Microarray expression profiling study of Runx1-null and wild type luminal mammary epithelial cells

RUNX1 encodes a RUNX family transcription factor (TF) and was recently identified as a novel mutated gene in human luminal breast cancers. We found that Runx1 is expressed in all subpopulations of murine mammary epithelial cells (MECs) except the secretory alveolar luminal cells. Conditional knockout of Runx1 in MECs by MMTV-Cre led to a decrease in luminal MECs, largely due to a profound reduction in the estrogen receptor (ER)-positive mature luminal subpopulation, a phenotype that could be rescued by loss of either Trp53 or Rb1. Mechanistically RUNX1 represses Elf5, a master regulatory TF gene for alveolar cells, and activates Foxa1, a key mature luminal TF gene involved in the ER program. Collectively, our data identified a key regulator of the ER+ luminal lineage whose disruption may contribute to development of ER+ luminal breast cancer when under the background of either TP53 or RB1 loss.

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van Bragt MP, Hu X, Xie Y, Li Z