"Alox5" gene knockout mice exhibit an increase in the lung tumor volume and liver metastasis of Lewis lung carcinoma cells that were directly implanted into their lungs; this result differs from many in vitro studies which implicated human ALOX5 along with certain of its metabolites with promoting cancer cell growth in that it finds that mouse Alox5 and, perhaps, certain of its metabolites inhibit cancer cell growth. Studies in this model suggest that Alox5, acting through one or more of its metabolites, reduces growth and progression of the Lewis carcinoma by recruiting cancer-inhibiting CD4+ T helper cells and CD8+ T Cytotoxic T cells to the sites of implantation. This striking difference between human in vitro and mouse in vivo studies may reflect species differences, in vitro versus in vivo differences, or cancer cell type differences in the function of ALOX5/Alox5.