No abstract

The glutamate transporter gene, EAAT2/GLT-1, is induced by epidermal growth factor (EGF) and downregulated by tumor necrosis factor a (TNFa). While TNFa is generally recognized as a positive regulator of NF-jB-dependent gene expression, its ability to control transcriptional repression is not well characterized. Additionally, the regulation of NF-jB by EGF is poorly understood. Herein, we demonstrate that both TNFa-mediated repression and EGFmediated activation of EAAT2 expression require NF-jB. We show that EGF activates NF-jB independently of signaling to IjB. Furthermore, TNFa can abrogate IKKb-and p65-mediated activation of EAAT2. Our results suggest that NF-jB can intrinsically activate EAAT2 and that TNFa mediates repression through a distinct pathway also requiring NF-jB. Consistently, we find that N-myc is recruited to the EAAT2 promoter with TNFa and that N-myc-binding sites are required for TNFa-mediated repression. Moreover, N-myc overexpression inhibits both basal and p65-induced activation of EAAT2. Our data highlight the remarkable specificity of NF-jB activity to regulate gene expression in response to diverse cellular signals and have implications for glutamate homeostasis and neurodegenerative disease.

Graft-versus-host disease (GVHD) represents a major hurdle impeding the efficacy of allogeneic bone marrow transplantation (BMT). Bortezomib is a proteasome inhibitor that was recently approved for treatment of myeloma. We found that bortezomib potently inhibited in vitro mixed lymphocyte responses and promoted the apoptosis of alloreactive T cells. Bortezomib given at the time of allogeneic BMT in mice resulted in significant protection from acute GVHD. Reductions in GVHD-associated parameters and biological evidence of proteasome inhibition were observed with this regimen but with no adverse effects on long-term donor reconstitution. Assessment of graft-versus-tumor responses in advanced leukemia-bearing mice demonstrated that only the combination of allogeneic BMT and T cells with bortezomib promoted significant increases in survival. Increased cytotoxic T cell killing of the tumor was also observed. Thus, the combination of proteasome inhibition with selective immune attack can markedly increase the efficacy of BMT in cancer