Morphometric analysis of cell differentiation induced by GSIs, 13-cis RA, or GSIs+13-cis RA. SH-SY5Y and IMR-32 neuroblastoma cells underwent treatment for 5 days treatment with GSI alone or in combination with 13-cis RA, and then neuronal differentiation was evaluated by measuring neurite length. The percentage of differentiated cells was calculated, considered as cells with neurites ≥50 µM in length, in SH-SY5Y and IMR-32 cells. Data are representative of at least 5 experiments. *P < .05; **P < .001 vs 13-cis RA.