Metastatic clones selected from an RSV-induced mouse sarcoma share a common marker chromosome

Previous work has shown that the metastatic potential of RSV-transformed fibroblasts is correlated with the ability to form colonies in 0.6% ('hard') agar. Metastatic subclones were selected by this property from the non-metastasizing fibrosarcoma B77-313 line. A marker chromosome was found at high frequency (90% of cells) in all the subclones studied. This marker was detectable in only 0.5% of the parental B77-3T3 cells, demonstrating that metastatic clone precursors pre-existed, as a small minority, in the parental line. The genotypic marker appeared to be steadily associated with the metastatic phenotype since, after prolonged in vitro propagation, the subclones retained both the marker chromosome and the high metastatic potential. Although the marker chromosome was constantly present, chromosomal numerical and structural aberrations were also found in 20% of the long-term-propagated subclone cells, supporting the suggestion that metastatic properties are associated with cytogenetic instability.