Debinski W, Obiri N I, Pastan I, Puri R K
Milton S. Hershey Medical Center, Department of Surgery, Pennsylvania State University, Hershey 17033, USA.
J Biol Chem. 1995 Jul 14;270(28):16775-80. doi: 10.1074/jbc.270.28.16775.
Chimeric proteins provide a unique opportunity to target therapeutic bacterial toxins to a subset of specific cells. We have generated a new recombinant chimeric toxin composed of human interleukin 13 (hIL13) and a Pseudomonas exotoxin A (PE) mutant, PE38QQR. The hIL13-PE38QQR chimera is highly cytotoxic to cell lines derived from several human epithelial carcinomas such as adenocarcinoma of stomach, colon, and skin. The cytotoxic action of hIL13-PE38QQR, which can only occur upon internalization of ligand-receptor complex, is blocked by an excess of hIL13 but not of hIL2. This action is not solely hIL13-specific because an excess of hIL4 also blocks the cytotoxicity of hIL13-toxin. Conversely, hIL13 blocks the cytotoxicity of a hIL4-PE38QQR chimera. Binding studies showed that hIL13 displaces competitively 125I-labeled hIL4-PE38QQR on carcinoma cells. These results indicate that IL4 and IL13 compete for a common binding site on the studied human cell lines. Despite this competition, hIL4 but not hIL13 decreased protein synthesis in malignant cells susceptible to the cytotoxicity of both hIL13- and hIL4-PE38QQR. Our results suggest that a spectrum of human carcinomas express binding sites for IL13. Furthermore, hIL13 and hIL4 compete reciprocally for a form of the receptor that is internalized upon binding a ligand. Thus, cancer cells represent an interesting model for studying receptors for these two growth factors. Finally, hIL13-PE38QQR may be a useful agent in the treatment of several malignancies.
嵌合蛋白为将治疗性细菌毒素靶向特定细胞亚群提供了独特的机会。我们构建了一种新的重组嵌合毒素，它由人白细胞介素13（hIL13）和铜绿假单胞菌外毒素A（PE）突变体PE38QQR组成。hIL13-PE38QQR嵌合体对源自多种人类上皮癌的细胞系具有高度细胞毒性，如胃癌、结肠癌和皮肤腺癌。hIL13-PE38QQR的细胞毒性作用只有在配体-受体复合物内化后才会发生，过量的hIL13可阻断该作用，但过量的hIL2则不能。这种作用并非hIL13所特有，因为过量的hIL4也能阻断hIL13-毒素的细胞毒性。相反，hIL13可阻断hIL4-PE38QQR嵌合体的细胞毒性。结合研究表明，hIL13在癌细胞上竞争性地取代125I标记的hIL4-PE38QQR。这些结果表明，IL4和IL13在研究的人类细胞系上竞争一个共同的结合位点。尽管存在这种竞争，但hIL4而非hIL13可降低对hIL13-和hIL4-PE38QQR细胞毒性敏感的恶性细胞中的蛋白质合成。我们的结果表明，一系列人类癌症表达IL13的结合位点。此外，hIL13和hIL4相互竞争一种在结合配体后会内化的受体形式。因此，癌细胞是研究这两种生长因子受体的一个有趣模型。最后，hIL13-PE38QQR可能是治疗多种恶性肿瘤的有用药物。
