Tribius S, Pidel A, Casper D
Department of Radiation Oncology, The Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, NY 10467, USA.
Int J Radiat Oncol Biol Phys. 2001 Jun 1;50(2):511-23. doi: 10.1016/s0360-3016(01)01489-4.
Glioblastoma multiforme (GBM) is one of the malignancies most resistant to radiation therapy. In contrast, cells derived from individuals with ataxia telangiectasia (AT), possessing mutations in the ATM gene, demonstrate increased sensitivity to ionizing radiation. Using a collection of glioma specimens adapted to tissue culture and several established GBM cell lines, we investigated the relationship between ATM protein expression and radiosensitivity. The three aims of our study were to: (1) quantify ATM protein levels in cultured glioma cells; (2) measure the correlation between ATM protein levels and radiation sensitivity; and (3) examine the dependence of ATM on p53 status.
Glioma specimens were collected, catalogued, and adapted to grow in culture. Levels of ATM, p53, and p21 proteins were determined by Western blot. Radiation sensitivities were determined by clonogenic assays. p53 mutation status was determined by DNA sequencing. Correlations were identified by linear regression analysis.
ATM protein levels were variable in the primary gliomas. Glioma cell lines demonstrated significantly lower levels of ATM protein. Clonogenic assays of cell strains and cell lines yielded survival fractions (SF2s) consistent with the radioresistant behavior of GBM tumors in vivo. Regression analysis revealed a high correlation between ATM protein levels and SF2 for primary glioma cell strains, but not for established GBM cell lines. p53 status failed to predict radiosensitivity.
We have demonstrated that while our collection of low passage cell cultures depends on ATM for their resistance to IR, established cell lines may acquire adaptive characteristics which downplay the role of the ATM gene product in vitro. Therefore, attenuating ATM gene expression may be a successful strategy in the treatment of GBM tumors.
多形性胶质母细胞瘤（GBM）是对放射治疗最具抗性的恶性肿瘤之一。相比之下，共济失调毛细血管扩张症（AT）患者的细胞由于ATM基因发生突变，对电离辐射表现出更高的敏感性。我们使用一组适应组织培养的胶质瘤标本和几种已建立的GBM细胞系，研究了ATM蛋白表达与放射敏感性之间的关系。我们研究的三个目标是：（1）量化培养的胶质瘤细胞中ATM蛋白水平；（2）测量ATM蛋白水平与放射敏感性之间的相关性；（3）研究ATM对p53状态的依赖性。
收集胶质瘤标本，进行分类，并使其适应培养生长。通过蛋白质免疫印迹法测定ATM、p53和p21蛋白的水平。通过克隆形成试验确定放射敏感性。通过DNA测序确定p53突变状态。通过线性回归分析确定相关性。
原发性胶质瘤中ATM蛋白水平各不相同。胶质瘤细胞系中ATM蛋白水平显著较低。细胞株和细胞系的克隆形成试验产生的存活分数（SF2s）与GBM肿瘤在体内的放射抗性行为一致。回归分析显示，原发性胶质瘤细胞株的ATM蛋白水平与SF2之间存在高度相关性，但已建立的GBM细胞系则不然。p53状态无法预测放射敏感性。
我们已经证明，虽然我们收集的低传代细胞培养物对电离辐射的抗性依赖于ATM，但已建立的细胞系可能获得了适应性特征，从而在体外淡化了ATM基因产物的作用。因此，减弱ATM基因表达可能是治疗GBM肿瘤的一种成功策略。
