PI3K isoform inhibition associated with anti Bcr-Abl drugs shows in vitro increased anti-leukemic activity in Philadelphia chromosome-positive B-acute lymphoblastic leukemia cell lines

// Simona Ultimo 1, * , Carolina Simioni 1, * , Alberto M. Martelli 2 , Giorgio Zauli 1 , Camilla Evangelisti 3 , Claudio Celeghini 4 , James A. McCubrey 5 , Giorgia Marisi 6 , Paola Ulivi 6 , Silvano Capitani 1, 7 , Luca M. Neri 1 1 Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy 2 Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy 3 Institute of Molecular Genetics, Rizzoli Orthopedic Institute, National Research Council, Bologna, Italy 4 Department of Life Sciences, University of Trieste, Trieste, Italy 5 Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC, USA 6 Biosciences Laboratory, Istituto Scientifico Romagnolo per lo Studio e Cura dei Tumori (IRST) IRCCS, Meldola, Italy 7 LTTA Center, University of Ferrara, Ferrara, Italy * These authors contributed equally to this work Correspondence to: Luca M. Neri, email: luca.neri@unife.it Silvano Capitani, email: silvano.capitani@unife.it Keywords: PI3K isoforms, Bcr-Abl, Ph + B-acute lymphoblastic leukemia, autophagy, tyrosine kinase inhibitors Received: December 08, 2016      Accepted: February 12, 2017      Published: February 20, 2017 ABSTRACT B-acute lymphoblastic leukemia (B-ALL) is a malignant disorder characterized by the abnormal proliferation of B-cell progenitors. Philadelphia chromosome-positive (Ph + ) B-ALL is a subtype that expresses the Bcr-Abl fusion protein which represents a negative prognostic factor. Constitutive activation of the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) network is a common feature of B-ALL, influencing cell growth and survival. In the present study, we aimed to investigate the efficacy of PI3K isoform inhibition in B-ALL cell lines harboring the Bcr-Abl fusion protein. We studied the effects of anti Bcr-Abl drugs Imatinib, Nilotinib and GZD824 associated with PI3K isoform inhibitors. We used a panel of six compounds which specifically target PI3K isoforms including the pan-PI3K inhibitor ZSTK474, p110α BYL719 inhibitor and the dual p110γ/p110δ inhibitor IPI145. The effects of single drugs and of several drug combinations were analyzed to assess cytotoxicity by MTS assays, apoptosis and autophagy by flow cytometry and Western blot, as well as the phosphorylation status of the pathway. ZSTK474, BYL719 and IPI145 administered in combination with imatinib, nilotinib and GZD824 for 48 h, decreased cell viability, induced apoptosis and autophagy in a marked synergistic manner. These findings suggest that selected PI3K isoform inhibitors used in combination with anti Bcr-Abl drugs may be an attractive novel therapeutic intervention in Ph + B-ALL.