Abstract A38: Overexpression of FAT1 in human GBM (glioblastoma multiforme) and high-grade glioma cell lines

Abstract

Abstract FAT1, a human homologue of Drosophila tumor suppressor gene fat, is located on chromosome 4q35 in humans. In Drosophila, fat gene is known to be acting as an apical regulator of the tumor suppressor signaling, Salvador-Warts-Hippo (SWH) pathway. In mammalian cells, FAT1 is known to have a role in cell migration. The role of FAT1 in cancer is not clear and not much literature is available. In this study, we analyzed the expression of FAT1 in GBM (glioblastoma multiforme, grade IV glioma) samples at both mRNA and protein levels by means of q-PCR and immunohistochemistry. Herein, we demonstrate that 51.4% (18/35) of GBM samples had high expression of FAT1 mRNA, and 53.33% (8/15) of GBM samples had high FAT1 protein expression. We also checked the expression of FAT1 in glioma cell lines by q-PCR. Of the six glioma cell lines analyzed, four were GBM cell lines (U87MG, A172, U373MG and T98G) and two were astrocytoma grade 3 cell lines (GOS3 and SW1088). All GBM cell lines had high FAT1 expression while grade 3 cell lines had no or very low FAT1 expression. Since U87MG had maximum FAT1 expression we chose this cell line to study the effects of FAT1 knockdown by siRNA. FAT1 knockdown resulted in altered morphology and reduced migration of U87MG cells as compared to control siRNA treated cells. Since FAT1 is known to be an apical regulator of hippo pathway in Drosophila, we checked the expression of hippo pathway molecules by q-PCR and found that Mst2 (mammalian homolog of Drosophila hippo) expression was reduced up to 65% while other molecules like LATS and YAP were not altered at mRNA level. Considering the fact that regulation of SWH pathway primarily occurs at posttranslational level and depends upon phosphorylation status of the molecules, we are in process of analyzing the expression of these molecules at protein level and their phosphorylation status using phosphospecific antibodies, which would provide better understanding of the role of FAT1 in influencing SWH pathway. Since FAT1 is overexpressed in 50% of GBM samples studied and also found to have high expression in high-grade glioma cell lines as compared to low-grade glioma cell lines, it might act as an oncogene and may be involved in progression from low-grade to high-grade glioma. Thus, we propose FAT1 as a novel molecular target for therapeutic intervention in glioma. 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 A38.