Transduction of human colony-stimulating factor-1 (CSF-1) receptor into interleukin-3-dependent mouse myeloid cells induces both CSF-1-dependent and factor-independent growth.

A retroviral vector encoding the receptor for human colony-stimulating factor-1 (CSF-1) was introduced into murine myeloid FDC-P1 cells which require interleukin-3 (IL-3) for their proliferation and survival in culture. Cells expressing the CSF-1 receptor (CSF-1R), selected by fluorescence-activated cell sorting in the continued presence of murine IL-3, formed colonies in semisolid medium and were able to proliferate continuously in liquid cultures containing human recombinant CSF-1. Thus, although they do not synthesize endogenous murine CSF-1R, FDC-P1 cells express the downstream components of the CSF-1 mitogenic pathway necessary for its signal-response coupling. After receptor transduction, slowly proliferating factor-independent variants that produced neither CSF-1 nor growth factors able to support the proliferation of parental FDC-P1 cells also arose. When the human CSF-1R was expressed in FDC-P1 cells under the control of an inducible metallothionein promoter, the frequencies of both CSF-1-responsive and factor-independent variants increased after heavy-metal treatment. In addition, a monoclonal antibody to human CSF-1R arrested colony formation by both the CSF-1-dependent and factor-independent cells but did not affect their growth in response to IL-3. Therefore, the induction of both the CSF-1-dependent and factor-independent phenotypes depended on expression of the transduced human CSF-1R.