Fig. 1.

Papilloma frequency and size are greater in TGFβ1+/+ mice, but conversion to SCC is reduced. TGFβ1+/+ and +/− mice were initiated with DMBA and promoted with TPA twice per week for 25 weeks. The number of papillomas >2 mm was determined on a weekly basis. (A) Papillomas per mouse from mice promoted with 5 μg (top) and 10 μg (middle) TPA and percent of mice with papillomas (bottom). The papilloma frequency was significantly higher in TGFβ1+/+ mice promoted with 5μg TPA (P = 0.0013) and 10 μg TPA (P = 0.01). At each dose, 21/28 and 20/24 TGFβ1+/+ and 13/20 and 19/20 TGFβ1+/− mice developed tumors. (B) Tumor volumes between weeks 20–30 were measured using a digital micrometer. Average volumes were determined from measurements of length × width × height, and statistical significance determined using a T-test to compare genotypes at each time point. (C) The total papilloma and SCC yield and percent conversion for each genotype. Percent conversion at each TPA dose was determined by dividing the total number of SCC that formed during the course of the study by the maximum number of papillomas; P, papilloma; C, carcinoma.