MIF and neoplasm: In the mouse model of 4T1 metastatic breast carcinoma, accumulation of CD11b+Gr-1+MDSCs within the tumor tissue has been associated with tumor progression and bone metastasis (Bunt et al., 2007; Danilin et al., 2012) and a recent report showed that MDSC recruitment is triggered by Macrophage Migration Inhibitory Factor, an inflammatory cytokine expressed by the tumor (Simpson et al., 2012).