In this study, we showed that the treatment with a mixture of fish oil rich in omega-3 and soybean oil rich in omega-6 in a ratio of 1:1 during five consecutive days after the coinjection of B16F10 cells in the subcutaneous tissue of C57BL/6 mice was able to reduce not only the tumor growth, but also the levels of pro-inflammatory mediators (LTB4 and PGE2) and CXCL1 in the tumor microenvironment. The gene discussed is CXCL1; the disease is neoplasm.