CHFR调控ALC1降解的分子机制及其在三阴性乳腺癌治疗中的意义

Triple-negative breast cancer (TNBC) is disgnosed more frequently with BRCA1/2 mutations, suggesting that TNBC in BRCA carriers are more sensitive to DNA-damaging agents than other chemotherapeutic ones. Poly (ADP-ribose) polymerase (PARP) inhibitors are being developed as single therapeutic agents for TNBC patients. However, several large phase III clinical trials showed that the PARP inhibitors in the advance TNBC didn’t significantly improve the poor prognosis as they were originally expected. Our previous research found that ALC1 (Amplified in liver cancer protein 1) had a higher rate of expression in TNBC, which was related to the poorer prognosis of the TNBC patients. In addition, we found CHFR, an E3 ligase, can interact with and ubiquitinate ALC1, then regulates the stability of ALC1. This process is controlled by ALC1’s parylation, which modified by PARP1. PARP1 inhibitor can inhibit the interaction between CHFR and ALC1, and the ubiquitination of ALC1 by CHFR. Although the role of ALC1 is established, the molecular mechanism of ALC1 stability is unclear. In this study, we will future demonstrate that the molecular mechanism of the interaction between ALC1 and CHFR, and the significance in TNBC development. We will also provide a new insight to the clinical application or PARP1 inhibitors in TNBC patients.

三阴性乳腺癌中BRCA1/2突变比例大，理论上对损伤DNA的药物敏感。但临床上发现DNA损伤修复关键酶PARP1抑制剂效果欠佳。我们前期研究发现ALC1（肝癌扩增蛋白1）在三阴性乳腺癌中高表达，与患者预后差有关；体外研究发现泛素连接酶CHFR与ALC1相互作用，而且可泛素化ALC1，调节该蛋白的稳定性。这一过程依赖于PARP1对ALC1的修饰，PARP1抑制剂能干扰CHFR与ALC1的相互作用，阻滞ALC1被CHFR泛素化和降解。然而，目前调节ALC1蛋白稳定性的确切分子机制目前还不清楚。因此，为揭示三阴性乳腺癌中ALC1对PARP1抑制剂疗效的影响，本课题拟在前期研究基础上，采用组织芯片，体外泛素化，质谱分析等方法，阐明CHFR与ALC1相互作用的分子机制，并诠释ALC1在三阴性乳腺癌中的作用，为PARP1抑制剂的应用提供新的治疗策略

Poly(ADP-ribose) polymerases (PARP)是参与DNA损伤修复过程的关键酶，PARP抑制剂对DNA损伤修复缺陷的乳腺癌和卵巢癌（如BRCA1/2突变）显示出喜人的应用前景。然而，多种PARP抑制剂在不同的研究人群以及不同的临床研究中的疗效并不一致，参与调控PARP抑制剂敏感性和耐药的机制不明。我们研究发现ALC1（肝癌扩增蛋白1）在乳腺癌中高表达，其表达与乳腺癌组织学分级和临床分期密切相关，ALC1高表达与患者预后差有关。基于该临床研究结果，我们体外研究发现泛素连接酶CHFR与ALC1通过多个结构域相互作用，而且CHFR可泛素化ALC1，调节该蛋白的稳定性。这一过程依赖于PARP1对ALC1的修饰，PARP1抑制剂能干扰CHFR与ALC1的相互作用，阻滞ALC1被CHFR泛素化和降解。