Effect of RA and RARα antagonist on EPO-induced differentiation of FDCPmix.

RA inhibits and RARα antagonist stimulates EPO-induced differentiation of FDCP-mixA4 cells in vitro. (A) The RARα antagonist Ro41-5253 was previously described.38 FDCP-mixA4 cells were induced to differentiate in the presence or absence of indicated retinoids, and after 5 days in culture, cells were scored for morphology as in Figure 1A. (B) Effects of retinoids on differentiation of FDCP-mixA4 cells, which were derived from a different passage than those that were used to obtain the results shown in panel A. Cells treated with indicated GF conditions and retinoids were scored for morphology after 5 days in culture. Note that the effects of RARα antagonist on erythroid differentiation of these 2 different passages of FDCP-mixA4 cells are comparable. RARα-specific agonist (Ro40-6055), which as RA stimulates myelomonocytic differentiation of FDCP-mixA4 cells, has previously been described.38