Multiple Cytokines Inhibit Interleukin-6-Dependent Murine Hybridoma/Plasmacytoma Proliferation

Abstract

A panel of cytokines was tested for inhibitors of interleukin-6 (IL-6)-dependent cell proliferation. Murine type I and II interferons (mIFNs) strongly inhibited proliferation of IL-6-dependent B9 and 7TD1 cells in a dose-dependent manner. Human tumor necrosis factor-α (hTNF-α) and human transforming growth factor-β (hTGF-β) potently inhibited B9 and to a lesser extent 7TD1 cells, while hIL-11, human oncostatin M (hOSM), and human leukemia inhibitory factor (hLIF) had no inhibitory effects on IL-6-dependent growth. Conversely, IL-11 and OSM but not LIF stimulated B9 and 7TD1 cell growth. However, compared with IL-6, up to 1000-fold higher IL-11 and OSM concentrations were required to induce maximal cell proliferation. Increasing concentrations of IL-6 (up to 100 ng/ml) could not overcome the antiproliferative effects of mIFNs, hTNF-α, and hTGF-β. Supernatants from mIFN-γ and lipopolysaccharide (LPS)-treated mouse macrophages (ANA-1 cell line) were tested in B9 cell assays to identify cytokines among stimulatory and inhibitory biological activities that can inhibit IL-6-dependent proliferation. Undiluted or relatively concentrated supernatants from ANA-1 macrophages treated with mIFN-γ and/or LPS did not contain detectable IL-6 bioactivity. However, diluted samples contained considerable amounts of detectable IL-6 bioactivity (nanogram levels). Testing the same samples for IL-6 immunoreactivity using enzyme-linked immunoabsorbent assay revealed comparable levels of mIL-6. We conclude that IFNs, TNF-α, and TGF-β and possibly other factors are potent, dominant inhibitors of IL-6-dependent plasmacytoma/hybridoma growthin vitro.