HDAC2 and breast cancer: Consistent with immunohistochemical analyses, basal-like breast cancers exhibited significantly higher HDAC1 and HDAC2 expression compared to other subtypes (P = 4.9 × 10−19 and P = 4.5 × 10−156, respectively), while luminal A and luminal B cases also featured higher HDAC1 expression (P = 6.2 × 10−8 and P = 8.7 × 10−21, respectively) compared with non-luminal cases (Fig. 1E, F).