Clonal origin of metastasis in B16 murine melanoma: a cytogenetic study.

A cell line isolated from the B16 melanoma and carried in continuous culture for 8 years (the parent line) exhibited great heterogeneity in terms of marker chromosome content. A lung metastasis from a C57BL/6 mouse inoculated im with cells of this line showed karyotypic homogeneity. Inoculation iv of cells from the parent line produced numerous tumor foci in various organs. Cytogenetic analyses of 18 such lesions led to the following conclusions: Cells from each metastatic colony exhibited relatively homogeneous karyotypic characteristics, indicating that metastases are of clonal origin; many parental cells with different marker chromosomes had metastatic potential; and some genomes maintained homogeneity longer than others.