Transfection of interferon-γ gene in a mouse bone marrow stromal preadipocyte cell line causes apoptotic cell death

It has been reported that bone marrow and serum of patients with aplastic anemia or chronic myeloproliferative disorders contain an abnormal concentration of cytokines. In the present study, we tried to isolate mouse bone marrow stromal cell lines that were stably transformed with a variety of cytokine genes and that expressed them constitutively. From mouse bone marrow stromal cell lines MBA-1, MBA-13, and 14F1.1, we isolated clones secreting interleukin-3 (IL-3), IL-4, granulocyte-macrophage colony-stimulating factor (GM-CSF), or granulocyte (G)-CSF. Interferon-γ (IFNγ)-producing stable transformants could not be established from 14F1.1 cells in spite of repeated transfection trials. At early stages of transfection, 14F1.1 cells did secrete IFN-γ; however, exogenously added mouse IFN-γ could not inhibit 14F1.1 cell growth. We discovered that chromosomal DNA isolated from 14F1.1 after transfection with the mouse IFN-γ gene was fragmented. This is characteristic of cells undergoing apoptotic cell death. DNA fragmentation was also observed in 14F1.1 cells transfected with the human IFN-γ gene. These results indicate that intracellular IFN-γ induces apoptotic cell death of 14F1.1 stromal cells.