HUWE1 is a colonic tumor suppressor. Especially, HUWE1 is a critical colonic tumour suppressor gene that prevents MYC signalling, DNA damage accumulation and tumor initiation.
HUWE1 is a pleiotropic E3 ubiquitin ligase that modulates the function of several proteins involved in oncogenesis and DNA damage response including MYC, MYCN, MCL1 and H2AX. Crucially, HUWE1 catalyses the attachment of both lysine 48 and lysine 63 linked polyubiquitin chains, impacting on the function of a number of proteins involved in tumorigenic. The ubiquitin ligase HUWE1 associates with MYC. HUWE1 regulates the stability of MCL1 and TP53 via addition of lysine 48 linked polyubiquitin chains.

To identify potential inhibitors of HUWE1, Stefanie Peter, et al configured an in vitro assay of HUWE1 activity for high-throughput screening of small molecules, exploiting the fact that the HECT-domain of HUWE1 auto-ubiquitinates. Screening of 840,243 compounds result in 2,765 hits that inhibit HUWE1 activity. After hit confirmation in repeat experiments, Stefanie Peter, et al identified inhibitors of UBA1 or UbcH5b. Furthermore, researchers determine dose responses in both HUWE1 and NEDD4 auto-ubiquitination assays. They also eliminate compounds inhibiting NEDD4 auto-ubiquitination. From these experiments, Stefanie Peter, et al selected BI8622 that inhibited HUWE1 with an IC50 value of 3.1 μM. Moreover, BI8622 induces HUWE1 ectopically expresses to abolish ubiquitination of MCL1 with an IC50 value of 6.8 μM in HeLa cells. BI8622 also suppresses colony formation of Ls174T cells with estimated IC50 values of 8.4 μM.

All in all, BI8622 is an inhibitor of HUWE1, which inhibit MYC-dependent transactivation in colorectal cancer cells.

Peter S, et al. Tumor cell-specific inhibition of MYC function using small molecule inhibitors of the HUWE1 ubiquitin ligase. EMBO Mol Med. 2014 Dec;6(12):1525-41.