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Solid tumor cells have an altered metabolism that can protect them from cytotoxic lymphocytes. The antidiabetic drug metformin modifies tumor cell metabolism and several clinical trials are testing its effectiveness for the treatment of solid cancers. The use of metformin in hematologic cancers has received much less attention, although allogeneic cytotoxic lymphocytes are very effective against these tumors. We show here that metformin induces expression of Natural Killer G2-D (NKG2D) ligands (NKG2DL) and intercellular adhesion molecule-1 (ICAM-1), a ligand of the lymphocyte function-associated antigen 1 (LFA-1). This leads to enhance sensitivity to cytotoxic lymphocytes. Overexpression of antiapoptotic Bcl-2 family members decrease both metformin effects. The sensitization to activated cytotoxic lymphocytes is mainly mediated by the increase on ICAM-1 levels, which favors cytotoxic lymphocytes binding to tumor cells. Finally, metformin decreases the growth of human hematological tumor cells in xenograft models, mainly in presence of monoclonal antibodies that recognize tumor antigens. Our results suggest that metformin could improve cytotoxic lymphocyte-mediated therapy.

Multiple Sclerosis (MS) is a debilitating neurological disease characterized by inflammatory demyelination in the central nervous system (CNS), and tumor necrosis factor (TNF-α) has been implicated in its pathogenesis. TNF-α is toxic to the myelin forming oligodendrocytes and their connected myelin sheaths, and its expression is elevated in MS lesions. However, the precise mechanism for TNF-α-mediated toxicity to oligodendrocytes remains unknown. Moreover, the role of regulatory molecules, including SHP-1, in controlling both TNF-α signaling and susceptibility to TNF-α-mediated demyelinating diseases in the CNS is unclear. Here, we show that compared to normal littermate controls, oligodendrocytes of SHP-1-deficient mice (motheaten), which are highly susceptible to inflammatory demyelination, display a significant increase in inflammatory gene expression in response to TNF-α. Unexpectedly, the most highly induced of these inflammatory genes is arginase-1, an enzyme that converts arginine to L-ornithine with major effects on allergic-type immune responses. To elucidate the mechanism underlying this induction, we are determining how TNF-α induces transcriptional activation of the arginase-1 promoter in an SHP-1-dependent manner. Further, we are investigating if abnormal expression of arginase-1 in oligodendrocytes is responsible for the oligodendrocyte dysfunction and increased demyelination observed in SHP-1-deficient mice.

Viral infections in the central nervous system (CNS) may have devastating clinical consequences to the host. Neurotropic virus infections often begin in peripheral tissues, which then spread to the CNS via peripheral nerves following entry into nerve terminals by receptor-mediated endocytosis and subsequent retrograde axonal transport into the CNS compartment. In our lab, a possible novel role for the protein tyrosine phosphatase, SHP-1, in regulating neuroinvasion via peripheral nerves of a neurotropic virus (Theiler’s Murine Encephalomyelitis Virus, TMEV) is being investigated. Preliminary data using immunohistochemistry of TMEV showed extensive staining of spinal cord neurons after intraperitoneal inoculation in mice with a null mutation in the SHP-1 gene (me/me mice) compared to wild type mice. Further, intramuscular (IM) inoculations of TMEV caused virus infection in spinal cord neurons and subsequent paralysis of SHP-1-deficient mice but not of wild type mice. IM and intraperitoneal injections (IP) of retrograde axonal transport tracers fluorogold and horseradish peroxidase showed increased tracer levels in the spinal cords of SHP-1-deficient mice compared to wild type mice. Therefore, we propose SHP-1 may play a role in regulating viral neuroinvasion by controlling retrograde axonal transport from peripheral sites of infection. In this sense, SHP-1 may play novel roles in antiviral responses including inhibition of virus invasion and spreading in the CNS.

Microbial infections elicit inflammatory responses that eradicate infection and remove damaged cells. Regulation of these events is critical as excessive inflammation may cause substantial bystander tissue destruction in the process of pathogen clearance while a deficient response may be insufficient to clear infections and damaged cells. Defective clearance of dying cells can trigger devastating chronic inflammatory diseases, and we report an unanticipated role for SHP-1 in facilitating this process. SHP-1 restricts innate immunity to pathogens, and therefore mice lacking SHP-1 suffer macrophage-mediated destruction of myelin in the CNS following infection with Theiler’s murine encephalomyelitis virus (TMEV). To the contrary, we have discovered that although resistant to CNS disease, TMEV-infected wild type animals develop a severe debilitating skeletal muscle disease not seen in SHP-1-/- mice. We show that SHP-1-mediated restriction of macrophage responses in WT mice corresponds with insufficient clearance of damaged tissue and increased muscle dysfunction. As SHP-1 controls macrophage phagocytic activity, our data suggests that increased macrophage activity in SHP-1-/- mice restricts muscle disease through rapid clearance of infected and damaged myofibers. These findings demonstrate a unique role of SHP-1 in exacerbating rather than resolving disease pathology by inhibiting clearance of cellular debris. These data suggest novel therapies for chronic inflammatory diseases.

Cytokine signaling pathways play a central role in the pathogenesis of inflammatory bowel disease (IBD). Numerous clinical studies have shown that several inflammatory cytokines are elevated in active IBD and recently genome-wide association studies further confirmed and advanced our knowledge of intricate immune pathways that confer susceptibility to IBD. This study aims to delineate the cytokine signaling pathways in colonic mucosa of CD and UC patients, explore possible molecular markers for IBD diagnosis, and identify novel immune-mediators of IBD pathogenesis. Based on established clinical diagnosis and strict histopathological criteria, 93 colon biopsy samples were from severe/active UC or CD, quiescent UC or CD, and normal control subjects. Gene expression is analyzed by quantitative real-time RT-PCR. This study analyzes the expression of more than 30 genes, including cytokines, signaling molecules, and downstream inflammatory mediators. Cytokines like IL-17, IL-6 and IL-33 and transcription factors like T-bet, GATA-3, Foxp3are differentially regulated between UC and CD and among disease severity. These data provide insights into the pathogenesis of IBD though identifying novel immune-mediators and elucidating distinct signaling networks in CD and UC. Finally, several biologic agents are novel promising IBD treatments and this study provides an easy approach that can be used to identify molecular markers that can predict the response to those individual treatments.