Study did not detect an initial increase of PrPC expression, most likely due to the different status of cells at the point of induction. Stimulation of the glucocorticoid receptor by dexamethasone induces the proliferation and expansion of erythroid progenitors and delays the terminal differentiation of erythrocytes. In our hands, dexamethasone did not prevent the HMBA-induced initial upregulation of PrPC in MEL cells, suggesting that it precedes the effect of dexamethasone, which is known to suppress the HMBA-mediated commitment to terminal cell division at a relatively late step in this process. However, dexamethasone prevented the increase of PrPC protein levels in confluent MEL cells after 120 h of culture, demonstrating that the activation of the glucocorticoid receptor can interfere with the transcriptional activation of the Prnp gene mediated by cell-cycle arrest. The mechanism of dexamethasone’s action on the prevention PrPC protein upregulation in confluent MEL cells is unknown at present. Dexamethasone has been shown to induce cell-cycle arrest in number of various cell lines, but not in MEL cells, in which it increases cell viability, both in induced and uninduced culture. In summary, our results demonstrate that the regulation of PrPC levels in differentiating MEL cells resembles, at least in part, its regulation in maturing mouse erythroid precursors in vivo. To learn more about the importance of PrPC in the process of MEL cells’ differentiation, we created cell lines using RNAi to stably inhibit expression of the protein. RNAi administered by shRNA from a retrovector had previously been employed efficiently to inhibit PrPC expression in vitro and in vivo. The main objective for using RNAi to suppress PrPC was to study its therapeutic potential in preventing propagation of infectious prions. To the best of our knowledge, our model is the first murine cell line of non-neuronal origin with stably silenced PrPC expression. Inhibition of the protein’s expression at both the mRNA and protein levels was efficiently Perifosine maintained during the differentiation of MEL cells, although it varied between 75 and 95% in individual time points. Despite the silencing, the induction of differentiation led to a detectable increase of PrPC signal on blots after 24 h, suggesting that the regulation of the protein’s expression in LP1- and LP2-transduced cell lines follows similar pattern as in unmodified MEL cells, although at a suppressed level. Growth curve and viability of LP1-, LP2- and control LNtransduced cell lines after the induction of differentiation was similar, although the LP2-transduced cell line exhibited a higher proliferation capacity. Since the LP1-transduced cell line did not differ from control LN-transduced cell line, we could not assign the LP2-transduced cell line’s divergence solely to PrPC silencing. All cell lines observed here demonstrated similar dynamics and level of hemoglobinization and regulation of the transferrin receptor on their cell membranes. This finding suggested that silencing of PrPC in MEL cells does not lead to gross perturbation of iron homeostasis, although the involvement of PrPC in iron-cell uptake was described recently.