Macrophage migration inhibitory factor (MIF), a pro-inflammatory cytokine, is overexpressed and supports tumor growth in CLL patients (201) by stimulating signaling pathways, such as MAPK, NFκB, and AKT, on binding to receptors CD74 and CXCR2/CXCR4 (202–204). This evidence concerns the gene MIF and B-cell chronic lymphocytic leukemia.