Holmes Suzanne E, Bachran Christopher, Fuchs Hendrik, Weng Alexander, Melzig Matthias F, Flavell Sopsamorn U, Flavell David J
The Simon Flavell Leukaemia Research Laboratory, Southampton General Hospital , Southampton , UK .
Immunopharmacol Immunotoxicol. 2015 Feb;37(1):42-55. doi: 10.3109/08923973.2014.971964. Epub 2014 Oct 27.
Saponinum album (SA) is a complex mixture of triterpenoid saponins previously shown to augment the cytotoxicity of the type I ribosome-inactivating protein saporin and an EGF-saporin target toxin that could potentially be used to improve the therapeutic window of targeted toxins.
To investigate the augmentative property of SA on saporin and saporin-based immunotoxins (IT) directed against five different cell surface target molecules on human leukemia and lymphoma cells.
After determining the optimum dose of SA for each cell line, the extent of SA-mediated augmentation was established for saporin and five saporin-based ITs using XTT and an annexin V apoptosis assay. Immunospecificity was investigated using three different blocking assays. Dose-scheduling was also investigated using the XTT assay.
Uncorrected SA-mediated augmentation ranged at best from 31.5 million-fold to, at worse, 174-fold. However, when the calculated fold-increases were adjusted for the non-immunospecific effects of SA on an off-target IT, the true augmentative effects of SA were found to be largely non-immunospecific. Antibody blocking studies demonstrated that the augmentative effect of SA was only partially immunospecific. Separate exposure of target cells to IT and SA at different times demonstrated that immunospecific augmentation of IT by SA could be achieved but only if cells were exposed to IT first and SA second.
SA significantly, although variably, augments the cytotoxicity of saporin and saporin-based immunotoxins. Concomitant exposure to both IT and SA can result in non-immunospecific cytotoxicity that can be overcome by temporally separating exposure to each.
白皂草素（SA）是一种三萜皂苷的复杂混合物，先前已证明它可增强I型核糖体失活蛋白皂草素和一种表皮生长因子-皂草素靶向毒素的细胞毒性，该毒素可能用于改善靶向毒素的治疗窗口。
研究SA对针对人类白血病和淋巴瘤细胞上五种不同细胞表面靶分子的皂草素和基于皂草素的免疫毒素（IT）的增强特性。
在确定每种细胞系的SA最佳剂量后，使用XTT和膜联蛋白V凋亡检测法确定SA介导的皂草素和五种基于皂草素的IT的增强程度。使用三种不同的阻断检测法研究免疫特异性。还使用XTT检测法研究给药方案。
未经校正的SA介导的增强作用最佳范围为3150万倍，最差为174倍。然而，当针对SA对脱靶IT的非免疫特异性作用调整计算出的增加倍数时，发现SA的真正增强作用在很大程度上是非免疫特异性的。抗体阻断研究表明，SA的增强作用仅部分具有免疫特异性。在不同时间将靶细胞分别暴露于IT和SA表明，SA对IT的免疫特异性增强作用可以实现，但前提是细胞先暴露于IT，然后再暴露于SA。
SA显著增强了皂草素和基于皂草素的免疫毒素的细胞毒性，尽管增强程度有所不同。同时暴露于IT和SA会导致非免疫特异性细胞毒性，通过在时间上分开暴露于每种物质可以克服这种毒性。
