Vorinostat had an IC50 at HDAC2 of 0.12 μM and an IC50 in the cellular HDAC assay in T47D cells of 0.79 μM, which is comparable to the IC50 of 0.88 μM in the squamous carcinoma cell line Cal27 previously reported by us [29]. Here, HDAC9 is linked to squamous cell carcinoma.