In summary, these data demonstrate that TCDD inhibits tumor growth and lung and liver metastasis of AHR-deficient LLC cells in mice fed an ω3-rich diet, but stimulates these parameters in ω6-fed mice, and provides evidence that these effects are mediated by the corresponding epoxides, although other metabolites of the PUFA may also be involved. The gene discussed is AHR; the disease is neoplasm.