NICD1 mice are susceptible to malignant neoplasms. (A) Representative image showing multiplying soft tissue sarcomas (white triangles) in the tail of NICD1 mice (left) and histological examination by hematoxylin and eosin staining (right). Scale (left panel) in centimeters. (B) Kaplan-Meier curves showing the cumulative incidence rates of soft tissue sarcoma in NICD1 mice and controls. (C) Impaired tumor-specific CD8⁺ T-cell response in NICD1 mice. NICD1 mice and controls were injected subcutaneously with 5 × 10⁵ B16-OVA melanoma cells. Tumor-infiltrating lymphocytes were isolated and the percentage of OVA-specific CD3⁺ CD8⁺ T cells was examined by flow cytometry. The mean percentage of cells from 4 individual mice per group is shown. Data in the bar graphs are expressed as the mean and SEM. *P < .05 (Student t test). (D) Expression of mRNA encoding FOXP3 in inoculated B16-OVA melanoma tissue in NICD1 mice and controls, as evaluated by quantitative PCR. Expression levels are expressed relative to those detected in tumors from control mice. Data in the bar graphs are expressed as the mean and SEM from 4 individual mice per group. **P < .01 (Student t test).