Fig. 3.

a The effects of ATRA treatment on H19 expression are reversible in both NB4-LR1 and NB4-LR1^SFD. After culturing cells for 8 days in the presence of ATRA (1 μM), the NB4-LR1 cell culture was switched to ATRA-free medium. (− 7) refers to the NB4-LR1 cells that were cultured 7 days after ATRA removal. Expression levels of H19, hTERT mRNA, and hTR were quantified and normalized to GAPDH expression. Results were expressed as means +/− SEM. One way ANOVA with post-hoc Tukey, ns p > 0.05, *p < 0.05, ***p < 0.001, ****p < 0.0001. b Establishment of an NB4-LR1^SFD like cell line from NB4-LR1 cell line cultured in the continuous presence of ATRA (1 μM). By day 50, in several experiments, most of the cells underwent cell death. However, in two separate experiments a new population, similar to the NB4-LR1^SFD, overcame this cell death step. The lower panel shows the population doublings of one of the two cultures. At the indicated times, RNA was extracted and hTERT, H19, and hTR expressions measured. Expression levels were normalized to GAPDH expression. Note from day 53 the decrease of H19 expression (upper panel) associated with hTERT re-expression (middle panel) t-test or one way ANOVA with post-hoc Tukey, ns p > 0.05, *p < 0.05, ***p < 0.001. ****p < 0.0001