SPHK1 and glioblastoma: It has been demonstrated that glioblastoma cell lines and tissue specimens show high SK1 expression [142,143], which correlates with worse prognosis and poor patient survival [140], and that silencing or pharmacological inhibition of SK1 and SK2 (i) decreases the proliferation rate of glioblastoma cells, which prevents their entry into the cell cycle [140,142]; and (ii) restores the sensitivity of glioma stem cells to temozolomide [144].