HDAC9 and neoplasm: As a member of the HDAC family, HDAC1 functions as an enzyme that catalyzes the lysine deacetylation of both histone and nonhistone proteins, exerting its primary role in diminishing the accessibility of transcription and further regulating the expression of some genes.[46, 47] Moreover, previous studies indicated that HDAC1 was closely associated with tumor progression; for example, downregulation of HDAC1 inhibited the proliferation, migration and invasion of non‐small cell lung cancer cells,[48] which indicated that HDAC1 could be a potential indicator for patient treatment.