By analysis of the promoter P2, we previously discovered in three different breast cancer cell lines that basal expression of PLAC1 is governed by the concerted action of the transcription factors SP1 and isoform 2 of CCAAT/enhancer binding protein β (C/EBPβ) that is selectively expressed in placental tissue and breast cancer cells[7]. This evidence concerns the gene SP1 and breast carcinoma.