Epigenomic Medicine, Baker IDI Heart and Diabetes Institute, The Alfred Medical Research and Education Precinct, 75 Commercial Road, Melbourne, VIC, 3004, Australia.
J Membr Biol. 2014 Apr;247(4):291-307. doi: 10.1007/s00232-014-9637-0. Epub 2014 Feb 27.
Current cancer management strategies fail to adequately treat malignancies with multivariable dose-restricting factors such as systemic toxicity and multi-drug resistance limiting therapeutic benefit, quality of life and complete long-term remission rates. The targeted delivery of a therapeutic compound aims to enhance its circulation and cellular uptake, decrease systemic toxicity and improve therapeutic benefit with disease specificity. The transferrin peptide, its receptor and their biological significance, has been widely characterised and vastly relevant when applied to targeting strategies. Utilising knowledge about the physiological function of the transferrin-transferrin receptor complex and the efficiency of its receptor-mediated endocytosis provides rationale to continue the development of transferrin-targeted anticancer modalities. Furthermore, multiple studies report an upregulation in expression of the transferrin receptor on metastatic and drug resistant tumours, highlighting its selectivity to cancer. Due to the increased expression of the transferrin receptor in brain glioma, the successful delivery of anticancer compounds to the tumour site and the ability to cross the blood brain barrier has shown to be an important discovery. Its significance in the development of cancer-specific therapies is shown to be important by direct conjugation and immunotoxin studies which use transferrin and anti-transferrin receptor antibodies as the targeting moiety. Such conjugates have demonstrated enhanced cellular uptake via transferrin-mediated mechanisms and increased selective cytotoxicity in a number of cancer cell lines and tumour xenograft animal models. In addition, incubation of chemotherapy-insensitive cancer cells with transferrin-targeted conjugates in vitro has resulted in a reversal of their drug resistance. Transferrin immunotoxins have also shown similar promise, with a diphtheria toxin mutant covalently bound to transferrin (Tf-CRM107) currently involved in human clinical trials for the treatment of glioblastoma. Despite this, the inability to translate preliminary research into a clinical setting has compelled research into novel targeting strategies including the use of nanoparticulate theory in the design of drug delivery systems. The main objective of this review is to evaluate the importance of the transferrin-transferrin receptor complex as a target for cancer therapy through extensive knowledge of both the physiological and pathological interactions between the complex and different cell types. In addition, this review serves as a summary to date of direct conjugation and immunotoxin studies, with an emphasis on transferrin as an important targeting moiety in the directed delivery of anticancer therapeutic compounds.
目前的癌症治疗策略未能充分治疗多变量剂量限制因素的恶性肿瘤，如全身毒性和多药耐药性，限制了治疗益处、生活质量和完全长期缓解率。治疗化合物的靶向递送旨在增强其循环和细胞摄取，降低全身毒性，并提高疾病特异性的治疗益处。转铁蛋白肽、其受体及其生物学意义已得到广泛描述，在应用于靶向策略时具有重要意义。利用关于转铁蛋白-转铁蛋白受体复合物的生理功能及其受体介导的内吞作用效率的知识，为继续开发转铁蛋白靶向抗癌模式提供了依据。此外，多项研究报告称，转移瘤和耐药瘤中转铁蛋白受体的表达上调，突出了其对癌症的选择性。由于脑胶质瘤中转铁蛋白受体表达增加，抗癌化合物成功递送到肿瘤部位并能够穿过血脑屏障已被证明是一项重要发现。通过直接缀合和免疫毒素研究表明，转铁蛋白和抗转铁蛋白受体抗体作为靶向部分在癌症特异性治疗的发展中具有重要意义。这些缀合物已证明通过转铁蛋白介导的机制增强了细胞摄取，并在许多癌细胞系和肿瘤异种移植动物模型中增加了选择性细胞毒性。此外，体外孵育转铁蛋白靶向缀合物对化疗不敏感的癌细胞可逆转其耐药性。转铁蛋白免疫毒素也显示出类似的前景，一种与转铁蛋白（Tf-CRM107）共价结合的白喉毒素突变体目前正在参与治疗胶质母细胞瘤的人类临床试验。尽管如此，将初步研究转化为临床环境的能力不足促使研究人员探索新的靶向策略，包括在药物递送系统的设计中使用纳米颗粒理论。本综述的主要目的是通过广泛了解该复合物与不同细胞类型之间的生理和病理相互作用，评估转铁蛋白-转铁蛋白受体复合物作为癌症治疗靶点的重要性。此外，本综述还总结了迄今为止直接缀合和免疫毒素研究的情况，重点介绍了转铁蛋白作为靶向递送达癌治疗化合物的重要靶向部分。
