title: Leukotriene B4 creates a favorable microenvironment for murine melanoma growth.
abstract: 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.
authors.affiliation: Disciplina de Imunologia, Universidade Federal de São Paulo, São Paulo, SP 04023-900, Brazil.
authors.forename: André Luis Lacerda
authors.initials: AL
authors.lastname: Bachi
authors.forename: Fabiana Jin Kyung
authors.initials: FJ
authors.lastname: Kim
authors.forename: Suely
authors.initials: S
authors.lastname: Nonogaki
authors.forename: Célia Regina Whitaker
authors.initials: CR
authors.lastname: Carneiro
authors.forename: José Daniel
authors.initials: JD
authors.lastname: Lopes
authors.forename: Miriam Galvonas
authors.initials: MG
authors.lastname: Jasiulionis
authors.forename: Mariangela
authors.initials: M
authors.lastname: Correa
mesh_terms: 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
chemical_list: 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