The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor AG1478 increases the formation of inactive untethered EGFR dimers - Implications for combination therapy with monoclonal antibody 806
The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor AG1478 increases the formation of inactive untethered EGFR dimers - Implications for combination therapy with monoclonal antibody 806
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DOI：
10.1074/jbc.m605136200
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发表时间：
2007-02-02
影响因子：
4.8
通讯作者：
Johns, Terrance G.
中科院分区：
文献类型：
--
作者：
Gan, Hui K.;Walker, Francesca;Johns, Terrance G.
表皮生长因子受体(EGFR)至少有两种基本构象：一种是非活性的拴系构象，另一种是活性的、非拴系的、与配体结合的“Back-Toback”二聚体，它可能是寡聚复合体的一部分。单抗(MAb)806是一种EGFR特异性抗体，仅在解链后形成背靠背连接的活性寡聚体之前与过渡形式的受体结合。我们已经证明，AG1478，一种EGFR的酪氨酸激酶抑制剂，当与单抗806结合使用时，协同抑制过度表达EGFR的肿瘤的生长，但其机制尚未阐明(Johns，T.G.，Luwor，R.B.，Murone，C.，Walker，F.，Weinstock，J.，Vitali，A.A.，Perera，R.M.，JungBluth，A.A.，Stockert，E.，Old，L.J.，Nice，E.C.，Burgess，A.W.，和Scott，A.M.(2003)Proc.娜塔莉。阿卡德。SCI。美国，100,15871 15876)。我们现在证明，AG1478通过两种不同的机制增加单抗806与细胞表面的结合：对EGFR构象的即时影响和长期增加细胞表面糖基化的EGFR，这一事件已知会增加单抗806的反应性。交联性研究表明，在过度表达EGFR的细胞表面存在自发产生的mAb806反应性二聚体，AG1478使其迅速增加。因为它们与mAb806反应，这些二聚体必须以不同于连接的背靠背二聚体的构象存在。事实上，我们在表达EGFR的293T细胞中发现了类似的二聚体，缺乏形成背靠背二聚体所必需的小二聚化/激活臂。因此，癌细胞表面的一些EGFR必须以一种未被报道的非活性构象的二聚体形式存在。这一信息被用于在异种移植模型中优化单抗806和AG1478之间的治疗协同作用。
The epidermal growth factor receptor (EGFR) has at least two fundamental conformations: an inactive tethered conformation and an active untethered, ligand-bound "back-toback" dimer, which may be part of an oligomeric complex. Monoclonal antibody (mAb) 806 is an EGFR-specific antibody that only binds a transitional form of the receptor after it untethers but before forming the back-to-back, ligated, active oligomer. We have shown that AG1478, a tyrosine kinase inhibitor of the EGFR, synergistically inhibits the growth of tumors overexpressing EGFR when used in combination with mAb 806 but the mechanism for this was not elucidated (Johns, T. G., Luwor, R. B., Murone, C., Walker, F., Weinstock, J., Vitali, A. A., Perera, R. M., Jungbluth, A. A., Stockert, E., Old, L. J., Nice, E. C., Burgess, A. W., and Scott, A. M. (2003) Proc. Natl. Acad. Sci. U. S. A. 100, 15871 15876). We now show that AG1478 increases binding of mAb 806 to the cell surface through two distinct mechanisms: an immediate effect on the conformation of EGFR and a longer term increase in cell surface under-glycosylated EGFR, an event known to increase mAb 806 reactivity. Cross-linking studies demonstrated the presence of spontaneously occurring mAb 806-reactive dimers on the surface of cells overexpressing EGFR, which are rapidly increased by AG1478. Because they react with mAb 806, these dimers must exist in a conformation distinct from the ligated back-to-back dimer. Indeed, we detected similar dimers in 293T cells expressing the EGFR lacking the small dimerization/activation arm essential to the formation of the back-to-back dimer. Thus, some of the EGFR on the cell surface of cancer cells must exist as an untethered dimer that adopts a previously unreported conformation that is inactive. This information was used to optimize the therapeutic synergy between mAb 806 and AG1478 in a xenograft model.