IDH1 R132H mutation regulates glioma chemosensitivity through Nrf2 pathway

Abstract

PurposeNumerous studies have reported that glioma patients with isocitrate dehydrogenase 1(IDH1) R132H mutation are sensitive to temozolomide treatment. However, the mechanism of IDH1 mutations on the chemosensitivity of glioma remains unclear. In this study, we investigated the role and the potential mechanism of Nrf2 in IDH1 R132H-mediated drug resistance.MethodsWild type IDH1 (R132H-WT) and mutant IDH1 (R132H) plasmids were constructed. Stable U87 cells and U251 cells overexpressing IDH1 were generated. Phenotypic differences between IDH1-WT and IDH1 R132H overexpressing cells were evaluated using MTT, cell colony formation assay, scratch test assay and flow cytometry. Expression of IDH1 and its associated targets, nuclear factor-erythroid 2-related factor 2 (Nrf2), NAD(P)H quinine oxidoreductase 1 (NQO1), multidrug resistant protein 1 (MRP1) and p53 were analyzed.ResultsThe IDH1 R132H overexpressing cells were more sensitive to temozolomide than WT and the control, and Nrf2 was significantly decreased in IDH1 R132H overexpressing cells. We found that knocking down Nrf2 could decrease resistance to temozolomide. The nuclear translocation of Nrf2 in IDH1 R132H overexpressing cells was lower than the WT and the control groups after temozolomide treatment. When compared with WT cells, NQO1 expression was reduced in IDH1 R132H cells, especially after temozolomide treatment. P53 was involved in the resistance mechanism of temozolomide mediated by Nrf2 and NQO1.ConclusionsNrf2 played an important role in IDH1 R132H-mediated drug resistance. The present study provides new insight for glioma chemotherapy with temozolomide.

Wild-type and mutated IDH1/2 enzymes and therapy responses

“…Moreover, NADPH is necessary for the synthesis of deoxynucleotides and thus for DNA damage repair [ 58 ]. IDH1/2 mutations cause loss of IDH1/2 wild-type functions [ 28 , 29 ], resulting in decreased NADPH and GSH levels and increased ROS levels, both in steady-state conditions and after induction of ROS production [ 29 , 41 , 48 , 52 , 59 , 60 ]. In addition, d - 2HG accumulation induces oxidative stress independently of IDH1/2 mutations [ 32 – 34 ].…”

“…For example, IDH1 mutations induce a gene expression signature that render AML cells vulnerable to all- trans retinoic acid (ATRA/tretinoin), which promotes the expression of genes that induce differentiation of IDH1 -mutated AML cells [ 61 ]. Furthermore, the epigenetic effects of IDH1/2 mutations may underlie many of the synthetic lethalities already described in this review, including the downregulation of NAPRT1 to sensitize cells to NAMPT inhibition [ 52 ], the downregulation of NRF2 and ATM to sensitize cells to chemo/radiotherapy [ 60 , 74 ], the downregulation of BCAT1 to increase the dependency on glutaminolysis [ 90 ], and the induction of homologous recombination defects to sensitize cells to PARP inhibitors, as described above in more detail [ 75 ].…”

PI3K/mTOR inhibition of IDH1 mutant glioma leads to reduced 2HG production that is associated with increased survival

“…However, this model has lost 2HG production due to loss of the wild-type IDH allele, a phenomenon that has been shown to occur in IDH mutant gliomas 71 . In contrast, the U87IDHmut model is an easy to grow and very stable model that has been frequently used, not only by our group, but also in several other studies in the literature 72–76 . Importantly, we have previously demonstrated that 2HG levels in our U87IDHmut tumor tissue extracts (9.8 ± 1.6 μmol/g of tissue) were comparable to 2HG levels reported in patients (5–35 μmol/g) 77 .…”

Radiosensitization and a Less Aggressive Phenotype of Human Malignant Glioma Cells Expressing Isocitrate Dehydrogenase 1 (IDH1) Mutant Protein: Dissecting the Mechanisms

“…Due to the fact that almost all patients with a malignant glioma receive a single treatment or a combined therapy it is difficult to specify whether IDH1 mutation is associated with a less aggressive phenotype or directly linked to increased sensitivity to therapy. Thus, different studies or clinical trials have been focused on the effect of expression of mutated IDH1 on cellular behavior and response to therapy since the first mutations of IDH1 were discovered in 2008 [17,38,39,40].…”