We seek to reach a more fundamental understanding of the biological dynamics of breast cancer. High-throughput molecular data at multiple levels (eg DNA, mRNA, miRNA and protein level) have become available on increasing numbers of patients, and various m olecular profiles have been associated with tumor aggressiveness, response to therapy and patient outcome. Still, it is very rare that all or most analyses are performed on the same patient material. In this project we will use 4 sample sets (Oslo I,II,II I, MDG/NOWAC) and obtain molecular profiles at all levels. This will facilitate identification of risk factors, search for novel diagnostic markers, prediction of therapeutic effects and prognosis as well as identification of new targets for therapy. Thi s is a very ambitious project, but with the existing and ongoing collection of high quality patient materials in Norway with a genetically homogeneous population, the very high participation rate of Norwegian women, the high quality clinical data and the expertise in molecular and statistical analyses combined in this project, we are confident that we will be able to advance and translate our knowledge into improvement of patient care. The project is part of a larger collaborative BC program between Radiu mhospitalet, Ulleval and Akershus University Hospitals, as well the MR-center at NTNU/Trondheim University Hospital. Systematic studies performed at the cellular, genomic, and population levels, will be analyzed in an integrative manner in conjunction wit h epidemiological and clinical data. By bringing together several strong research teams that jointly cover a broad area of expertise; we have created an interdisciplinary BC research unit of high worldwide reputation. Only with joint forces will we be abl e to achieve sample numbers which eventually will lead to universally valid markers that can be used for the benefit of the patient.