beta-Ionone demonstrates potent anticancer activity both in vitro and in vivo. We determined
tumor incidence and the number of rats bearing
tumors as well as cell proliferation and apoptosis in a rat
mammary cancer model induced by 7, 12-dimethylbenz[a]
anthracene (DMBA). Rats were fed an AIN-76A diet containing
beta-ionone (0, 9, 18 or 36 mmol/kg), starting 2 weeks before DMBA administration and continuing for 24 weeks. A dose-dependent inhibition of mammary
carcinogenesis by dietary
beta-ionone was observed. Corresponding
tumor incidence values were 82.1, 53.3, 25.9 and 10.0% (p < 0.01 or 0.05). Time to
tumor appearance increased and
tumor multiplicity decreased with increasing dietary
beta-ionone. Histopathological and immunohistochemical evaluations of
tumors were performed on the 64, 31, 15 and 3
tumors, respectively, identified in rats from the respective groups of 30. The proportions of
adenocarcinomas,
adenomas and benign masses were equally distributed in the latter group. In proportions within the other groups, the proportions of
adenocarcinomas and benign masses decreased and increased with increasing dietary
beta-ionone.
Proliferating cell nuclear antigen (
PCNA),
cyclin D1 and Bcl-2 expression decreased, and Bax expression and nuclear fragmentation increased with increasing dietary
beta-ionone. These results demonstrate the potent capacity of dietary
beta-ionone to suppress DMBA-initiated
mammary cancer in rats.