[Inhibition of activation of nuclear factor-kappaB enhanced apoptosis of leukemic cells induced by homoharringtonine].

OBJECTIVE: To explore the effects of dexamethasone (DXM) and vincristine (VCR) on apoptosis of K562-n cells and activation of nuclear factor-kappaB-gene binding (NF-kappaB) in K562-n cells induced by homoharringtonine. METHODS: K562-n cells were cultured in RPMI-1640 medium. Homoharringtonine of various concentrations was added into the cultures. Twelve hours later, the apoptosis induced by homoharringtonine in K562-n cells was analysed by TdT-mediated X-dUTP nick and end labeling (TUNEL) and DNA electrophoresis. Another sample of K562-n cells was culture together with DXM (1 micro mol/L) or VCR (0.1 micro mol/L) for 2 hours, then homoharringtonine was added into the cultures. Twelve hours later, the apoptosis in K562-n cells was analysed by TUNEL and DNA electrophoresis. Still another sample of K562-n cells was cultured for 3 hours with homoharringtonine, then electrophoretic mobility shift assay (EMSA) was conducted to determine the DNA-binding activation of NF-kappaB. A fourth sample of K562-n cells was cultured together with DXM (1 micro mol/L) or VCR (0.1 micro mol/L) for 2 hours, then homoharringtonine was added into the cultures. Three hours later, EMSA was conducted. RESULTS: The apoptosis rates of K562-n cells induced by homoharringtonine of various concentrations were (30.00 +/- 3.34)%, (47.13 +/- 3.18)% and (68.63 +/- 8.14)%, respectively. The apoptosis rates of K562-n cells induced by homoharringtonine being pre-processed with DXM or VCR were (55.75 +/- 3.88)% and (64.38 +/- 4.60)%, respectively, being 85.8% and 114.6% higher than that induced by homoharringtonine alone (30.00 +/- 3.34)% (all P < 0.05). Activation of NF-kappaB in K562-n cells was induced significantly by homoharringtonine. Activation of NF-kappaB in K562-n cells induced by homoharringtonine could be suppressed by being pre-processed with 1.0 micro mol/L DXM or 0.1 micro mol/L VCR. The rate of suppression was 32.0% and 39.4% respectively. CONCLUSION: Homoharringtonine induces apoptosis of K562-n cells and induces NF-kappaB activation in K562-n cells. The mechanism of increased apoptosis of K562-n cells with DXM or VCR may be related to suppression of activation of NF-kappaB of K562-n cells.