Figure 3.
BET inhibitor JQ1 depletes BRD4 enrichment at the c-Myc putative super-enhancer region in MCC-3 xenograft tumors. (A) Significant suppression of tumor growth are detected in both MCC-3 (**P < 0.01) and MKL-1 (*P < 0.1) xenograft tumors. A greater reduction of tumor growth is observed in MCC-3 xenograft tumors with c-Myc overexpression (75.6% vs. 48.9%). Data is presented as final tumor volume ± SEM from tumor bearing NSG mice treated with vehicle or JQ1. (B-C) JQ1 significantly reduced c-Myc expression in MCC-3 xenograft tumors as demonstrated by representative immunoblotting (B) and qRT-PCR analysis (C) (**P < 0.01 vs. vehicle treatment) of 3 biological replicates. In the c-Myc immunoblot, the black dividing line separates images grouped from different parts of the same blot. The c-Myc mRNA expression has been normalized to that of MRPS2. (D) JQ1 depletes BRD4 occupancy at the putative c-Myc super-enhancer regions in MCC-3 xenograft tumors by ChIP-qPCR analysis (***P < 0.001 vs. vehicle treatment). Regions of 5000 base pairs (bp) upstream and downstream to the target sequence were used as controls to ensure that the enrichment is specific to the target region. Relative enrichment represents average fold enrichment of the target promoter in IP vs. input, normalized to β-actin. ChIP signal for H3K27Ac is normalized to total H3. Data is presented as mean ± SEM. Error bars in the graph represent SEM from independent analysis of 3 biological replicates. (+) and (−) represents drug (JQ1) and vehicle treatment, respectively.