去泛素化酶USP46调控同源重组修复在结肠癌奥沙利铂耐药中的作用和机制研究

RAD51介导的同源重组修复（HRR）是导致肿瘤奥沙利铂耐药的关键原因。研究证实去泛素化酶USP46在肿瘤进展和化疗耐药中起重要作用。本项目前期结果发现USP46在结肠癌组织和奥沙利铂耐药的结肠癌细胞中高表达；在耐药细胞中下调USP46可抑制RAD51入核和HRR，并增加奥沙利铂敏感性。结合我们既往关于微小染色体维持蛋白MCM7促进RAD51入核和HRR的研究发现，以及USP46与MCM7直接结合并稳定其蛋白的预实验结果，我们推测：USP46通过抑制MCM7的泛素化降解上调其表达，进而促进RAD51入核和HRR，最终导致结肠癌细胞对奥沙利铂耐药。为验证假说，本项目拟先明确USP46通过HRR促使结肠癌细胞对奥沙利铂耐药，再阐明USP46调控MCM7泛素化进而促进RAD51入核和HRR的分子机制，最后分析结肠癌组织中USP46、MCM7的表达与奥沙利铂耐药的关系，为逆转耐药提供新的靶点。

Rad51 mediated homologous recombination repair (HRR) is the key cause of oxaliplatin resistance. It has been demonstrated that the deubiquitinase USP46 plays an important role in tumor progression and chemotherapy resistance. The preliminary results of this project found that USP46 was highly expressed in colon cancer tissues and oxaliplatin-resistant colon cancer cells. Downregulation of USP46 in oxaliplatin-resistant cells can inhibit RAD51 nucleation and HRR, and increase oxaliplatin sensitivity. In combination with our previous research findings which microchromosome maintenance protein MCM7 promote RAD51 nucleation and HRR, and the results of preliminary experiments that USP46 directly binds to MCM7 and stabilizes its protein, we speculate that USP46 upregulates the expression of MCM7 by inhibiting its ubiquitination degradation, thereby promoting RAD51 nucleation and HRR, and eventually causing colon cancer cells to be resistant to oxaliplatin. In order to verify the hypothesis, this project plan to confirm that USP46 promotes colon cancer cells to be resistant to oxaliplatin via HRR, then clarify the molecular mechanism of USP46 regulating the ubiquitination of MCM7 to promote RAD51 nucleation and HRR, and finally analyze the relationship between the expression of USP46/MCM7 and oxaliplatin resistance in colon cancer. This project will provide a new target for reversing oxaliplatin resistance.