High Intake of Maternal Milk Prevents the Development of Mammary Cancer in Pups Maintaining Elevated Ingestion of Saturated Fat

Abstract

Environmental factors in early life have a strong implication on the development of diseases in adult life. Nutritional changes during perinatal life can modify the susceptibility to develop breast carcinoma. In this report, we studied the influence of a diet high in saturated fat in the development of breast cancer, in rats that maintained a differential milk intake during their lactation period. We also analysed the possible mechanisms involved in tumor development. We compared mammary carcinogenesis in Sprague-Dawley adult rats, grown-up in litters of 3 (L3) or 8 (L8) pups per mother during lactation to induce a differential consumption of maternal milk. After weaning all pups were fed with a diet high in saturated fat “HF” (40% of energy from lipids) until adulthood. At 55 days of age, the animals were treated with a single dose of dimethylbenzanthracene to study tumor latency, incidence and progression. Histological and immunohistochemical studies were performed. We observed that animals that maintained high milk intake (L3) had lower mammary cancer incidence than animals that maintained lower milk consumption (L8; P <0.05) when exposed to a HF diet. Tumor latency and rate of tumor growth did not show variations between the groups. However, the mitotic index (P< 0.05) and the expression of CD1 were significantly lower, in tumors of L3 respect to L8 (P <0.01). Animals with greater consumption of breast milk develop tumors that proliferate less and tend to have a more pronounced apoptotic process, although when maintaining a high consumption of saturated fat. These results may explain, in part, the lower incidence observed in this group of animals. Our work reflects the importance of lactation during postnatal life in the prevention of breast cancer, despite other nutritional factors that may act as promoters of tumor development throughout life, such as the consumption of saturated fat.