Epidermal growth factor receptor mutants from human lung cancers exhibit enhanced catalytic activity and increased sensitivity to gefitinib
Epidermal growth factor receptor mutants from human lung cancers exhibit enhanced catalytic activity and increased sensitivity to gefitinib
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DOI：
10.1158/0008-5472.can-06-4293
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发表时间：
2007-03-01
期刊：
影响因子：
11.2
通讯作者：
Settleman, Jeffrey
中科院分区：
文献类型：
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作者：
Mulloy, Roseann;Ferrand, Audrey;Settleman, Jeffrey
表皮生长因子受体（EGFR）激酶结构域内的体细胞突变在10%至30%的人类非小细胞肺癌中被检测到，并且与使用EGFR激酶抑制剂（如吉非替尼和厄洛替尼）治疗的一部分患者的显著临床反应相关。基于细胞的研究表明，这些突变的EGFR促进了EGFR cooh末端酪氨酸亚群的自磷酸化活性的增加，以及随后下游效应子亚群的参与。由于EGFR功能在体内受到多个水平的调节，因此很难评估这些突变对EGFR酶功能的直接影响，因此我们使用纯化的重组蛋白（与野生型和两种经常检测到的EGFR突变体（DeIL747-P753insS和L858R）的细胞质结构域相对应）在体外激酶试验中测量了EGFR的催化活性。与野生型EGFR相比，这两种突变体都表现出显著增加的自磷酸化活性，并且它们表现出不同的反应动力学。此外，突变激酶对吉非替尼的激酶抑制更敏感，这似乎反映了它们的药物亲和力增加。这些发现表明，在体内观察到的这些EGFR突变体的信号特性和药物敏感性的改变主要是由于激酶催化特性的差异。此外，我们发现EGFR的T790M继发性“耐药突变”经常出现在最初对治疗有反应的复发患者中，使原发性激活EGFR等位基因的激酶活性增强，因此在某些情况下可能致癌。
Somatic mutations within the epidermal growth factor receptor (EGFR) kinase domain are detected in 10% to 30% of human non-small cell lung cancers and are correlated with striking clinical responses in a subset of patients treated with EGFR kinase inhibitors, such as gefitinib and erlotinib. Cellbased studies suggest that these mutant EGFRs promote increased autophosphorylating activity on a subset of EGFR COOH-terminal tyrosines and the consequent engagement of a subset of downstream effectors. Because EGFR function is regulated at multiple levels in vivo, and it is therefore difficult to assess the direct consequences of these mutations on EGFR enzyme function, we measured EGFR catalytic activity in in vitro kinase assays using purified recombinant proteins corresponding to the cytoplasmic domain of wild-type and two frequently detected EGFR mutants (DeIL747-P753insS and L858R). Both mutants exhibit substantially increased autophosphorylating activity relative to wild-type EGFR, and they exhibit distinct reaction kinetics. In addition, the mutant kinases are more sensitive to kinase inhibition by gefitinib, which seems to reflect their increased drug affinity. These findings suggest that the altered signaling properties and drug sensitivity of these EGFR mutants that have been observed in vivo largely result from differences in the catalytic properties of the kinase. In addition, we find that the T790M secondary "drug resistance mutation" of EGFR, which frequently arises in relapsed patients that initially responded to treatment, confers enhanced kinase activity to primary activating EGFR alleles and may, therefore, be oncogenic in some contexts.