RB1 and breast carcinoma: Hopp et al. have already determine that PR-B act as a strong transcriptional activator while PR-A act as a transcriptional repressor and that a high PR-A:PR-B ratio is associated with a poorer diagnosis for breast cancer.33 According to our data, we can hypothesize that PR-B activates the transcription of protective enzymes in breast carcinomas, such as EST1E1.