PTD mutants only promote cluster formation, MC adhesion-, differentiation-, and neoplasm-related gene expression in Ba/F3 cells. (A) Cluster formation of Ba/F3 cells harboring various KIT mutants. Cells were seeded at 10⁵/mL in 12-well plates with or without mSCF or mIL-3. Six hours later, cells were photographed under an inverted microscopy (Leica DM IRB microscope with a 10×/0.25 objective lens). Images were captured with a CANON Powershot S50 camera and transferred directly to a PowerPoint file (v.2002 SP3). (B) Surface expression of ICAM-1 on Ba/F3 cells. A total of 1 × 10⁵ Ba/F3 cells were stained with phycoerythrin-conjugated antimouse ICAM-1 antibody or IgG isotype control antibody. Expression level is given as fold of control: (MFI_ICAM-1-MFI_isotype)/(MFI_{WT+SCF-ICAM-1}-MFI_{WT+SCF-isotype}). Data are mean ± SD of 3 independent experiments. (C) Expression of CD25 and MC-CPA mRNA in Ba/F3 cells induced by KIT mutants. RNA was isolated from Ba/F3 cells or KIT expressing Ba/F3 cells cultured as indicated. Expression of MC-CPA, CD25, and β-actin mRNA was analyzed by reverse-transcribed PCR as described in “RNA isolation and reverse-transcriptase PCR.”