Panobinostat increases histone H3 (Lys9) and H4 (Lys8) acetylation in TNBC cell lines. Cells were treated with panobinostat (100, 200 nM) or vehicle (DMSO) for 18 hours, fixed, permeabilized and stained for acetyl-histones (A) H3 (Lys9) or (B) H4 (Lys8) and subjected to flow cytometry. Data are presented as mean fluorescence intensity (mean ± SEM) of two independent experiments, (***, P < 0.001). (C-D) Confocal images of TNBC cell lines treated with panobinostat (100 nM) or vehicle for 18 hours, fixed, permeabilized and stained red (rhodamine phalloidin) for actin filaments and green (Alexa Fluor® 488) for acetyl-histones (C) H3 (Lys9) or (D) H4 (Lys8). Original magnification was 400× with scale bars at 20 microns. DMSO, dimethyl sulfoxide; SEM, standard error of the mean; TNBC, triple-negative breast cancer.