title: Improving nelarabine efficacy in T cell acute lymphoblastic leukemia by targeting aberrant PI3K/AKT/mTOR signaling pathway.
abstract: Although in recent years, the introduction of novel chemotherapy protocols has improved the outcome of T cell acute lymphoblastic leukemia (T-ALL) patients, refractory and/or relapsing disease remains a foremost concern. In this context, a major contribution was provided by the introduction of the nucleoside analog nelarabine, approved for salvage treatment of T-ALL patients with refractory/relapsed disease. However, nelarabine could induce a life-threatening, dose-dependent neurotoxicity. To improve nelarabine efficacy, we have analyzed its molecular targets, testing selective inhibitors of such targets in combination with nelarabine.
  
  
  
  The effectiveness of nelarabine as single agent or in combination with PI3K, Bcl2, and MEK inhibitors was evaluated on human T-ALL cell lines and primary T-ALL refractory/relapsed lymphoblasts. The efficacy of signal modulators in terms of cytotoxicity, induction of apoptosis, and changes in gene and protein expression was assessed by flow cytometry, western blotting, and quantitative real-time PCR in T-ALL settings.
  
  
  
  Treatment with nelarabine as a single agent identified two groups of T-ALL cell lines, one sensitive and one resistant to the drug. Whereas sensitive T-ALL cells showed a significant increase of apoptosis and a strong down-modulation of PI3K signaling, resistant T-ALL cells showed a hyperactivation of AKT and MEK/ERK1/2 signaling pathways, not caused by differences in the expression of nelarabine transporters or metabolic activators. We then studied the combination of nelarabine with the PI3K inhibitors (both pan and dual γ/δ inhibitors), with the Bcl2 specific inhibitor ABT199, and with the MEK inhibitor trametinib on both T-ALL cell lines and patient samples at relapse, which displayed constitutive activation of PI3K signaling and resistance to nelarabine alone. The combination with the pan PI3K inhibitor ZSTK-474 was the most effective in inhibiting the growth of T-ALL cells and was synergistic in decreasing cell survival and inducing apoptosis in nelarabine-resistant T-ALL cells. The drug combination caused AKT dephosphorylation and a downregulation of Bcl2, while nelarabine alone induced an increase in p-AKT and Bcl2 signaling in the resistant T-ALL cells and relapsed patient samples.
  
  
  
  These findings indicate that nelarabine in combination with PI3K inhibitors may be a promising therapeutic strategy for the treatment of T-ALL relapsed patients.
authors: Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy.
authors: Annalisa
authors: A
authors: Lonetti
authors: Department of Human Social and Health Sciences, University of Cassino, Cassino, Italy.
authors: Alessandra
authors: A
authors: Cappellini
authors: Department of Pediatric Hematology-Oncology, IRCCS, Bambino Gesù Children's Hospital, Rome, Italy.
authors: Alice
authors: A
authors: Bertaina
authors: Department of Pediatric Hematology-Oncology, IRCCS, Bambino Gesù Children's Hospital, Rome, Italy.
authors: Franco
authors: F
authors: Locatelli
authors: Department of Pediatrics, "Lalla Seràgnoli" Hematology-Oncology Unit, University of Bologna, Bologna, Italy.
authors: Andrea
authors: A
authors: Pession
authors: Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy.
authors: Francesca
authors: F
authors: Buontempo
authors: Institute of Molecular Genetics, Rizzoli Orthopedic Institute, National Research Council, Bologna, Italy.
authors: Camilla
authors: C
authors: Evangelisti
authors: Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy.
authors: Cecilia
authors: C
authors: Evangelisti
authors: Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy.
authors: Ester
authors: E
authors: Orsini
authors: Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy.
authors: Laura
authors: L
authors: Zambonin
authors: Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy.
authors: Luca Maria
authors: LM
authors: Neri
authors: Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy. alberto.martelli@unibo.it.
authors: Alberto Maria
authors: AM
authors: Martelli
authors: Institute of Molecular Genetics, Rizzoli Orthopedic Institute, National Research Council, Bologna, Italy. francesca.chiarini@cnr.it.
authors: Francesca
authors: 0000-0002-4568-3189
authors: F
authors: Chiarini
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use* / Q000633:toxicity; D017209:Apoptosis / Q000187:drug effects; D001087:Arabinonucleosides / Q000627:therapeutic use / Q000633:toxicity; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000627:therapeutic use; D002470:Cell Survival / Q000187:drug effects; D004357:Drug Synergism; D006801:Humans; D000081082:Phosphoinositide-3 Kinase Inhibitors; D054218:Precursor T-Cell Lymphoblastic Leukemia-Lymphoma / Q000150:complications / Q000188:drug therapy*; D051057:Proto-Oncogene Proteins c-akt; D011728:Pyridones / Q000627:therapeutic use; D011744:Pyrimidinones / Q000627:therapeutic use; D015398:Signal Transduction / Q000187:drug effects*; D013449:Sulfonamides / Q000627:therapeutic use; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D014227:Triazines / Q000627:therapeutic use; D014407:Tumor Cells, Cultured
chemical_list: D001087:Arabinonucleosides; D019086:Bridged Bicyclo Compounds, Heterocyclic; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011728:Pyridones; D011744:Pyrimidinones; D013449:Sulfonamides; D014227:Triazines; C510150:ZSTK474; C560077:trametinib; C104457:nelarabine; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; C579720:venetoclax
keywords: Apoptosis; Combination therapy; Drug resistance; PI3K signaling