Effects of Raf-1, MAPK kinase, and MAPK pathway inhibitor compounds on the proliferation (A), the phosphorylation of MAPK (B), and the adhesion (C) of constitutively active type H-Ras–transfected Baf3 cells (designated as constitutively active) without IL-3 stimulation and constitutively active type H-Ras–transfected Baf3 cells, wild-type H-Ras–transfected Baf3 cells (designated as wild-type), and dominant-negative type H-Ras–transfected Baf3 cells (designated as dominant-negative) induced by IL-3. In (A), [³H]-thymidine incorporation of those transfected Baf3 cells in the absence or presence of either 1 mmol/L 8-Br-cAMP, 1 mmol/L Dibutyryl-cAMP, or 50 μmol/L PD98059 was measured. Data represent the means (±SD) of triplicate samples from a representative experiment of three. In (B), the factor-starved transfected Baf3 cells were incubated at 37°C for 3 hours in the absence or presence of either 1 mmol/L 8-Br-cAMP, 1 mmol/L Dibutyryl-cAMP, or 50 μmol/L PD98059 and incubated for an additional 15 minutes with or without 0.1 ng/mL IL-3. Cells were lysed in lysis buffer, separated by 11.25% SDS-PAGE, immunoblotted with anti–phospho-MAPK antibody, and reblotted with anti-MAPK antibody to detect the total MAPK levels. Anti-MAPK antibody used here recognized only p42 MAPK of Baf3 cells. This is a representative result of three independent experiments. In (C), transfected Baf3 cells were labeled with ⁵¹Cr and incubated at 37°C for 3 hours in the absence or presence of either 1 mmol/L 8-Br-cAMP, 1 mmol/L Dibutyryl-cAMP, or 50 μmol/L PD98059. Cells were subsequently transferred to FN-coated wells and incubated at 37°C for an additional 30 minutes with or without 0.1 ng/mL IL-3, and the percentage of adherent cells was measured. Data represent the means (±SD) of triplicate samples from a representative experiment of three. *P value (P < .01) comparing each treatment with the control.