New genetic mechanism has been identified linking diet to breast cancer

Experiments carried out by scientists at the Universitat Autònoma de Barcelona on experimentally induced breast cancer tumours in laboratory rats show that an excess of certain fats in the diet, commonly known as omega-6, accelerates breast cancer, increasing the malignancy of the disease.

The research team at the Departament de Biologia Celular, de Fisiologia i d'Immunologia of the Universitat Autònoma de Barcelona has identified four genes, one which has a completely unknown function, whose expression may be involved in this effect caused by dietary lipids. More extensive research into these genes is required to discover whether the mechanism discovered works in the same way in human breast cancer. The authors of the study emphasise the importance of a moderate consumption of fats although some of them, such as blue fish and olive oils, have been shown to be beneficial to health. These oils are common elements in the Mediterranean diet.

Breast cancer is the most frequent form of cancer in women around the world. The fact that this cancer is more frequent in the developed world suggests that life style and environmental factors may be involved. Nutritional factors are particularly important, given people's continual exposure through dietary habits. Among them, dietary fats are the main element involved in breast cancer. Fats do not cause cancer, however some of them, such as animal fats or certain vegetable fats, accelerate the clinical development of the disease, while blue fish and olive oil appear to delay its development.

A research team headed by Dr. Eduard Escrich, lecturer in the Departament de Biologia Celular, de Fisiologia i d'Immunologia at the UAB and head of the Grup Multidisciplinari per a l'Estudi del Càncer de Mama (Multi-disciplinary group on Breast Cancer Studies) has established a specific mechanism by which some of these fats favour the development of breast cancer. According to research, diets rich in the polyunsaturated fatty acids n-6 reduce the expression of a group of four genes, three of which are related to cellular differentiation (a-2u-globulin, VDUP1 and H19) and the fourth of which is a sequence with a totally unknown function (known as EST Rn.32385), thereby accelerating the proliferation of tumours.

The scientists have reached these conclusions from results, obtained using microarrays, that compare the expression of 6,000 genes in breast cancer tumours in animals fed with n-6 fat-rich diets and in animals with low-fat diets. The tumours in the rats with the fat-rich diets proliferated, on average, more than the others, apparently associated with a lesser expression of the four genes. According to the UAB researchers, in an article published in Molecular Carcinogenesis, "this is the first time that the influence of a fat-rich diet on the expression of these genes has been investigated. The discovery opens a new line of research into its implication in changes on the state of cellular differentiation induced by dietary lipids in breast cancer tumours and the degree of malignity of the cancer.

In general, the research carried out by the Grup Multidisciplinari per a l'Estudi del Càncer de Mama aims to establish possible activity of common elements in human diet, beyond the nutritional value, which may permit scientific opinions to be formulated on the health of the population of the risk of disease. It is therefore involved in the field of secondary and especially primary prevention of breast cancer.