GM-CSF hypersensitivity in the 2-oncogene compared with the 1-oncogene model. (A-C) Cytokine stimulation assay of murine bone marrow cells stably transduced with MN1+ND13 or MN1+CTL. Cells were cultured in the presence of the indicated cytokines (6 ng/mL IL-3, 10 ng/mL IL-6, 20 ng/mL SCF, or 10 ng/mL GM-CSF), and viable cells were counted and replated every 3 to 4 days (mean ± SD, n = 4). (D) Quantitative gene expression analysis of Gm-csfrα, Il-3rα, and G-csfrα in bone marrow cells of moribund mice that received a transplant of MN1+ND13- and MN1+CTL-expressing cells (mean ± SD). (E-F) Quantitative gene expression analysis of agonistic (E) and antagonistic (F) signaling molecules downstream of the GM-CSFR in leukemic cell lines MN1+CTL and MN1+ND13 in relation to gene expression in the nonleukemic cell line ND13 (mean ± SD, n = 4). $ND13 was used as a nonleukemic calibrator.