Identification of the molecular mechanism that leads to a resistance against pseudomonas exotoxin A based immunotoxins

在过去的几十年里，通过将细菌毒素组分，如假单胞菌外毒素A的催化结构域，与抗体或受体结合配体融合，开发了各种不同的免疫毒素。这种靶向治疗的一个广泛评价的代表是融合蛋白HA22，它是CD22结合的Fab和PE的组合，在许多B细胞淋巴瘤中通过延长因子2(EF2)的ADP核糖基化而有效，随后通过抑制蛋白质的生物合成而有效。由于这一事件，细胞被驱使进入程序性细胞死亡。一些淋巴瘤细胞对免疫毒素具有先天抵抗力。Ira Pastan的研究小组发现了对HA22具有抗性的细胞，在这些细胞中，EF2被ADP核糖化，蛋白质合成停止，但细胞不会发生凋亡。其中一些原始的HA22抗性细胞可以通过特定的小分子化合物对HA22敏感。在这里提出的项目中，我们将比较初级耐药细胞、二次致敏细胞和初级敏感细胞的蛋白质表达谱，以阐明这种抗性背后的分子机制。这些知识将被用来预测治疗反应，从而使患者免于无效的治疗，此外，还将增强ADP核糖化毒素的效果。由于广泛使用的ADP核糖化免疫毒素白喉毒素、霍乱毒素、蓖麻毒素和假单胞菌外毒素具有共同的细胞凋亡诱导机制，这项工作对现代肿瘤学中的许多靶向治疗非常有意义。

During the last decades, a vast variety of different immunotoxins were developed by fusing bacterial toxin components like the catalytic domain of pseudomonas exotoxin A (PE) to antibodies or receptor-binding ligands. A broadly evaluated representative of such targeted therapeutics is the fusion protein HA22 which is a combination of a CD22-binding FAB and PE which is effective in many B-cell lymphomas by ADP-ribosylation of the elongation factor 2 (EF2) and subsequently by inhibition of protein biosynthesis. Due to this event, the cell is driven into programmed cell death. Some lymphoma cells are resistant to the immunotoxin a priori. The group of Ira Pastan discovered HA22-resistant cells in which the EF2 gets ADP-ribosylated and protein synthesis stops, but the cells do not undergo apoptosis. Some of these primary HA22-resistant cells can be sensitized to HA22 by specific small molecule compounds. In the project proposed here, we will compare the protein expression profile of primary resistant, secondarily sensitized and primary sensitive cells with each other to elucidate the underling molecular mechanism behind this resistance. This knowledge will be used to predict response to therapy and thus save patients from ineffective treatment and, in addition, to boost the effects of ADP-ribosylating toxins.Since the broadly used ADP-ribosylating immunotoxins diphtheria toxin, cholix toxin, ricin, and pseudomonas exotoxin share a common apoptosis-inducing mechanism, this work is of great interest for numerous targeted therapies in modern oncology.