USP7去泛素化调控EXO1促进膀胱癌顺铂耐药的作用和机制研究

Cisplatin resistance is a major obstacle to the clinical management and progression of bladder cancer. Of note, aberrantly enhanced DNA repair capacity serves as one of the fundamental mechanisms to cisplatin resistance. As to repair cisplatin induced DNA damages relays on multiple DNA repair pathways, the existing strategies which inhibit one pathway at one time could not commendably overcome cisplatin resistance, thus we assume that targeting a single key protein that involved in multiple pathways could be more effective. The multifunctional DNA repair protein EXO1 is one of such candidates. Based on the primitive observations that EXO1 is over-expressed in bladder cancer and its stability is largely dependent on deubiquitinase USP7, by using variety of techniques at molecular, cellular, experimental animal as well as clinical sample level, we are going to verify the effects that USP7 promoted EXO1 over expression on cisplatin resistance, and further investigate the underlying mechanisms by mapping their interaction domain and the possible phosphorylation based regulation sites, and lastly, trying to reverse the aberrant high expression level of EXO1 by inhibit the interaction between USP7 and EXO1. This study will not only elucidates the new regulation mechanism of EXO1 from the point of deubquitination, but also will shed new lights on the searching of effective targets that enhances the sensitivity of tumor cell to cisplatin based chemotherapy regimes.

顺铂耐药严重影响膀胱癌治疗与预后，DNA损伤修复能力异常增强是其重要机制之一。由于修复顺铂诱导的DNA损伤需要多条DNA修复途径，而目前抑制单一途径的策略未能良好地逆转顺铂耐药，因此我们设想通过靶向多条DNA修复途径的共同分子同时抑制多条途径可望更有效地降低或逆转顺铂耐药。本项目着眼于参与多条DNA修复途径的关键分子EXO1，基于膀胱癌中EXO1高表达以及去泛素化酶USP7可能维持EXO1蛋白稳定性等前期线索，我们将从分子、细胞、动物与临床等层面深入研究USP7通过去泛素化维持EXO1高表达，进而EXO1通过增强膀胱癌细胞DNA修复促进膀胱癌顺铂耐药的作用与机制，并将解析介导EXO1与USP7相互作用的蛋白结构域和磷酸化调控位点，以寻找阻断EXO1去泛素化并逆转EXO1高表达的新策略。本项目不仅将揭示去泛素化调控EXO1蛋白稳定性的新机制，同时有望为提高膀胱癌顺铂敏感性提供新思路。