TPA partially mimics N-Ras*.

Data show the effect of TPA induction during EPO-independent culture. (A) Effect of TPA on CD41 and CD34 expression on day 7 control cells following 24-hour exposure to the indicated concentration of TPA (n = 3). (B) Effect of prolonged exposure to low-dose TPA on CD41 and CD34 expression on day 6 cells, following 72-hour exposure (n = 4). Error bars represent SD. Significant effect of TPA compared with vehicle alone is indicated as follows: *P < .05, **P < .01.