In vitro lines of the BN rat promyelocytic leukemia that differ from the parent

Cells from the spleens of Brown Norway rats made leukemic with the in vivo-passaged promyelocytic line BNML have been adapted to in vitro culture in RPMI-1640 medium supplemented with 4% rat serum and 6% fetal bovine serum. The presence of rat serum, which also was associated with suppression of fibroblasts, appeared to be required for initial growth. In contrast to the parent this new cell line (BNML-RS) was predominantly myeloblastic under standard conditions of culture with only 4-10% of cells showing granules or stainable peroxidase. However, when passaged through an animal, 60-70% contained both granules and peroxidase. Neither parent nor established line evolved to the polymorph stage when assessed for terminal maturation after exposure to dimethyl sulfoxide or retinoic acid. These cells now extend the limited number of myeloid lines available and potentially are a useful model in which to study the controlling events in early myeloblast maturation.