Wykosky Jill, Gibo Denise M, Debinski Waldemar
Department of Neurosurgery, Brain Tumor Center of Excellence, Comprehensive Cancer Center of Wake Forest University, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA.
Mol Cancer Ther. 2007 Dec;6(12 Pt 1):3208-18. doi: 10.1158/1535-7163.MCT-07-0200.
We have previously shown that the EphA2 receptor tyrosine kinase is overexpressed in glioblastoma multiforme (GBM) and represents a novel, attractive therapeutic target for the treatment of brain tumors. Here, we have developed an EphA2-targeted agent, ephrinA1-PE38QQR, a novel cytotoxin composed of ephrinA1, a ligand for EphA2, and PE38QQR, a mutated form of Pseudomonas aeruginosa exotoxin A. EphrinA1-PE38QQR showed potent and dose-dependent killing of GBM cells overexpressing the EphA2 receptor in cell viability and clonogenic survival assays, with an average IC(50) of approximately 10(-11) mol/L. The conjugate was also highly effective in killing breast and prostate cancer cells overexpressing EphA2. The cytotoxic effect of ephrinA1-PE38QQR was specific, as it was neutralized by an excess of EphA2 ligands. Moreover, normal human endothelial cells and breast cancer cells that do not overexpress EphA2, as well as GBM cells that have down-regulated EphA2, were not susceptible to the cytotoxin. EphrinA1-PE38QQR-mediated cytotoxicity induced caspase-dependent apoptosis, which was, however, not responsible for cell death in response to the conjugate. In addition, the conjugate elicited no changes in the activity of survival pathways such as phosphoinositide 3-kinase, measured by AKT phosphorylation. This is the first attempt to create a cytotoxic therapy using any of the ephrin ligands of either class (A or B) conjugated to a bacterial toxin. EphrinA1-PE38QQR is very potent and specific, produces cell death that is caspase independent, and forms the basis for the further development of clinically applicable EphA2-targeted cytotoxins.
我们之前已经表明，EphA2受体酪氨酸激酶在多形性胶质母细胞瘤（GBM）中过表达，是治疗脑肿瘤的一个新的、有吸引力的治疗靶点。在此，我们开发了一种靶向EphA2的药物，ephrinA1-PE38QQR，一种新型细胞毒素，由EphA2的配体ephrinA1和铜绿假单胞菌外毒素A的突变形式PE38QQR组成。在细胞活力和克隆形成存活试验中，ephrinA1-PE38QQR对过表达EphA2受体的GBM细胞表现出强效且剂量依赖性的杀伤作用，平均半数抑制浓度（IC50）约为10^(-11) mol/L。该偶联物对过表达EphA2的乳腺癌和前列腺癌细胞也有高效杀伤作用。ephrinA1-PE38QQR的细胞毒性作用具有特异性，因为它可被过量的EphA2配体中和。此外，未过表达EphA2的正常人内皮细胞和乳腺癌细胞，以及下调了EphA2的GBM细胞对该细胞毒素不敏感。ephrinA1-PE38QQR介导的细胞毒性诱导了半胱天冬酶依赖性凋亡，但这并非该偶联物导致细胞死亡的原因。此外，通过AKT磷酸化检测发现，该偶联物未引起磷脂酰肌醇3激酶等存活通路活性的变化。这是首次尝试利用A类或B类任何一种ephrin配体与细菌毒素偶联来创建细胞毒性疗法。ephrinA1-PE38QQR非常强效且具有特异性，可导致半胱天冬酶非依赖性的细胞死亡，并为临床上适用的靶向EphA2的细胞毒素的进一步开发奠定了基础。
