Characterizing effects of small molecule inhibition of WDR5 in colorectal cancer

Abstract WDR5 is a core subunit of the MLL-WRAD methyltransferases, NSL-MOF acetyltransferases and MYC-MAX transcription factors. Dysregulation of these complexes has been implicated in numerous cancers. Despite links between colorectal cancer (CRC) and WDR5, little is known about its role. Using OICR11824, an internally developed novel chemical antagonist of WDR5, we investigated the biological effects of targeting the arginine binding pocket of WDR5 in CRC. Firstly, we evaluated the ability of OICR11824 to bind and disrupt WDR5-MLL interaction in cells. We then utilized OICR11824 and shRNA knockdown to investigate effects of WDR5 inhibition on proliferation in CRC cell lines. In addition, Western blot and RT-PCR were performed to confirm modulation of H3K4 methylation and expression of MYC-transcriptional targets. Finally, flow cytometry was used to evaluate effects of WDR5 inhibition on cell cycle. Our research shows that OICR11824 binds and inhibits the WDR5-MLL interaction. As well, OICR11824 displays a range of anti-proliferation potencies in CRC cell lines with the greatest sensitivity seen in COLO205 demonstrating a G1 accumulation and S-phase depletion. Finally, OICR11824 affects the actions of WDR5-complexes in MYC-WDR5 gene targets and H3K4 trimethylation. Our research provides new insights into the role of WDR5 in CRC and will contribute to not only developing new therapeutics against CRC, but will also help elucidate the role of WDR5 complexes in cancer.M.Sc