ESR1 and breast cancer: In our most recent work, we demonstrated that expression and enzymatic activity of the glycerophosphodiesterase EDI3 is highest in HER2+ breast cancer cells that are also estrogen receptor negative (ER-), and in agreement, higher EDI3 mRNA expression was also observed in human ER-HER2+ breast cancers in an analysis of publicly available Affymetrix gene expression microarray datasets [6].