Abstract B60: Interleukin-1 expression and inflammasome activation in human malignant glioma

Introduction: Interleukin 1 (IL-1) is a major proinflammatory cytokine produced by myeloid cells and is implicated in neurodegeneration. In human brain, IL-1 is expressed by microglia and contributes to neuroinflammation and neuronal toxicity. IL-1 is also the major activator of human astrocyte and glioma cells. In this study, we investigated the mechanism of IL-1 α and IL-1β expression and activation in human glioma cells. Methods: Human glioblastoma cell lines (U87, U251, and SN19) as well as patient-derived glioma cell lines were stimulated with cytokines (IL-1/IFNγ) or TLR ligands (LPS or poly IC) and the expression of IL-1α and IL-1β was studied by real-time PCR, western blot analysis, and ELISA. The glioma secretome was investigated using quantitative mass spectrometry. Results: We found that while primary human astrocytes show IL-1 translational block (no protein made despite high level of mRNA), but GBM cells responded strongly to IL-1 itself to produce large amounts of IL-1α and IL-1β mRNA and proteins. Furthermore, GBM cells processed pro-IL-1β (31kDa) to mature IL-1β (17kDa) by activating the NALP3 inflammasome. Both ATP and nigericin induced IL-1β processing by upregulating NALP3. Proteomics analysis of IL-1 stimulated GBM cell secretome revealed several highly upregulated proteins (IL-8, MCP-1, tenascin-C, pentraxin 3, galectin 1, and MMP2), all of which are implicated in glioma progression. Furthermore, many extracellular matrix proteins (ECM) and ECM-related proteins were downregulated by IL-1 in the glioma secretome. Discussion: We propose that the ability of malignant glioma cells to produce IL-1 protein can set off chronic smoldering inflammation and induce epithelial-mesenchymal transition (EMT) resulting in increased migratory capacity, a unique gene signature, and increased immune signaling (NF-κB, pStat3). There is potential for IL-1 to be a biomarker/surrogate marker for a subset of GBM and that IL-1 blockade could benefit GBM patients. Citation Format: Leonid Tarassishin, Jihyeon Lim, Sunhee C. Lee. Interleukin-1 expression and inflammasome activation in human malignant glioma. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr B60.