a. H/E morphological staining, CRABP‐II oriented immunocytochemical staining and TUNEL assay performed on UW228‐2 cells transfected with CRABP‐II expressing plasmids and cultured without (Transfection only) or with 10 μM RA supplementation (Transfection/RA). b. Trypan blue viable/nonviable cell discrimination performed on UW228‐2 cells under six experimental conditions: N. normal culture; RA, 10 mM RA treatment; Lipo2000, treatment with transfection reagent only; Lipo2000/RA, co‐treatment with transfection reagent and 10 μM RA; Transfection, CRABP‐II siRNA transfection; Transfection/RA, co‐treatment with CRABP‐II siRNA and 10 μM RA. *, indicates p < 0.01.