ANALYSIS OF CELL-DEATH IN MYELOID CELLS INDUCIBLY EXPRESSING THE CELL-CYCLE PROTEIN P55CDC

p55Cdc, a cell cycle protein is expressed in cycling mammalian cells a nd is required for normal cell division. Expression of this protein is regulated during the cell cycle, peaking in late G1 and S. We have pr eviously shown that constitutive expression of p55Cdc results in inhib ition of granulocyte differentiation. Degradation of p55Cdc is also re quired for apoptosis in growth factor and serum starved cells. in the present study we prepared stably transfected cells conditionally expre ssing p55Cdc in response to zinc stimulation to investigate the role o f inducible p55Cdc expression in apoptosis of myeloid cells. We report that inducible expression of p55Cdc in the myeloid leukemic cell line 32Dcl3 resulted in increased cell death. p55Cdc overexpression led to a statistically significant decrease in the viability of 32Dcl3 cells compared with that of control cells. Furthermore, cell staining and f low cytometry analysis revealed that p55Cdc-overexpressing 32Dcl3 cell s progressed to apoptosis much earlier than uninduced cells. These res ults suggest that inducible expression of p55Cdc leads to earlier incr eases in cell death in the absence of growth factor and serum in myelo id leukemic cells.