These genes include cytochrome P450, family 1, subfamily A, polypeptide 2 (Cyp1a2), which is involved in hydrogen peroxide synthesis, histidine-rich glycoprotein (Hrg), which positively regulates the immune response to tumor cells, several genes in the steroid or eicosanoid pathway including cytochrome P450, family 2, subfamily A, polypeptide 12 (Cyp2a12), and retinol dehydrogenase 7(Rdh7), and genes involved in amino acid biosynthesis of arginine from ornithine via ornithine transcarbamylase (Otc) or tryptophan catabolism via tryptophan 2,3-dioxygenase (Tdo2). The gene discussed is TDO2; the disease is neoplasm.