FCGR1A and neoplasm: In the hearts, a significant elevation in the macrophage population (F480+, CD64+) was observed in tumor-bearing MDX mice compared with non-tumor-bearing mice (Figure 4A,B), even though M2 macrophage polarization occurred already in naive MDX mice, and no further elevation in M2 macrophage population occurred in tumor-bearing MDX mice as shown by RT-PCR using M1/M2 markers (Figure 4D–F, Supplemental Figure S4A,B).