Quantitative polymerase chain reaction (qPCR) analysis of GSCs, normal brain tissue and differentiated glioblastoma cell lines by Hsieh et al. (2010) showed that IGFBP2 was overexpressed in GSCs independently of IGFBP5, IGF1 and IGF1R [220]. Here, IGFBP2 is linked to glioblastoma.