Inhibition of mTORC1/C2 signaling improves anti-leukemia efficacy of JAK/STAT blockade in CRLF2 rearranged and/or JAK driven philadelphia chromosome-like acute B-cell lymphoblastic leukemia

// Qi Zhang 1, * , Ce Shi 1, 6, * , Lina Han 1, 6 , Nitin Jain 1 , Kathryn G. Roberts 2 , Helen Ma 1 , Tianyu Cai 1 , Antonio Cavazos 1 , Yoko Tabe 3 , Rodrigo O. Jacamo 1 , Hong Mu 1 , Yang Zhao 4 , Jing Wang 4 , Shuo-Chieh Wu 5 , Fenglin Cao 6 , Zhihong Zeng 1 , Jin Zhou 6 , Yingchang Mi 7 , Elias J. Jabbour 1 , Ross Levine 8 , Sarah K. Tasian 9 , Charles G. Mullighan 2 , David M. Weinstock 5 , David A. Fruman 10 and Marina Konopleva 1 1 Department of Leukemia, The University of Texas M.D. Anderson Cancer Center, Houston, TX, USA 2 Department of Pathology, St. Jude Children's Research Hospital, Memphis, TN, USA 3 Department of Next Generation Hematology Laboratory Medicine, Juntendo University School of Medicine, Tokyo, Japan 4 Department of Bioinformatics & Comp Biology, The University of Texas M.D. Anderson Cancer Center, Houston, TX, USA 5 Department of Medical Oncology/Hematologic Neoplasia, Dana-Farber Cancer Institute, Boston, MA, USA 6 Department of Hematology, The First Hospital Affiliated Harbin Medical University, Harbin, China 7 Department of Leukemia, Institute of Hematology & Blood DiseasesHospital, Chinese Academy of Medical Science & Peking Union Medical College, Tianjin, China 8 Hematologic Malignancies, Memorial Sloan Kettering Cancer Center, New York, NY, USA 9 Division of Oncology and Center for Childhood Cancer Research, The Children’s Hospital of Philadelphia, Philadelphia, PA, USA 10 Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, CA, USA * These authors have contributed equally to this work Correspondence to: Marina Konopleva, email: mkonople@mdanderson.org Keywords: Ph-like ALL; JAK; mTOR Received: January 03, 2018 Accepted: January 09, 2018 Published: January 17, 2018 ABSTRACT Patients with cytokine receptor-like factor 2 rearranged ( CRLF2 -re) subgroup Philadelphia chromosome–like B-cell acute lymphoblastic leukemia(Ph-like B-ALL) have a high relapse rate and poor clinical outcomes. CRFL2 -re Ph-like B-ALL is characterized by heightened activation of multiple signaling pathways, including the JAK/STAT and PI3K/AKT/mTOR pathways. We hypothesized that the combined inhibition by JAK2 and mTOR inhibitors would induce an additive antileukemia effect in CRLF2 -re Ph-like B-ALL. In this study, we tested the antileukemia efficacy of the type I JAK inhibitor ruxolitiniband type II JAK inhibitor NVP-BBT594 (hereafter abbreviated BBT594) [ 1 ] alone and combined with allosteric mTOR inhibitor rapamycin and a second generation ATP-competitive mTOR kinase inhibitor AZD2014. We found that BBT594/AZD2014 combination produced robust anti-leukemic effects in Ph-like cell lines in vitro and in patient-derived xenograft (PDX) cells cultured ex vivo . JAK2/mTOR inhibition arrested the cell cycle and reduced cell survival to a greater extent in Ph-like B-ALL cells with CRLF2 -re and JAK2 mutation. Synergistic cell killing was associated with the greater inhibition of JAK2 phosphorylation by BBT594 than by ruxolitiniband the greater inhibition of AKT and 4E-BP1 phosphorylation by AZD2014 than by rapamycin. In vivo , BBT594/AZD2014 co-treatment was most efficacious in reducing spleen size in three Ph-like PDX models, and markedly depleted bone marrow and spleen ALL cells in an ATF7IP-JAK2 fusion PDX. In summary, combined inhibition of JAK/STAT and mTOR pathways by next-generation inhibitors had promising antileukemia efficacy in preclinical models of CRFL2- re Ph-like B-ALL.