Iron regulation of transferrin receptor and ferritin expression in differentiating friend leukemia cells

Transferrin receptor (TfR) and ferritin expression has been investigated in Friend erythroleukemia cells (FLCs) induced to differentiate by dimethylsulfoxide (Me(2)SO). In differentiating FLCs, administration of hemin increases the ferritin content approximately 20-25 fold; conversely iron salts have only mild stimulatory effects on ferritin accumulation and iron chelators only slightly inhibit the stimulatory effect exerted by hemin. Moreover, in Me(2)SO-induced FLC, the negative feedback reported in a variety of other cell types for the regulation of TfR expression by heme is not operative. We conclude that in FLCs induced to differentiate, hemin acts synergistically with the differentiation inducer increasing ferritin expression and is not able to down modulate the TfR number. These effects appear characteristic of differentiating erythroid cells since they are not observed in other cell types (i.e. fibroblastic cell lines).