We have previously shown that in interspecific mouse-human melanoma cell hybrids obtained by fusion of nonmetastatic mouse with metastatic human melanoma cells, the metastatic phenotype predominates. The purpose of this study was to identify human chromosome(s) which could be responsible for conferring metastatic potential upon nonmetastatic mouse melanoma cells and therefore harbor the genes important for the metastatic properties of human melanoma cells. Seven mouse-human melanoma hybrids were examined; five were derived from the fusion of nonmetastatic (C19) and metastatic (C3) mouse K-1735 melanoma clones with highly metastatic clone (C15) of human melanoma A375 and the two others had as a human partner a nonmetastatic clone (Cls) of the A375 melanoma. The hybrids were examined during segregation of human chromosomes in vitro and in vivo for metastatic properties in nude mice and for the retaining human chromosomes. In the hybrid H7, which demonstrated the highest metastatic potential, the presence of human chromosomes was studied by GTG-banding and by fluorescence in situ hybridization (FISH) analysis. In the other hybrids, only FISH detection of human chromosomes was applied. All hybrids derived from nonmetastatic mouse and metastatic human melanoma cells demonstrated metastatic properties from early passages, when they contained the majority of the human chromosomes. Their metastatic phenotype remained stable during further segregation of most of the human chromosomes except for 17. Chromosome 17 was retained most consistently in all examined hybrids. However, the metastatic phenotype of the hybrids was associated only with the presence of chromosome 17 from the metastatic human donor cells. This chromosome was also found in almost 100% of cells recovered from lung metastases derived from the hybrid cells. In one lung metastasis developed from the H7 hybrid, chromosome 17 was detected as the sole human chromosome and these cells preserved the acquired high metastatic properties. Based on these results we conclude that human chromosome 17 from metastatic melanoma cells (A375 C15), when functional in the mouse genetic background, can be sufficient to render the recipient nonmetastatic mouse cells to a fully malignant phenotype. Additional data suggest that this ability might be related to the expression of the mutated human p53 gene.

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