Truncation of the c-myb gene by a retroviral integration in an interleukin 3-dependent myeloid leukemia cell line

Among a series of myeloid leukemia cell lines, one (NSF-60) was found to have a rearrangement of the c-myb locus. The rearrangement involved the integration of a retro-virus into the region of the gene corresponding to the sixth exon of the avian c-myb locus. The insertion is associated with production of a truncated RNA and the introduction of a terminator codon at the juncture of the long terminal repeat and the c-myb locus. The properties of the NSF-60 cells were compared with those of other myeloid cell lines, and the known sequences of differentiation induced by interleukin 3. Similar to other myeloid cell lines, the NFS-60 cells do not terminally differentiate in response to interleukin 3, granulocyte/macrophage, or granulocyte colony-stimulating factor suggesting that the cells are transformed with regard to their ability to differentiate. The NFS-60 cells are totally dependent on interleukin 3 for growth and maintenance of viability in vitro but also proliferate in response to granulocyte colony-stimulating factor. The properties of cells support the concept that the c-myb protooncogene is involved in the control of normal differentiation of hematopoietic cells.