Discovery of Specific Inhibitors of Human USP7/HAUSP Deubiquitinating Enzyme

Abstract

The human USP7 deubiquitinating enzyme was shown to regulate many proteins involved in the cell cycle, as well as tumor suppressors and oncogenes. Thus, USP7 offers a promising, strategic target for cancer therapy. Using biochemical assays and activity-based protein profiling in living systems, we identified small-molecule antagonists of USP7 and demonstrated USP7 inhibitor occupancy and selectivity in cancer cell lines. These compounds bind USP7 in the active site through a covalent mechanism. In cancer cells, these active-site-targeting inhibitors were shown to regulate the level of several USP7 substrates and thus recapitulated the USP7 knockdown phenotype that leads to G1 arrest in colon cancer cells. The data presented in this report provide proof of principle that USP7 inhibitors may be a valuable therapeutic for cancer. In addition, the discovery of such molecules offers interesting tools for studying deubiquitination.

Histone H2B monoubiquitination: roles to play in human malignancy

“…HBX 41 108, a cyano-indenopyrazine derivative that reversibly inhibits USP7 in a non-competitive fashion, has been shown to stabilise p53, with concomitant increase in the levels of the cell cycle inhibitor p21 and inhibition of cancer cell growth (Colland et al 2009). Other USP7 inhibitors, HBX 19 818 and HBX 28 258, have been identified as possible irreversible inhibitors of USP7 (Reverdy et al 2012). Furthermore, the USP7 inhibitor P5091 has been shown to be well tolerated by animals in human tumour xenograft models of multiple myeloma and to have a synergistic effect with drugs such as HDAC inhibitors that are used in combination with the proteasome inhibitor bortezomib (Chauhan et al 2012).…”

“…USP7 is further implicated to be part of the H2Bub1 ligation machinery as it forms a complex with the H2Bub1 E2 conjugating enzyme UBE2E1, attenuating its role (Sarkari et al 2013). Given the eminent druggability of DUBs, and the particular interest in USP7 given its influence on p53 levels, interest in developing small-molecule USP7 inhibitors as therapeutics for some cancers is emerging (Colland et al 2009, Colland 2010, Chauhan et al 2012, Reverdy et al 2012. HBX 41 108, a cyano-indenopyrazine derivative that reversibly inhibits USP7 in a non-competitive fashion, has been shown to stabilise p53, with concomitant increase in the levels of the cell cycle inhibitor p21 and inhibition of cancer cell growth (Colland et al 2009).…”

A novel small molecule inhibitor of deubiquitylating enzyme USP14 and UCHL5 induces apoptosis in multiple myeloma and overcomes bortezomib resistance

“…Importantly, many human diseases are linked to dysfunction of ubiquitin ligases and/or deubiquitylating enzymes (DUBs), suggesting that inhibitors of ubiquitylating or DUB enzymes represent a potential therapeutic strategy. 3,4 The human genome encodes approximately 100 putative DUBs, which are classified into five families: USP (ubiquitin-specific processing protease), UCH (ubiquitin C-terminal hydrolase), OTU (ovarian tumor ubiquitin), MJD (Josephin domain), and JAMM (Jab1/Mov34 metalloenzyme). 5,6 Note that the first 4 families are cysteine proteases, whereas the fifth family consists of metalloproteases; to date, USP and UCH are the best characterized families.…”

Deubiquitylase Inhibition Reveals Liver X Receptor-independent Transcriptional Regulation of the E3 Ubiquitin Ligase IDOL and Lipoprotein Uptake

“…We tested this in HepG2 cells, and despite obtaining effective silencing of USP7, both expression of IDOL and the response to DUB inhibition remained unaffected (data not shown). A potential explanation for this result is recent evidence indicating that HBX41-108 has a much broader substrate specificity and is able to inhibit a large panel of cysteine DUBs, similar to PR-619 (35,36). The fact that multiple DUBs are sensitive to these inhibitors has precluded us from identifying a specific DUB responsible for the induction of IDOL.…”