When IGFBP3 was transfected into LCC9 endocrine-resistant breast cancer cells, it was shown, by co-immunoprecipitation, to interact with the 78-kDa glucose regulated protein (GRP78), which is highly expressed in LCC9 and other endocrine-resistant breast cancer cells (31), and to dissociate caspase 7 from GRP78, thus sensitizing LCC9 cells to growth inhibition by fulvestrant (ICI 182,780) (32). Here, IGFBP3 is linked to breast cancer.