RESUMO
BACKGROUND: Although it has been previously demonstrated that acute inflammation can promote the tumor growth of a sub-tumorigenic dose of melanoma cells through of 5-lipoxygenase inflammatory pathway and its product leukotriene B4, and also that the peritumoral treatment with eicosapentaenoic acid and its product, leukotriene B5, reduces the tumor development, the effect of the treatment by gavage with omega-3 and omega-6 in the tumor microenvironment favorable to melanoma growth associated with acute inflammation has never been studied. METHODS: C57BL/6 mice were coinjected with 1 × 106 apoptotic cells plus 1 × 103 viable melanoma cells into the subcutaneous tissue and treated by gavage with omega-3-rich fish oil or omega-6-rich soybean oil or a mixture of these oils (1:1 ratio) during five consecutive days. RESULTS: The treatment by gavage with a mixture of fish and soybean oils (1:1 ratio) both reduced the melanoma growth and the levels of leukotriene B4 (LTB4), prostaglandin E2 (PGE2), PGE2/prostaglandin E3 (PGE3) ratio, and CXC ligand 1 (CXCL1) and increased the levels of interleukin 10 (IL-10) to IL-10/CXCL1 ratio in the melanoma microenvironment. CONCLUSION: The oral administration of a 1:1 mixture of fish oil and soybean oil was able to alter the release of inflammatory mediators that are essential for a microenvironment favorable to the melanoma growth in mice, whereas fish oil or soybean oil alone was ineffective.