Understanding how to target cell vulnerabilities induced by high Notch signalling as a potential anti-cancer strategy.

Notch是一种跨膜定位的信号受体，在发育和成体干细胞调控中都有应用，其失调经常涉及不同的人类癌症。Notch是通过蛋白水解去除细胞外结构域（NECD）和随后的γ分泌酶依赖的膜内切割来释放Notch细胞内结构域（NICD）而激活的。一旦进入细胞核，NICD与转录因子Su(H)/CBF结合，该复合体与募集的共激活因子一起激活基因特异性转录。结果依赖于环境，Notch在发育中发挥许多作用，影响不同的细胞命运、增殖和细胞死亡/存活，以及许多组织的决定。Notch信号与癌症干细胞调控有关，因此它使Notch成为控制其信号活动的治疗的一个有吸引力的靶点。已经有一些针对高Notch信号的药物，但由于存在不可接受的副作用，许多试验都没有成功。在这个项目中，正在开发的策略是通过使用Notch作为生物标志物来确定哪些肿瘤对靶向其他成分敏感，这些成分会杀死肿瘤细胞，但不会影响正常细胞。在果蝇细胞培养模型系统中使用全基因组筛选，我们已经确定了在异常高Notch信号条件下有用的候选靶点，以及在异常低Notch信号条件下有用的靶点。通过研究果蝇的细胞培养和体内系统，该项目旨在了解不同水平的Notch信号使细胞对不同靶基因的敲除敏感的机制，并确定一种合成的致死组合，这可能在长期内转化为一种治疗方法。然后将在人类癌细胞系中获得原理证明。

Notch is a transmembrane localised signalling receptor utilised both in development and adult stem cell regulation and whose misregulation is frequently involved in different human cancers. Notch is activated by proteolytic removal of the extracellular domain (NECD) and subsequent gamma-secretase dependent intramembrane cleavage to release the Notch intracellular domain (NICD). Once in the nucleus NICD combines with a transcription factor Su(H)/CBF and the complex along with recruited coactivators activates gene-specific transcription. The outcomes are context-dependent and Notch plays many roles in development affecting different cell fate, proliferation and cell death/survival, decisions across many tissues. Notch signalling has been linked to cancer stem cell regulation and therefore it makes Notch an attractive target for therapies that control its signal activity. There are already some drugs which target high Notch signalling but a number of trials have not ben successful because there are unacceptable side effects. In this project the strategy is being developed ovecome this by using Notch instead as a biomarker to determine which tumours are sensitive to targeting other components that will kill the tumour cell but leave normal cells unaffected. Using a whole genome screen in a Drosophila cell culture model system we have identified candidate targets which would be useful to inhibit in conditions of aberrantly high Notch signalling and set of targets which would be useful to inhibit in conditions of aberrantly reduced Notch signalling. By studying cell culture and in vivo systems in the fly this project aims to understand the mechanisms by which Notch signalling at different levels sensitises the cells to knock down of different sets of target genes and identify a synthetic lethal combination, which may in the longer term be translated into a therapeutic approach. Proof of principle will then be obtained in human cancer cell lines.