Increased blood levels of human S100 in melanoma chick embryo xenografts' circulation

The chorioallantoic membrane (CAM) of the fertilized egg allows grafting of human melanomas for short-term investigations and offers the opportunity t o investigate the behavior of metastasizing cells and the release of S100 b eta into peripheral blood. Tissue from one primary melanoma as well as cuta neous and subcutaneous metastases of 10 melanoma patients with elevated lev els of S100 in the peripheral blood before surgery were transplanted onto t he CAM of chick embryos at day 5/6 of development. Grafts were nourished by the host blood supply 2 days after transplantation. Histologically, 3 days after grafting, metastasizing melanoma cells could be found near the vesse ls of the host membrane, penetrating the endothelial layer and entering the blood system. Growth conditions remained stable for 6 days after transplan tation. Blood samples were taken from a larger CAM vessel before collecting the xenografts 5 days after grafting, Measurement of human S100 in periphe ral blood was performed in a blinded manner. No negative control shelved el evated levels of human S100 protein. Samples deriving from melanoma xenogra fts contained highly elevated levels of S100 protein in 80% of cases. The d ata strongly support the concept of graft-host interaction concerning adher ence of tumors and extravasation of human melanoma cells.