(A) Relative aromatase RNA expression in breast cancer cell lines using Heiser RNASeq data downloaded from UCSC Xena platform. (B) Schematic representation of the different tissue-specific CYP19A1 promoters: I.1, 2a, I.4, I.3 and pII. (C) Identification of aromatase active promoters in breast cancer cell lines (MCF7, MDA-MB-231, BT-549 and MDA-MB-468), non-cancer breast cell line (MCF12F) and placental cell line (JEG3) by end-point PCR. Amplification of three distal promoters, between 93 to 73Kb from ATG: placental aromatase transcripts (I.1, 2a) and skin/ adipose tissue transcript (I.4), two proximal, 0.2 Kb from ATG or less: adipose/breast cancer (I.3) and ovary/breast cancer (pII), exon II (ExII) common in all aromatase transcripts and beta-actin as control. (D) Expression of I.1 promoter in breast cancer TissueScan array (Origene) by real time qPCR, represented as average fold change of I.1 promoter respect to beta-actin and normalized to normal tissue.