Effect of the RARα antagonist Ro 41-5253 in blocking the ATRA-induced and AM580-induced reduction of CP and TF expression in S-NB4 cells. The cells were cultured for 96 hours with 10⁻⁸ mol/L ATRA ± 10⁻⁶ mol/L Ro 41-5253 or with 10⁻⁸ mol/L AM580 ± 10⁻⁶ mol/L Ro 41-5253. Results are the mean of at least three experiments. Statistical analysis to compare untreated and treated samples as in Fig1. *P < .05; **P < .01 versus untreated control samples.