Glioblastoma cells overexpressing EGFR-VIII are characterized by higher levels of extracellular S1P and increased sphingosine kinase-1 (SK1) activity than empty vector expressing cells and the EGFR overexpressing cells are resistant to TMZ and have higher invasiveness properties compared to the empty vector expressing cell [66,163]. This evidence concerns the gene SPHK1 and glioblastoma.