Dnmt1 Reduces the Net Growth Rate and Multiplicity of Intestinal Adenomas in C57BL/6-Multiple Intestinal Neoplasia (Min)/1 Mice Independently of p53 but Demonstrates Strong Synergy with the Modifier of Min 1 Resistance Allele

Altered patterns of the 5-cytosine methylation of genomic DNA are associated with the development of a wide range of human cancers. We have studied the mechanisms and genetic pathways by which a targeted heterozygous deficiency in the murine 5-cytosine DNA methyltransferase gene (Dnmt1) diminishes intestinal tumorigenesis in C57BL/6-multiple intestinal neoplasia (Min)/1 mice. We found that Dnmt1 retards the net growth rate of intestinal adenomas and reduces tumor multiplicity by approximately 50%. This tumor resistance affects the entire intestinal tract and is independent of the status of modifier of Min 1 and p53, two loci that have been found to confer strong resistance to Min-induced neoplasia. Interestingly, Dnmt1 and modifier of Min 1 resistance interact synergistically, together virtually eliminating tumor incidence. This finding may provide an insight into potential combinatorial therapeutic approaches for treating human colon cancer.