Athauda Gagani, Giubellino Alessio, Coleman Jonathan A, Horak Christine, Steeg Patricia S, Lee Ming-Jung, Trepel Jane, Wimberly Jennifer, Sun Jan, Coxon Angela, Burgess Teresa L, Bottaro Donald P
Urologic Oncology Branch, Laboratory of Molecular Pharmacology, and Medical Oncology Branch, National Cancer Institute, NIH, Bethesda, Maryland 20892-1107, USA.
Clin Cancer Res. 2006 Jul 15;12(14 Pt 1):4154-62. doi: 10.1158/1078-0432.CCR-06-0250.
Many proteins are proteolytically released from the cell surface by a process known as ectodomain shedding. Shedding occurs under normal physiologic conditions and can be increased in certain pathologies. Among the many receptors for which ectodomain shedding has been shown is c-Met, the hepatocyte growth factor (HGF) receptor tyrosine kinase. HGF stimulates mitogenesis, motogenesis, and morphogenesis in a variety of cellular targets during development, homeostasis, and tissue regeneration. Inappropriate HGF signaling resulting in unregulated cell proliferation, motility, and invasion occurs in several human malignancies. This can occur through paracrine signaling, autocrine loop formation, receptor mutation, gene amplification, or gene rearrangement, accompanied frequently with overexpression of ligand and/or receptor proteins. We hypothesized that c-Met overexpression in cancer might result in increased ectodomain shedding, and that its measure could be a useful biomarker of tumor progression.
We developed a sensitive electrochemiluminescent immunoassay to quantitate c-Met protein in cell lysates, culture supernatants, and biological samples.
A survey of cultured cell models of oncogenic transformation revealed significant direct correlations (P < 0.001, t test or ANOVA) between malignant potential and the rate of c-Met ectodomain shedding that was independent of steady-state receptor expression level. Moreover, weekly plasma and urine samples from mice harboring s.c. human tumor xenografts (n = 4 per group) displayed soluble human c-Met levels that were measurable before tumors became palpable and that correlated directly with tumor volume (R2 > 0.92, linear regression).
For a variety of human cancers, c-Met ectodomain shedding may provide a reliable and practical indicator of malignant potential and overall tumor burden.
许多蛋白质通过一种称为胞外域脱落的过程从细胞表面被蛋白水解释放。脱落发生在正常生理条件下，并且在某些病理状态下会增加。已显示存在胞外域脱落现象的众多受体中，有肝细胞生长因子（HGF）受体酪氨酸激酶c-Met。在发育、稳态和组织再生过程中，HGF在多种细胞靶点中刺激有丝分裂、运动发生和形态发生。在几种人类恶性肿瘤中会出现导致细胞增殖、运动和侵袭失控的不适当HGF信号传导。这可通过旁分泌信号传导、自分泌环形成、受体突变、基因扩增或基因重排发生，并且经常伴随着配体和/或受体蛋白的过表达。我们推测癌症中c-Met的过表达可能导致胞外域脱落增加，并且其检测可能是肿瘤进展的一个有用生物标志物。
我们开发了一种灵敏的电化学发光免疫测定法，用于定量细胞裂解物、培养上清液和生物样品中的c-Met蛋白。
对致癌转化的培养细胞模型进行的一项调查显示，恶性潜能与c-Met胞外域脱落速率之间存在显著的直接相关性（P < 0.001，t检验或方差分析），且该相关性与稳态受体表达水平无关。此外，携带皮下人肿瘤异种移植物的小鼠（每组n = 4）的每周血浆和尿液样本显示，在肿瘤可触及之前就能检测到可溶性人c-Met水平，并且该水平与肿瘤体积直接相关（R2 > 0.92，线性回归）。
对于多种人类癌症，c-Met胞外域脱落可能提供恶性潜能和总体肿瘤负荷的可靠且实用的指标。
