Modulation of IFN-gamma production by TNF-alpha in macrophages from the tumor environment: significance as an angiogenic switch.
BACKGROUND
The role of macrophages in tumor angiogenesis has been known to influence in the production of angiogenic cytokines and growth factors including TNF-alpha. Recently, macrophages were also found to produce INF-gamma, which were found to be involved in angiogenic inhibition. Thus, the importance of macrophages in tumor angiogenesis might be the angiogenic switch. The hypothesis tested here is that TNF-alpha can modulate the INF-gamma production in macrophages in tumor environment as part of the tumor angiogenic switch.


METHODS
Macrophages in tumor environment were obtained from peritoneal cavity and s.c. grown tumor of C57BL/6 mice injected with B16F10 melanoma cell line for 6 and 11 days, respectively. Mac1+-macrophages were purified using magnetic beads (MACs; Milteny Biotech, Germany) and cultured with various concentrations of TNF-alpha at various time points at 37 degrees C. The supernatants were analyzed for IFN-gamma or VEGF by ELISA kit.


RESULTS
Residential macrophages from peritoneal cavity did not respond to LPS or TNF-alpha to produce INF-gamma. However, the cells from tumor environment produced IFN-gamma as well as VEGF. Upregulation of IFN-gamma production by the addition of LPS or TNF-alpha was observed in macrophages from the tumor bearing peritoneal cavity. RT-PCR analysis revealed external TNF-alpha-induced IFN-gamma gene expression in macrophages from tumor environment.


CONCLUSIONS
The overall data suggest that the macrophages in tumor environment might play an important role not only in angiogenic signal but also in anti-angiogenic signal by producing related cytokines. Moreover, TNF-alpha might be a key cytokine functioning as a tumor angiogenic switch.
Lee
Hyunah
H
The Cancer Center, Samsung Medical Center, School of Medicine, Sungkyunkwan University, 50 IL-Won Dong, Kang-Nam Gu, 135-710, Seoul, Korea. hlee@smc.samsung.co.kr
Baek
Soyoung
S
Joe
Sung-Jun
SJ
Pyo
Suhk-Neung
SN
D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D005260:Female; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000096:biosynthesis* / Q000235:genetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000187:drug effects* / Q000276:immunology*; D008546:Melanoma, Experimental / Q000098:blood supply* / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D009389:Neovascularization, Pathologic / Q000209:etiology* / Q000276:immunology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000494:pharmacology*; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis
D008070:Lipopolysaccharides; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D014409:Tumor Necrosis Factor-alpha; D042461:Vascular Endothelial Growth Factor A; D007371:Interferon-gamma