SP1 and breast carcinoma: In attempts to elucidate the promoter of AP-2γ in mammary carcinoma cells, the results revealed that its promoter lacks the TATA-box and canonical binding sites for general transcription factors.[22] Instead, Sp1 and Sp3 were identified to determine the transcription of AP-2γ via binding to 3 Sp1/SP3-binding sites in the CpG island in the AP-2γ promoter region[23] (Fig. 1).