S100 proteins are used as markers for human melanoma cells. They have been studied also in various animal models including even exotic melanomas but their biochemical characterization in B16 and CloudmanS91 murine melanomas, common models of human melanoma disease, has been still lacking. Histoimmuno chemical analysis showed its presence in B16 and S91 melanomas grown in inbred C57BL6J and DBA2 mice, respectively. The immunochemical dot-blot technique revealed that the S100 level was more than an order lower compared with human brain. S100 proteins were purified from murine melanomas and for comparison also from human brain. Disc polyacrylamide electrophoresis demonstrated the presence both of S100a and S100b subunits. Their molecular weight determined by means of SDS-PAGE was found to be 10 000 whereas the molecular weight of the whole S100 dimer (studied by gel filtration) was 21 000 and did not differ from that of S100 protein from human brain. Incubation of S100 isolated from human brain with autooxidating L-DOPA did not change its electrophoretic mobility. Polyclonal antibody against bovine brain S100 gave positive reaction with S100 proteins of murine melanomas and human brain origin. The identity of biochemical and immunological properties of the S100 proteins studied underlines the phylogenetic conservation of S100 structure and its stability even during tumour transformation.

Keywords: B16 melanoma, S100 protein, S91 melanoma