Effect of Autophagy on Homoharringtonine-treated K562 Cells / 中国实验血液学杂志

<p><b>OBJECTIVE</b>To study the effect of homoharringtonine (HHT) alone or combined with 3-methyladenine (3-MA) , an autophagy inhibitor, on the apoptosis and autophagy of K562 cells.</p><p><b>METHODS</b>K562 cells were treated with HHT(10 ng/ml) or HHT(10 ng/ml) combined with 3-MA (1.5 mmol/L) for 1 to 8 days. The apoptosis of treated cells was tested by means of flow cytometry(FCM), and the autophagy levels were tested with RT-PCR, Western blot and electron microscopy.</p><p><b>RESULTS</b>In the early stage of HHT-treated group, the apoptosis rate increased and decreased later. Beclin1 mRNA expression level and the LC3II/I ratio were declined firstly and increased later in HHT group. While combining with autophagy inhibitor 3-MA, both the Beclin1 mRNA expression level and the LC3II/I ratio were declined continually during the treated period. The activated caspase-3 protein expression level was also raised sustainability during both HHT and 3-MA cultured period.</p><p><b>CONCLUSIONS</b>HHT can induce apoptosis of K562 cells, but the sustaining effect of HHT can induc autophagy of K562 cells, the combination of HHT with 3-MA may enhance the cytotoxicitic effect of HHT on K562 cells.</p>

Time rhythm of homoharringtonine inducing K562 cell apoptosis and its mechanism / 中国实验血液学杂志

This study was aimed to explore the change of K562 cell apoptosis at different time point after homoharringtonine (HHT) treatment and its mechanism. After treatment of K562 cells with 10 ng/ml HHT, the cell viability was tested with MTT assay; the expression of caspase-3 was detected with Western blot; the BCL-2 expression was analyzed with flow cytometry; the autophagosome was observed by electron microscopy. The results showed that the viability of K562 cells reduced gradually from day 1 to day 5 and ascended from day 6 to day 8 after HHT treatment. At the same time, the cleaved caspase-3 expression level of K562 cells increased gradually from day 1 to day 7, but reduced at the day 8 (P < 0.05). From day 1 to day 8 after HHT treatment, the BCL-2 expression level declined firstly and then went up (P < 0.05). Autophagosome was also seen remarkably at day 8 after HHT treatment. It is concluded that the apoptosis level of K562 cells after being treated with HHT enhances firstly and then declines , which may be associated with higher autophagy level in the late stage of HHT treatment.

Effect of homoharringtonine on expression of NF-κB and BCL-2 proteins in K562 cells / 中国实验血液学杂志

This study was aimed to investigate the effect of homoharringtonine (HHT) on K562 cell proliferation, apoptosis and expression of BCL-2 and NF-κB proteins. The cells proliferation was assayed with MTT method, the cell apoptosis, cell cycle and BCL-2 expression were analyzed with flow cytometry, NF-κB protein expression was detected with Western blot. The results showed that HHT concentration-dependently inhibited proliferation of K562 cells, the IC50 at 48 h was 43.89 ng/ml. Treated with HHT 10 ng/ml for 48 h, K562 cell apoptosis significantly increased, cell cycle was blocked at G0/G1, the expression level of BCL-2 and NF-κB proteins was lower than that in control group (P < 0.05). It is concluded that HHT may inhibit the proliferation of K562 cells, and down-regulating expression levels of BCL-2 and NF-κB may be one of its anti-CML mechanisms.

Effects of interferon-α combined with homoharringtonine on K562 cell proliferation and β-catenin expression / 中国实验血液学杂志

The study was aimed to investigate the synergistically effect of interferon-α (IFN-α) and homoharringtonine (HHT) on the proliferation, apoptosis, cell cycle of K562 cells and the expression of β-catenin. The proliferation, apoptosis, cell cycle and β-catenin mRNA expression of K562 cells treated with IFN-α and/or HHT were assayed with MTT, flow cytometry or RT-PCR respectively. The results showed that HHT alone, but not IFN-α alone, displayed a proliferation inhibition, apoptosis induction, G(0)/G(1) phase block and down-regulation of β-catenin expression in K562 cells with concentration- and time-dependent manners. The expression level of β-catenin mRNA after being treated with HHT was 0.5576 ± 0.0373, which were lower than that in control group (0.9369 ± 0.0142). The down-regulation of β-catenin expression in group of IFN-α combined with HHT was higher significantly than that in HHT group (0.3737 ± 0.0529 vs 0.5576 ± 0.0373, P < 0.05). Otherwise, HHT combined with IFN-α did not demonstrate obvious toxicologic effect on bone marrow mononuclear cells. It is concluded that IFN-α combined with HHT can enhance the cytotoxic effect of HHT on K562 cells, which may be associated with down-regulation of β-catenin expression.