Apoptotic Induction And Mechanism Action Of Harringtonine In Human Acute Promyelocytic Leukemia Cells

Objective:To investigate the growth inhibition effect, cytotoxicity and apoptotic induction of harringtonine (HT) in human acute promyelocytic leukemia (APL)NB4cells, and discuss the mechanism of action of the cytotoxic effect of HT in NB4cells.Materials and MethodsNB4cells were treated with HT. Total cell numbers were counted by using hemocytometer, and cell viabilities were determined by trypan blue exclusion. Apoptotic cells were determined by using fluorescence microscope and FACS after staining with AO and EB or PI, respectively. The cleavage of PARP and the activation of Bax and the expression of anti-apoptotic proteins were determined by Western Blot. siRNA was used to silence the expression target gene. Primary cells were isolated following Ficoll-Hypaque density gradient centrifugation.ResultsGrowth inhibition, cytotoxitic effect and apoptotic induction of HT in NB4cells were in dose and time dependent manner. Apoptosis induced by HT was correlated with the down-regulation of Mcl-1and the cleavage of PARP, while HT did not prompt the protein level of Bax and Bak or changed the protein level of Bcl-2. To silence Bcl-XL can sensitize HT-induced apoptosis in NB4cells. Apoptosis induced by HT in APL primary sample cells was also correlated with the down-regulation of Mcl-1.ConclusionsHT inhibits the growth and induces apoptosis in NB4cells, and the killing effect of HT in NB4cells may through down regulation of Mcl-1.