IGF-1R blockade reinstates IFN-γ–driven inhibition of ST4 cell growth in SCID mice. (A-B) Anti-asialo GM1-treated SCID mice were challenged subcutaneously with 10 × 106 ST4-WT (○, •) or ST4-DN (□, ▪) cells. After 2 hours, mice were injected at the site of tumor challenge with 0.4 mL vehicle solution (○, □) or 1000 U IFN-γ (•, ▪). This treatment was repeated daily for 5 days, and neoplastic masses were evaluated twice a week with calipers. Results are indicated (A) as the kinetics of the mean ± SD of the tumor diameter and (B) as percentage of tumor-free mice. (C) SCID mice were challenged with 10 × 106 ST4-DN cells as described. After 10 days, 3 mice were killed and tumor sample sections were evaluated by histologic analysis. Samples were collected, formalin fixed, and embedded in paraffin. Sections were rehydrated and stained with hematoxylin-eosin and examined under a microscope. The picture was taken with a B×51 Olympus microscope (Olympus, Hamburg, Germany) equipped with a 4×/0.10 NA Plan objective and a Nikon Coolpix 995 digital camera (Nikon, Melville, NY). The image was processed with Adobe Photoshop 7.0 software (Adobe Systems, San Jose, CA) (inset). The remaining mice were treated with vehicle (□) or IFN-γ (▪) daily for 10 days, starting from day 10 after the inoculum. The graph represents the kinetics of the mean ± SD of the tumor diameter, evaluated as described. Each group consisted of 6 mice, except the ST4-DN–challenged and IFN-γ–treated group (7 mice). *P < .05, IFN-γ–treated versus vehicle-treated ST4-DN–challenged mice.
