Liver metastasis of a human colorectal cancer containing two actively growing subclones.

A common pattern of karyotype evolution between clones involves gradual changes of one or only a few chromosomes. Karyotypes of one day-old cultures derived from a tumor nodule of colorectal cancer liver metastasis were studied by GTG chromosome banding. Two karyotypically distinct aneuploid CC-9-a and CC-9-b clones were found respectively, at about 1:3 ratio. Both clones showed common karyotype characteristics with the same number of copies for 13 normal and four marker chromosomes, indicating their common genetic origin. However, CC-9-b differed from CC-9-a by the loss of one copy each of eight normal and four common marker chromosomes. This mode of gross single-chromosome losses is also seen in established cell lines, and probably plays an important role in the drastic chromosome changes associated with the duplication-reduction cycle of karyotype evolution.