ANGI-06. FUNCTION OF FORMIN-LIKE 1 (FMNL1) IN GLIOBLASTOMA MULTIFORME
Abstract INTRODUCTION Glioblastoma multiforme is the most common primary malignant brain tumour in adults. It is characterised by rapid proliferation, aggressive migration, and invasion into normal brain tissue. Formin proteins have been implicated in cancer progression, invasion, and migration. However, the role of FMNL1 in cancer remains unclear. We are the first to investigate FMNL1 in GBM. METHODS Clinical specimens were obtained from tumours surgically removed and pathologically confirmed as GBM from 217 GBM patients treated from 2000 to 2015 at the Department of Neurosurgery, Kagoshima University Hospital. We studied the expression of FMNL1 in glioblastoma samples by immunohistochemistry to analyse the correlation between FMNL1 expression, clinicopathologic variables, and patient survival. Migration and invasion assays were used to verify the effect of FMNL1 on glioblastoma cell lines. Microarray data were downloaded from TCGA and analysed using Gene Set Enrichment Analysis (GSEA). RESULTS FMNL1 was found to be a predictor of poor prognosis in a cohort of 217 cases (P < 0.001). GSEA showed that upregulation and downregulation of FMNL1 were associated with mesenchymal and proneural markers, respectively. Contrarily, downregulation of FMNL1 suppressed migration and invasion of glioblastoma multiforme cells via DIAPH1 and GOLGA2, respectively. Downregulation of FMNL1 also suppressed assembly of actin fibres, induced morphological changes, and diminished filamentous actin. CONCLUSION Our studies show that abundant FMNL1 expression in GBM patients is correlated with an unfavourable prognosis. FMNL1 is a promising therapeutic target and a useful biomarker for GBM progression.