Figure 2. HDAC inhibitors transcriptionally decrease MyD88.

(A) Western blot showing downregulation of MyD88 in HBL-1 after treatment with 8 different HDAC inhibitors (SNDX-275, mocetinostat, romidepsin, SAHA, belinostat, and panobinostat) and 2 BET inhibitors (JQ1 and CPI-203) at their IC₅₀ dose for 12 and 24 hours. Drug activity is demonstrated by increased acetylation of histone H3. Cell death is associated to PARP cleavage. (B) Change in relative mRNA levels of MyD88 over time in HBL-1 after treatment with 3 different HDAC inhibitors (panobinostat, romidepsin, and SAHA) at their IC₅₀ dose (0.05, 0.01, and 3 μM, respectively) for the indicated time. Error bars represent SEM of triplicate experiments. (C) Change in relative mRNA levels of MyD88 over time in B cell lymphoma cell line panel (GCB n = 3 and ABC n = 4) after treatment with romidepsin 0.01 μM for 6 and 24 hours. Error bars represent SEM of triplicate experiments. (D) Box and whiskers plot showing decrease of MyD88 in B cell lymphoma cell line panel (GCB n = 3 and ABC n = 5) after treatment with either 0.05 μM panobinostat or romidepsin 0.01 μM for 6 hours. Error bars represent SEM of triplicate experiments. (E) Representative Western blot confirming decrease in MyD88 level after treatment with 0.01 μM romidepsin for 6 and 24 hours in our B cell lymphoma panel. (F) Relative MyD88 promoter-luciferase activity in 2 representative ABC (HBL-1 and OCI-LY-10) cell lines and 1 GCB (SUDHL-4) cell line. Cells were treated for 12 hours with indicated concentration of either panobinostat, romidepsin, or DMSO. Cells were incubated with 500 ng/ml of INF-γ as positive control for TLR activation. Error bars represent SEM of triplicates. Differences between groups were calculated with 2-way ANOVA with Bonferroni’s test. ***P < 0.0005; ****P < 0.0001.