Whereas McHugh et al. showed the phosphorylation of p44/42 for NAGly in stable transfected GPR18-HEK293 cells [54], Finlay et al. (2016) could not observe a cAMP modulation and failed to induce the p44/42 MAPK phosphorylation in HEK293-hGPR18 cells and in endogenously expressing GPR18 glioblastoma cells [8]. This evidence concerns the gene GPR18 and glioblastoma.