Table 1.

The inhibitory effect of EGCG on NNK-induced lung tumorigenesis^*

Group #	Treatment	Duration (weeks)	Mice (n)	Incidence	Tumors/mouse	Volume (mm3/mouse)
1	Saline	5, 10, 15, 20	16	0/16	0	0
2	NNK	5	8	0/8	0	0
3	NNK	10	8	1/8	0.25	0.21
4	NNK	15	8	8/8	12.0 ± 0.76	2.27 ± 0.31
5	NNK	20	30	30/30	22.0 ± 1.47	4.72 ± 0.37
6	NNK + 0.5% EGCG	20	30	30/30	17.9 ± 0.92†	2.84 ± 0.28†

^*One week before the first NNK injection, mice were treated with 0.5% EGCG in diet and sacrificed at different time points. Under a dissecting microscope, tumors > 0.1 mm were scored. Tumor volumes (mm³) were measured using the formula $\mathrm{V}=4/3\mathrm{\pi }{\mathrm{r}}^3$, where r is the radius of the tumor determined by the mean values of the longest and shortest diameters.

^†Indicating significant difference as compared with 20 weeks NNK treatment group using student’s t-test.