title: Rapamycin stimulates apoptosis of childhood acute lymphoblastic leukemia cells.
abstract: The phosphatidyl-inositol 3 kinase (PI3k)/Akt pathway has been implicated in childhood acute lymphoblastic leukemia (ALL). Because rapamycin suppresses the oncogenic processes sustained by PI3k/Akt, we investigated whether rapamycin affects blast survival. We found that rapamycin induces apoptosis of blasts in 56% of the bone marrow samples analyzed. Using the PI3k inhibitor wortmannin, we show that the PI3k/Akt pathway is involved in blast survival. Moreover, rapamycin increased doxorubicin-induced apoptosis even in nonresponder samples. Anthracyclines activate nuclear factor kappaB (NF-kappaB), and disruption of this signaling pathway increases the efficacy of apoptogenic stimuli. Rapamycin inhibited doxorubicin-induced NF-kappaB in ALL samples. Using a short interfering (si) RNA approach, we demonstrate that FKBP51, a large immunophilin inhibited by rapamycin, is essential for drug-induced NF-kappaB activation in human leukemia. Furthermore, rapamycin did not increase doxorubicin-induced apoptosis when NF-kappaB was overexpressed. In conclusion, rapamycin targets 2 pathways that are crucial for cell survival and chemoresistance of malignant lymphoblasts--PI3k/Akt through the mammalian target of rapamycin and NF-kappaB through FKBP51--suggesting that the drug could be beneficial in the treatment of childhood ALL.
authors.affiliation: Department of Biochemistry and Medical Biotechnologies, Federico II University, Via S. Pansini 5, 80131 Naples, Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Avellino
authors.forename: Simona
authors.initials: S
authors.lastname: Romano
authors.forename: Rosanna
authors.initials: R
authors.lastname: Parasole
authors.forename: Rita
authors.initials: R
authors.lastname: Bisogni
authors.forename: Annalisa
authors.initials: A
authors.lastname: Lamberti
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Poggi
authors.forename: Salvatore
authors.initials: S
authors.lastname: Venuta
authors.forename: Maria Fiammetta
authors.initials: MF
authors.lastname: Romano
mesh_terms: D000293:Adolescent; D017209:Apoptosis / Q000187:drug effects*; D001752:Blast Crisis / Q000188:drug therapy / Q000473:pathology; D001854:Bone Marrow Cells / Q000187:drug effects / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D004317:Doxorubicin / Q000494:pharmacology; D004357:Drug Synergism; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D016328:NF-kappa B / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy / Q000473:pathology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology*; D022021:Tacrolimus Binding Proteins / Q000378:metabolism; D014407:Tumor Cells, Cultured; D000099159:Tacrolimus Binding Protein 5
chemical_list: D004317:Doxorubicin; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D020123:Sirolimus; D022021:Tacrolimus Binding Proteins; D000099159:Tacrolimus Binding Protein 5; C494918:AKT1 protein, human