Confirmation of expression of retinoid-regulated genes in NB4, NB4-R2, or CD34⁺ cells. (A) Northern blot analysis of ELF4, BCL2, TNFR2, TNFAIP2, and HoxA1 expression by RA. NB4 and NB4-R2 cells were treated with ATRA (1 μM) at the indicated time points. Northern blot analysis was carried out using total RNA (10 μg/lane) and hybridized with ³²P-labeled RT-PCR-generated probes. The same blot was rehybridized for GAPDH to ensure equal RNA loading. (B) TNFR2, TNFAIP2, and ELF4 expression in CD34⁺ cells during granulocytic differentiation as measured by semiquantitative RT-PCR. Human CD34⁺ hematopoietic stem cells were cultured in the presence of cytokines (stem cell factor, IL-3, and GM-CSF) for 12 days to induce granulocytic differentiation. Control RT-PCR reactions were performed for differentiation marker genes, such as CD34, CD11b, and lactoferrin. In addition, RT-PCR for 18S was carried out as an internal control to ensure equal loading of the samples.