Nevertheless, since ATP efflux is one of the main functions of ABCB1, as noted by the significant decrease of extracellular ATP released by U3017MG upon knockdown of ABCB1 (Fig. 5K), we sought to assess the levels of extracellular ATP in GBM cells before and after treatment with A5 or C1, combined or not with TMZ. This evidence concerns the gene ABCB1 and glioblastoma.