Liang Ke, Ang K Kian, Milas Luka, Hunter Nancy, Fan Zhen
Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
Int J Radiat Oncol Biol Phys. 2003 Sep 1;57(1):246-54. doi: 10.1016/s0360-3016(03)00511-x.
The epidermal growth factor (EGF) receptor is frequently overexpressed in malignant tumors, and its level is correlated with increased cellular resistance to ionizing radiation. However, no precedent studies have investigated whether expression of EGF receptor would by itself confer on cancer cells resistance to radiation. The current study is aimed to address this question.
A full-length human EGF receptor expression vector was transfected into the OCA-I murine ovarian carcinoma cells for stable clones expressing various levels of EGF receptors. Apoptosis and cell clonogenic survival assays were used to evaluate the sensitivity of the resulting cell clones to ionizing radiation.
OCA-I cell clones expressing various levels of EGF receptor (OCA-I EGFR) were obtained. These clones showed an EGF receptor level-dependent increase in resistance to ionizing radiation, measured by apoptosis and cell clonogenic survival assays. Compared with the results for parental OCA-I and control vector-transfected OCA-I cells at the 10% cell survival level, the radioresistance was increased by a factor of 1.60 for EGFR-C5 (high level of EGF receptor expression), 1.37 for EGFR-C3 (intermediate level of EGF receptor expression), and 1.28 for EGFR-C1 (low level of EGF receptor expression). Treatment of the OCA-I EGF receptor transfectants with the anti-EGF receptor monoclonal antibody C225 downregulated the levels of EGF receptor, reduced the phosphorylation levels of EGF receptor downstream substrates (such as Akt and MAPK), and reversed the cellular radioresistance.
Our results demonstrate that overexpression of the EGF receptor conferred cellular resistance to ionizing radiation. The EGF receptor is thus a valid target for potential radiosensitization.
表皮生长因子（EGF）受体在恶性肿瘤中常过度表达，其水平与细胞对电离辐射的抗性增加相关。然而，此前尚无研究调查EGF受体的表达本身是否会赋予癌细胞辐射抗性。本研究旨在解决这一问题。
将全长人EGF受体表达载体转染至OCA-I小鼠卵巢癌细胞中，以获得表达不同水平EGF受体的稳定克隆。采用凋亡和细胞克隆形成存活分析来评估所得细胞克隆对电离辐射的敏感性。
获得了表达不同水平EGF受体的OCA-I细胞克隆（OCA-I EGFR）。通过凋亡和细胞克隆形成存活分析测量，这些克隆显示出对电离辐射的抗性呈EGF受体水平依赖性增加。在10%细胞存活水平下，与亲本OCA-I细胞和转染对照载体的OCA-I细胞相比，EGFR-C5（EGF受体高表达水平）的辐射抗性增加了1.60倍，EGFR-C3（EGF受体中等表达水平）增加了1.37倍，EGFR-C1（EGF受体低表达水平）增加了1.28倍。用抗EGF受体单克隆抗体C225处理OCA-I EGF受体转染细胞，可下调EGF受体水平，降低EGF受体下游底物（如Akt和MAPK）的磷酸化水平，并逆转细胞的辐射抗性。
我们的结果表明，EGF受体的过度表达赋予细胞对电离辐射的抗性。因此，EGF受体是潜在放射增敏的有效靶点。
