No associations were found between placental growth factor (PLGF), hepatocyte growth factor (HGF), transforming growth factor beta 1 (TGFβ1), fibroblast growth factor 2 (FGF2) and transforming growth factor alpha (TGFα) levels and pre-diagnostic glioma patients (8, 12, 13). Here, HGF is linked to central nervous system cancer.