O'Rourke D M, Nute E J, Davis J G, Wu C, Lee A, Murali R, Zhang H T, Qian X, Kao C C, Greene M I
Department of Neurosurgery, University of Pennsylvania, School of Medicine, Philadelphia 19104, USA.
Oncogene. 1998 Mar 5;16(9):1197-207. doi: 10.1038/sj.onc.1201635.
Mutant Epidermal Growth Factor Receptor (EGFR) oncoproteins lacking most of subdomains I and II of the extracellular region, a deletion which includes most of the first of two cysteine-rich sequences, have been observed in multiple human epithelial tumors, including malignant gliomas. These EGFR oncoproteins, designated deltaEGFR or EGFRvIII, confer increased tumorigenicity in vivo and are often coexpressed with full-length EGFR in human tumors. We have expressed an ectodomain-derived, carboxyl-terminal deletion mutant of the p185neu oncogene (T691stop) in human glioblastoma cells coexpressing endogenous EGFR and activated deltaEGFR oncoproteins. The p185neu ectodomain-derived mutant forms heterodimers with deltaEGFR proteins and reduces the phosphotyrosine content and kinase activity of deltaEGFR monomers. As a consequence of T691stop neu expression and surface localization, cell proliferation in conditions of full growth and reduced serum and anchorage-independent growth in soft agar was reduced in glioblastoma cells expressing either endogenous EGFR alone or coexpressing EGFR and elevated levels of deltaEGFRs. T691stop neu mutant receptors abrogate the dramatic growth advantage conferred by deltaEGFR in vivo, suggesting that physical associations primarily between subdomains III and IV of the p185neu and EGFR ectodomains are sufficient to modulate signaling from activated EGFR complexes. Receptor-based inhibitory strategies exploit the thermodynamic preference for erbB ectodomains to heterodimerize, thereby creating erbB receptor assemblies which are defective in signaling and do not internalize. Pharmaceuticals which mimic the p185neu ectodomain may therefore have important therapeutic applications in advanced human malignancies expressing erbB receptors.
在包括恶性胶质瘤在内的多种人类上皮肿瘤中，已观察到缺乏细胞外区域大部分结构域I和II的突变型表皮生长因子受体（EGFR）癌蛋白，这种缺失包括两个富含半胱氨酸序列中第一个序列的大部分。这些EGFR癌蛋白，称为δEGFR或EGFRvIII，在体内具有更高的致瘤性，并且在人类肿瘤中常与全长EGFR共表达。我们在共表达内源性EGFR和活化的δEGFR癌蛋白的人胶质母细胞瘤细胞中表达了p185neu癌基因的细胞外结构域衍生的羧基末端缺失突变体（T691stop）。p185neu细胞外结构域衍生的突变体与δEGFR蛋白形成异二聚体，并降低δEGFR单体的磷酸酪氨酸含量和激酶活性。由于T691stop neu的表达和表面定位，在仅表达内源性EGFR或共表达EGFR和高水平δEGFR的胶质母细胞瘤细胞中，完全生长和血清减少条件下的细胞增殖以及软琼脂中的非锚定依赖性生长均降低。T691stop neu突变受体消除了δEGFR在体内赋予的显著生长优势，这表明p185neu和EGFR细胞外结构域的结构域III和IV之间的主要物理关联足以调节来自活化EGFR复合物的信号传导。基于受体的抑制策略利用了erbB细胞外结构域异二聚化的热力学偏好，从而产生在信号传导方面有缺陷且不内化的erbB受体组装体。因此，模拟p185neu细胞外结构域的药物可能在表达erbB受体的晚期人类恶性肿瘤中具有重要的治疗应用。
