HDAC1 and neoplasm: In the last decade, several papers have highlighted the role of HDAC1/2 as regulators of the Hedgehog (Hh) signaling in tumor cells, through deacetylation and transcriptional activation of Gli1 and Gli2 proteins and, consequently, the possible use of HDACis as potential modulators of this pathway in some types of tumors (21, 22).