title: Molecular basis of pregnancy-induced breast cancer protection.
abstract: We have postulated that the lifetime protective effect of an early pregnancy against breast cancer is due to the complete differentiation of the mammary gland characterized by a specific genomic signature imprinted by the physiological process of pregnancy. In the present work, we show evidence that the breast tissue of postmenopausal parous women has had a shifting of stem cell 1 to stem cell 2 with a genomic signature different from similar structures derived from postmenopausal nulliparous women that have stem cell 1. Those genes that are significantly different are grouped in major categories on the basis of their putative functional significance. Among them are those gene transcripts related to immune surveillance, DNA repair, transcription, chromatin structure/activators/co-activators, growth factor and signal transduction pathway, transport and cell trafficking, cell proliferation, differentiation, cell adhesion, protein synthesis and cell metabolism. From these data, it was concluded that during pregnancy there are significant genomic changes that reflect profound alterations in the basic physiology of the mammary gland that explain the protective effect against carcinogenesis. The implication of this knowledge is that when the genomic signature of protection or refractoriness to carcinogenesis is acquired by the shifting of stem cell 1 to stem cell 2, the hormonal milieu induced by pregnancy or pregnancy-like conditions is no longer required. This is a novel concept that challenges the current knowledge that a chemopreventive agent needs to be given for a long period to suppress a metabolic pathway or abrogate the function of an organ.
authors.affiliation: Breast Cancer Research Laboratory, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA. J_russo@fccc.edu
authors.forename: Jose
authors.initials: J
authors.lastname: Russo
authors.forename: Gabriela A
authors.initials: GA
authors.lastname: Balogh
authors.forename: Rebecca
authors.initials: R
authors.lastname: Heulings
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Mailo
authors.forename: Raquel
authors.initials: R
authors.lastname: Moral
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Russo
authors.forename: Fathima
authors.initials: F
authors.lastname: Sheriff
authors.forename: Johana
authors.initials: J
authors.lastname: Vanegas
authors.forename: Irma H
authors.initials: IH
authors.lastname: Russo
mesh_terms: D017209:Apoptosis / Q000235:genetics; D001940:Breast / Q000166:cytology / Q000378:metabolism*; D001943:Breast Neoplasms / Q000276:immunology / Q000517:prevention & control*; D002454:Cell Differentiation; D049109:Cell Proliferation; D004260:DNA Repair; D005260:Female; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D008954:Models, Biological; D010298:Parity / Q000235:genetics* / Q000502:physiology; D011247:Pregnancy / Q000235:genetics*