Chao Sun1,2, Yuanlin Zhao2, Jiankuan Shi2,3, Jin Zhang2, Yuan Yuan2, Yu Gu2, Feng Zhang2, Xing Gao2, Chao Wang4, Yingmei Wang2, Zhe Wang2, Peizhen Hu2, Junhui Qin2, Liming Xiao2, Ting Chang1, Liang Wang5, Yibin Xi6, Hong Yin6, Huangtao Chen7, Lijun Zhang8, Guang Cheng9, Jiaji Lin1, MingMing Zhang10, Zhuyi Li11, Jing Ye12,13. 1. Department of Neurology, Tangdu Hospital, The Fourth Military Medical University, Xi'an, 710032, Shaanxi, China. 2. State Key Laboratory of Cancer Biology and Department of Pathology, Xijing Hospital, The Fourth Military Medical University, Xi'an, 710032, China. 3. Department of Neurology, Shaanxi People Hospital, Xi'an, 710032, China. 4. Department of Pathology, Chengdu Military General Hospital, Chengdu, 610083, China. 5. Department of Neurosurgery, Tangdu Hospital, The Fourth Military Medical University, Xi'an, 710032, Shaanxi, China. 6. Department of Radiology, Xijing Hospital, The Fourth Military Medical University, Xi'an, 710032, Shaanxi, China. 7. Health Science Center, Xi'an Jiaotong University, Xi'an, 710061, Shaanxi, China. 8. Department of Clinical Laboratory, Tangdu Hospital, The Fourth Military Medical University, Xi'an, 710032, China. 9. Department of Neurosurgery, Xijing Hospital, The Fourth Military Medical University, Xi'an, 710032, Shaanxi, China. 10. Department of Cardiology, Tangdu Hospital, The Fourth Military Medical University, Xi'an, 710032, Shaanxi, China. 11. Department of Neurology, Tangdu Hospital, The Fourth Military Medical University, Xi'an, 710032, Shaanxi, China. lizhuyi@fmmu.edu.cn. 12. Department of Neurology, Tangdu Hospital, The Fourth Military Medical University, Xi'an, 710032, Shaanxi, China. yejing@fmmu.edu.cn. 13. State Key Laboratory of Cancer Biology and Department of Pathology, Xijing Hospital, The Fourth Military Medical University, Xi'an, 710032, China. yejing@fmmu.edu.cn.
Abstract
INTRODUCTION: Tumour-associated angiogenesis is associated with the malignancy and poor prognosis of glioma. Isocitrate dehydrogenase (IDH) mutations are present in the majority of lower-grade (WHO grade II and III) and secondary glioblastomas, but their roles in tumour angiogenesis remain unclear. METHODS: Using magnetic resonance imaging (MRI), the cerebral blood flow (CBF) of IDH-mutated glioma was measured and compared with the IDH-wildtype glioma. The densities of microvessels in IDH-mutated and wildtype astrocytoma and glioblastoma were assessed by immunohistochemical (IHC) staining with CD34, and the pericytes were labelled with α-smooth muscle antigen (α-SMA), neural-glial antigen 2 (NG2) and PDGF receptor-β (PDGFR-β), respectively. Furthermore, glia-specific mutant IDH1 knock-in mice were generated to evaluate the roles of mutant IDH1 on brain vascular architectures. The transcriptions of the angiogenesis-related genes were assessed in TCGA datasets, including ANGPT1, PDGFB and VEGFA. The expressions of these genes were further determined by western blot in U87-MG cells expressing a mutant IDH1 or treated with 2-HG. RESULTS: The MRI results indicated that CBF was reduced in the IDH-mutated gliomas. The IHC staining showed that the pericyte coverages of microvessels were significantly decreased, but the microvessel densities (MVDs) were only slightly decreased in IDH-mutated glioma. The mutant IDH1 knock-in also impeded the pericyte coverage of brain microvessels in mice. Moreover, the TCGA database showed the mRNA levels of angiogenesis factors, including ANGPT1, PDGFB and VEGFA, were downregulated, and their promoters were also highly hyper-methylated in IDH-mutated gliomas. In addition, both mutant IDH1 and D-2-HG could downregulate the expression of these genes in U87-MG cells. CONCLUSIONS: Our results suggested that IDH mutations could reduce the pericyte coverage of microvessels in astrocytic tumours by inhibiting the expression of angiogenesis factors. As vascular pericytes play an essential role in maintaining functional blood vessels to support tumour growth, our findings imply a potential avenue of therapeutic strategy for IDH-mutated gliomas.
INTRODUCTION:Tumour-associated angiogenesis is associated with the malignancy and poor prognosis of glioma. Isocitrate dehydrogenase (IDH) mutations are present in the majority of lower-grade (WHO grade II and III) and secondary glioblastomas, but their roles in tumour angiogenesis remain unclear. METHODS: Using magnetic resonance imaging (MRI), the cerebral blood flow (CBF) of IDH-mutated glioma was measured and compared with the IDH-wildtype glioma. The densities of microvessels in IDH-mutated and wildtype astrocytoma and glioblastoma were assessed by immunohistochemical (IHC) staining with CD34, and the pericytes were labelled with α-smooth muscle antigen (α-SMA), neural-glial antigen 2 (NG2) and PDGF receptor-β (PDGFR-β), respectively. Furthermore, glia-specific mutant IDH1 knock-in mice were generated to evaluate the roles of mutant IDH1 on brain vascular architectures. The transcriptions of the angiogenesis-related genes were assessed in TCGA datasets, including ANGPT1, PDGFB and VEGFA. The expressions of these genes were further determined by western blot in U87-MG cells expressing a mutant IDH1 or treated with 2-HG. RESULTS: The MRI results indicated that CBF was reduced in the IDH-mutated gliomas. The IHC staining showed that the pericyte coverages of microvessels were significantly decreased, but the microvessel densities (MVDs) were only slightly decreased in IDH-mutated glioma. The mutant IDH1 knock-in also impeded the pericyte coverage of brain microvessels in mice. Moreover, the TCGA database showed the mRNA levels of angiogenesis factors, including ANGPT1, PDGFB and VEGFA, were downregulated, and their promoters were also highly hyper-methylated in IDH-mutated gliomas. In addition, both mutant IDH1 and D-2-HG could downregulate the expression of these genes in U87-MG cells. CONCLUSIONS: Our results suggested that IDH mutations could reduce the pericyte coverage of microvessels in astrocytic tumours by inhibiting the expression of angiogenesis factors. As vascular pericytes play an essential role in maintaining functional blood vessels to support tumour growth, our findings imply a potential avenue of therapeutic strategy for IDH-mutated gliomas.