Retinoid-dependent CHOP mRNA expression in various cell lines. NB4, KG-1, Jurkat, LNCaP, MCF-7, MDA-MB-231, SAOS, and C33A cells were exposed (+) or not exposed (-) to ATRA (10^-6 M) for 2 hours; these cells were harvested for total RNA, and total RNA (20 μg) from each paired sample was loaded for Northern blot analysis. (top panel) Hybridization with CHOP cDNA. (bottom panel) Rehybridization of the blot with the loading control, GAPDH. Retinoid-dependent induction of CHOP mRNA expression occurred only in the APL cell line NB4.