Stem cell factor-mediated wild-type KIT receptor activation is critical for gastrointestinal stromal tumor cell growth

Figure 1 Heterozygous c-kit mutations in primary gastrointestinal stromal tumors. The mutant nucleotide sequence is indicated in the upper diagram, and the wild-type nucleotide sequence is indicated in the lower diagram. Nucleotide changes are shown in red capital letters. A: Cryopreserved specimens; B: Fresh specimens.

Figure 2 The expression of stem cell factor in primary gastrointestinal stromal tumors. Sections of gastrointestinal stromal tumors (GISTs) (n = 51) were immunostained with stem cell factor (SCF), KIT (CD117), pHH3 and Ki-67 antibodies (magnification, ×200). Apoptosis was assessed in situ by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining (magnification, ×200). Representative images are shown. Bar = 50 μm.

Figure 3 Western blotting analysis of phosphorylated KIT. A: KIT phosphorylation (p-KIT Y703) was analysed in gastrointestinal stromal tumor (GIST) samples (n = 51). A representative western blotting of p-KIT Y703 (top) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) (bottom) in patients with exon 11 or 9 mutations or wild-type c-kit-bearing tumors; B: GIST primary cells were incubated with 100 ng/mL stem cell factor (SCF) for the indicated times. KIT phosphorylation (p-KIT Y703) was analysed by western blotting.

Figure 4 Stem cell factor stimulates gastrointestinal stromal tumors cell proliferation in vitro. Gastrointestinal stromal tumor (GIST) primary cells were incubated for 72 h with exogenous stem cell factor (SCF) (0-100 ng/mL, A) or KIT immunoblocking antibody (100 ng/mL, B), cell proliferation was analysed by methyl thiazolyl tetrazolium assay. The data are presented as the mean ± SD (n = 4 for each). ^aP < 0.05, ^bP < 0.01 vs untreated cells.

Figure 5 Stem cell factor inhibits gastrointestinal stromal tumor cell apoptosis in vitro. Representative flow cytometric contour of annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) dual-colour flow cytometry after 12 h of treatment with exogenous stem cell factor (SCF) or KIT immunoblocking antibody. The lower right quadrant represents early apoptotic cells. The data are presented as the mean ± SD (n = 4 for each). ^aP < 0.01 vs untreated cells.