The CAST/Ei Strain Confers Significant Protection against ApcMin Intestinal Polyps, Independent of the Resistant Modifier of Min 1 (Mom1R) Locus

Intestinal adenoma development in Apc Min mice is influenced by genetic background. We generated a congenic line between the CAST and B6 inbred strains to study the effects of a resistant CAST background in the absence of a major modifier locus, Modifier of Min 1 ( Mom1 R ). Progeny from a CAST.B6 Mom1 R/S × B6 Apc Min /+ intercross were 110 or 200 days of age and screened for intestinal polyps. There was a significant decrease ( P Mom1 R/S , Apc Min /+ and CASTB6F1 Mom1 S/S , Apc Min /+ progeny compared with B6 Mom1 S/S , Apc Min /+ controls. A complete absence of colon polyps was observed in all mice heterozygous for the CAST background. These results demonstrate that the CAST strain carries dominant modifier loci, in addition to Mom1 R , that dramatically reduce polyp burden in the small intestine and eliminate polyp burden in the colon of Apc Min mice.