Development of novel cytotoxin therapy that targets tumor-associated surface molecules of biliary tract carcinoma

免疫组织化学分析显示，胆道癌（BTC）组织中的癌上皮（例如，胆囊癌、肝外胆管癌和肝内胆管癌）以高密度原位表达IL-4受体。表达率在50%以上。此外，培养的BTC细胞系已显示表达受体。另一方面，正常胆囊组织和胆管组织不表达该受体。因此，该受体可能成为未来分子靶向治疗的新靶点。将细胞毒素或免疫毒素靶向肿瘤细胞表面受体代表了治疗癌症的新方法。在本研究项目中，由白细胞介素-4（IL-4）靶向部分和假单胞菌外毒素A的截短形式组成的细胞毒素（IL-4-PE）针对人胆道癌（BTC）细胞测试抗肿瘤活性。八个BTC细胞系表达IL-4 R的细胞表面上的放射性标记的配体结合测定。当用IL-4-PE处理这些细胞时，通过蛋白质合成的抑制来确定观察到显著的细胞毒性。在所研究的8种BTC细胞系中，发现引起蛋白质合成50%抑制的药剂浓度（IC 50）小于10 ng/mL。针对皮下植入免疫缺陷小鼠中的人BTC细胞评估IL-4-PE的抗肿瘤活性。通过瘤内注射IL-4-PE，在40%的动物中观察到已建立的肿瘤完全消失。与未处理的动物相比，以耐受剂量向具有腹膜播散BTC的动物腹膜内施用IL-4-PE表现出显著延长的存活。总之，这些结果表明IL-4受体靶向的细胞毒素是一种有效的药物，可以为BTC提供新的治疗选择。

Immunohistochemical analysis has shown that cancerous epithelia in biliary tract carcinoma (BTC) tissue (e.g., gallbladder carcinoma, extraheaptic cholangiocarcinoma, and intrahepatic cholangiocarcinoma) expressed receptors for IL-4 in situ at high densities. The expression rate is more than 50%. Also, cultured BTC cell lines have been shown to express the receptor. On the other hand, normal gallbladder tissues and bile duct tissues do not express the receptor. Therefore, the receptor can be a novel target for molecular target therapy in future. Targeting cytotoxins or immunotoxins to tumor cell surface receptors represents a new approach for the treatment of carcinomas. In this research project, the antitumor activity of a cytotoxin (IL-4-PE), that is composed of an interleukin-4 (IL-4) targeting moiety and a truncated form of Pseudomonas exotoxin A, was tested against human biliary tract carcinoma (BTC) cells. Eight BTC cell lines expressed IL-4R on the cell surface as determined by radiolabeled ligand binding assays. When these cells were treated with IL-4-PE, significant cytotoxicity was observed as determined by the inhibition of protein synthesis. The concentration of agent causing 50% inhibition of protein synthesis (IC50) was found to be less than 10 ng/mL in 4 of the 8 BTC cell lines studied. The anti-tumor activity of IL-4-PE was assessed for human BTC cells implanted subcutaneously in immunodeficient mice. By intratumoral injection of IL-4-PE, complete disappearance of the established tumors was observed in 40% of animals. Intraperitoneal administration of IL-4-PE at tolerated doses to animals with peritoneally disseminated BTC exhibited significantly prolonged survival compared to untreated animals. Taken together, these results indicate that IL-4 receptor-targeted cytotoxin is a potent agent that may provide a new therapeutic option for BTC.