Evaluation of the expression of RA signaling components (RARα, RARβ, RARγ, RXRα, RXRβ, RXRγ, CRABP‐I, CRABP‐II and CYP26A1) and neuronal differentiation biomarker NGN1 in Med‐3, UW228‐2 and UW228‐3 cells by RT‐PCR (a), followed by Western blotting (b) and ICC staining (c) for CRABP‐I and ‐II. Grayscale quantitative analysis was performed on the RT‐PCR and Western blot results. N, normal culture; RA, treatment with 10 μM RA for 72 h.