Moreover, a comparison of the chemopreventive efficacy of dietary DHA with 4-OXO-DHA in well-defined animal models of mammary carcinogenesis will be pursued; such a comparison will provide ample opportunity to examine the effects of these agents on molecular targets including PGE2 and an established marker of cell proliferation (e.g. Ki67) in the rat mammary tumor as well as non-involved tissue. This evidence concerns the gene MKI67 and breast cancer.