In sum, the loss of HDAC1 and HDAC2 increases C3 and NCOA2, but not CLU, ERBB2, MYC, or PGR, providing evidence that C3 and NCOA2 are repressed in breast cancer cells by the HDAC1/2 components of the Sin3A repressive complex. This evidence concerns the gene NCOA2 and breast carcinoma.