Semisynthetic homoharringtonine induces apoptosis via inhibition of protein synthesis and triggers rapid myeloid cell leukemia-1 down-regulation in myeloid leukemia cells.
Semisynthetic homoharringtonine (ssHHT) is now being evaluated in phase II clinical trials for the treatment of chronic myelogenous leukemia and acute myelogenous leukemia patients. Here, we examined the mechanism of the apoptosis induced by ssHHT in myeloid leukemia cells. First, we have shown that ssHHT induces apoptosis in HL60 and HL60/MRP cell lines in a time- and dose-dependent manner, and independently of the expression of Bax. The decrease of mitochondrial membrane potential and the release of cytochrome c were observed in the apoptotic cells induced by ssHHT. To unveil the relationship between ssHHT and the mitochondrial disruption, we have shown that ssHHT decreased myeloid cell leukemia-1 (Mcl-1) expression and induced Bcl-2 cleavage in HL60 and HL60/MRP cell lines. The Bcl-2 cleavage could be inhibited by the Z-VAD.fmk caspase inhibitor. However, Mcl-1 turnover was very rapid and occurred before caspase activation. The Mcl-1 turnover was only induced by ssHHT and cycloheximide, but not by daunorubicin and cytosine arabinoside, and could be restored by proteasome inhibitors. Second, we confirmed that ssHHT rapidly induced massive apoptosis in acute myelogenous leukemia patient cells. We have also confirmed the release of cytochrome c and a rapid turnover of Mcl-1 in these patient cells, taking place only in apoptotic cells induced by ssHHT but not in cells undergoing spontaneous apoptosis. Finally, we have shown that ssHHT inhibits protein synthesis in both cell line and patient cells. We suggest that the inhibition of protein synthesis and resulting Mcl-1 turnover play a key role in the apoptosis induced by ssHHT. Our results encourage further clinical trials for the use of ssHHT in acute myelogenous leukemia.
Tang
Ruoping
R
Université Pierre et Marie Curie; INSERM UMRS 736, Hôpital Hôtel Dieu, 1 place du Parvis-Notre-Dame, 75181 Paris cedex 04, France. ruoping.tang@htd.ap-hop-paris.fr
Faussat
Anne-Marie
AM
Majdak
Patricia
P
Marzac
Christophe
C
Dubrulle
Sabine
S
Marjanovic
Zora
Z
Legrand
Ollivier
O
Marie
Jean-Pierre
JP
D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D003561:Cytarabine / Q000494:pharmacology; D045264:Cytochromes a / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D003630:Daunorubicin / Q000494:pharmacology; D015536:Down-Regulation; D018922:HL-60 Cells; D006248:Harringtonines / Q000737:chemistry / Q000494:pharmacology*; D000077863:Homoharringtonine; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000378:metabolism*; D061988:Proteasome Inhibitors; D014176:Protein Biosynthesis / Q000187:drug effects*; D011500:Protein Synthesis Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D000972:Antineoplastic Agents, Phytogenic; D061945:Caspase Inhibitors; D006248:Harringtonines; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D061988:Proteasome Inhibitors; D011500:Protein Synthesis Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D003561:Cytarabine; D000077863:Homoharringtonine; D045304:Cytochromes c; D045264:Cytochromes a; D020169:Caspases; D003630:Daunorubicin