van der Kuip H, Goetz A W, Miething C, Duyster J, Aulitzky W E
Dr Margarete Fischer-Bosch Institute for Clinical Pharmacology, Stuttgart, Germany.
Blood. 2001 Sep 1;98(5):1532-41. doi: 10.1182/blood.v98.5.1532.
The phenotype of Bcr-Abl-transformed cells is characterized by a growth factor-independent survival and a reduced susceptibility to apoptosis. Furthermore, Bcr-Abl kinase alters adhesion features by phosphorylating cytoskeletal and/or signaling proteins important for integrin function. Integrin-mediated adhesion to extracellular matrix molecules is critical for the regulation of growth and apoptosis. However, effects of integrin signaling on regulation of apoptosis in cells expressing Bcr-Abl are largely unknown. The influence of adhesion on survival and apoptosis in Bcr-Abl+ and Bcr-Abl- BaF3 cells was investigated. p185bcr-abl-transfected BaF3 cells preadhered to immobilized fibronectin had a significant survival advantage and reduced susceptibility to apoptosis following gamma-irradiation when compared with the same cells grown on laminin, on polylysin, or in suspension. Both inhibition of Bcr-Abl kinase by STI571 and inhibition of specific adhesion reversed the fibronectin-mediated antiapoptotic effect in BaF3p185. The DNA damage response of Bcr-Abl- BaF3 cells was not affected by adhesion to fibronectin. In contrast to parental BaF3 cells, BaF3p185 adherent to fibronectin did not release cytochrome c to the cytosol following irradiation. The fibronectin-mediated antiapoptotic mechanism in Bcr-Abl-active cells was not mediated by overexpression of Bcl-XL or Bcl-2 but required an active phosphatidylinositol 3-kinase (PI-3K). Kinase-active Bcr-Abl in combination with fibronectin-induced integrin signaling led to a hyperphosphorylation of AKT. Thus, cooperative activation of PI-3K/AKT by Bcr-Abl and integrins causes synergistic protection of Bcr-Abl+ cells from DNA damage-induced apoptosis.
Bcr-Abl转化细胞的表型特征为不依赖生长因子存活且对凋亡的敏感性降低。此外，Bcr-Abl激酶通过磷酸化对整合素功能至关重要的细胞骨架和/或信号蛋白来改变黏附特性。整合素介导的与细胞外基质分子的黏附对于生长和凋亡的调节至关重要。然而，整合素信号传导对表达Bcr-Abl的细胞中凋亡调节的影响在很大程度上尚不清楚。研究了黏附对Bcr-Abl+和Bcr-Abl- BaF3细胞存活和凋亡的影响。与在层粘连蛋白、聚赖氨酸上生长或悬浮培养的相同细胞相比，预先黏附于固定化纤连蛋白的p185bcr-abl转染BaF3细胞在γ射线照射后具有显著的存活优势且对凋亡的敏感性降低。STI571对Bcr-Abl激酶的抑制以及特异性黏附的抑制均逆转了纤连蛋白介导的BaF3p185细胞中的抗凋亡作用。Bcr-Abl- BaF3细胞的DNA损伤反应不受与纤连蛋白黏附的影响。与亲本BaF3细胞相反，黏附于纤连蛋白的BaF3p185细胞在照射后未将细胞色素c释放到细胞质中。Bcr-Abl活性细胞中纤连蛋白介导的抗凋亡机制不是由Bcl-XL或Bcl-2的过表达介导的，而是需要活性磷脂酰肌醇3激酶（PI-3K）。激酶活性的Bcr-Abl与纤连蛋白诱导的整合素信号传导相结合导致AKT的过度磷酸化。因此，Bcr-Abl和整合素对PI-3K/AKT的协同激活导致Bcr-Abl+细胞对DNA损伤诱导的凋亡产生协同保护作用。
