CCL21 and glioblastoma: These resultssuggested that the presence of extracellular NAD+ in thetumor microenvironment may rescue NAMPT inhibition and intracellularNAD+ depletion in the tumor cancer cells.48 ,56,57 In glioblastoma, extracellularNAD+ can be transported inside cells by membrane transportersnamed SLC (solute carrier family) or by gap junction with neighboringcells.