SP1 and breast cancer: While the gene product of MIER1 is a fibroblast growth factor (FGF)-activated transcriptional regulator, studies recently have shown that MIER1 is associated with breast cancer progression16 and may control transcription using several distinct mechanisms, including recruitment of HDAC117, inhibition of the histone acetyltransferase activity of CBP and displacement of Sp1 from its associated sites in the promoters of target genes18, 19.