IGF1 and breast cancer: Since this epigenetic alteration of the Igf1 Pr1 was observed in mammary stromal cells from prepubertal animals, and DNA methylation is a stable epigenetic marker that can be inherited through multiple cell divisions [13,45], our results also indicate that methylation of the Igf1 Pr1 promoter in mammary tissues could be used as an epigenetic biomarker for early breast cancer risk assessment.