Leukotriene B4 creates a favorable microenvironment for murine melanoma growth.
Chronic inflammation has long been associated with neoplastic progression. Our group had recently shown that the addition of a large number of apoptotic tumor cells to the tumor microenvironment induces a potent acute inflammatory reaction capable of promoting melanoma growth; however, primarily necrotizing cells do not cause such a reaction. Here, we show that potent inflammatory agents, such as lipopolysaccharide (LPS) and carrageenan, also promote growth of subtumorigenic doses of melanoma cells, having no effect on melanoma proliferation in vitro. Inhibition of 5-lipoxygenase (5-LOX) seems to have a pivotal role in this model because caffeic acid and MK886, a FLAP (5-LOX-activating protein) inhibitor, partially hindered tumor growth induced by apoptotic cells or LPS. Other enzymes of the arachidonic acid pathway, cyclooxygenase-1 and cyclooxygenase-2, seem to have no participation in this tumor promoter effect, as the inhibitor of both enzymes (indomethacin) did not alter melanoma growth. Leukotriene B4 (LTB4), the main product of the 5-LOX pathway, was able to induce growth of subtumorigenic inocula of melanoma cells, and a LTB4 receptor antagonist inhibited acute inflammation-associated tumor growth. Addition to the tumor inflammatory microenvironment of eicosapentaenoic acid, an omega3-polyunsaturated fatty acid with anti-inflammatory properties, or leukotriene B5, an eicosapentaenoic acid-derived leukotriene, significantly inhibited tumor development. These results give new insights to the mechanisms through which inflammation may contribute to tumor progression and suggest that LOX has an important role in tumor progression associated with an inflammatory state in the presence of apoptosis, which may be a consideration for apoptosis-inducing treatments, such as chemotherapy and radiotherapy.
Bachi
André Luis Lacerda
AL
Disciplina de Imunologia, Universidade Federal de São Paulo, São Paulo, SP 04023-900, Brazil.
Kim
Fabiana Jin Kyung
FJ
Nonogaki
Suely
S
Carneiro
Célia Regina Whitaker
CR
Lopes
José Daniel
JD
Jasiulionis
Miriam Galvonas
MG
Correa
Mariangela
M
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D002351:Carrageenan / Q000494:pharmacology; D048708:Cell Growth Processes / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D018450:Disease Progression; D015118:Eicosapentaenoic Acid / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D006651:Histocytochemistry; D007213:Indomethacin / Q000494:pharmacology; D007249:Inflammation / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology*; D007975:Leukotriene B4 / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D016859:Lipoxygenase Inhibitors; D008545:Melanoma / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism
D008070:Lipopolysaccharides; D016859:Lipoxygenase Inhibitors; D007975:Leukotriene B4; C040212:leukotriene B5; D002351:Carrageenan; D015118:Eicosapentaenoic Acid; D001094:Arachidonate 5-Lipoxygenase; D011451:Prostaglandin-Endoperoxide Synthases; D007213:Indomethacin