To determine if Zn2+-dependent signaling is generally mediated in breast cancer cells, we studied ZnR/GPR39 activity in BT20, MDA-MB-453 cell lines, which are ERα and PR negative, but overexpress some level of HER2 (CCLE microarray data; https://portals.broadinstitute.org/ccle)45. The gene discussed is ESR1; the disease is breast cancer.