Banding karyotype analysis of murine leukemia L1210 cell lines with special regard to changes associated with a shift from in vivo to in vitro growth.

An attempt was made to establish permanent in vitro cultures of L1210 leukemia cells under close chromosome control. The investigations involved three independent adaptations. The karyotype was analyzed by the G-banding method. Chromosome analysis of the in vitro cell populations was carried out as soon as they could be analyzed, i.e. immediately after they obtained stable growth in the culture. By comparing the karyotype of the in vivo parental cell line with that of the derivative sublines in vitro, it was found that only some karyotypic variants present in the heterogeneous original population in vivo were able to produce cell lineages. In some cases rapid overgrowth of the cell populations by newly formed karyotypic variants was observed. In all independently obtained sublines changes in the karyotype involved the same chromosomes, thus suggesting that these changes were non-random for the process of cell line establishment in the system investigated. The observed changes in the number of copies of chromosomes 9 and 15 in the cells from the culture seem to indicate that the ratio of the genes localized in these chromosomes may be important for the growth in perpetuation of the cells.