When we further tested the effect of SFRP1 expression in a panel of breast cancer cell lines, we found that SFRP1 reduced the mRNA levels of EGR2 in T47D cells but not in TMX2–28 cells (a Tamoxifen resistant variant of MCF7) or MDA-MB-231 cells (Additional file 1: Figure S1). Here, EGR2 is linked to breast cancer.