INHIBITION OF TUMOR CELL GROWTH BY IMMUNOTOXINS

与毒素化学连接的肿瘤选择性单克隆抗体 在一些实施方案中，多肽（IMT）抑制相应癌细胞的生长。 虽然这些缀合物在消除靶向药物方面非常有效， 肿瘤细胞，它们在体内的应用是有限的，由于i） 可变的细胞毒性，ii）少数细胞群逃逸 iii）缀合物在循环中的不稳定性 和iv）减少肿瘤定位。 最后两个问题是 对于IMT的系统应用至关重要，但可能 在肿瘤治疗中， 解剖空间，如腹膜（如卵巢上皮 癌）。 在最近的过去已经制备了许多IMT 对乳腺癌和卵巢癌细胞有选择性。 一些 由重组蓖麻毒素A链制成的这些缀合物中有 不活跃，尽管有效的内部化。 的化学连接 抗体和毒素部分之间的相互作用也在 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方法，以克服缺乏 的功效。 早期的研究表明， 亲溶酶体试剂增加抗体的细胞毒性- 毒素结合物。 然而，这种方法不能用于 由于增强化合物的更快清除， 因此，在本发明中， 亲溶酶体试剂如莫能菌素与 大分子可以增加其生物半衰期， 可提高体内IMT的疗效。 莫能菌素是 通过第二抗体（载体）识别肿瘤细胞 一种独特的抗原 或者，将莫能菌素包封在 用于特异性递送至肿瘤细胞的免疫脂质体。 改善的肿瘤细胞消除也可以通过以下方式实现： 通过抗原上存在的双表位靶向毒素分子 或通过癌细胞上存在的两种不同抗原。 As毒素 多肽在它们的作用方式和位点上不同，它可能是 可能通过连接两个毒素部分来改善IMT活性 抗体。 将检测这些试剂的能力， 增强体外和体内裸鼠肿瘤细胞消除 小鼠异种移植肿瘤模型系统。 就像化疗一样， 一小部分肿瘤细胞确实逃脱了IMT治疗。 将进行调查，以了解 在此基础上，提出了抑制 将研究这些肿瘤细胞变体的生长。

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.