TY - JOUR T1 - Irradiation of juvenile, but not adult, mammary gland increases stem cell self-renewal and estrogen receptor negative tumors. JF - Stem Cells Y1 - 2014 A1 - Tang, Jonathan A1 - Fernandez-Garcia, Ignacio A1 - Vijayakumar, Sangeetha A1 - Martinez-Ruis, Haydeliz A1 - Illa-Bochaca, Irineu A1 - Nguyen, David H A1 - Jiang-Hua Mao A1 - Costes, Sylvain V A1 - Barcellos-Hoff, Mary Helen KW - Aging KW - Animals KW - Biomarkers KW - Cell Line KW - Cell Lineage KW - Cell Proliferation KW - Computer Simulation KW - Dose-Response Relationship, Radiation KW - Epithelial Cells KW - Female KW - Humans KW - Mammary Glands, Animal KW - Mammary Neoplasms, Animal KW - Mice KW - Morphogenesis KW - Radiation, Ionizing KW - Receptors, Estrogen KW - Receptors, Notch KW - Stem Cells KW - Transforming Growth Factor beta AB -

Children exposed to ionizing radiation have a substantially greater breast cancer risk than adults; the mechanism for this strong age dependence is not known. Here we show that pubertal murine mammary glands exposed to sparsely or densely ionizing radiation exhibit enrichment of mammary stem cell and Notch pathways, increased mammary repopulating activity indicative of more stem cells, and propensity to develop estrogen receptor (ER) negative tumors thought to arise from stem cells. We developed a mammary lineage agent-based model (ABM) to evaluate cell inactivation, self-renewal, or dedifferentiation via epithelial-mesenchymal transition (EMT) as mechanisms by which radiation could increase stem cells. ABM rejected cell inactivation and predicted increased self-renewal would only affect juveniles while dedifferentiation could act in both juveniles and adults. To further test self-renewal versus dedifferentiation, we used the MCF10A human mammary epithelial cell line, which recapitulates ductal morphogenesis in humanized fat pads, undergoes EMT in response to radiation and transforming growth factor β (TGFβ) and contains rare stem-like cells that are Let-7c negative or express both basal and luminal cytokeratins. ABM simulation of population dynamics of double cytokeratin cells supported increased self-renewal in irradiated MCF10A treated with TGFβ. Radiation-induced Notch concomitant with TGFβ was necessary for increased self-renewal of Let-7c negative MCF10A cells but not for EMT, indicating that these are independent processes. Consistent with these data, irradiating adult mice did not increase mammary repopulating activity or ER-negative tumors. These studies suggest that irradiation during puberty transiently increases stem cell self-renewal, which increases susceptibility to developing ER-negative breast cancer.

VL - 32 IS - 3 U1 - http://www.ncbi.nlm.nih.gov/pubmed/24038768?dopt=Abstract ER -