Spontaneous in vitro neoplastic evolution: selection of specific karyotypes in Chinese hamster cells.

Recurrent cytogenetic changes occurred reproducibly in vitro during the spontaneous neoplastic evolution of cultured Chinese hamster cells. In particular, excess 3q material appeared shortly after immortalization in numerous independent trials. By contrast, when clones were isolated at the earliest possible time after immortalization, a wide spectrum of types of cytogenetic evolution followed, which also resulted in transformed and tumorigenic cells. Clones with stable distinct colonial morphologies were used to demonstrate growth rate interactions when subpopulations compete. We conclude that specific recurring karyotypes are associated with specific stem lines with transient growth advantage during the early stages of in vitro carcinogenesis. Stem lines with other karyotypic change or no detectable karyotypic change are almost equally capable of undergoing the entire spontaneous neoplastic process in vitro.