SFRP1-regulated gene expression in premalignant breast lesions

• Atypical hyperplasias (AH) provide insights into early changes that may predispose breast epithelial cells to oncogenic transformation. • Of genes associated with premalignancy in prior studies, only mRNA levels of ESR1 and SFRP1 were detected in the present study. • Transcriptional profiling defined signatures distinguishing atypical hyperplasias. The patterns of expression were similar among hyperplastic lesions of lobular and ductal phenotype suggesting a common set of alterations underlying both lesions. Pathway analyses identified elevated expression of estrogen receptor alpha, androgen receptor and EGFR receptors and Rho signaling as central events nodes in the pathways altered in AH. • A set of 43 genes were identified as common targets using 2 different algorithms to detect signatures associated with AH. Knockdown of SFRP1 in a TERT immortalized breast epithelial cell line resulted in 14 genes from this signature being either up-regulated or down-regulated as observed in the expression profiles from AH. • The results demonstrate a signature of genes representing alterations that are common to the development of hyperplasias in both ductal and lobular epithelium. Loss of SFRP1 expression is a key player underlying the transcriptional changes in AH that directs a module of genes that can be used to improve reproducibility of diagnosis of AH. In the present study, patients with atypical hyperplasia (AH) but no history of breast cancer were selected. Laser capture microdissection was used to collect both histologically normal benign epithelium (HNB) as well as AH tissues from each patient. The complete transcriptome was evaluated using microarrays and used to define signatures that distinguish AH lesions from the HNB tissues.