HER2 positive (HER2+) breast cancer overexpresses the HER2/neu gene. There are a few foods and spices that have been shown to be especially potent in inhibiting HER2+ breast cancer growth and proliferation. Extra-virgin olive oil (with a high omega-9 fat content) appears to be especially beneficial in preventing HER2+ breast cancer and inhibiting its progression. In addition, a relatively high dietary omega-3 to omega-6 fat ratio in the diet has been shown to be associated with reduced risk of HER2+ disease. Now a new study has reported that fish oil inhibits early stages of mammary tumor development in a mouse model of HER-2/neu overexpressing breast cancer.

Foods with significant omega-3 content

The following foods have been shown to be associated with reduced breast cancer risk as well as being good sources of omega-3 fats:

Canola oil
Flaxseed oil
Herring
Mackerel
Salmon, wild
Sardines
Walnuts and walnut oil

Fish oil inhibits early stages of HER-2/neu mammary tumor development

The study referenced at the beginning of this news article was designed to investigate whether dietary omega-3 fats influence the earliest stages of HER2+ breast cancer development. The authors demonstrated in a previous study that lifelong feeding of diets enriched with the marine omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) inhibited mammary tumor development in a mouse model of HER2+ breast cancer. To conduct the present study, the authors again used MMTV-HER-2/neu transgenic mice, which spontaneously develop HER2+ mammary tumors.

At age seven weeks, the mice were divided into equal groups that were fed either a fish oil- or corn oil-based diet (25% of calories). The animals' mammary glands were evaluated at ages 25, 30, and 35 weeks for atypical ductal hyperplasia, cell proliferation, and cyclooxygenase-2 gene (COX-2) expression. Mice fed the fish oil-enriched diet were found to have significantly lower atypia grades and an eightfold lower percentage of proliferation (as measured by Ki-67 expression) compared to mice fed corn oil. COX-2 expression was also lower in the fish oil group. The authors conclude that dietary fish oil inhibits atypical ductal hyperplasia at early stages of HER-2/neu-mediated mammary tumor development compared to corn oil. This histologic effect is associated with lower COX-2 expression and mammary epithelial cell proliferation.

Please see our article on breast cancer diet for HER2+ patients and survivors for more information.