Identification and Characterization of SLUG-Regulating Deubiquitinases (DUBs) in Breast Cancer

Abstract

Most solid tumor metastases are initiated by reactivation of the epithelialto mesenchymal transition (EMT), a highly conserved cellular process thatendows epithelial cells with migratory and invasive capabilities. SLUG/SNAI2, azinc-finger transcription factor, has been established as one of the key promotersof EMT. SLUG is overexpressed in various types of cancers, correlating withincreased metastasis and relapse rates as well as shorter survival periods forpatients. Despite SLUG’s pivotal role in promoting EMT and metastasis in breastcancer, so far there is no effective way to directly target SLUG pharmaceutically.SLUG is a labile protein that is degraded through the ubiquitin-proteasomesystem; however, the molecular mechanisms regulating SLUG stability duringcancer development remain poorly understood. Thus, to study SLUG regulationin the context of breast cancer and to search for potential therapeutic targets, weseek to identify and investigate the deubiquitinases (DUBs) that protect SLUGproteins from proteasomal degradation. In this study, we identify USP20 as aSLUG-regulating DUB using siRNA library and cDNA library screenings. Wereport that USP20 stabilizes SLUG via deubiquitination in vitro. Throughfunctional characterization, we show that depletion and overexpression of USP20affect cell migratory and invasive capabilities, implicating its potential role inaffecting EMT. Moreover, we report that USP20 has clinical relevance forpatients. Based on our results, we recommend future work to test the effect ofUSP20 depletion in vivo in order to further elucidate how SLUG is regulated byubiquitination, and to test the validity of USP20 as a potential drug target fortherapeutics in breast cancer.