title: Inhibition of the Akt/survivin pathway synergizes the antileukemia effect of nutlin-3 in acute lymphoblastic leukemia cells.
abstract: The phosphatidylinositol 3-kinase (PI3K)/Akt and p53 pathways play antiapoptotic and proapoptotic roles in cell death, respectively. Cancer cell growth and progression are associated with high levels of PI3K/Akt activation by loss of PTEN expression and the inactivation of p53 by MDM2 overexpression. We report that inhibition of PI3K/Akt, either by the PI3K inhibitor Ly294002 or by expression of PTEN, synergized the ability of the MDM2 antagonist nutlin-3 to induce apoptosis in acute lymphoblastic leukemia (ALL). We used a set of ALL cell lines with wild-type p53 and MDM2 overexpression, but different status of PTEN expression/PI3K/Akt activation, to test the ability of nutlin-3 to induce p53 and apoptosis. Nutlin-3 activated p53 in all the ALL cell lines; however, induction of apoptosis was dependent on PTEN status. Nutlin-3 induced potent apoptosis in cells with PTEN expression but not in those without PTEN, suggesting that PTEN/PI3K/Akt pathway may play a role in this process. Furthermore, nutlin-3 significantly down-regulated survivin expression in PTEN-positive cells but not in PTEN-negative cells. When these nutlin-3-resistant cells were either pretransfected with the PTEN gene or simultaneously treated with the PI3K inhibitor Ly294002, survivin was down-regulated and sensitivity to nutlin-3 was increased. Furthermore, direct silencing of survivin by small interfering RNA also increased the proapoptotic effect of nutlin-3 on the PTEN-negative, nutlin-3-resistant ALL cells. Our results suggest that Akt-mediated survivin up-regulation in PTEN-negative ALL cells may counteract the proapoptotic effect of nutlin-3, and indicate that a combination of MDM2 antagonist and PI3K/Akt inhibitor may be a promising approach for treating refractory ALL.
authors.affiliation: Department of Pediatrics, Emory University School of Medicine, 2015 Uppergate Drive, Atlanta, GA 30322, USA.
authors.forename: Ningxi
authors.initials: N
authors.lastname: Zhu
authors.forename: Lubing
authors.initials: L
authors.lastname: Gu
authors.forename: Fengzhi
authors.initials: F
authors.lastname: Li
authors.forename: Muxiang
authors.initials: M
authors.lastname: Zhou
mesh_terms: D000208:Acute Disease; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis; D016923:Cell Death; D002867:Chromones / Q000494:pharmacology; D004357:Drug Synergism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D051034:Inhibitor of Apoptosis Proteins; D007945:Leukemia, Lymphoid / Q000188:drug therapy* / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors*; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000187:drug effects*; D000077022:Survivin; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: C107489:BIRC5 protein, human; D002867:Chromones; D007093:Imidazoles; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D009025:Morpholines; D009363:Neoplasm Proteins; D010879:Piperazines; D034741:RNA, Small Interfering; D000077022:Survivin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C482205:nutlin 3; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human