HDAC2 (Histone deacetylase 2) is a protein that in humans is encoded by the HDAC2 gene. It is part of various complexes such as the core histone deacetylase complex and the nucleosome remodeling and deacetylase (NuRD) repressor complex. HDAC2 plays a role in gene regulation by controlling the acetylation state of histones, which affects chromatin structure and the transcriptional activity of genes. HDAC2 is crucial for embryonic development and influences cytokine signaling relevant for immune responses. It is often significantly overexpressed in solid tumors and has been identified as an independent marker of poor prognosis in various cancers, including oral, prostate, ovarian, endometrial, or gastric cancer. The expression and activity of HDAC2 are regulated at multiple levels, including transcriptional, posttranscriptional, and posttranslational modifications.