IDH1R132H Causes Resistance to HDAC Inhibitors by Increasing NANOG in Glioblastoma Cells

Geon-Hee Kim,Sang-Yeon Kan,Taek-In Oh,So Young Choi,Sujin Lee,Hyeji Kang,Taerim Oh,Ji-Hong Lim,Hyun Myung Ko

doi:10.3390/ijms20112679

Abstract

The R132H mutation in isocitrate dehydrogenase 1 (IDH1R132H) is commonly observed and associated with better survival in glioblastoma multiforme (GBM), a malignant brain tumor. However, the functional role of IDH1R132H as a molecular target for GBM treatment is not completely understood. In this study, we found that the overexpression of IDH1R132H suppresses cell growth, cell cycle progression and motility in U87MG glioblastoma cells. Based on cell viability and apoptosis assays, we found that IDH1R132H-overexpressing U87MG and U373MG cells are resistant to the anti-cancer effect of histone deacetylase inhibitors (HDACi), such as trichostatin A (TSA), vorinostat (SAHA), and valproic acid. Octyl-(R)-2-hydroxyglutarate (Octyl-2HG), which is a membrane-permeable precursor form of the oncometabolite (R)-2-hydroxyglutarate (R-2HG) produced in IDH1-mutant tumor cells, significantly increased HDACi resistance in glioblastoma cells. Mechanistically, IDH1R132H and Octyl-2HG enhanced the promoter activation of NANOG via increased H3K4-3Me, consequently increasing NANOG mRNA and protein expression. Indeed, HDACi resistance was attenuated in IDH1R132H-expressing glioblastoma cells by the suppression of NANOG using small interfering RNAs. Furthermore, we found that AGI-5198, a selective inhibitor of IDH1R132H, significantly attenuates HDACi resistance and NANOG expression IDH1R132H-expressing glioblastoma cells. These results suggested that IDH1R132H is a potential molecular target for HDACi-based therapy for GBM.

Highlights

Isocitrate dehydrogenase 1 (IDH1) is a key metabolic enzyme for the conversion of citrate to α-ketoglutarate (α-KG) [1,2,3]
We showed that IDH1R132H and its synthetic oncometabolite, R-2HG, significantly increase NANOG expression by activating its proximal promoter region, resulting in increased histone deacetylase inhibitors (HDACi) resistance
To determine the mechanism by which IDH1R132H overexpression suppresses cell viability in U87MG glioblastoma cells, we investigated the alteration of cell cycle progression

Summary

Introduction

Isocitrate dehydrogenase 1 (IDH1) is a key metabolic enzyme for the conversion of citrate to α-ketoglutarate (α-KG) [1,2,3]. The most prevalent mutation in IDH1, R132H (IDH1R132H), was originally identified in acute myeloid leukemia (AML) and glioblastoma multiforme (GBM) [4,5,6]. The functional role of IDH1R132H as a tumor suppressive, or oncogenic factor in tumor development and aggressiveness is debated [7,8,9,10,11,12,13,14]. A previous report has shown that conditionally overexpressed IDH1R132H in hematopoietic lineages increases progenitor cell populations and extra-medullary hematopoiesis [15]. Increasing evidence has shown that the IDH1R132H mutation suppresses glioma growth by the upregulation of microRNA-128a and downregulation of Wnt/β-catenin signaling [8,12,13]. Large-scale genomic studies of central nervous system tumors have shown that patients with IDH1R132H have better clinical outcomes than those of patients with wild-type IDH1 [5,6]

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Results

Conclusion