To investigate the importance of Smad7 for HDAC6 and c-Jun expression, Smad7 was knocked down by siRNA in the prostate cancer cell lines PC3U, LNCaP, and DU145; this led to a decreased expression of both c-Jun and HDAC6 mRNA (Figures 1A–1C, S1A, and S2A) and protein (Figures 1D, S1B, and S2B). Here, HDAC6 is linked to prostate cancer.