Qi Lin, Nett Terry M, Allen Matthew C, Sha Xiaoming, Harrison Gail S, Frederick Barbara A, Crawford E David, Glode L Michael
Department of Medicine, Division of Medical Oncology, University of Colorado Health Sciences Center, 4200 East Ninth Avenue, Denver, CO 80262, USA.
Cancer Res. 2004 Mar 15;64(6):2090-5. doi: 10.1158/0008-5472.can-3192-2.
Pokeweed antiviral protein (PAP) is a plant-derived, highly potent ribosome inactivating protein that causes inhibition of protein translation and rapid cell death. We and others have delivered this protein to various cell types, including cancer cells, using hormones to specifically target cells bearing the hormone receptor. Here, we compare binding and cytotoxicity of GnRH-PAP hormonotoxins prepared either by protein conjugation (GnRH-PAP conjugate) or through recombinant DNA technology (GnRH-PAP fusion). Although GnRH-PAP conjugate protein bound specifically to and caused cell death in cells bearing the gonadotropin-releasing hormone (GnRH) receptor, we could not detect binding or cytotoxicity using two different versions of the fusion protein in receptor-positive cells. We conclude that generation of an active GnRH-PAP fusion protein may not be feasible either because both ends of the GnRH molecule are required for receptor binding, but only the NH(2) terminus is free in the fusion protein and/or that more potent analogues of GnRH (inclusion of which is not feasible in the fusion protein) are needed for efficient targeting. In contrast, the GnRH-PAP conjugate shows promise as a novel anticancer agent, capable of targeting cancer cells expressing the GnRH receptor such as prostate, breast, ovarian, endometrial, and pancreatic cells. It may also be useful as a therapeutic agent to eliminate pituitary gonadotrophs, eliminating the need for chronic GnRH analogue administration to treat hormone-sensitive diseases.
商陆抗病毒蛋白（PAP）是一种源自植物的高效核糖体失活蛋白，可抑制蛋白质翻译并导致细胞快速死亡。我们和其他人已使用激素将这种蛋白递送至包括癌细胞在内的各种细胞类型，以特异性靶向带有激素受体的细胞。在此，我们比较了通过蛋白质偶联制备的促性腺激素释放激素 - 商陆抗病毒蛋白（GnRH - PAP）激素毒素（GnRH - PAP偶联物）或通过重组DNA技术制备的（GnRH - PAP融合蛋白）的结合能力和细胞毒性。尽管GnRH - PAP偶联蛋白能特异性结合促性腺激素释放激素（GnRH）受体阳性细胞并导致其死亡，但我们在受体阳性细胞中使用两种不同版本的融合蛋白时，未能检测到结合或细胞毒性。我们得出结论，生成活性GnRH - PAP融合蛋白可能不可行，这可能是因为GnRH分子的两端对于受体结合都是必需的，但在融合蛋白中只有NH(2)末端是游离的，和/或高效靶向需要更有效的GnRH类似物（而在融合蛋白中包含这些类似物是不可行的）。相比之下，GnRH - PAP偶联物有望成为一种新型抗癌药物，能够靶向表达GnRH受体的癌细胞，如前列腺、乳腺、卵巢、子宫内膜和胰腺细胞。它也可能作为一种治疗剂用于消除垂体促性腺细胞，从而无需长期给予GnRH类似物来治疗激素敏感性疾病。
