Few studies have addressed CYP27B1 expression in relation to clinical outcomes in breast cancer, although as noted above its expression has been shown to confer growth inhibition in response to 25D (the major circulating metabolite) in vitro and in mouse models.(4, 68, 69) Using the same approaches discussed for VDR, we found that 10% of breast cancers in the METABRIC data set displayed alterations at the CYP27B1 locus, with >95% of these being amplifications or mRNA upregulations. The gene discussed is CYP27B1; the disease is breast cancer.