Zhang Weiping, Stabile Laura P, Keohavong Phouthone, Romkes Marjorie, Grandis Jennifer R, Traynor Anne M, Siegfried Jill M
Department of Pharmacology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213-1863, USA.
J Thorac Oncol. 2006 Sep;1(7):635-47.
The epidermal growth factor receptor (EGFR) is involved in the development and progression of lung cancer. Somatic EGFR mutations are predictors of response to treatment with EGFR tyrosine kinase (TK) inhibitors (TKIs) for lung cancer, especially among never smokers. EGFR mutations may occur independently of other genetic alterations.
The authors sequenced the EGFR-TK domain and the K-ras and p53 genes from lung tumor tissues from 44 never smokers and 46 smokers. A case-control study also was conducted to examine the relationship between an EGFR single nucleotide polymorphism in the TK domain and the lung cancer through a multivariate logistic regression analysis. In addition, the authors compared cell growth kinetics, EGFR-TKI sensitivity by MTT, and activation of signaling molecules by immunoblot in lung cancer cell lines with and without EGFR-TK mutations.
EGFR-TK mutations were more frequently observed in never smokers (25%) than in smokers (2.2%) (p = 0.001). Excluding cases with a K-ras mutation, the frequency of EGFR-TK domain mutation was still significantly higher in never smokers than in smokers, 26.2% versus 4.5% (p = 0.046). EGFR-TK mutations and K-ras mutations (p = 0.015), and p53 and K-ras mutations (p = 0.015) were mutually exclusive, but p53 and EGFR-TK mutations were not (p = 1.00). During sequencing of the EGFR-TK domain in tumors, an EGFR polymorphism (G2607A) was identified. The genotype AA and AA + AG occurred at a significantly higher frequency in lung cancer cases (n = 122) when compared with controls (n = 147) (odds ratio, 3.39 and 2.67; 95% confidence interval, 1.41-8.17 and 1.17-6.08, p = 0.006 and p = 0.02, respectively). This polymorphism was found independently of EGFR-TK mutations in lung cancer cases, indicating that it does not predispose to mutations. In vitro, lung cancer cell lines with EGFR-TK mutations also did not contain K-ras mutations and displayed a lower growth rate (50%, p = 0.013) than EGFR-TK wild-type cell lines. EGFR-TK mutant cell lines were more sensitive to both gefitinib and erlotinib, although relative sensitivity to erlotinib compared with wild-type was less pronounced than for gefitinib. Cell lines with a lower growth rate also expressed higher levels of E-cadherin than faster growing cell lines.
EGFR-TK mutation frequency is high in never-smoking lung cancer patients and is exclusive of mutation in K-ras but not p53. In addition to somatic EGFR-TK mutations that arise in lung tumors, germline variation in the EGFR-TK domain might also be associated with an increased risk of lung cancer. Somatic EGFR-TK mutations alter cell biology and response to EGFR-TKIs and may be mutation specific.
表皮生长因子受体（EGFR）参与肺癌的发生和发展。体细胞EGFR突变是肺癌患者对EGFR酪氨酸激酶（TK）抑制剂（TKIs）治疗反应的预测指标，尤其是在从不吸烟者中。EGFR突变可能独立于其他基因改变而发生。
作者对44名从不吸烟者和46名吸烟者的肺肿瘤组织中的EGFR-TK结构域以及K-ras和p53基因进行了测序。还进行了一项病例对照研究，通过多因素逻辑回归分析来检验TK结构域中EGFR单核苷酸多态性与肺癌之间的关系。此外，作者比较了有无EGFR-TK突变的肺癌细胞系的细胞生长动力学、通过MTT法检测的EGFR-TKI敏感性以及通过免疫印迹法检测的信号分子激活情况。
从不吸烟者中EGFR-TK突变的发生率（25%）高于吸烟者（2.2%）（p = 0.001）。排除K-ras突变的病例后，从不吸烟者中EGFR-TK结构域突变的频率仍显著高于吸烟者，分别为26.2%和4.5%（p = 0.046）。EGFR-TK突变与K-ras突变（p = 0.015）以及p53与K-ras突变（p = 0.015）相互排斥，但p53与EGFR-TK突变并不相互排斥（p = 1.00）。在肿瘤的EGFR-TK结构域测序过程中，鉴定出一种EGFR多态性（G2607A）。与对照组（n = 147）相比，肺癌病例组（n = 122）中基因型AA和AA + AG的出现频率显著更高（优势比分别为3.39和2.67；95%置信区间分别为1.41 - 8.17和1.17 - 6.08，p分别为0.006和0.02）。在肺癌病例中，这种多态性独立于EGFR-TK突变被发现，表明它不会诱发突变。在体外，具有EGFR-TK突变的肺癌细胞系也不含有K-ras突变，并且其生长速率比EGFR-TK野生型细胞系低（50%，p = 0.013）。EGFR-TK突变细胞系对吉非替尼和厄洛替尼均更敏感，尽管与野生型相比，其对厄洛替尼的相对敏感性不如对吉非替尼明显。生长速率较低的细胞系也比生长较快的细胞系表达更高水平的E-钙黏蛋白。
从不吸烟的肺癌患者中EGFR-TK突变频率较高，且与K-ras突变相互排斥，但与p53突变不相互排斥。除了肺肿瘤中出现体细胞EGFR-TK突变外，EGFR-TK结构域的种系变异也可能与肺癌风险增加有关。体细胞EGFR-TK突变会改变细胞生物学特性以及对EGFR-TKIs的反应，并且可能具有突变特异性。
