INHIBITION OF TUMOR CELL GROWTH BY IMMUNOTOXINS

与毒素化学连锁的肿瘤选择性单抗 多肽(IMT)可抑制相应癌细胞的生长。 虽然这些偶联物在消除目标方面非常有效 肿瘤细胞在体外，其在体内的应用因i)而受到限制 可变的细胞毒性，II)少数细胞逃逸 来自IMT治疗，III)循环中的结合物的不稳定性 以及iv)肿瘤定位减少。最后两个问题是 对IMT的系统应用至关重要，但可能是 在治疗受限的肿瘤时的规避 与腹膜类似的解剖空间(如卵巢上皮 癌症)。最近已经准备了许多IMT 对乳腺和卵巢癌细胞有选择性。一些人 在这些由重组蓖麻毒素A链制成的结合物中 在有效内部化的情况下，激励不积极。化学键 在抗体和毒素部分之间也起着关键作用 测定细胞毒性。因此，在拟议的研究中， 将试图了解减少的原因 免疫毒素活性和开发克服缺乏的方法 效率的问题。早期的研究表明， 溶酶体亲和性试剂增加抗体的细胞毒性- 毒素结合在一起。但是，这种方法不能用于 由于增效剂化合物的清除速度更快，因此可在体内释放。因此， 类溶酶变性剂莫能菌素的偶联作用 大分子可以增加其生物半衰期，进而 可提高IMT的体内疗效。莫能菌素将是 通过第二抗体(载体)识别肿瘤细胞 一种独特的抗原。或者，莫能菌素可以被包裹起来 在免疫脂质体中进行肿瘤细胞的特异性递送。 改进的肿瘤细胞清除也可以通过以下方式实现 通过抗原上的双重表位靶向毒素分子 或者通过癌细胞上存在的两种不同的抗原。作为毒素 多肽在作用方式和作用部位上不同，它可能是 可能通过连接两个毒素部分来提高IMT活性 对抗体的影响。这些试剂将接受测试，看它们是否有能力 增强肿瘤细胞在体内外的清除作用 小鼠异种移植瘤模型系统。就像在化疗中一样， 一小部分肿瘤细胞确实逃脱了IMT治疗。 将进行调查，以了解 并在上述工作的基础上，提出了抑制赤潮的方法 这些肿瘤细胞变异体的生长将被研究。

Tumor selective monoclonal antibodies chemically linked to toxin polypeptides (IMT) inhibit the growth of respective cancer cells. While these conjugates are very efficient in eliminating target tumor cells in vitro, their application in vivo is limited due to i) variable cytotoxicity, ii) escape of a minor population of cells from IMT treatment, iii) instability of the conjugate in circulation and iv) reduced tumor localization. The last two issues are critical for the systemic application of IMT but could be circumvent in treatment of tumors confined to restricted anatomical space like the peritoneum (e.g. ovarian epithelial carcinoma). Many IMTs have been prepared in the recent past that are selective against breast and ovarian cancer cells. Some of these conjugates made from recombinant ricin A-chain are inactive inspite of efficient internalization. The chemical linkage between antibody and the toxin moiety also plays a critical role in determining the cytotoxicity. Therefore, in the proposed study, attempts will be made to understand the reasons for reduced immunotoxin activity and develop methods to overcome the lack of efficacy. Earlier studies have shown that the presence of lysosomotropic reagents increase the cytotoxicity of antibody- toxin conjugates. However, this approach could not be used in vivo due to faster clearance of the potentiating compound. Thus, conjugation of lysosomotropic reagent like monensin to macromolecules could increase its biological half-life and in turn could improve the efficacy of IMT in vivo. Monensin would be directed to tumor cells via a second antibody (carrier) recognizing a distinct antigen. Alternatively, monensin would be encapsulated in immunoliposomes for the specific delivery to tumor cells. Improved tumor cell elimination could also be achieved by targeting toxin molecules via dual epitopes present on the antigen or via two distinct antigens present on the cancer cells. As toxin polypeptides differ in their mode and site of action, it may be possible to improve the IMT activity by linking two toxin moieties to antibodies. These reagents will be tested for their ability to enhance tumor cell elimination in vitro and in vivo in a nude mouse xenograft tumor model system. Like in chemotherapy, a small fraction of tumor cells do escape IMT treatment. Investigations will be carried out to understand the mechanism of resistance and based on the above work, methods to inhibit the growth of these tumor cell variants will be studied.