目的：研究Rac1 GTP酶的活化对白血病细胞静息的影响，并探索其机制。 方法：构建Rac1组成活化型慢病毒载体，以此感染急性髓系白血病KG-1a细胞，比较感染了组成活化型Rac1的KG-1a （Rac1-V12-KG-1a）细胞和感染空载体的KG-1a（pCDH-KG-1a）细胞在G0期的比例差异。以Rac1特异性抑制剂NSC23766处理感染后KG-1a细胞，4 d后检测两组细胞G0期比例的变化。实时定量PCR检测两组细胞中与细胞周期和细胞静息相关分子的表达。流式细胞术检测小鼠Rac1GTP酶高度活化的AMLI-ETO9a白血病细胞模型中促血小板生成素受体myeloproliferative leukemia MPL) - 和MPL + 细胞群在G0期的比例。 结果： 感染了组成活化型Rac1的Rac1-V12-KG-1a细胞的G0期细胞比例显著高于感染空载体的pCDH-KG-1a细胞的比例[ （15.30±0.60)% vs (11.50±0.17)%，P<0.05]；抑制剂处理KG-1a细胞后，随着抑制剂浓度的增加G0期细胞比例显著下降（P<0.05）。实时定量PCR检测结果显示，周期抑制因子P21 、 P27 、 P57的mRNA表达水平在Rac1-V12-KG-1a细胞表达均有不同程度的上调，静息相关调节分子N-Cadherin和MPL mRNA表达水平均显著升高（P<0.05）；流式检测结果显示，MPL + 白血病细胞群的比例在G0期显著高于MPL - 组[ （40.3±3.5)% vs (19.05±7.65)%，P<0.05]。 结论： 白血病细胞中Rac1 GTP酶的活化通过上调MPL等细胞外在调节因子的表达增加休眠期细胞的比例，从而促进白血病细胞维持静息状态。

Objective: To determine the role of Rac1 GTPase activation in the regulation of leukemia cell quies-cence and investigate the possible mechanism. Methods: Constitutively active Rac1 lenti-virus vector was construct-ed to transfect KG-1a leukemia cells (Rac1-V12-KG-1a). The G0 phase cell ratio in sorted Rac1-V12-KG-1a and KG-1a cells transfected with empty vector (pCDH-KG-1a) was compared. Furthermore, after 4 days treatment with NSC23766, the Rac1-specific inhibitor, the G0 phase cell ratio in KG-1a cells was also detected. The expression lev-els of cell quiescence and cell cycle associated moleculars were then determined by RT-PCR. The G0 phase cell ra-tio of MPL - and MPL + leukemia cells in AML1-ETO9a leukemia mouse was detected by flow cytometry. Results:The results showed that the G0 phase cell ratio in Rac1-V12-KG-1a cells was significantly higher than that in pCDH-KG-1a cells ([15.30±0.60]% vs [11.50 ± 0.17]%, P<0.05). After the treatment of Rac1-specific inhibitor, the G0 phase cell ratio of the KG-1a cells was decreased significantly (P<0.05), and the effect was concentration depen-dent. RT-PCR showed that mRNA transcription levels of cell cycle related factors (P21 ， P27 ， P57) were up-regulat-ed in Rac1-V12-KG-1a cells at different level; moreover, the expressions of N-Cadherin and MPL were also signifi-cantly higher in Rac1-V12-KG-1a cells (P<0.05). Flow cytometry analysis showed that the percentage of G0 phase MPL + leukemia cells was significantly higher than that of MPL - leukemia cells ([40.3±3.5])% vs [19.05±7.65]%, P<0.05). Conclusion: Activation of Rac1 GTPase could increase the ratio of leukemia cells at G0 phase, and promote leukemia cells quiescence by up-regulating MPL.

国家自然科学基金资助项目（No. 81370599）