Some scholars disagree with the view that the ratio of FABP5/CRABP2 determines the direction of cell differentiation: Bai Gang believe that the ratio of CRABP2/FABP5 cannot be used as a target for retinoic acid to act on craniopharyngio cells, and the proportional relationship between RARα and PPARβ/δ may be the molecular target that determines the ultimate effect of retinoic acid [19]; in another glioblastoma study, it was found that the expression patterns of CRABP2 and FABP5 had nothing to do with the tumor grade or the sensitivity of RA [20]. This evidence concerns the gene PPARD and neoplasm.