Abstract Benzyl isothiocyanate (BITC) is a hydrolysis product of glucotropaeolin, a compound found in cruciferous vegetables. We previously observed that chronic consumption of a high-fat diet increased the breast cancer progression and lung metastasis in the 4T1 orthotopic BALB/c mouse model. In the present study, we determined whether BITC inhibits high-fat diet-induced acceleration of breast cancer growth and metastasis in the 4T1 model. 4-week old, female BALB/c mice were fed on a high-fat diet (HFD, 60 kcal% fat) or control diet (CD, 10 kcal% fat) and BITC was administered daily with oral gavage (0, 5, or 10 mg/kg body weight/day). After 16 weeks, 4T1 cells (5 × 104 cells) were injected into the mammary fat pads of syngeneic, female, BALB/c mice and the mice were continuously fed on the same diets and BITC. 26 day after the cancer cell injection, animals were killed. The weights of tumors and lungs were significantly increased in the HFD group as compared to the CD group, and the increases were suppressed by BITC treatment. Additionally, chronic consumption of the HFD markedly increased the number and volume of tumor nodules in the lung; the increases were markedly suppressed by BITC treatment. Immunohistochemical staining of tumor tissues revealed that the expression of platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31, an angiogenesis marker), vascular endothelial growth factor (VEGF)-A, LYVE-1 (lymphatic vessel endothelial receptor-1), VEGF-D, Ki67, cyclin-dependent kinase 2, cyclin A, cyclin D1, and hypoxia-inducible factor 1α (HIF-1α) was markedly increased in the HFD group as compared to the CD group; the increases were blocked by BITC treatment. Chronic consumption of the HFD reduced TUNEL-positive apoptotic cells, which was prevented by BITC treatment. The present results demonstrate that BITC suppressed HFD-stimulated breast cancer progression, which may have been mediated via the suppression of cell cycle progression, tumor angiogenesis and lymph angiogenesis, and induction of apoptosis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 589. doi:1538-7445.AM2012-589