Background and objective: Epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI), which targets EGFR, plays an important role in non-small cell lung cancer (NSCLC) treatment. Patients with somatic activating mutations in the EGFR gene exhibit significant initial response but eventually develop resistance to TKI. The second mutation (T790M) of the EGFR gene is the possible main cause of drug resistance. The aim of this study is to investigate the effect of ionizing radiation on EGFR-TKI resistance caused by T790M mutation in NSCLC cell lines.
Methods: We selected H1975 and H3255 as research subjects and tested the mutation states by real-time PCR analysis. Radiosensitivity was determined by clone-forming test, and drug resistance was detected in different groups by MTT assay.
Results: H1975 is an EGFR double mutant (L858R plus T790M), whereas H3255 is an EGFR single mutant (L858R). The cell survival fractions of H1975 and H3255 did not vary in different treatment groups (P=0.952). Thus, T790M mutation did not affect the radiosensitivity of NSCLC cell lines. The IC50 of H1975 in the 2.5 Gy group [(0.678; 2±0.373) μmol/L] was statistically significant compared with that in the 0 Gy normal control group [(3.520±0.821) μmol/L] (P=0.008). The drug tolerance of the H1975 cell line by 89.5 dropped to 39.2 times.
Conclusions: Ionizing radiation can reduce TKI resistance caused by T790M mutation in NSCLC cell lines. Our results provide a research basis for future in vivo and clinical studies. Radiotherapy combined with EGFR-TKI treatment can be a promising strategy to overcome T790M-mediated drug resistance. .
背景与目的 以表皮生长因子受体（epidermal growth factor receptor, EGFR）为靶点的分子靶向治疗在非小细胞肺癌（non-small cell lung cancer, NSCLC）的治疗中发挥重要的作用。EGFR突变的患者对EGFR酪氨酸激酶抑制剂（EGFR-tyrosine kinase inhibitor, EGFR-TKI）治疗敏感、疗效显著，但无论近期疗效如何，患者最终都不可避免地产生耐药。大量研究证实，EGFR基因的二次突变（T790M）是患者耐药的主要原因。本研究旨在探讨电离辐射对NSCLC细胞株T790M突变所致EGFR-TKI耐药的影响。方法 选择NSCLC细胞株H1975和H3255为研究对象，实时荧光定量PCR法检测两株细胞的突变状态、克隆形成实验观察两株细胞的放射敏感性，MTT法检测各处理组两株细胞对EGFR-TKI的抗药性。结果 H1975为T790M+L858R双突变株、H3255是仅有L858R的单突变株；各处理组H1975及H3255的存活分数未见明显差异（P=0.952），提示T790M突变对NSCLC细胞株的放射敏感性无影响；2.5 Gy X线辐射组，H1975的 IC50为（0.678,2±0.373）μmol/L，较0 Gy对照组的（3.520±0.821）μmol/L明显下降，差异有统计学意义（P=0.008），H1975相较于H3255的抗药性也从85.9倍下降为39.2倍。结论 电离辐射可降低NSCLC细胞株T790M突变所致的TKI耐药，本实验的研究结果为后续的体内和临床研究提供了研究依据；EGFR-TKI治疗期间联合放射治疗对克服T790M突变介导的耐药性有望成为一种有希望的治疗策略。.