Mouse parenchymal liver cells in culture secrete a growth inhibitor for myeloma cells

: Growth inhibitory activity in the conditioned medium of mouse parenchymal liver cells was examined in three strains of myeloma cells. Results: Two strains of myeloma cells were highly sensitive to a low concentration of mouse parenchymal liver cell derived growth inhibitor, whereas one strain was resistant to the same concentration. Interfero-αβ and transforming growth factor-β activity were detected in mouse parenchymal liver cells, while interferon-γ and tumor necrosis factor-α were not. The growth suppresion exerted by mouse parenchymal liver cell derived growth inhibitor in the three myeloma strains was distinct from that exerted by transforming growth factor-β, tumor necrosis factor-α, interferon-αβ and interferon-γ. The mouse parenchymal liver cell derived growth inhibitor was eluted with a peak activity in the 18 kDa range and focused into pI values of 3.8–4.0, and it was lost when mouse parenchymal liver cells were treated with heat or trypsin. Conclusion: These results indicate that mouse parenchymal liver cell derived growth inhibitor differs from the well-characterized growth inhibitors, transforming growth factor-β, tumor necrosis factor-α, interferon-αβ and interferon-γ.