Fig. 4. PMA induced CREB phosphorylation or Egr-1 expression in wild-type or PMA-resistant K562 cells. Wild-type or PMA-resistant K562 cells were treated with or without PMA in the presence or absence of PD098059, and the degree of CREB phosphorylation (A) or the induction of Egr-1 expression (B) was analyzed as described in "Materials and Methods."