Autophagy and oxidative stress in gliomas with IDH1 mutations
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IDH1 mutations in gliomas associate with longer survival. Prooxidant and antiproliferative effects of IDH1 mutations and its d-2-hydroxyglutarate (2-HG) product have been described in vitro, but inconsistently observed. It is also unclear whether overexpression of mutant IDH1 in wild-type cells accurately phenocopies the effects of endogenous IDH1-mutations on tumor apoptosis and autophagy. Herein we investigated the effects of 2-HG and mutant IDH1 overexpression on proliferation, apoptosis, oxidative stress, and autophagy in IDH1 wild-type glioma cells, and compared those results with patient-derived tumors. 2-HG reduced viability and proliferation of U87MG and LN18 cells, triggered apoptosis in LN18 cells, and autophagy in U87MG cells. In vitro studies and flank xenografts of U87MG cells overexpressing R132H IDH1 exhibited increased oxidative stress, including increases of both manganese superoxide dismutase (MnSOD) and p62. Patient-derived IDH1-mutant tumors showed no significant differences in apoptosis or autophagy, but showed p62 accumulation and actually trended toward reduced MnSOD expression. These data indicate that mutant IDH1 and 2-HG can induce oxidative stress, autophagy, and apoptosis, but these effects vary greatly according to cell type.
KeywordsIDH1 Autophagy Oxidative stress Apoptosis Glioma
C.H. was supported by K08 CA155764 (National Cancer Institute), 2P20 RR020171 COBRE pilot grant (National Institute of General Medical Sciences), The Peter and Carmen Lucia Buck Training Program in Translational Clinical Oncology, and the University of Kentucky College of Medicine Physician Scientist Program. The Markey Biospecimen and Tissue Procurement (BSTP) Shared Resource Facility facilitated the construction of tissue microarrays and immunohistochemical studies. Special thanks to Dana Napier for her excellent histologic expertise. Study data were collected and managed using REDCap electronic data capture tools hosted at the University of Kentucky. This research was also supported by the Markey Cancer Center Free Radical Biology in Cancer (FRBC) Shared Resource Facility. Flow cytometry and cell sorting was carried out at the University of Kentucky Flow Cytometry and Cell Sorting (FCCS) Core Facility, which is supported in part by the Office of the Vice President for Research, the Markey Cancer Center and a grant from the NIH Shared Instrument Program (S10 RR026827-01A1). The BSTP, FRBC, and FCCS Shared Resource Facilities are all supported by the University of Kentucky Markey Cancer Center (P30CA177558). We thank Dr. Hai Yan of Duke University Medical Center for supplying us with pEGFP-N1-IDH1 and pEGFP-N1-IDH1R132H plasmids. We thank Dr. Haining Zhu and Dr. Jozsef Gal, Department of Molecular and Cellular Biochemistry of the University of Kentucky, for providing the GFP-LC3 plasmid. We thank Dr. Daret St. Clair, Department of Toxicology, for her excellent suggestions involving MnSOD experiments. We also thank Drs. Jeremy Rich and Monica Venere from the Cleveland Clinic Foundation for their generous help and training with the patient-derived glioma cultures.
Conflict of interest
None of the authors have any conflicts of interest pertaining to the data in this study.
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