Establishment of cancer metastases is “successful” only if premetastatic niches are prepared in certain organs. Exosomes derived from cancer cells, are presumed to contribute to this process. In this project the biogenesis of exosomes is studied, and transgenic animals will be applied. Last but not least, exosome markers will be traced in organs (lymph nodes, bone marrow, lung) from cancer patients, as predictive markers.