Spontaneous Neoplastia Evolution of Chinese Hamster Cells in Culture: Multistep Progression of Karyotype1

Chromosomes from successive passages of a Chinese ham ster cell strain (WCHE/5) that spontaneously progressed from a euploid primary cell culture to a heteroploid tumorigenic cell line were isolated and analyzed by Giemsa banding and high-reso lution flow karyotype analysis. The frequency and identification of aneuploid and marker chromosomes were determined at both preand postcrisis culture stages and preand posttumorigenic stages. The combination of Giemsa banding and flow karyotypes provided detailed analysis of karyotype instability at each stage of cell culture progression. Aneuploidy (trisomy of chromosome 5) preceded the appearance of tumorigenicity in nude mice as well as In vitro indicators of neoplasia. The four stages of neoplastic progression defined in the previous paper correlated with a steady progression in karyotypic instability, including, in sequence: trisomy of chromosome 5; an 8q marker chromo some; a 3q+ insertion; and trisomy of chromosome 8. Additional changes continued to appear as the cells acquired classical properties of in vitro transformation.