Overall, AIB1 protein levels were significantly higher in tumor tissue than in normal tissue and the highest levels of nuclear staining were found exclusively in breast tumor tissues in 9.8% of the cases.
Using in situ hybridization and reverse transcription-PCR assays, the expression of two coactivators (SRA and AIB1) and one repressor (REA) of the estrogen receptor was compared between matched breast tumors and adjacent normal human breast tissue.