Importantly, confocal microscopic analysis of tissues from 4T1 cell-bearing mice revealed that MDSCs inside the primary tumor and lung strongly expressed IL-6 while those in spleen tissues from the same mice expressed little IL-6, but MDSCs in the primary tumor site of EMT6-bearing mice did not show increased expression of IL-6 (Figure 3E and see Additional file 1, Figure S6). The gene discussed is IL6; the disease is neoplasm.