The present study was designed to study the effect of
dietary fat intake on the modulation of dimethylbenz[a]
anthracene (DMBA)-induced mammary
carcinogenesis in rats injected with the
methanol extract residue of Bacillus Calmette-Guerin (
MER-BCG). Rats were maintained on either a 5% or a 20%
corn oil diet for the entire duration of the experiment. When
MER-BCG was administered 2 and 3 weeks before DMBA, mammary
tumorigenesis was suppressed in the 2 dietary groups with different levels of fat intake. This was in contrast to when
MER-BCG was administered 3 and 5 weeks after DMBA; in this case the development of mammary
tumors was noticeably enhanced regardless of the fat intake of the host. The magnitude of inhibition or increase by
MER-BCG was similar in animals fed either fat level, although a high fat diet consistently stimulated mammary
tumorigenesis in the 2 experiments. In vitro assays on T cell
mitogen-induced blastogenesis and natural killer cell activity in splenocytes isolated from the untreated rats showed that
dietary fat failed to elicit any differential response in these immune functions.