PO-162 The transcription factor GATA4 is overexpressed in malignant meningioma enhancing proliferation via downregulation of miR-15 family members

Introduction Meningioma is the most common primary brain tumour and is classified as benign (WHO I, 80%), atypical (WHO II, 15%–20%) and anaplastic (WHO III, 1%–3%). The 3 year recurrence rate in WHO I meningioma is ~50% and it is much greater in WHO II and III. Recent studies showed that cyclin D1 and E1 positively correlated with meningioma grade and higher recurrence rates, suggesting them as potential prognostic markers. Here, we show that cyclin D1-D2 and E1 overexpression in malignant meningioma is driven by downregulation of the miR-15 family members via GATA4, a transcription factor overexpressed in WHO III meningioma cells and tissues. Therefore, we propose GATA4 as a novel possible biomarker for monitoring meningioma progression. Material and methods Meningioma (MN) specimens were collected from consented patients according to the ethical approval for this study. All cell lines and primary MN cells were isolated from tumour specimens and cultured following recommended conditions. Real Time PCR was conducted using TaqMan reagents (Applied Biosystems), according to the manufacturer’s instructions following the 2 -ΔΔC T method. In silico studies were conducted using TargetScanHuman7.1 to search for putative miRNA targets. P-values were calculated using the Student’s t-Test or the ANOVA one-way analysis of variance, led by the GraphPad Prism 5.01 and MS Excel 2016 software (p values Results and discussions Proteomic analysis showed an increase of cyclin D1 in Ben Men-1, primary WHO I and KT21-MG1 cells, and an increase of cyclin D2 in KT21-MG1 cells only. In silico studies identified cyclin D1-D2-D3 and E1 as targets of the miR-15 family members. QPCR showed that miR-195 and −497 are downregulated in WHO II and III samples compared to WHO I (3.38 and 6.02 folds, respectively; p=0.02); these results were consistent in cell culture exosomes. Analysis of GATA4 revealed that the protein is highly overexpressed in KT21-MG1 cells but not in Ben Men-1 and primary meningioma cells (17940.19 and 4899.34 folds, respectively, p=0.03). These results were consistent in tissues (2640.53 folds). Conclusion Our data show that members of the miR-15 family are downregulated in WHO III meningioma cells and tissues, suggesting their contribution to control tumour progression. In addition, in WHO III cells and tissues the transcription factor GATA4, involved in miR-15 family regulation, is overexpressed. Ongoing studies will address GATA4 role in the biological progression of meningioma. (DB and COH contributed equally).