GM-CSF, but not TNF-α, increased Raf-1 activation in JMML cells.

(A) Raf-1 was constitutively phosphorylated in JMML cells, and this activation was further enhanced upon adding GM-CSF (5 minutes, 10 ng/mL), but not TNF-α (5 minutes, 10 ng/mL). Similarly, the weak but constitutive activation of the MAPKs ERK-1 (B) and JNK-1 (C) was increased upon addition of GM-CSF (10 ng/mL, 5 minutes), but not TNF-α (10 ng/mL). The data are from immunoprecipitated proteins of JMML cell lysates and combined with Western blotting of their phosphorylated forms (denoted PO₄). The total amounts of the proteins were equal (bottom lanes). The data are from one experiment on one JMML case and are representative of 7 other JMML cases.