The identification of PMCA2 mRNA in breast cancer cell lines20, 26, PMCA2 protein in clinical breast cancer specimens19, and a role for PMCA2 in the transport of Ca2+ into milk during lactation4, highlight the relevance of this p-type ATPase in the context of human breast cancer and the physiology of the human breast. The gene discussed is ATP2B2; the disease is breast cancer.