Establishment and chromosome studies of in vitro lines of chemically induced rat erythroblastic leukemia cells.

Eight cultured lines with a normal diploid karyotype, no. 2 trisomy, and markers involving chromosome No. 2 were established from three 7,12-dimethylbenz[a]anthracene (DMBA)- and two N-butyl-N-nitrosourea (BNU)-induced erythroblastic leukemias in noninbred Long-Evans rats. Serial in vivo and in vitro passage of these cells frequently evoked karyotype changes in stemline cells. In both lines from DMBA- and BNU-induced leukemias, ordinary and translocation no. 2 trisomy cells appeared and gradually replaced the normal diploid stemline cells. Obvious secondary karyotypic changes were also recognized in the "cloned" leukemia cells. Nucleolar chromosomes such as chromosomes no. 3 and no. 12 were frequently involved in aneuploidy and translocation. One cell line from a BNU-induced leukemia did not change its normal diploid karyotype during 12 months of in vitro passage. The above preferential growth of cells with no. 2 trisomy and the related changes during in vivo and in vitro passage as well as in-colony formation in soft agar suggest that these chromosome changes are somehow associated with the growth behavior of the leukemia cells. No positive correlation was demonstrated between karyotype and dimethyl sulfoxide-induced erythroid differentiation of the leukemia cells.