TMPO-AS1 stabilizes ESR1 mRNA. (A to C) Effects of TMPO-AS1 knockdown on ESR1 mRNA expression in MCF-7 (A), OHTR (B), and T47D (C) cells. Data are normalized to GAPDH levels and presented as mean fold changes ± SD versus levels for siControl (n = 3). (D to F) TMPO-AS1 knockdown represses ERα protein levels in MCF-7 (D), OHTR (E), and T47D (F) cells. ERα and β-actin protein levels were evaluated by immunoblot analysis. β-Actin was used as a loading control. (G to I) TMPO-AS1 siRNAs more rapidly and severely decrease the stability of ESR1 mRNA in MCF-7 (G), OHTR (H), and T47D (I) cells. Actinomycin D (ActD; 10 nM) was added to culture medium 24 h after siRNA transfection. Cells were collected at the indicated times (0, 2, 4, 6, and 8 h after ActD treatment). ESR1 levels were normalized to GAPDH levels and are presented as mean fold changes ± SD versus basal values at 0 h. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ns, not significant.