Figure 6. CD40 ligation does not directly inhibit GIST cells.

Untreated Kit^V558Δ/+ mice (n=4) were analyzed for (A) CD40 expression on Kit⁺ tumor cells by flow cytometry and (B) CD40 expression was quantitated as a percent of Kit⁺ cells or TAMs. (C) CD40 expression as percent of Kit⁺ cells with the indicated treatment at 2 weeks (4-6 mice/group). Anti-CD40 (αCD40); Imatinib (IM). (D) CD40 expression by flow cytometry. (E) GIST T1 cells were treated in vitro for 8 hours, as indicated, and tested for relative CD40 mRNA levels. (F) GIST T1 cells were treated in vitro for 6 hours, as indicated, and tested for relative CD40 mRNA levels. (G) Relative IFNγ, TNF, and TGFβ mRNA expression in bulk tumor from Kit^V558Δ/+ mice at 2 weeks. (H) Mice (5-6 mice/group) with established GIST T1 xenografts were injected once with anti-human CD40 followed by starting continuous imatinib 3 days later. Tumors were measured by calipers every 2-4 days. Treatments are as follows: IgG (black), anti-human CD40 (purple), IgG and imatinib (blue), anti-human CD40 and imatinib (red). Data represent mean ± SEM, *P < 0.05 using Student’s t test.