Che-1 depletion sensitizes MM cells to BET inhibitors. (A) Western blot (WB) analysis with the indicated antibodies of total cell extracts and chromatin extracts of MM196 cells nucleofected with siRNA control (siControl) or siRNA Che-1 (siChe-1) oligonucleotides. (B) Enrichment density of BRD4 ChIP-seq significant peaks identified in siControl (blue) and siChe-1 (yellow) samples. Enrichment density was calculated on the relative size of each peak extended 500 bp upstream and downstream. (C) JQ1 sensitivity of MM196 cells nucleofected as in A calculated by measurement of cell viability after 72 hours of treatment with JQ1 (10, 50, 250, or 500 nM). Error bars represent the standard deviation of triplicate experiments. (D) Total levels of serum Ig in recipient C57BL/6J mice transplanted with CD138⁺ MM cells isolated from bone marrow of Vk*Myc mice, transfected with siChe-1 or siControl oligonucleotides and treated with 100 nM JQ1 for 2 days. In vivo treatment with JQ1 (or vehicle control) was initiated at day 10 after transplantation. *P < .0001. (E) Representative serum protein electrophoresis (SPEP) (left), fluorescence-activated cell sorter (FACS) analysis (middle), and bone marrow hematoxylin and eosin (H&E) analysis (right) of recipient C57BL/6J mice transplanted and treated as in D. Scale bar, 100 μm. See also supplemental Figure 6.