Mammary gland biology and breast cancer

The EMBO Molecular Medicine Conference on Common Molecular Mechanisms of Mammary Gland Development and Breast Cancer Progression was held jointly with a meeting of the COST B20 (European cooperation in the field of scientific and technical research)—a group of about 35 scientists from 23 European countries who have been meeting regularly during the past five years to discuss questions about mammary gland development, function and cancer. Introduction As a model system for biological investigations, the mouse mammary gland is as versatile as the Drosophila eye. This comparison does not reflect any ignorance of comparative anatomy, but rather it highlights the multitude of possibilities that the mammary gland offers to experimental biologists. The mammary gland has many unique developmental features: it goes through embryonal, puberty, pregnancy, lactation and post-lactation phases, and many of the genetic determinants that regulate cell specification, proliferation, differentiation, survival and death have been studied in great detail. Growth, differentiation and regression of the mammary epithelial cells occur repeatedly in the adult organism. Each cycle of pregnancy, lactation and involution is accompanied by massive cellular proliferation, functional differentiation and cell death. These developmental stages are regulated by epithelial stromal cell interactions, and by systemically and locally acting steroid and peptide hormones (Hennighausen & Robinson, 2005). Genetic analyses can be carried out using tissue-specific knockout mice, or genetically mofified primary cells can be transplanted into fat pads cleared of endogenous epithelium. These experimental strategies have been recently complemented by the isolation and genetic manipulation of adult mammary stem cells. The basic scientific aspects of mammary gland biology are not only fascinating but also central to our understanding of breast cancer, which is at present the most common cancer in women in the Western world. Extensive research is underway to being carried out the basic biology of the mammary gland and to use this information in the fight against the disease.