Macrophage migration-inhibitory factor (MIF) is an upstream regulator of innate immunity and a potential molecular link between inflammation and cancer. The unusual structural homology between MIF and certain tautomerases, which includes both a conserved substrate-binding pocket and a catalytic N-terminal proline (Pro1), has fueled speculation that an enzymatic reaction underlies MIF's biologic function. To address the functional role of the MIF tautomerase activity in vivo, we created a knock-in mouse in which the endogenous mif gene was replaced by one encoding a tautomerase-null, Pro13Gly1 MIF protein (P1G-MIF). While P1G-MIF is completely inactive catalytically, it maintains significant, albeit reduced, binding to its cell surface receptor (CD74) and to the intracellular binding protein JAB1/CSN5. P1G-MIF knock-in mice (mif P1G/P1G ) and cells derived from these mice show a phenotype in assays of growth control and tumor induction that is intermediate between those of the wild type (mif ؉/؉ ) and complete MIF deficiency (mif ؊/؊ ). These data provide genetic evidence that MIF's intrinsic tautomerase activity is dispensable for this cytokine's growth-regulatory properties and support a role for the N-terminal region in protein-protein interactions.Macrophage migration-inhibitory factor (MIF) is a widely expressed cytokine and upstream regulator of the immune response (23). Immunoneutralization and genetic knockout studies have established a central position for MIF in the host response to infection and tissue invasion (5, 9, 15). MIF's importance in human disease also has been revealed by the association of high-expression MIF alleles with clinical severity of different autoimmune disorders (18).An important role for MIF in tumorigenesis and in the contribution of inflammation to cancer development also has been proposed (7,20). Different tumor types express high levels of MIF, and clinical studies have shown that MIF production correlates with tumor aggressiveness and metastatic potential (1,22,27). Studies using genetically engineered MIFdeficient cells and mice show that MIF contributes to the development of the malignant phenotype by several mechanisms, including enhancement of cell cycle progression by sustained mitogen-activated protein kinase (MAPK) activation (28, 30), decreased proteasomal protein degradation (33) leading to altered expression of key cell cycle-regulatory proteins (15,21,35), and tumor promotion by neoangiogenesis (10, 48). Importantly, MIF also inhibits the proapoptotic and cell cycleregulatory function of the p53 tumor suppressor, thereby allowing for the accumulation of oncogenic mutations (20, 32). MIF's role in tumor progression additionally is supported by human genetic studies, and a recent report has described an association between high-expression MIF alleles and incidence of prostate cancer, which is a tumor type in which recurrent inflammation is considered to have an etiologic role (27).Information regarding MIF structure and function has emerged only in the last few year...

IntroductionChronic lymphocytic leukemia (CLL) is a clonal B-cell disorder that is not curable by conventional chemoimmunotherapies. The leukemic transformation may be initiated by specific genomic alterations (eg, del13q) that may cause the deletion of specific micro-RNA genes (eg, miR15 and miR16) and increase the resistance of B cells toward apoptosis. 1,2 Survival of CLL cells depends on a permissive microenvironment composed of cellular components, such as macrophages, T cells, or stromal follicular dendritic cells. [3][4][5] This microenvironment provides various chemokines and angiogenic factors, which interact with leukemic cells via appropriate surface receptors and adhesion molecules. 2,5 Macrophage migration inhibitory factor (MIF) is a proinflammatory and immunoregulatory cytokine that seems to be involved in the pathogenesis of various malignant diseases. 6-9 MIF was identified as a product of T cells 10 but also other cells of the immune system (B cells, monocytes/macrophages). 11 Later, MIF was found to be an almost ubiquitous mediator secreted by a wide variety of cells in the mammalian organism, such as endothelial cells, epithelial cells, or fibroblasts. 12 Macrophages are considered to be a prime source for MIF, as they are able to secrete large amounts of MIF in response to various stimuli. 13 MIF binds to the surface receptors CD74 and CXCR2/CXCR4, thereby stimulating signaling pathways, such as MAPK, NF-B, and AKT. [14][15][16] In B cells, activation of the surface receptor complex CD74/CD44 by MIF induces the proteolytic release of the intracellular domain of CD74, which in turn initiates a signaling cascade composing Syk, AKT, and NF-B; this leads to the production of IL-8 and to an increased resistance to apoptosis via the up-regulation of BCL-2. 17,18 Thus, the MIF-MIF receptor system may be seen as a part of the B-cell costimulatory signals that are required for full B-cell activation and maturation. MIF-deficient mice do not show developmental abnormalities and appear to have normal numbers of B cells. 6 However, they exhibit a number of immune dysfunctions when challenged by antigens or infectious agents. [19][20][21][22] Even more importantly, MIF seems to be required for bone marrow-derived dendritic cells to maintain mature B cells in the bone marrow compartment. 23 Submitted May 22, 2012; accepted October 14, 2012. Prepublished online as Blood First Edition paper, November 1, 2012; DOI 10.1182/blood-2012-05-431452.The online version of this article contains a data supplement.The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked ''advertisement'' in accordance with 18 USC section 1734. MIF is overexpressed in a variety of malignancies compared with the respective primary tissues (eg, prostate, 24 colon, 25 melanoma, 26 glioblastoma, 27 breast cancer 28,29 ). This overexpression might be caused by the tumor-activated HSP90 chaperone complex that protects MIF from degradation, a...

Survival of chronic lymphocytic leukemia (CLL) cells strictly depends on the support of an appropriate tumor microenvironment. Here, we demonstrate that LYN kinase is essential for CLL progression. Lyn deficiency results in a significantly reduced CLL burden in vivo. Loss of Lyn within leukemic cells reduces B cell receptor (BCR) signaling including BTK phosphorylation, but surprisingly does not affect leukemic cell expansion. Instead, syngeneic CLL transplantation of CLL cells into Lyn- or Btk-deficient recipients results in a strongly delayed leukemic progression and prolonged survival. Moreover, Lyn deficiency in macrophages hinders nursing functions for CLL cells, which is mediated by direct contact rather than secretion of soluble factors. Taken together, LYN and BTK seem essential for the formation of a microenvironment supporting leukemic growth.

BACKGROUND Scarce systematic trial data have prevented uniform therapeutic guidelines for T‐cell prolymphocytic leukemia (T‐PLL). A central need in this historically refractory tumor is the controlled evaluation of multiagent chemotherapy and its combination with the currently most active single agent, alemtuzumab. METHODS This prospective multicenter phase 2 trial assessed response, survival, and toxicity of a novel regimen in previously treated (n = 9) and treatment‐naive (n = 16) patients with T‐PLL. Induction by fludarabine, mitoxantrone, and cyclophosphamide (FMC), for up to 4 cycles, was followed by alemtuzumab (A) consolidation, up to 12 weeks. RESULTS Of the 25 patients treated with FMC, 21 subsequently received alemtuzumab. Overall response rate to FMC was 68%, comprising 6 complete remissions (all bone‐marrow confirmed) and 11 partial remissions. Alemtuzumab consolidation increased the intent‐to‐treat overall response rate to 92% (12 complete remissions; 11 partial remissions). Median overall survival after FMC‐A was 17.1 months and median progression‐free survival was 11.9 months. Progression‐free survival tended to be shorter for patients with high‐level T‐cell leukemia 1 oncoprotein expression. Hematologic toxicities were the most frequent grade 3/4 side effects under FMC‐A. Exclusively in the 21 alemtuzumab‐consolidated patients, 13 cytomegalovirus reactivations were observed; 9 of these 13 represented a clinically relevant infection. CONCLUSIONS FMC‐A is a safe and efficient protocol in T‐PLL, which compares favorably to published data. Cancer 2013;119:2258–2267. © 2013 American Cancer Society.