title: The Akt/mammalian target of rapamycin signal transduction pathway is activated in high-risk myelodysplastic syndromes and influences cell survival and proliferation.
abstract: The Akt/mammalian target of rapamycin (mTOR) signaling pathway is important for both cell growth and survival. In particular, an impaired regulation of the Akt/mTOR axis has been strongly implicated in mechanisms related to neoplastic transformation, through enhancement of cell proliferation and survival. Myelodysplastic syndromes (MDS) are a group of heterogeneous hematopoietic stem cell disorders characterized by ineffective hematopoiesis and by a high risk of evolution into acute myelogenous leukemia (AML). The pathogenesis of the MDS evolution into AML is still unclear, although some recent studies indicate that aberrant activation of survival signaling pathways could be involved. In this investigation, done by means of immunofluorescent staining, we report an activation of the Akt/mTOR pathway in high-risk MDS patients. Interestingly, not only mTOR was activated but also its downstream targets, 4E-binding protein 1 and p70 ribosomal S6 kinase. Treatment with the selective mTOR inhibitor, rapamycin, significantly increased apoptotic cell death of CD33(+) (but not CD33(-)) cells from high-risk MDS patients. Rapamycin was ineffective in cells from healthy donors or low-risk MDS. Moreover, incubation of high-risk MDS patient CD34(+) cells with rapamycin decreased the in vitro clonogenic capability of these cells. In contrast, the phosphoinositide 3-kinase inhibitor, LY294002, did not significantly affect the clonogenic activity of high-risk MDS cells. Taken together, our results indicate that the Akt/mTOR pathway is critical for cell survival and proliferation in high-risk MDS patients. Therefore, this signaling network could become an interesting therapeutic target for treating more advanced MDS cases.
authors.affiliation: Cell Signaling Laboratory, Dipartimento di Scienze Anatomiche Umane e Fisiopatologia dell'Apparato Locomotore, Sezione di Anatomia and Istituto di Ematologia ed Oncologia Medica "L. e A. Seràgnoli," Università di Bologna, Bologna, Italy.
authors.forename: Matilde Y
authors.initials: MY
authors.lastname: Follo
authors.forename: Sara
authors.initials: S
authors.lastname: Mongiorgi
authors.forename: Costanza
authors.initials: C
authors.lastname: Bosi
authors.forename: Alessandra
authors.initials: A
authors.lastname: Cappellini
authors.forename: Carlo
authors.initials: C
authors.lastname: Finelli
authors.forename: Francesca
authors.initials: F
authors.lastname: Chiarini
authors.forename: Veronica
authors.initials: V
authors.lastname: Papa
authors.forename: Massimo
authors.initials: M
authors.lastname: Libra
authors.forename: Giovanni
authors.initials: G
authors.lastname: Martinelli
authors.forename: Lucio
authors.initials: L
authors.lastname: Cocco
authors.forename: Alberto M
authors.initials: AM
authors.lastname: Martelli
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000368:Aged; D000906:Antibodies / Q000737:chemistry / Q000276:immunology; D000918:Antibody Specificity; D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D018797:Cell Cycle Proteins; D048708:Cell Growth Processes / Q000502:physiology; D019070:Cell Lineage; D002470:Cell Survival / Q000502:physiology; D005260:Female; D018922:HL-60 Cells; D006801:Humans; D007150:Immunohistochemistry; D007963:Leukocytes, Mononuclear / Q000201:enzymology / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009190:Myelodysplastic Syndromes / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000276:immunology / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000276:immunology / Q000378:metabolism*; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D012307:Risk Factors; D063268:Sialic Acid Binding Ig-like Lectin 3; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000906:Antibodies; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; C571163:CD33 protein, human; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; D010750:Phosphoproteins; D063268:Sialic Acid Binding Ig-like Lectin 3; D011494:Protein Kinases; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus