For validation of M344-mediated inhibition of HDAC enzymes in NB cells, NB cell lines lacking MYCN amplification (Figure 2A, Neuro-2a) or harboring MYCN amplification (Figure 2B, 9464D) were treated for 24 h prior to immunoblotting for detection of acetylated histone H3. Here, HDAC9 is linked to neuroblastoma.