Induction of apoptosis by homoharringtonine in G1 phase human chronic myeloid leukemic cells.
BACKGROUND
Homoharringtonine (HHT) is a cephalotaxine ester derived from an evergreen tree found wildely throughout southern China, which has antileukemic activities against a variety of acute myeloid leukemic cells. For the sake of illustrating the mechanisms of HHT in the treatment of leukemia, we assessed the effect of HHT on the apoptosis of human chronic myeloid leukemic cell line K562.


METHODS
The apoptosis of K562 cells induced by HHT was analyzed by transmission electron microscopy, agarose gel electrophoresis of DNA, flow cytometry and terminal deoxyribonucleotidyl transferase-mediated dUTP-biotin nick labeling.


RESULTS
Characteristic apoptosis-related features emerged in K562 cells after exposed to HHT at a concentration 0.05-100 microg/ml. Transmission electron microscopy of HHT treated K562 cells displayed chromatin condensation and aggregation under the nuclear membrane, nuclear fragmentation and apoptosis body formation. Typical DNA ladder in agarose gel electrophoresis was observed in the cells exposed to HHT. The cell cycle analysis measured by flow cytometry showed G1 phase cells decreased with the increase of S phase cells while apoptosis was induced by HHT in K562 cells. The percentage of apoptotic cells in K562 cells treated with 50 microg/ml of HHT decreased significantly when pretreated with 1 microg/ml of cycloheximide, 0.05 microg/ml of Actinomycin D respectively.


CONCLUSIONS
HHT has apoptotic effects on K562 cells. The HHT induced apoptosis mainly of the cells in G1 phase and this process required RNA transcription and protein synthesis.
Mai
Wen-yuan
WY
Department of Hematology, First Affiliated Hospital of Zhejiang University, Hangzhou 310003, China. maiwenyuan@hotmail.com
Lin
Mao-fang
MF
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D016193:G1 Phase / Q000187:drug effects*; D006248:Harringtonines / Q000494:pharmacology*; D000077863:Homoharringtonine; D006801:Humans; D020014:K562 Cells; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy* / Q000473:pathology
D000972:Antineoplastic Agents, Phytogenic; D006248:Harringtonines; D003609:Dactinomycin; D000077863:Homoharringtonine; D003513:Cycloheximide