Initiation of deregulated growth of multipotent progenitor cells by bcr-abl in vitro.

Expression of the bcr-abl oncogene in multipotent progenitor cells (MPPCs) is implicated as a key event in the development of chronic myelogenous leukemia. Bone marrow enriched for MPPCs was infected with a retrovirus that carried bcr-abl. The mixed-lineage colonies that resulted were responsive to growth factors and could differentiate. These cells later became growth factor-independent but, when injected into severe combined immunodeficient mice, were not leukemogenic. Thus, the presence of bcr-abl alone does not cause growth factor independence, although it initiates a stepwise process. This system may prove useful in the study of other oncogenes that cause leukemia.