To elucidate the underlying mechanism of radioresistance, we recently established a stable, radioresistant GBM model and also presented evidence partly attributing the radioresistance of GBM cells to radiation-induced upregulation of tumor promoters acid ceramidase (ASAH1) and sphingosine-1-phosphate (S1P) [8, 9]. Here, ASAH1 is linked to glioblastoma.