title: Hyperforin inhibits Akt1 kinase activity and promotes caspase-mediated apoptosis involving Bad and Noxa activation in human myeloid tumor cells.
abstract: BACKGROUND
  The natural phloroglucinol hyperforin HF displays anti-inflammatory and anti-tumoral properties of potential pharmacological interest. Acute myeloid leukemia (AML) cells abnormally proliferate and escape apoptosis. Herein, the effects and mechanisms of purified HF on AML cell dysfunction were investigated in AML cell lines defining distinct AML subfamilies and primary AML cells cultured ex vivo.
  
  
  RESULTS
  HF inhibited in a time- and concentration-dependent manner the growth of AML cell lines (U937, OCI-AML3, NB4, HL-60) by inducing apoptosis as evidenced by accumulation of sub-G1 population, phosphatidylserine externalization and DNA fragmentation. HF also induced apoptosis in primary AML blasts, whereas normal blood cells were not affected. The apoptotic process in U937 cells was accompanied by downregulation of anti-apoptotic Bcl-2, upregulation of pro-apoptotic Noxa, mitochondrial membrane depolarization, activation of procaspases and cleavage of the caspase substrate PARP-1. The general caspase inhibitor Z-VAD-fmk and the caspase-9- and -3-specific inhibitors, but not caspase-8 inhibitor, significantly attenuated apoptosis. HF-mediated apoptosis was associated with dephosphorylation of active Akt1 (at Ser(473)) and Akt1 substrate Bad (at Ser(136)) which activates Bad pro-apoptotic function. HF supppressed the kinase activity of Akt1, and combined treatment with the allosteric Akt1 inhibitor Akt-I-VIII significantly enhanced apoptosis of U937 cells.
  
  
  CONCLUSIONS
  Our data provide new evidence that HF's pro-apoptotic effect in AML cells involved inhibition of Akt1 signaling, mitochondria and Bcl-2 members dysfunctions, and activation of procaspases -9/-3. Combined interruption of mitochondrial and Akt1 pathways by HF may have implications for AML treatment.
authors: INSERM U872, Université Pierre et Marie Curie, Université Paris Descartes, Centre de Recherche des Cordeliers, Paris, France.
authors: Faten
authors: F
authors: Merhi
authors: Ruoping
authors: R
authors: Tang
authors: Marion
authors: M
authors: Piedfer
authors: Julie
authors: J
authors: Mathieu
authors: Isabelle
authors: I
authors: Bombarda
authors: Murhaf
authors: M
authors: Zaher
authors: Jean-Pierre
authors: JP
authors: Kolb
authors: Christian
authors: C
authors: Billard
authors: Brigitte
authors: B
authors: Bauvois
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D015470:Leukemia, Myeloid, Acute / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010696:Phloroglucinol / Q000031:analogs & derivatives* / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors* / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013729:Terpenes / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects; D051025:bcl-Associated Death Protein / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D016328:NF-kappa B; C498702:PMAIP1 protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; D013729:Terpenes; D051025:bcl-Associated Death Protein; D010696:Phloroglucinol; D051057:Proto-Oncogene Proteins c-akt; D020169:Caspases; C001654:hyperforin