Malignant gliomas are an aggressive, highly invasive, neurologically destructive and deadly tumors of the brain. The diffusively infiltrative nature of gliomas is one of the major causes of mortality in patients afflicted with this cancer. Recently, dysregulation of the inflammatory response has been implicated in the pathobiology of gliomas. The NF-KB family of transcription factors are responsible for mediating immune/inflammatory responses, and constitutive activation of NF-KB has been correlated with gliomagenesis. NF-KB activation is normally transient and regulated by a variety of mechanisms, including interactions with other proteins. One such protein, ING4, has recently been shown to inhibit NF-KB-mediated expression of IL-8, IL-6 and COX-2 in glioma cells. This inhibition may occur through interactions between ING4 and the p65 NF-KB isoform. Thus, the NF-KB pathway and ING4 protein represent potential therapeutic targets for the treatment of gliomas. We have made the novel observation that ING4 differentially affects NF-KB-mediated gene induction in human glioma cells, inhibiting IL-8 expression, yet enhancing expression of matrix metalloproteinase-9 (MMP-9). These results suggest that the influence of ING4 on NF-KB-mediated genes is complex, i.e., ING4 may have either a positive or negative effect on gene expression that is dependent on promoter context, co- factor composition, chromatin accessibility, and kinetics of gene expression. We believe that studies to investigate the molecular mechanisms of ING4-mediated regulation of NF-KB activity in gliomas are warranted, focusing on ING4 regulation of expression of IL-8, IL-6, MMP-9 and CXCR4, all genes dependent on NF-KB for activation, and involved in glioma growth, invasion and angiogenesis. We will examine the status and integrity of the ING4 gene and the activation status of NF-KB in human glioma tissues, and determine if correlates exist. The effect of ING4 on NF-KB's ability to translocate into the nucleus, bind DNA in vitro and in vivo, and regulate expression of IL-8, IL-6, MMP-9 and CXCR4 will be analyzed in human glioma cells that inducibly express ING4 (Aim 1).
In Aim 2, translational studies will validate the influence of ING4 on NF-KB-mediated gene expression in vivo. Human glioma cells inducibly expressing ING4 will be transplanted into the brains of scid mice, and the effects of changes in ING4 expression on NF-KB activity, gene expression, glioma growth, invasion and angiogenesis assessed in vivo. This combination of basic science experimentation and translational studies represent the first systematic study of the functional involvement of NF-KB and ING4 in gliomagenesis, and will lead to a greater understanding of the potential for therapeutic intervention of the NF-KB pathway and/or ING4 in malignant gliomas. ? ?
