Table 2.

Inhibitory effect of topical applications of caffeine on tumor formation in UVB-pretreated high-risk mice.

Treatment	Keratoacanthomas		Squamous cell carcinomas
	Percent of mice with tumors	Tumors per mouse	Percent of mice with tumors	Tumors per mouse
Acetone	82	7.07 ± 1.27	64	1.18 ± 0.25
Caffeine	77 (6% ↓)	3.93 ± 0.74a (44% ↓)	23a (64% ↓)	0.33 ± 0.12a (72% ↓)

High-risk UVB-pretreated SKH-1 mice (30/group) were treated topically with 100 μl acetone or caffeine (6.2 μmol) in 100 μl acetone once daily 5 days a week for 18 weeks. The numbers in parentheses represent percent inhibition. Each value represents the mean ± SE ^ap < 0.01. Taken from Lu et al. (2002).