Following this, sphingosine kinase 1 (SPHK1) or 2 (SPHK2) phosphorylates sphingosine to produce sphingosine-1-phosphate (S1P), which promotes GBM invasiveness via the upregulation of the urokinase plasminogen activator, its receptor, and the pro-invasive molecule CCN1 (cysteine-rich angiogenic protein 61) (Figure 2) [69,72,73,74]. This evidence concerns the gene SPHK1 and glioblastoma.