Insights into mechanisms of IGFBP7 expression in the glioblastoma environment have come from in vitro experiments, which demonstrated that TGF-β1 secreted from glioblastoma tumour cells stimulate IGFBP7 production in human brain endothelial cells (HBECs) (Pen et al, 2008). Here, IGFBP7 is linked to glioblastoma.