Su Hongbin, Qin Mengdi, Liu Qiang, Jin Bo, Shi Xianjun, Xiang Zheng
Department of Gastrointestinal Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
Chongqing Key Laboratory of Department of General Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
Front Oncol. 2021 Jul 14;11:691347. doi: 10.3389/fonc.2021.691347. eCollection 2021.
Ubiquitin D (UBD) is a member of the ubiquitin-like modifier (UBL) family and is highly expressed in a variety of cancers including colorectal cancer (CRC). However, the mechanisms of its regulatory roles in CRC are largely elusive. In this study, we revealed the effect of UBD on the proliferation of CRC.
The expression of UBD in clinical tissue samples of CRC and seven CRC cell lines was detected using qRT-PCR, immunohistochemistry (IHC) and Western blotting. CCK-8, colony formation, EdU and flow cytometry assays were used to detect the functional changes of CRC cells transfected with UBD stable expression plasmids . A xenograft model was constructed to assess the effect of UBD on the growth of CRC cells . The connection between UBD and p53 was analyzed using Western blotting, immunoprecipitation, proteasome inhibition assay and Cycloheximide (CHX) chase assay.
UBD was overexpressed in CRC tumor tissues compared with nontumor tissues, and its overexpression was positively associated with the tumor size and TNM stage of CRC patients. Functionally, UBD significantly accelerated CRC cell viability and proliferation and promoted tumorigenesis . Mechanistically, UBD interacted with p53 in CRC cells, downregulated the expression of p53 by regulating its degradation, shortened the p53 half-life, thereby further affecting the decrease in p21 and the increase in Cyclin D1, Cyclin E, CDK2, CDK4 and CDK6. Moreover, experiments showed that UBD-induced tumor growth in nude mice was dependent on a decrease in p53.
Our study proved that UBD mediates the degradation of p53, thereby facilitating the growth of CRC cells and ultimately promoting the progression of CRC. Therefore, UBD may be a potential therapeutic target and a promising prognostic biomarker for CRC.
泛素D（UBD）是泛素样修饰因子（UBL）家族的成员，在包括结直肠癌（CRC）在内的多种癌症中高表达。然而，其在结直肠癌中发挥调节作用的机制尚不清楚。在本研究中，我们揭示了UBD对结直肠癌细胞增殖的影响。
采用qRT-PCR、免疫组织化学（IHC）和蛋白质印迹法检测UBD在结直肠癌临床组织样本和7种结直肠癌细胞系中的表达。使用CCK-8、集落形成、EdU和流式细胞术检测转染UBD稳定表达质粒的结直肠癌细胞的功能变化。构建异种移植模型以评估UBD对结直肠癌细胞生长的影响。采用蛋白质印迹法、免疫沉淀法、蛋白酶体抑制试验和环己酰亚胺（CHX）追踪试验分析UBD与p53之间的关系。
与非肿瘤组织相比，UBD在结直肠癌肿瘤组织中过表达，其过表达与结直肠癌患者的肿瘤大小和TNM分期呈正相关。在功能上，UBD显著加速了结直肠癌细胞的活力和增殖，并促进肿瘤发生。机制上，UBD在结直肠癌细胞中与p53相互作用，通过调节其降解下调p53的表达，缩短p53半衰期，并进一步影响p21的减少以及细胞周期蛋白D1、细胞周期蛋白E、细胞周期蛋白依赖性激酶2（CDK2）、细胞周期蛋白依赖性激酶4（CDK4）和细胞周期蛋白依赖性激酶6（CDK6）的增加。此外，实验表明UBD诱导的裸鼠肿瘤生长依赖于p53的减少。
我们的研究证明UBD介导p53的降解，从而促进结直肠癌细胞的生长并最终促进结直肠癌的进展。因此，UBD可能是结直肠癌的潜在治疗靶点和有前景的预后生物标志物。
