Table II.

Incidence of colon tumors in hCYP1A-mice

Genotype	Treatment	Duration (weeks)	No. of mice examined	Colon tumor total		Adenoma multiplicity	Adenocarcinoma multiplicity
				Incidence (%)	Multiplicity
hCYP1A	200 mg/kg PhIP + 1.5% DSS	6	20	85	3.75 ± 0.70*	0.20 ± 0.13*	3.5 ± 0.95*
		10	29	86	3.90 ± 0.61*	0.60 ± 0.16*	2.4 ± 0.45*
		12–21a	7	100	4.57 ± 1.39*	0	4.57 ± 1.39*
hCYP1A	100 mg/kg PhIP + 1% DSS	24–25b	11	9	0.09 ± 0.09	0	0.09 ± 0.09
hCYP1A	200 mg/kg PhIP	16–40c	38	0	0	0	0
hCYP1A	DMSO	24	17	0	0	0	0
Wild-type	200 mg/kg PhIP + 1.5% DSS	12–24d	9	0	0	0	0
Wild-type	200 mg/kg PhIP	14–40e	26	0	0	0	0
Wild-type	DMSO	24	17	0	0	0	0

Mice were given 100 or 200 mg/kg PhIP or vehicle (DMSO) by oral gavage and 1 week later were given 0, 1 or 1.5% DSS in the drinking water for 7 days. Duration indicates the number of weeks following PhIP or DMSO administration, when the mice were sacrificed. Histological analysis was used to determine whether colon tumor was an adenoma or adenocarcinoma. Multiplicity values are mean ± standard error.

^aMice examined at weeks 12 (n = 2), 14 (n = 2), 18 (n = 1) and 21 (n = 2).

^bMice examined at weeks 24 (n = 7) and 25 (n = 4).

^cMice examined at weeks 16 (n = 7), 20 (n = 8), 24 (n = 13), 30 (n = 5) and 40 (n = 5).

^dMice examined at weeks 12 (n = 2), 18 (n = 3) and 24 (n = 6).

^eMice examined at weeks 14 (n = 4), 20 (n = 6), 24 (n = 7), 30 (n = 4) and 40 (n = 5).

*P < 0.02, statistically different from the value for wild-type mice given 200 mg/kg PhIP + 1.5% DSS (two-tailed Student’s t-test).