NOS2 and neoplasm: Since NO can be produced by macrophages, we assessed by IHC iNOS expression, to denote type 1 macrophages and arginase expression, to denote type 2 macrophages.37 The levels of these proteins (both of mouse origin) were significantly higher in MCF-7 tumours (Fig. 4f; iNOS: 3284 ± 888 MCF-7 vs. 850 ± 182 MDA-MB-231; arginase: 10,111 ± 2542 MCF-7 vs. 1002 ± 298 MDA-MB-231).