Gefitinib-sensitive EGF receptor mutants in lung cancer

描述(申请人提供)：约10%的非小细胞肺癌患者对表皮生长因子受体(EGFR)的选择性抑制剂吉非替尼(Iressa)有显著反应，肿瘤中体细胞EGFR突变的存在准确地预测了临床反应。突变的EGFR在EGF诱导的信号转导过程中表现出质的变化，这表明突变的EGFR的不同信号转导有助于某些肺肿瘤的药物反应。在这里，这些EGFR突变的致癌机制和吉非替尼敏感性的机制将被建立。在一小部分缺乏EGFR突变的肿瘤患者中看到的药物反应的分子基础也将被检查。提出了四个具体的目标：1：建立EGFR突变促进肺癌发生的生化机制。这将包括通过用纯化的激酶和合成肽底物进行体外酶研究来阐明突变的EGFR的生化差异。将对野生型和几种肿瘤来源的EGFR突变体的酶活性、底物特异性和信号复合体进行比较。细胞培养试验将用于将突变的EGFR的信号特性变化与对EGF的不同生物反应联系起来。2：确定携带EGFR突变的肿瘤的药物敏感性和对EGFR依赖的基础。酶和细胞分析将用于比较药物对野生型和突变型EGFR的影响。“癌基因成瘾”假说将在突变的EGFR信号传导的细胞培养模型中得到检验。3：探讨其他ErbB受体在突变型EGFR致癌功能和药物敏感性中的作用。这一假设将被检验，即突变的EGFR和另一种ErbB受体的异源二聚体有助于突变的EGFR的致癌作用和/或药物敏感性。4：确定在无EGFR突变的情况下吉非替尼应答的分子基础。将在缺乏EGFR突变的药物敏感肿瘤中寻找候选基因的突变。为了建立以细胞为基础的环境来研究反应机制，将对肺癌细胞株进行筛选，以确定缺乏EGFR突变的药物敏感株。最后，基于微阵列的基因表达谱将用于识别定义药物反应性的基因表达特征。总之，这些研究有望为这类新型EGFR突变体的致癌活性以及携带这些突变的肿瘤表现出的药物超敏反应的分子机制提供重要的见解。

DESCRIPTION (provided by applicant): ~10% of non-small cell lung cancer patients respond dramatically to Gefitinib (Iressa), a selective inhibitor of epidermal growth factor receptor (EGFR), and the presence of somatic EGFR mutations in tumors accurately predicts a clinical response. Mutant EGFRs exhibit a qualitative alteration of EGF-induced signaling suggesting that distinct signaling by mutant EGFRs contributes to drug-responsiveness in some lung tumors. Here, the oncogenic mechanism of these EGFR mutations and the mechanism underlying gefitinib-sensitivity will be established. The molecular basis for drug-response seen in a small subset of patients with tumors lacking EGFR mutations will also be examined. Four Specific Aims are proposed: 1: To establish the biochemical mechanism by which EGFR mutants contribute to lung tumors. This will involve elucidating biochemical distinctions of mutant EGFRs through in vitro enzyme studies with purified kinase and synthetic peptide substrates. Enzyme activity, substrate specificity, and signaling complexes will be compared for wild-type and several tumor-derived EGFR mutants. A cell culture assay will be used to link the altered signaling properties of mutant EGFRs to distinct biological responses to EGF. 2: To determine the basis for drug-sensitivity and EGFR-dependence in tumors harboring EGFR mutants. Enzyme and cellular assays will be used to compare drug effects on wild-type and mutant EGFRs. The "oncogene addiction" hypothesis will be examined in a cell culture model of signaling by mutant EGFRs. 3: To examine the role of other ErbB receptors in the oncogenic function and drug sensitivity of mutant EGFR. The hypothesis will be tested that heterodimers of mutant EGFR and another ErbB receptor contribute to the oncogenic actions of mutant EGFR and/or drug sensitivity. 4: To determine the molecular basis for gefitinib-response in the absence of EGFR mutations. A search for mutations in candidate genes in drug responsive tumors lacking EGFR mutations will be conducted. To establish a cell-based setting to study the response mechanism, lung cancer cell lines will be screened to identify drug-sensitive lines lacking EGFR mutations. Finally, microarray-based gene expression profiling will be used to identify a gene expression signature that defines drug-responsiveness. Together, these studies are expected to provide important insights into the molecular mechanisms that underlie the oncogenic activity of this novel class of EGFR mutants and the drug hypersensitivity exhibited by tumors that harbor these mutations.