Molecular Signatures of CB-6644 inhibition of the RUVBL1/2 complex in Multiple Myeloma [ATAC-seq]

Multiple Myeloma is the second most hematological cancer. RUVBL1 and RUVBL2 forms a subcomplex of many chromatin remodeling complexes implicated in cancer progress. As an inhibitor specific to the RUVBL1/2 complex, CB-6644 exhibits remarkable anti-tumor activity in xenograft models of Burkitt’s lymphoma and multiple myeloma (MM). In this work, we defined transcriptional signatures corresponding to CB-6644 treatment in MM cells and determined underlying epigenetic changes in terms of chromatin accessibility.CB-6644 upregulated biological processes related to interferon response and downregulated those linked to cell proliferation in MM cells. Transcriptional regulator inference identified ATF4/CEBP and E2Fs as regulators for downregulated genes and MED1 and MYC as regulators for upregulated genes. CB-6644-induced changes in chromatin accessibility occurred mostly in non-promoter regions. Footprinting analysis identified transcription factors implied in modulating chromatin accessibility in response to CB-6644 treatment, including ATF4/CEBP and IRF4. Lastly, integrative analysis of transcription responses to various chemical compounds of the molecular signature genes from public gene expression data identified CB-5083, a p97 inhibitor, as a synergistic candidate with CB66-44 in MM cells, but experimental validation refuted this hypothesis. To characterized the regulome (chromatin accessibility) signatures of CB-6644 treatment in MM cells. We inferred the underling epigenetic regulatory mechanisms by analyzing chromatin accessibility using Omni-ATAC in MM.1S, treated with 120nm of CB-6644 (72 hours) and compared to DMSO-treated cells.