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（如胆囊癌、肝外胆管癌和肝内胆管癌）的癌上皮在原位高密度表达IL-4受体。表达率大于50%。此外，培养的BTC细胞系已显示出表达受体。另一方面，正常的胆囊组织和胆管组织不表达该受体。因此，该受体有望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是治疗肿瘤的新途径。本研究以白细胞介素-4 （IL-4）靶向片段和假单胞菌外毒素a的截断形式组成的细胞毒素（IL-4- pe）对人胆道癌（BTC）细胞的抗肿瘤活性进行了测试。通过放射性标记配体结合测定，8个BTC细胞系在细胞表面表达IL-4R。当这些细胞用IL-4-PE处理时，通过抑制蛋白质合成观察到显著的细胞毒性。在8个BTC细胞系中，有4个细胞系的IC50浓度小于10 ng/mL。研究了IL-4-PE对免疫缺陷小鼠皮下植入人BTC细胞的抗肿瘤活性。通过瘤内注射IL-4-PE， 40%的动物肿瘤完全消失。腹腔注射耐受剂量的IL-4-PE给腹膜弥散性BTC的动物，与未治疗的动物相比，存活时间明显延长。综上所述，这些结果表明，IL-4受体靶向细胞毒素是一种有效的药物，可能为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.