and second-line (docetaxel) treatments for advanced PCa. Our findings reveal the role of Thr199 and Thr234/237 phosphorylated NPM1 in PCa progression and define N6L as a new drug candidate for PCa therapy.