The MAP kinase family is essential for Epo-dependent cell growth. Various concentrations (0 to 30 μmol/L) of antisense S-oligo (•) or sense S-oligo (○) of p38 (B), JNK1 (C), JNK2 (D), a mixture of JNK1 and JNK2 (D), ERKs (E), or scrambled S-oligo (A) were mixed with FD-EPO cells in the presence of Epo, and the cell growth was measured by MTT assay. Values shown are the means of six experiments. (F) Immunoblot analyses of FD-EPO cells treated (+) or untreated (−) with antisense S-oligos (30 μmol/L) with specific antibody against each corresponding kinase.