In vitro differentiation of Rauscher-virus-induced myeloid leukemia cells

Three cell lines were established in vitro from myeloid leukemias of C57Bl/6 strain mice which had been inoculated with Rauscher virus at birth. The use of heated conditioned medium from peritoneum proved helpful for the initial growth of leukemic cells. At early in vitro passage levels, cell line R433 differentiated only to macrophages after contact with conditioned medium from peritoneum but it appeared to have lost the ability to differentiate during an extended period of cultivation. Cell line R448 was cytologically promyelocyte. When exposed to conditioned medium, this cell line differentiated only to neutrophilic granulocytes. Cell line R453 maintained the ability to differentiate either to neutrophilic granylocytes or to macrophages. Single cells recloned three times still gave rise to both types of mature cells containing conditioned medium. Occasional cases of "spontaneous" differentiation in clonal lines of R453 also occurred.