PSEN1 and neuroblastoma: Real-time RT–PCR revealed that, in differentiated SK-N-BE neuroblastoma cells, a single treatment with 27-OH (1 μm) induced a statistically significant increase (1.5-fold) in PS1 mRNA levels compared to untreated cells; conversely, cell treatment with 24-OH (1 μm) did not modify basal PS1 mRNA levels (Fig. 3A).