| Abstract: | The normal cellular counterpart of the v-fms oncogene product is a receptor for the mononuclear phagocyte colony-stimulating factor, CSF-1. An interleukin-3 (IL-3)-dependent mouse myeloid cell line, FDC-P1, was infected with a murine retrovirus vector containing v-fms linked to a gene encoding resistance to neomycin (neo). Infected cells selected for resistance to the aminoglycoside G418 contained few proviral DNA copies per haploid genome, expressed low levels of the v-fms-coded glycoprotein, remained IL-3 dependent for growth, and were nontumorigenic in nude mice. In contrast, infected cells selected for their ability to grow in the absence of IL-3 contained an increased number of proviral insertions, expressed high levels of the v-fms-coded glycoprotein, and were tumorigenic in nude mice. The IL-3-independent cells expressed IL-3 receptors of comparable number and affinity to those detected in uninfected FDC-P1 cells and did not produce a growth factor able to support replication of the parental cells. Thus, the synthesis of high levels of the v-fms gene product in FDC-P1 cells abrogated their requirement for IL-3 and rendered the cells tumorigenic by a nonautocrine mechanism. The data suggest that v-fms encodes a promiscuous tyrosine kinase able to transform cells of the myeloid lineage that do not normally express CSF-1 receptors. |
