The stimulating effect of a high-fat n-6 polyunsaturated diet on rat DMBA-induced mammary tumors is not related to changes in c-Ha-rasl mRNA tumor expression

The aim of this study was to investigate if the modulation of the tumor c-Ha-ras1 mRNA expression may be one of the mechanisms implicated in the effect of the dietary n-6 polyunsaturated lipids on experimental mammary carcinogenesis. Sprague-Dawley rats were treated with dimethylbenz(alpha )anduacene and fed a low-fat or high-fat com oil diet following an initiation-promotion experimental design. Results showed a shorter latency and significantly higher incidence of affected animals, total tumor yield and total tumor volume in groups of rats fed the high-fat diet than in the control low-fat diet group. This stimulating effect on mammary carcinogenesis, which was produced above all on the promotion stage, did not result in a modification of the tumor c-Ha-ras1 mRNA levels. Moreover, c-Ha-ras1 was not amplified in these experimental mammary tumors. These results do not discard the possible implication of this gene, and suggest that dietary fat may act on c-Ha-ras1 at a different level, maybe on protein function. (C) 2001 Elsevier Science Inc. All rights reserved.