Abstract A67: Transcription factor IRF3 inhibits glioma cell invasiveness
Authors: Tarassishin Leonid , Lee Sunhee C. 
Published: June 2012

Malignant gliomas are the most common primary brain tumors with a high rate of mortality. The major problem for successful cure of gliomas is the ability of tumor cells to infiltrate into surrounding brain tissue. The prevention of infiltration will allow localizing the tumor following surgical dissection. A number of different approaches have been used to inhibit glioblastoma cell invasiveness. In the present work, we have tested the possibility that the transcription factor interferon regulatory factor 3 (IRF3) gene transfer could inhibit glioma invasiveness. IRF3 is a known component of TLR3 and TLR4 signaling which is required for IFNβ transcription and antiviral immunity.

We used glioblastoma cell lines U251 and U87 as in vitro model systems. Tumor cells were transfected with an adenovirus construct bearing IRF3 (Ad-IRF3) or Ad-GFP as a control and were subsequently treated with a combination of cytokines (IL-1 β and IFNγ) to mimic the inflammatory tumor environment. Parallel experiments were performed with primary human fetal astrocytes. Subsequent analyses included the wound healing assay, BD Matrigel invasion assay, real-time PCR, microarray, Western blotting, and ELISA.

First, we observed inhibition of astrocyte migration by IRF3, especially when the cells were exposed to cytokines. Then we found that IRF3 significantly inhibits the migration and invasion of the glioma cells. Real-time PCR with primary astrocytes and glioma cells indicated that IRF3 inhibited the expression of a number metalloproteases including MMP-7 and MMP-9. Additionally, we examined the expression of cytokines and chemokines which participate in the brain innate immune response and neuroinflammatory responses to tumors. In primary astrocytes, we found unique ability of IRF3 to regulate glial immune responses, i.e., upregulation of anti-inflammatory or regulatory cytokine genes (IFNβ, IL-27, and IL-13) and downregulation of proinflammatory genes (iNOS, CXCL1, IL-8, and TNFα). A similar picture was observed in glioma cells as well, including the production of antiangiogenic and antiproliferative cytokine, IFNβ. Interestingly, we found that glioma cells produced robust amounts of IL-1β in response to cytokine treatment, whereas normal human astrocytes produced none, and this was significantly inhibited by IRF3. As IL-1β is a neurotoxin and is a major proinflammatory cytokine that activates MMPs and other inflammatory mediators, these results have implications for the pathogenesis and therapy of malignant gliomas. Our data implicate IL-1 as a potential mediator of glioma invasiveness and neurotoxicity and IRF3 as a potential therapy target for malignant gliomas.

Acknowledgement: This work was supported by the Einstein Molecular Neuropathology Training Grant T32NS007098, NIH RO1 MH55477, and the Einstein Human Fetal Tissue Repository.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr A67.