Significant accumulation of CD11bhiGr-1dim F4/80+ and iNOS+ cells was observed after tumor induction, increasing from 1% of all splenocytes (2.4 × 105 ± 45 × 103) to 4-6% of cells (2.6 ×106 ± 8.5 ×105) at a tumor size of 400 mm3. This evidence concerns the gene NOS2 and neoplasm.