Leukemia Research 39 (2015) 1088–1095 Contents lists available at ScienceDirect Leukemia Research j ourna l h om epa ge: www.elsevier.com/locate/leukres The NO-modified HIV protease inhibitor as a valuable drug for hematological malignancies: Role of p70S6K Danijela Maksimovic-Ivanic a , Marija Mojic a , Mirna Bulatovic a , Milica Radojkovic b , Milos Kuzmanovic c , Slobodan Ristic b , Stanislava Stosic-Grujicic a , Djordje Miljkovic a , Eugenio Cavalli d , Massimo Libra d , Paolo Fagone d , James McCubrey e , Ferdinando Nicoletti d,∗ , Sanja Mijatovic a a Department of Immunology, Institute for Biological Research “Sinisa Stankovic”, Belgrade University, Belgrade, Serbia b Clinical Center “Dr Dragisa Misovic”, Medical Faculty, University of Belgrade, Belgrade, Serbia c Institute for Health Care of Mother and Child of Serbia “Dr Vukan Cupic”, Medical Faculty, University of Belgrade, Belgrade, Serbia d Department of Biomedical Sciences and Biotechnology, University of Catania, Catania, Italy e Department of Microbiology and Immunology, Brody School of Medicine at East Carolina University, Greenville, NC 27858, USA a r t i c l e i n f o Article history: Received 5 November 2014 Received in revised form 9 June 2015 Accepted 19 June 2015 Available online 28 June 2015 Keywords: Saquinavir Saquinavir-NO Acute lymphoid leukemia Acute myeloid leukemia p70S6 kinase a b s t r a c t Covalent attachment of NO to the first approved HIV protease inhibitor Saquinavir (Saq-NO) expands the therapeutic potential of the original drug. Apart from retained antiviral activity, the modified drug exerts strong antitumor effects and lower toxicity. In the present study, we have evaluated the sen- sitivity of different hematological malignancies to Saq-NO. Saq-NO efficiently diminished the viability of Jurkat, Raji, HL-60 and K562 cells. While Jurkat and Raji cells (established from pediatric patients) displayed abrogated proliferative potential, HL-60 and K652 cells (originated from adults) exposed to Saq-NO treatment underwent caspase dependent apoptosis. In addition, similar sensitivity to Saq-NO was observed in mononuclear blood cells obtained from pediatric patients with acute lymphoblastic leukemia (ALL) and adult patients with acute myeloid leukemia (AML). Western blot analysis indicated p70S6 kinase as a possible intracellular target of Saq-NO action. Moreover, the addition of a NO moiety to Lopinavir resulted in improved antitumor potential as compared to the parental compound, suggesting that NO-derived HIV protease inhibitors are a potential new source of anticancer drugs with unique mode of action. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Over the last few decades many discoveries have been achieved in the field of cancer therapy, and in particular in the area of small molecule inhibitors of oncogenic cell signaling pathways [1]. Unfortunately, therapy failure due to relapsed or primary resistant disease is still frequent and is associated to severe toxicity and side effects [2]. Thus, further studies are warranted to identify novel anticancer compounds with similar mode of action but with lower toxicity. Drugs used for the treatment of viral infection such as HIV protease inhibitors (HPIs) may represent a promising therapeutic option in the cancer setting [3]. Their anticancer properties were incidentally noticed when it was observed that patients exposed to ∗ Corresponding author at: Department of Biomedical Sciences and Biotechnology, University of Catania, Via Androne 83, 95124 Catania, Italy. E-mail address: ferdinic@unict.it (F. Nicoletti). HPIs, exhibited significantly lower rate of HIV associated cancers [3]. Independently of HIV protease inhibition, these drugs reduce angiogenesis, cell invasion and viability of malignant cell through induction of apoptosis/autophagy, accompanied with Akt inhibi- tion [4–11]. Beside their effectiveness on solid cancers, HPIs were found efficient in the treatment of blood cancers [12–14]. Ritona- vir induced apoptosis and inhibited NF-kB activity in adult T cell leukemia. Ritonavir, Saquinavir (Saq) and Nelfinavir through their inactivation of STAT3 and ERK1/2 led to growth arrest and apo- ptosis of human multiple myeloma cells [15]. Nelfinavir was also found to induce mitochondria independent apoptosis of leukemia cell lines and impaired proteasome activity and proliferation of multiple myeloma cells in vitro and in vivo [16]. Importantly, Saq displayed antiproliferative activity even against imatinib-resistant chronic myelogenous leukemia cell lines [6]. Beside direct effects, HPIs are able to potentiate the effect of 1,25-dihydroxyvitamin D3 or ATR on myelioid leukemia cells [14,17]. Recently, Kraus et al. [12] demonstrated that Nelfinavir augments proteasome inhibition by http://dx.doi.org/10.1016/j.leukres.2015.06.013 0145-2126/© 2015 Elsevier Ltd. All rights reserved.