Karyotype changes of human urinary bladder carcinoma T24 cell line were studied in the course of 5-year in vitro cultivation. It has been found that the modal number of chromosomes gradually shifted from hypotetraploidy to triploidy during long-term cultivation. The number of endoreduplications was decreasing simultaneously and minute chromosomes occurring in a number of 4--5 in early passages appeared only rarely in later passages. Using conventional Giemsa staining, persistent marker chromosomes were detected in the wild population as well as in the eight sublines derived from T24 cells by cloning. The marker chromosomes were: metacentrics, subtelocentrics, telocentrics and long acrocentrics. Occasionally, there were found dicentrics, double-minutes, breaks and pulverization. The most characteristic marker was the metacentric chromosome the length of which corresponded approximately to the arm length of the chromosome No. 1. The metacentric chromosome in a number of 1--3 was present in 100% of T24 cells of the wild population and derived sublines at all passage levels examined.
Cell Line Chromosome Aberrations