Gefitinib-sensitive EGF receptor mutants in lung cancer

描述（由申请人提供）：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（易瑞沙）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EGFRs表现出egf诱导的信号质的改变，这表明突变的EGFRs的不同信号有助于某些肺肿瘤的药物反应性。在这里，将建立这些EGFR突变的致癌机制和吉非替尼敏感性的机制。在一小部分缺乏EGFR突变的肿瘤患者中观察到的药物反应的分子基础也将被研究。提出了四个具体目标：1 .建立EGFR突变体参与肺肿瘤的生化机制。这将涉及通过纯化激酶和合成肽底物的体外酶研究阐明突变型egfr的生化差异。将比较野生型和几种肿瘤源性EGFR突变体的酶活性、底物特异性和信号复合物。细胞培养试验将用于将突变egfr信号特性的改变与对EGF的不同生物学反应联系起来。2：确定EGFR突变体肿瘤的药物敏感性和EGFR依赖性的基础。酶和细胞试验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egfr信号传导的细胞培养模型中进行检验。3：探讨其他ErbB受体在突变型EGFR的致瘤功能和药物敏感性中的作用。突变EGFR的异源二聚体和另一种ErbB受体有助于突变EGFR的致癌作用和/或药物敏感性，这一假设将得到验证。4：在没有EGFR突变的情况下，确定吉非替尼反应的分子基础。研究人员将在缺乏EGFR突变的药物反应性肿瘤中寻找候选基因突变。为了建立基于细胞的环境来研究反应机制，我们将筛选肺癌细胞系，以鉴定缺乏EGFR突变的药物敏感细胞系。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，这些研究有望对这类新型EGFR突变体的致瘤活性的分子机制以及含有这些突变的肿瘤所表现出的药物超敏性提供重要的见解。

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.