The sequence-specific transcription factor activator protein 2α (AP-2α) is a transcription factor that binds the consensus sequence 5'-GCCNNNGGC-3'. The protein functions as either a homodimer or as a heterodimer with similar family members. This protein activates the transcription of some genes while inhibiting the transcription of others. Decreased or loss of AP-2α expression has been observed in many different types of human cancers including breast cancer, ovarian cancer, melanoma and prostate cancer. These findings suggest that AP-2α expression plays a crucial role in tumorigenicity.