[Blocking PAK1 kinase activity promotes the differentiation of acute megakaryocytic leukemia cells and induces their apoptosis].

Objective: To investigate the effect of blocking P21 activated kinase 1 (PAK1) activity on the proliferation, differentiation, and apoptosis of acute megakaryocytic leukemia (AMKL) cell lines (CHRF and CMK) . Methods: Cell counts were used to detect the effects of PAK1 inhibitors (IPA-3 and G5555) on AMKL cell proliferation inhibition and colony formation, and flow cytometry was used to detect its effects on AMKL cell cycle. The effect of PAK1 inhibitor on the expression of cyclin D1 and apoptosis-related protein Cleaved caspase 3 was detected using Western blot, while interference with the protein expression level of PAK1 in AMKL cells was assessed using lentivirus-mediated shRNA transfection technology. Flow cytometry was used to detect the effects of knockdown of PAK1 kinase activity on the ability of polyploid DNA formation and cell apoptosis in AMKL cells. Results: PAK1 inhibitors inhibited the proliferation of AMKL cells in a dose-dependent manner and reduced the ability of cell colony formation, and the difference was statistically significant when compared with the control group (P<0.05) . Moreover, they also reduced the percentage of AMKL cells in S phase, and Western blot detection showed that the expression levels of phosphorylated PAK1 and cyclin D1 decreased significantly. Finally, PAK1 inhibitors induced AMKL cell apoptosis by up-regulating Cleaved caspase 3 and showed different abilities to increase the content of polyploid DNA in megakaryocytes. Only high concentrations of IPA-3 and low doses of G5555 increased the number of polyploid megakaryocytes, while knockdown of PAK1 kinase activity promoted AMKL cell differentiation and increased the apoptosis rate. Conclusion: PAK1 inhibitor significantly arrests AMKL cell growth and promotes cell apoptosis. Knocking down the expression of PAK1 promotes the formation of polyploid DNA and induces AMKL cell apoptosis. The above findings indicate that inhibiting the activity of PAK1 may control AMKL effectively.目的： 探讨阻断p21蛋白激活激酶1（P21 Activated Kinase 1，PAK1）活性对急性巨核细胞白血病（AMKL）细胞株（CHRF和CMK）增殖、分化和细胞凋亡的影响。 方法： 采用细胞计数法检测PAK1抑制剂（IPA-3和G5555）作用前后AMKL细胞增殖及集落形成能力；应用流式细胞术检测PAK1抑制剂对AMKL细胞周期的影响；Western blot法检测细胞周期蛋白cyclin D1和细胞凋亡相关蛋白Cleaved caspase 3的表达；使用慢病毒介导的shRNA转染技术干扰AMKL细胞中PAK1的蛋白表达水平，应用流式细胞术检测敲低PAK1激酶的活性对AMKL细胞中多倍体DNA形成能力和细胞凋亡的影响。 结果： PAK1抑制剂以剂量依赖性的方式抑制AMKL细胞的增殖并降低细胞集落形成能力，与对照组相比差异均有统计学意义（P值均<0.05）；PAK1抑制剂降低了S期AMKL细胞的百分比，Western blot法检测显示磷酸化PAK1及cyclin D1的表达水平显著下降（P值均<0.05）；PAK1抑制剂通过上调Cleaved caspase 3表达诱导AMKL细胞凋亡；PAK1抑制剂IPA-3和G5555分别显示出不同的增加巨核细胞中多倍体DNA含量的能力，仅有高浓度的IPA-3及低浓度的G5555可增加多倍体的巨核细胞的数目；敲低PAK1激酶活性，CHRF细胞多倍体DNA含量从14%增至22%，CMK细胞从8%增至16%，凋亡比例分别增至16%和12%（P<0.05）。 结论： PAK1抑制剂显著诱导AMKL细胞生长停滞并促进AMKL细胞凋亡；敲低PAK1的表达促进多倍体DNA的形成并诱导AMKL细胞凋亡。抑制PAK1的活性可能是控制AMKL的有效方法。.