Dabrosin N, et al. - Researchers investigated in vivo levels of Growth hormone (GH), insulin-like binding proteins (IGFBPs), and other pro-tumorigenic proteins in the extracellular microenvironment in breast cancer, in normal breast tissue with various breast density in postmenopausal women, and premenopausal breasts. In addition, they investigated possible associations between these determinants. Using microdialysis, they gathered extracellular in vivo proteins intratumorally from breast cancers prior to surgery and from normal human breast tissue from premenopausal women and postmenopausal women with mammographic dense or nondense breasts. Increased extracellular GH was observed in estrogen receptor positive breast cancers. Levels of GH in dense breasts of postmenopausal women were similar to premenopausal breasts and were significantly higher than nondense breasts. They observed similar results for IGFBP-1, -2, -3, and -7 and for IGFBP-6. They identified strong positive associations between GH and IGFBPs and pro-tumorigenic matrix metalloproteinases, urokinase-type plasminogen activator, Interleukin 6, Interleukin 8, and vascular endothelial growth factor in normal breast tissue. These findings suggest that for cancer prevention therapeutics in postmenopausal women with dense breast tissue, GH pathways may be targeted.