Synergistic cytotoxic effects of bortezomib and CK2 inhibitor CX-4945 in acute lymphoblastic leukemia: turning off the prosurvival er chaperone BIP/GRP78 and turning on the pro-apoptotic NF-κB.

// Francesca Buontempo 1 , Ester Orsini 1 , Annalisa Lonetti 2 , Alessandra Cappellini 3 , Francesca Chiarini 4,5 , Camilla Evangelisti 4,5 , Cecilia Evangelisti 1 , Fraia Melchionda 2 , Andrea Pession 2 , Alice Bertaina 6 , Franco Locatelli 6 , Jessika Bertacchini 7 , Luca Maria Neri 8 , James A. McCubrey 9 and Alberto Maria Martelli 1 1 Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy 2 Pediatric Oncology and Hematology Unit “Lalla Seragnoli”, S. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy 3 Department of Human Social and Health Sciences, Campus Folcara, University of Cassino, Cassino, Italy 4 Muscoloskeletal Cell Biology Laboratory, IOR, Bologna, Italy 5 Institute of Molecular Genetics, National Research Council-Rizzoli Orthopedic Institute, Bologna, Italy 6 Department of Pediatric Hematology and Oncology, IRCCS Bambino Gesu Children’s Hospital, Rome, Italy 7 Department of Surgery, Medicine, Odontostomatology and Morphological Sciences, University of Modena, Modena, Italy 8 Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy 9 Department of Microbiology and Immunology, School of Medicine, East Carolina University, Greenville, NC, USA Correspondence to: Alberto Maria Martelli, email: // Keywords : acute lymphoblastic leukemia, CK2, unfolded protein response, BIP/Grp78, NF-κB Received : June 19, 2015 Accepted : November 15, 2015 Published : November 22, 2015 Abstract The proteasome inhibitor bortezomib is a new targeted treatment option for refractory or relapsed acute lymphoblastic leukemia (ALL) patients. However, a limited efficacy of bortezomib alone has been reported. A terminal pro-apoptotic endoplasmic reticulum (ER) stress/unfolded protein response (UPR) is one of the several mechanisms of bortezomib-induced apoptosis. Recently, it has been documented that UPR disruption could be considered a selective anti-leukemia therapy. CX-4945, a potent casein kinase (CK) 2 inhibitor, has been found to induce apoptotic cell death in T-ALL preclinical models, via perturbation of ER/UPR pathway. In this study, we analyzed in T- and B-ALL preclinical settings, the molecular mechanisms of synergistic apoptotic effects observed after bortezomib/CX-4945 combined treatment. We demonstrated that, adding CX-4945 after bortezomib treatment, prevented leukemic cells from engaging a functional UPR in order to buffer the bortezomib-mediated proteotoxic stress in ER lumen. We documented that the combined treatment decreased pro-survival ER chaperon BIP/Grp78 expression, via reduction of chaperoning activity of Hsp90. Bortezomib/CX-4945 treatment inhibited NF-κB signaling in T-ALL cell lines and primary cells from T-ALL patients, but, intriguingly, in B-ALL cells the drug combination activated NF-κB p65 pro-apoptotic functions. In fact in B-cells, the combined treatment induced p65-HDAC1 association with consequent repression of the anti-apoptotic target genes, Bcl-xL and XIAP. Exposure to NEMO (IKKγ)-binding domain inhibitor peptide reduced the cytotoxic effects of bortezomib/CX-4945 treatment. Overall, our findings demonstrated that CK2 inhibition could be useful in combination with bortezomib as a novel therapeutic strategy in both T- and B-ALL.