The induction of lymphokine synthesis and cell growth in IL 3-dependent cell lines using antigen-antibody complexes.

Several IL 3-dependent murine bone marrow-derived cell lines can be stimulated to grow with antigen-antibody (Ag.Ab) complexes. The Ag.Ab complexes induced lymphokine gene expression and the synthesis of IL 2, GM-CSF, IL 3, and BSF-1 (IL 4). The lymphokines produced by these IL 3-dependent cells appeared to stimulate their own growth, as both IL 3 and BSF-1 (IL 4) stimulated the growth of IL 3-dependent cells. Ag.Ab complexes also stimulate the growth of primary cultures of bone marrow cells that have been previously activated with IL 3. Normal bone marrow, IL 2-, and GM-CSF-dependent bone marrow cell lines could bind Ag.Ab complexes, but binding did not result in the induction of lymphokine synthesis or cell growth. Hyperimmune serum from mice also stimulated lymphokine synthesis and cell growth in IL 3-dependent cells, and the stimulatory activity was removed by treatment with Staphylococcus aureus protein A, suggesting the presence of Ag.Ab complexes.

Expression of genes in cloned murine cell lines that can be maintained in both interleukin 2- and interleukin 3-dependent growth states.

Two cloned murine cell lines, FD.C/1 and 32Dcl-23 exhibit switching of lymphokine-dependent growth states. The bone marrow-derived FD.C/1 and 32Dcl-23 cell lines are normally grown in culture medium supplemented with interleukin 3 (IL3). The replacement of IL3 with interleukin 2 (IL2) in the medium results in an increase in IL2 receptor expression in FD.C/1 and 32Dcl-23 cells and the switching of cells to an IL2-dependent growth state. We have compared patterns of protein and phosphoprotein synthesis, as well as the expression of the c-abl, c-ras, c-myb, and c-fos oncogenes in these cell lines maintained in IL3- and IL2-dependent growth states. The synthesis of a series of proteins and phosphoproteins are identified with each of the lymphokine-dependent growth states. All of the oncogenes examined are expressed in both IL2- and IL3-dependent cells and are not altered by phenotypic changes in lymphokine growth dependence. The relationship of oncogene expression to intracellular pathways regulated by lymphokine-receptor interactions is considered.

Interleukin 2 regulates the expression of IL 2 receptors on interleukin 3-dependent bone marrow-derived cell lines.

Two IL 3-dependent bone marrow-derived cell lines, FD.C/1 and 32Dcl-23, have been converted to IL 2-dependent growth states. In the case of the FD.C/1 cell line, a small subpopulation of cells converted to IL 2 growth dependence, whereas for the 32Dcl-23 cell line, most cells readily converted to IL 2 growth dependence. IL 2 receptor expression was followed in FD.C/1 and 32Dcl-23 cells in both IL 3-and IL 2-dependent growth states, by analyzing transcription of IL 2 receptor-specific RNA and the subsequent expression of cell surface receptors. The exposure of IL 3-dependent cell lines to IL 2 resulted in rapid increases in the transcription of IL 2 receptor-specific RNA and receptor expression. The addition of IL 3 to IL 2-dependent cell lines did not alter the expression of the IL 2 receptor. When IL 2 was removed from the culture medium of these cells, the presence of IL 3 maintained a higher level of IL 2 receptor expression than was observed in the absence of lymphokines.

Cyclic AMP and c-myc gene expression in PY815 mouse mastocytoma cells.

The possibility was examined that inhibition of growth of PY815 mouse mastocytoma cells by N6,O2'-dibutyryladenosine 3',5'-cyclic monophosphate (DB cyclic AMP) results from inhibition of c-myc gene expression. Temporary increases in c-myc RNA which occurred soon after DB cyclic AMP treatment and upon removal of the drug were not consistent with direct inhibition of c-myc gene expression by DB cyclic AMP. The increases in c-myc RNA coincided with the passage through, or accumulation of cells in late G1-early S phase. It is proposed that cyclic AMP may stimulate c-myc gene expression which normally occurs only in late G1-early S phase in PY815 cells and that cyclic AMP prevents c-myc expression in cells at other phases of the cell cycle by inhibiting their progression past a cyclic AMP-sensitive restriction point in early G1 phase.