The invention relates to monoclonal antibodies that bind to the transcription factor NCOA6 (ASC-2, AIB-3, TRB, TRAP250, NRC). The antibodies have proven successful reagents for Western blotting and for purifying complexes containing NCOA6. The Western blot experiments revealed that NCOA6 is over-expressed in several breast cancer cell lines, and the purification experiments identified a protein complex containing NCOA6 (the ASCOM complex). The monoclonal antibodies may be useful reagents for studying the role of NCOA6 in transcription and for studying the ASCOM complex.