Inhibition of tumor cell mitochondrial respiration by macrophage cytotoxic mediators distinct from interferon-gamma.
Macrophage-mediated inhibition of mitochondrial respiration in EMT-6 murine mammary adenocarcinoma cells can be mimicked in vitro by treatment of the cells with interferon-gamma (IFN-gamma) in combination with tumor necrosis factor, interleukin-1, or lipopolysaccharide. Conditioned supernatants obtained from activated macrophages appear to contain interferon-gamma, suggesting that inhibition of mitochondrial respiration in tumor cells was caused by synergy of IFN-gamma with other cytokines. To further characterize monokines that cause inhibition of mitochondrial respiration in tumor cells, EA13.5 macrophage-like cells were isolated and selected for inhibition of mitochondrial respiration in EMT-6 tumor cells. After stimulation with IFN-gamma and lipopolysaccharide, the EA13.5 cells released into conditioned supernatants a cytotoxic mediator that induced nitric oxide synthesis and caused lesions in the electron transport chain of EMT-6 cells similar to the lesions caused by activated peritoneal macrophages. Enzyme-linked immunosorbent assay demonstrated that the conditioned supernatants produced by EA13.5 macrophage cells did not contain IFN-gamma. Treatment of the EA13.5 cell-conditioned supernatants with neutralizing antibody against IFN-gamma did not abrogate the inhibition of mitochondrial respiration in EMT-6 cells caused by these conditioned supernatants. This study demonstrated that unidentified macrophage cytotoxic mediators distinct from IFN-gamma are involved in the induction of nitric oxide synthesis and inhibition of mitochondrial respiration in tumor cells.
Tucker
S D
SD
Department of Medical Oncology, University of Texas M. D. Anderson Cancer Center, Houston 77030.
Auzenne
E J
EJ
Sivaramakrishnan
M R
MR
D000230:Adenocarcinoma; D000818:Animals; D000968:Antimycin A / Q000494:pharmacology; D002460:Cell Line; D017077:Culture Media, Conditioned; D016207:Cytokines / Q000494:pharmacology / Q000502:physiology*; D007371:Interferon-gamma / Q000494:pharmacology*; D007375:Interleukin-1 / Q000494:pharmacology; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000502:physiology*; D008325:Mammary Neoplasms, Experimental; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects; D012402:Rotenone / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D017077:Culture Media, Conditioned; D016207:Cytokines; D007375:Interleukin-1; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D012402:Rotenone; D000968:Antimycin A; D007371:Interferon-gamma