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.
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.