Abstract 2218: Radiation-induced hypomethylation triggers urokinase plasminogen activator (uPA) transcription in meningioma cells

Abstract

Abstract Our previous studies have shown the role of radiation-induced urokinase plasminogen activator (uPA) expression in meningioma tumor progression. In the present study, we investigated whether modulation of DNA methylation profiles could regulate uPA expression. Radiation treatment induced hypomethylation in meningioma cells with a decrease in DNMT1 and MBD expression. However, oxidative damage by H2O2 or pretreatment of irradiated cells with NAC did not show any influence on these proteins, thereby indicating a radiation-specific change in the methylation patterns among meningioma cells. Further, we identified that hypomethylation is coupled to an increase in uPA expression in these cells. Azacytidine treatment induced a dose-dependent surge of uPA expression while pretreatment with Sodium butyrate inhibited the radiation-induced uPA expression; these results complement our prior findings. Methylation-specific PCR on bisulfite treated genomic DNA revealed a diminished methylation of uPA promoter in irradiated cells, which supports the role of epigenetics in uPA gene regulation. Transfection with shRNA expressing plasmids targeting CpG islands of the uPA promoter showed a marked decline in uPA expression with subsequent decreases in invasion and proliferation of meningioma cells. Further, radiation treatment is coupled to the recruitment of SP1 transcription into the nuclear extracts, which was abrogated by shRNA treatment. Our experiments to study the signaling events demonstrated the activation of MEK-ERK in radiation treated cells while U0126 (MEK/ERK inhibitor) blocked hypomethylation, recruitment of SP1, and uPA expression. In agreement with our in vitro data, low DNMT1 levels and high uPA were found in intracranial tumors given radiation treatment as compared to untreated tumors. In conclusion, our data suggest radiation-mediated hypomethylation triggers uPA expression in meningioma cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2218. doi:1538-7445.AM2012-2218