Inhibition of Ubiquitin Specific Protease 1 Sensitizes Colorectal Cancer Cells to DNA-Damaging Chemotherapeutics.

Xin Xu,Songbing He,Jun Wang,Long Cui,Kunkun Han,Xiaodan Hou,Ximao Cui,Shaoyan Li,Jiecheng Xiao,Yili Yang

doi:10.3389/fonc.2019.01406

Abstract

Mutations and altered expression of deubiquitinating enzymes (DUBs) have been found associated with many human diseases including cancers. In this study, Ubiquitin specific protease 1 (USP1) expression was found significantly increased in some colorectal cancers (CRC). The elevated USP1 level was associated with short overall survival of patients and with advanced stages of cancers. In cultured CRC cells, knockdown of USP1 induced growth arrest at G2/M of cell cycle and reduced the expression of anti-apoptotic proteins Bcl-2 and Mcl-1. Its knockdown also led to reduction of DNA-repair related substrates FANCD2 and ID1. Further investigations found that small molecular inhibitor of USP1 ML323 sensitized CRC cells to DNA-targeting chemotherapeutics, including doxorubicin, TOPI/II inhibitors, and PARP inhibitor, but not to 5-Fu. These results indicate that USP1 plays a critical in colorectal cancer cell survival and is a promising target for anti-colorectal cancer chemotherapy. Targeting USP1 may represent an effective strategy to regulate the DNA-repairing system.

Highlights

Ubiquitination, the addition of ubiquitin through isopeptide bond to target proteins, usually requires the sequential actions of ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2), and ubiquitin ligase (E3)
In an effort to find deubiquitinating enzymes that affected the growth of colorectal cancers (CRC) cells, we screened a shRNA library in our previous study and found that Ubiquitin specific protease 1 (USP1) knockdown had a significant effect [3]
The expression level of USP1 was firstly analyzed by Gene Expression Profiling Interactive Analysis (GEPIA), and the results showed that USP1 expression was significantly higher in colon adenocarcinoma compared with that of controls (p < 0.05) (Figure 1A)

Summary

Introduction

Ubiquitination, the addition of ubiquitin through isopeptide bond to target proteins, usually requires the sequential actions of ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2), and ubiquitin ligase (E3) It controls the level, location, and activity of many proteins and participates in most, if not all, cellular processes, including signal transduction, cell cycle, growth, and apoptosis [1]. It has been shown that mutations and altered expression of DUBs are closely associated with various human cancers [4]. Since most of these DUBs are cysteine proteases and reactive to various electrophiles, they have been the preferred targets for developing novel chemotherapeutics. It is highly desirable to characterize and understand DUBs’ criticality for each cancer in precision cancer treatment

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Results

Conclusion