We were very happy to read of this work, and learn the possibility of using a non-malignant human mammary epithelial cell line for studies of the effects of estrogen and estrogenic compounds. Upon reading the paper, we immediately ordered MCF12A cells from ATCC. However, we have found that the MCF12A cells that we received from ATCC did not express detectable ERalpha protein as measured by immunoblotting with a commonly used commercial antibody (SP1). Our positive control cells (T47D) had abundant ERalpha protein by this assay. We also found that the MCF12A cells used in gene expression profiling work reported by Neve et al. (2006) were reportedly negative for ERalpha expression. Curious to resolve the discrepancy, we contacted Dr. Silva to request an aliquot of the cells used in her study. However, after almost a year of repeated requests, we have not received the cells.