Barnes Kay, McIntosh Elizabeth, Whetton Anthony D, Daley George Q, Bentley Johanne, Baldwin Stephen A
School of Biochemistry and Microbiology, University of Leeds, Leeds LS2 9JT, UK.
Oncogene. 2005 May 5;24(20):3257-67. doi: 10.1038/sj.onc.1208461.
In chronic myeloid leukaemia (CML) expression of the chimeric tyrosine kinase, Bcr-Abl, promotes the inappropriate survival of haemopoietic stem cells by a nonautocrine mechanism in the absence of IL-3. Stimulation of glucose uptake appears to play an important role in the suppression of apoptosis by this cytokine in normal haemopoietic cells. To investigate whether the cell survival mechanisms mediated by the oncoprotein and cytokine showed any similarities, we employed a haemopoietic cell line, TonB210, engineered for inducible expression of Bcr-Abl. Tyrosine kinase expression in cytokine-deprived cells was found to mimic the effect of IL-3 in maintaining a higher V(max) for hexose uptake. In both IL-3- treated cells and those expressing Bcr-Abl, high rates of hexose uptake were associated with the retention at the cell surface of approximately 80% of the total cellular content of the GLUT1 glucose transporter. In contrast, treatment of Bcr-Abl-expressing cells for 6 h with the Bcr-Abl kinase inhibitor Glivec (10 muM), in the absence of IL-3, led to internalization of approximately 90% of the cell-surface transporters and drastically decreased (4.4+/-0.9 (mean+/-s.e.m., 4)-fold) the V(max) for hexose uptake, without significant effect on the K(m) for this process or on the total cellular transporter content. These effects were not the result of any significant loss in cell viability, and preceded the onset of apoptosis caused by inhibition of Bcr-Abl. Both IL-3 treatment and expression of Bcr-Abl led to enhanced phosphorylation of Akt (protein kinase B). The stimulation of transport by IL-3 and Bcr-Abl in TonB210 cells was inhibitable by phosphatidylinositol 3-kinase inhibitors, indicating the involvement of this kinase in the signal transduction pathway. These findings suggest that inhibition of glucose transport plays an important role in the therapeutic action of Glivec, and that the signal transduction pathways involved in transport stimulation by Bcr-Abl may offer novel therapeutic targets for CML.
在慢性髓性白血病（CML）中，嵌合酪氨酸激酶Bcr-Abl的表达通过非自分泌机制在缺乏白细胞介素-3（IL-3）的情况下促进造血干细胞的异常存活。在正常造血细胞中，葡萄糖摄取的刺激似乎在这种细胞因子对细胞凋亡的抑制中起重要作用。为了研究由癌蛋白和细胞因子介导的细胞存活机制是否有任何相似之处，我们使用了一种造血细胞系TonB210，该细胞系经过基因工程改造可诱导表达Bcr-Abl。发现在细胞因子缺乏的细胞中酪氨酸激酶的表达模拟了IL-3在维持较高的己糖摄取Vmax方面的作用。在IL-3处理的细胞和表达Bcr-Abl的细胞中，高己糖摄取率都与GLUT1葡萄糖转运蛋白约80%的总细胞含量保留在细胞表面有关。相反，在没有IL-3的情况下，用Bcr-Abl激酶抑制剂格列卫（10μM）处理表达Bcr-Abl的细胞6小时，导致约90%的细胞表面转运蛋白内化，并使己糖摄取的Vmax大幅降低（4.4±0.9（平均值±标准误，n = 4）倍），而对该过程的Km或总细胞转运蛋白含量没有显著影响。这些效应不是细胞活力显著丧失的结果，并且在抑制Bcr-Abl引起的细胞凋亡开始之前就已出现。IL-3处理和Bcr-Abl表达均导致Akt（蛋白激酶B）磷酸化增强。磷脂酰肌醇3-激酶抑制剂可抑制IL-3和Bcr-Abl对TonB210细胞转运的刺激，表明该激酶参与了信号转导途径。这些发现表明，抑制葡萄糖转运在格列卫的治疗作用中起重要作用，并且Bcr-Abl刺激转运所涉及的信号转导途径可能为CML提供新 的治疗靶点。
