吲哚-3-甲醇对肺癌细胞放射敏感性的EGFR依赖性调节

EGFR-dependent Impact of Indol-3-Carbinol on Radiosensitivity of Lung Cancer Cells

背景与目的吲哚-3-甲醇(indole-3-carbinol,I3C)是十字花科蔬菜中一种主要的有效植物化学物质,且具有防癌和抗癌作用。本研究旨在观察I3C是否影响表皮生长因子受体(epidermal growth factor receptor,EGFR)表达水平不同的肺癌细胞放射敏感性。方法采用MTT和克隆形成实验方法分别检测肺癌细胞的生长和存活率;siRNA转染方法降低细胞中EGFR蛋白表达水平;Western blot和RT-PCR法分别测定EGFR蛋白和mRNA的表达。结果采用无明显毒副作用的5mol/L剂量的I3C预处理明显降低了EGFR表达阳性的人肺腺癌H1975和人肺鳞癌H226细胞对γ-射线照射的放射敏感性,而I3C对EGFR表达阴性的人肺鳞癌NIH-H520细胞的放射敏感性则影响非常小。Western blot结果显示I3C可以增加H1975和H226细胞中EGFR蛋白的表达水平和Y845位点磷酸化水平。EGFR siRNA降低了NIH-H1975细胞中EGFR蛋白的表达,增加了细胞的放射敏感性,并有效地降低和抑制了I3C导致的细胞耐辐射效应。结论我们的研究结果首次证实I3C可以通过调节EGFR表达和磷酸化水平从而影响肺癌细胞的放射治疗敏感性,提示EGFR可能是I3C影响肺癌放射治疗敏感性的重要靶蛋白.

Background and objective Indole-3-carbinol （I3C） is a naturally occurring phytochemical found in cruciferous vegetables. The aim of the present study is to investigate the influence of I3C on radiosensitivity in epidermal growth factor receptor （EGFR）-positive and EGFR-negative lung cancer cell lines. Methods Human lung adenocarcinoma NIH-H1975 cells and human lung squamous carcinoma NIH-H226 and NIH-H520 cells were routinely cultured in RPMI-1640. MTF assay and clonogenic assay were Used to detect cell growth and survival, respectively. Western blot and RT- PRC assay was employed to detect EGFR protein and mRNA expression. Results 5 μmol/L of I3C significantly reduced radiosensitivity of EGFR-positive NIH-H1975 and NIH-H226 cells, but failed to affect radiosensitivity of EGFR-negative NIH-HS20 cells. Furthermore, I3C caused an increased expression of total EGFR and pEGFR （Y845） protein in NIH-H1975 and NIH-H226 cell lines, but not in NIH-H520 cell line. A reduction of EGFR expression by EGFR-siRNA significantly inhib- ited I3C-caused radioresistance in NIH-H1975 cells. Conclusion Our data presented here for the first time demonstrate that I3C reduces radiosensitivity of lung cancer cells by mediating EGFR expression, indicating that EGFR may be an important tareet for I3C-mediated radioresistance in lung cancer.