Upregulation of p21 RAS levels in HL-60 cells during differentiation induction with DMSO, all-trans-retinoic acid and TPA.

The role of p21 RAS in the proliferation and differentiation of myeloid cells has been studied by analysing the changes in the level of expression of p21 RAS proteins by flow cytometry upon differentiation down the granulocytic and monocytic pathways. Differentiation resulted in upregulated p21 RAS expression despite a marked decline in the number of dividing cells. On the other hand, growth inhibition, without differentiation, resulted in a decline in expression. Cell cycle analysis showed that the increase in p21 RAS occurred throughout the cell cycle. These results suggest that p21 RAS has a role in the process of myeloid differentiation.