Multiple cell lines that represent the molecular diversity of breast cancer were equally sensitive to the cytotoxic effect of different HDACi (VPA, vorinostat, entinostat and panobinostat) independently of subtype, p53, RAS, hormone receptor expression (ER and PR), HER2 status (Table 1) or the basal expression of HDAC isoforms, TS or TP proteins (Supplementary Figure S1). Here, HDAC9 is linked to breast cancer.