慢性粒细胞性白血病患者骨髓源bcr/abl融合基因阳性Flk1^+CD31^-CD34^-干细胞体外抗STI571机制的初步研究

A Preliminary Study on Mechanisms for Resistance of CML Patient BM-derived bcr/abl^+ and Flk1+CD31^-CD34^- Stem Cells to STI571 in Vitro

为进一步了解STI571对慢性粒细胞性白血病(CML)患者体内bcr/abl融合基因阳性的原始及定向白血病干/祖细胞分化及增殖的影响,更深入阐明部分CML患者在经历一段血液学甚至是细胞遗传学水平上的完全缓解后复发及对STI571的耐药机制,利用从CML患者骨髓分离到的具有血管母细胞特性、bcr/abl融合基因阳性、免疫表型为Flk1+CD31-CD34-细胞,体外检测了STI571对其在造血集落培养基中的分化及处于分化阶段时的增殖抑制作用。结果显示:浓度为5μmol/LSTI571,维持作用96小时(病人体内维持96小时的STI571浓度只可能达到1-2μmol/L),即可有效抑制定向造血祖细胞的增殖。没有充分的证据显示,相对原始的bcr/abl融合基因阳性、免疫表型为Flk1+CD31-CD34-细胞的分化及增殖受到明显的抑制作用。结论:CML患者体内的原始白血病干/祖细胞对STI571具有一定的抗性,临床上所观察到的CML患者在运用STI571一段时间后出现正常的造血恢复现象,可能仅仅是因为STI571杀死或抑制了定向恶性白血病祖细胞的增殖,但随着时间的推移,在经历了短暂的血液学甚至是细胞遗传学水平上的缓解后,对STI571耐药的原始白血病干/祖细胞终究会再次导致CML的复发。

To evaluate the effect of imatinib mesylate （STI571 ） on primitive/committed malignant progenitor cells in chronic myelogenous leukemia （CML） and to further elucidate the mechanisms involved in CML relapse and in some CML cells resistant to ST1571, bone marrow-derived malignant bcr/abl-positive, Flk1^＋CD31CD34^- cells with hemangioblastic characteristics from CML patients were grown in Methocult GF ＋ media with or without STI571, and inhibitory effect of ST1571 on proliferation of differentiated and differentiating, bcr/abl^＋ , Flk1^＋CD31CD34^- cells with chemangioblastic characteristics was investigated in vitro. The results showed that in vitro exposure to 5μmol/L STI571 （the concentration of STI571 usually achieved in patients is 1 -2 μmol/L） for 96 hours inhibited bcr/abl ＋ committed progenitors （colony-forming cells, CFCs）. No evident suppression of normal primitive, bcr/abl^＋ , and Flk1^＋CD31^-CD34^- cells were observed. It is concluded that CML primitive stem cells remain viable in the presence of STI571 and that inhibition of bcr/abl tyrosine kinase by STI571 restores normal hematopoiesis by removing the proliferative advantage of CML committed progenitors but that elimination of all CML progenitors may not occur. So despite dramatic short-term responses in vivo, such in vitro resistance to STI571, may translate into disease relapse after prolonged therapy.