Inhibition of proliferation of retrovirus-immortalized macrophages by LPS and IFN-gamma: possible autocrine down-regulation of cell growth by induction of IL1 and TNF.
The GG2EE macrophage tumor cell line was previously established by immortalization of C3H/HeJ mouse bone marrow cells with the J2 retrovirus which contains the v-myc and v-raf oncogenes. Studies on the control of GG2EE cell proliferation in vitro have recently been performed. We observed that the combination of 5-25 U/ml recombinant mouse interferon-gamma (rmIFN-gamma) plus 0.03-0.3 micrograms/ml lipopolysaccharide (LPS) markedly inhibited the proliferation of GG2EE cells (by greater than 95%) in vitro, while either agent alone inhibited only by less than 40% and 0-10%, respectively. Subsequent studies established that biologically active IL1-like (2-4 U/ml) and TNF alpha-like (50-100 U/ml) activities were released into the supernatants of LPS-treated GG2EE cells. The combination of IFN-gamma + LPS induced more (6-8 U/ml) IL1 release. These results suggested that the inhibition of proliferation of GG2EE cells by IFN-gamma + LPS could have been mediated in part by cytokines produced by the cells themselves. rhIL1 alpha at a concentration of 10 U/ml inhibited GG2EE proliferation by 25-30%, while rmIFN-gamma (25 U/ml) + rhIL1 alpha (10 U/ml) inhibited proliferation by 98%. Thus, 10 U/ml rhIL1 alpha could completely replace LPS in the LPS + rmIFN-gamma combination. Further, the combination of low doses of rhIL1 alpha (0.1 to 1 U/ml) plus rmTNF alpha (250 U/ml), which together inhibited proliferation by less than 20% synergized with doses of 5 to 25 U/ml rmIFN-gamma to inhibit proliferation of GG2EE cells by 98-99%. These results suggest that cytokines produced by the cells themselves can synergize with rmIFN-gamma to inhibit the oncogene-driven proliferation of GG2EE cells.
Ayroldi
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Laboratory of Experimental Immunology, National Cancer Institute, Frederick Cancer Research and Development Center, Maryland 21702-1201.
Blasi
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Varesio
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Wiltrout
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RH
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002472:Cell Transformation, Viral / Q000235:genetics*; D015536:Down-Regulation / Q000502:physiology*; D007371:Interferon-gamma / Q000494:pharmacology*; D007375:Interleukin-1 / Q000096:biosynthesis* / Q000494:pharmacology; D008070:Lipopolysaccharides; D008264:Macrophages / Q000187:drug effects* / Q000473:pathology / Q000502:physiology; D051379:Mice; D008809:Mice, Inbred C3H; D011994:Recombinant Proteins; D012190:Retroviridae / Q000235:genetics*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*
D007375:Interleukin-1; D008070:Lipopolysaccharides; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma