Eke Iris, Sandfort Veit, Storch Katja, Baumann Michael, Röper Barbara, Cordes Nils
OncoRay - Center for Radiation Research in Oncology, Medical Faculty Carl Gustav Carus, Dresden University of Technology, Dresden, Germany.
Int J Radiat Biol. 2007 Nov-Dec;83(11-12):793-802. doi: 10.1080/09553000701727549.
Integrin-linked kinase (ILK) mediates signals from beta integrins and links integrins to epidermal growth factor receptor (EGFR). Previous studies have identified an antisurvival effect of ILK in irradiated cells. The aim of this study was to evaluate the role of EGFR tyrosine kinase (tk) activity for ILK-mediated radiosensitization.
Human FaDu squamous cell carcinoma (SCC) cells stably transfected with hyperactive ILK (ILK-hk) and ILK(fl/fl) and ILK(-/-) mouse fibroblasts were treated with the pharmacological EGFR-tk inhibitor BIBX1382BS without or in combination with single doses of X-rays. Clonogenic radiation survival, protein expression and phosphorylation (EGFR, v-akt murine thymoma viral oncogene homolog 1 (Akt), p42/44 mitogen-activated protein kinase), DNA-double strand break (DSB) repair measured by gammaH2AX foci, cell morphology and cell cycle distribution were examined.
Expression of ILK-hk or ILK(fl/fl) status resulted in significant radiosensitization relative to vector controls or ILK(-/-). Following BIBX1382BS, clonogenic survival of normal fibroblasts and vector controls remained unaffected while ILK-hk-related radiosensitization was significantly diminished. In contrast to BIBX1382BS, which did not affect DNA-DSB repair, ILK-hk-mediated radiosensitization was associated with reduced DNA-DSB repair. At 10 days after BIBX1382BS treatment, FaDu transfectants, in contrast to fibroblasts, showed reduced cell size, accumulation of G1 phase cells and reduced Akt-serine(S)473 phosphorylation.
Our findings confirm ILK as a cell type-independent antisurvival factor in irradiated cells, which actions in terms of radiosensitization critically depend on proper EGFR-tk activity.
整合素连接激酶（ILK）介导来自β整合素的信号，并将整合素与表皮生长因子受体（EGFR）相连。既往研究已证实ILK在受照射细胞中具有抗生存效应。本研究旨在评估EGFR酪氨酸激酶（tk）活性在ILK介导的放射增敏作用中的作用。
用药物性EGFR-tk抑制剂BIBX1382BS处理稳定转染高活性ILK（ILK-hk）的人FaDu鳞状细胞癌（SCC）细胞、ILK(fl/fl)细胞以及ILK(-/-)小鼠成纤维细胞，处理方式为单独使用或与单剂量X射线联合使用。检测克隆形成辐射存活率、蛋白表达及磷酸化水平（EGFR、v-akt鼠胸腺瘤病毒癌基因同源物1（Akt）、p42/44丝裂原活化蛋白激酶）、通过γH2AX焦点测量的DNA双链断裂（DSB）修复情况、细胞形态以及细胞周期分布。
相对于载体对照或ILK(-/-)，ILK-hk或ILK(fl/fl)状态的表达导致显著的放射增敏。使用BIBX1382BS后，正常成纤维细胞和载体对照的克隆形成存活率未受影响，而与ILK-hk相关的放射增敏作用显著减弱。与不影响DNA-DSB修复的BIBX1382BS相反，ILK-hk介导的放射增敏作用与DNA-DSB修复减少有关。在BIBX1382BS处理10天后，与成纤维细胞不同，FaDu转染细胞显示细胞大小减小、G1期细胞积累以及Akt丝氨酸（S）473磷酸化水平降低。
我们的研究结果证实ILK是受照射细胞中一种不依赖细胞类型的抗生存因子，其放射增敏作用在很大程度上取决于适当的EGFR-tk活性。
