Publicly available DNA array expression data (Geoprofiles, GDS2324) (Coser et al, 2003) had already indicated a tight co-regulation of Mb and ERα mRNAs in the breast cancer cell line MCF7 by showing that oestrogen starvation was able to induce, while oestrogen application suppressed, Mb and ERα transcripts in either a time- or dose-dependent manner (Supplementary Figure S5; ERα=ESR1 in figure). The gene discussed is ESR1; the disease is breast cancer.