Table 3.

Stimulatory effect of topical applications of caffeine on the formation of mitotic cells with cyclin B1–positive staining in skin tumors of high-risk mice previously treated with chronic UVB

TreatmentNo.of nontumor areas or tumors examinedNo.of cells examinedPercent of cells with mitosisPercent of cells with both mitosis and cyclin B1Percent of mitotic cells with cyclin B1
Nontumor areas
 Acetone7024,0000.013 ± 0.00100
 Caffeine6322,0000.013 ± 0.00100
 Percent change000
Keratoacanthoma
 Acetone3873,0000.300 ± 0.0280.029 ± 0.00310
 Caffeine2869,0000.280 ± 0.0360.048 ± 0.007a17
 Percent change−76670

NOTE: Female SKH-1 mice (7–8 weeks old) were irradiated with UVB (30 mJ/cm2) twice a week for 20 weeks and UVB treatment was stopped. Three weeks later, these tumor-free high-risk mice were randomized and divided into 2 groups (30 mice per group) and treated topically with 100 μL acetone or with caffeine (6.2 μmoles) in 100 μL acetone once daily 5 days a week for 18 weeks. Percent of cells with mitosis or mitotic cells with cyclin B1–positive staining were determined. Each value represents the mean ± S.E.