Rozenveld-Geugien Marjan, Baas Inge O, van Gosliga Djoke, Vellenga Edo, Schuringa Jan Jacob
Department of Hematology, University Medical Center Groningen, Groningen, The Netherlands.
Exp Hematol. 2007 May;35(5):782-92. doi: 10.1016/j.exphem.2007.02.006.
To determine the involvement of Rac signaling in self-renewal and expansion on bone marrow stroma of normal CD34+ cells vs leukemic CD34+ cells from acute myeloid leukemia (AML) patients.
Rac signaling was modulated by retroviral introduction of Racl-N17, Racl-V12, or by using the Rac inhibitor NSC23766. In long-term MS5 cocultures (leukemic) expansion, migration, adhesion, and presence of stem/progenitor cells were monitored in both normal as well as leukemic CD34+ cells.
Inhibition of Rac signaling impaired migration and adhesion of cord blood (CB) CD34+ cells on MS5 stroma. Long-term inhibition of Rac during a 5-week coculture period on stroma prevented association of hematopoietic progenitors with the bone marrow stromal cells and resulted in a dramatic decrease in the primitive stem cell frequency (long-term culture-initiating cell) in a dose-dependent manner. Many of these phenotypes were reversed in the presence of activated Racl-V12, including improved migration toward, and association with, MS5 cells. CD34+ AML cells were characterized by elevated levels of Rac activity (five of seven patients) and enhanced migration and adhesion to MS5 bone marrow stroma as compared to CB CD34+ cells. A dramatic decrease was observed in the formation of leukemic cobblestone area-forming cells as well as strongly diminished clonal expansion in the presence of the Rac inhibitor NSC23766.
Our data indicate that Rac signal transduction is required for the maintenance and expansion of both normal as well as leukemic stem/progenitor cells by mediating their interaction with stromal cells.
确定Rac信号传导在正常CD34+细胞与急性髓系白血病（AML）患者白血病CD34+细胞在骨髓基质上的自我更新和扩增中的作用。
通过逆转录病毒导入Racl-N17、Racl-V12来调节Rac信号传导，或使用Rac抑制剂NSC23766。在长期MS5共培养（白血病）扩增中，监测正常以及白血病CD34+细胞的迁移、黏附以及干/祖细胞的存在情况。
抑制Rac信号传导会损害脐血（CB）CD34+细胞在MS5基质上的迁移和黏附。在基质上进行为期5周的共培养期间长期抑制Rac，会阻止造血祖细胞与骨髓基质细胞的结合，并导致原始干细胞频率（长期培养起始细胞）以剂量依赖的方式显著降低。在存在活化的Racl-V12的情况下，许多这些表型会发生逆转，包括向MS5细胞的迁移和结合得到改善。与CB CD34+细胞相比，CD34+ AML细胞的特征是Rac活性水平升高（7例患者中的5例），并且对MS5骨髓基质的迁移和黏附增强。在存在Rac抑制剂NSC23766的情况下，观察到白血病鹅卵石区域形成细胞的形成显著减少，以及克隆扩增强烈减弱。
我们的数据表明，Rac信号转导通过介导正常以及白血病干/祖细胞与基质细胞的相互作用，对于它们的维持和扩增是必需的。
