A feedforward circuit shaped by ECT2 and USP7 contributes to breast carcinogenesis
A feedforward circuit shaped by ECT2 and USP7 contributes to breast carcinogenesis
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由 ECT2 和 USP7 形成的前馈电路有助于乳腺癌的发生
DOI：
10.7150/thno.46878
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发表时间：
2020
期刊：
影响因子：
12.4
通讯作者：
Lei Shi
中科院分区：
文献类型：
--
作者：
Qi Zhang;Cheng Cao;Wenchen Gong;Kaiwen Bao;Qian Wang;Yuejiao Wang;Liyuan Bi;Shuai Ma;Jiao Zhao;Ling Liu;Shanshan Tian;Kai Zhang;Jie Yang;Zhi Yao;Nan Song;Lei Shi
理论基础：包括上皮细胞转化因子ECT2在内的许多鸟嘌呤核苷酸交换因子(GEF)被认为通过激活不同的致癌GTP酶来推动癌症的发生。然而，ECT2不依赖于全球环境基金的活性是否也在肿瘤发生中发挥作用尚不清楚。方法：采用免疫组织化学(IHC)染色、集落形成和异种移植实验检测ECT2在乳腺癌发生中的作用。通过免疫共沉淀、免疫荧光染色、体内去泛素化和体外去泛素化实验，研究了ECT2和泛素特异性蛋白酶USP7之间的物理和功能相互作用。采用高通量RNA测序、定量逆转录-聚合酶链式反应和Western blotting方法研究ECT2和USP7相互作用的生物学意义。结果：我们报道了ECT2在乳腺癌中起到促进肿瘤的作用，而全球环境基金活性缺陷的ECT2能够减轻乳腺癌细胞中与ECT2缺失相关的生长缺陷。从机制上讲，我们证明了ECT2与泛素特异的蛋白酶USP7在物理上相互作用，并以一种不依赖于全球环境基金活性的方式在功能上促进了USP7分子间的自结合、去泛素化和稳定。USP7反过来，去泛素化和稳定ECT2，导致一个前馈调节电路，最终维持致癌蛋白MDM2的表达。结论：我们的研究揭示了ECT2在促进乳腺癌细胞存活中的不依赖于全球环境基金的作用，为ECT2和USP7的相互调控提供了分子基础，并支持将ECT2/USP7作为乳腺癌干预的潜在靶点。
Rationale: A number of guanine nucleotide exchange factors (GEFs) including epithelial cell transforming factor ECT2 are believed to drive carcinogenesis through activating distinct oncogenic GTPases. Yet, whether GEF-independent activity of ECT2 also plays a role in tumorigenesis remains unclear. Methods: Immunohistochemical (IHC) staining, colony formation and xenograft assays were used to examine the role of ECT2 in breast carcinogenesis. Co-immunoprecipitation, immunofluorescent stainings, in vivo deubiquitination and in vitro deubiquitination experiments were performed to examine the physical and functional interaction between ECT2 and ubiquitin-specific protease USP7. High-throughput RNA sequencing, quantitative reverse transcription-PCR and Western blotting were employed to investigate the biological significance of the interplay between ECT2 and USP7. Results: We report that ECT2 plays a tumor-promoting role in breast cancer, and GEF activity-deficient ECT2 is able to alleviate ECT2 depletion associated growth defects in breast cancer cells. Mechanistically, we demonstrated that ECT2 physically interacts with ubiquitin-specific protease USP7 and functionally facilitates USP7 intermolecular self-association, -deubiquitination and -stabilization in a GEF activity-independent manner. USP7 in turn, deubiquitinates and stabilizes ECT2, resulting in a feedforward regulatory circuit that ultimately sustains the expression of oncogenic protein MDM2. Conclusion: Our study uncovers a GEF-independent role of ECT2 in promoting survival of breast cancer cells, provides a molecular insight for the reciprocal regulation of ECT2 and USP7, and supports the pursuit of ECT2/USP7 as potential targets for breast cancer intervention.