HDAC9 and neoplasm: In this context, and in the light of the fact that activation of the HH pathway is critical for the maintenance of the stem cell compartment in tumours derived from dysregulation of different signalling mechanisms (ref. 3 and references therein), the NuRD-dependent synergism between ZNF521 and GLI might represent a valuable biomarker for the identification of patients with MB—and possibly other SHH-driven malignancies—who may potentially benefit from a combination of SHH and HDAC inhibitors.