1500 biopsies of metastases have been obtained from breast cancer patients. These biopsies were collected in the context of eight prospective clinical trials. DNA is available for all patients. We will perform whole exome sequencing in 1000 samples (250 already sequenced). We will then perform targeted sequencing in the bulk of 200 matched primary tumors, and multiregion sequencing in 20 matched primary tumors. Finally, we will perform RNA-seq in 500 tumors in order to validate expression of variants, identify new translocations and derive predictors for mTOR/CDK4 inhibitors.