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Nuclear FABP7 regulates cell proliferation of wild-type IDH1 glioma through caveolae formation.

ABSTRACT: Isocitrate dehydrogenase 1 (IDH1) is a key enzyme in cellular metabolism. IDH1 mutation (IDH1mut) is the most important genetic alteration in lower grade glioma, whereas glioblastoma (GB), the most common malignant brain tumor, often has wild-type IDH1 (IDH1wt). Although there is no effective treatment yet for neither IDH1wt nor IDHmut GB, it is important to note that the survival span of IDH1wt GB patients is significantly shorter than those with IDH1mut GB. Thus, understanding IDH1wt GB biology and developing effective molecular-targeted therapies is of paramount importance. Fatty acid-binding protein 7 (FABP7) is highly expressed in GB, and its expression level is negatively correlated with survival in malignant glioma patients; however, the underlying mechanisms of FABP7 involvement in tumor proliferation are still unknown. In this study, we demonstrate that FABP7 is highly expressed and localized in nuclei in IDH1wt glioma. Wild-type FABP7 (FABP7wt) overexpression in IDH1wt U87 cells increased cell proliferation rate, caveolin-1 expression, and caveolae/caveosome formation. In addition, FABP7wt overexpression increased the levels of H3K27ac on the caveolin-1 promoter through controlling the nuclear acetyl-CoA level via the interaction with ACLY. Consistent results were obtained using a xenograft model transplanted with U87 cells overexpressing FABP7. Interestingly, in U87 cells with mutant FABP7 overexpression, both in vitro and in vivo phenotypes shown by FABP7wt overexpression were disrupted. Furthermore, IDH1wt patient GB showed upregulated caveolin-1 expression, increased levels of histone acetylation, and increased levels of acetyl-CoA compared with IDH1mut patient GB. Taken together, these data suggest that nuclear FABP7 is involved in cell proliferation of GB through caveolae function/formation regulated via epigenetic regulation of caveolin-1, and this mechanism is critically important for IDH1wt tumor biology.

SUBMITTER: Kagawa Y

PROVIDER: S-EPMC8732344 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundGlioblastoma of the corpus callosum (ccGBM) are rare tumors, with a dismal prognosis marked by a rapid clinical deterioration. For a long time, surgical treatment was not considered beneficial for most patients with such tumors. Recent studies claimed an improved survival for patients undergoing extensive resection, albeit without integration of the molecular profile of the lesions. The purpose of this study was to investigate the effect of biopsy and surgical resection on oncological and functional outcomes in patients with IDH wild-type ccGBM.MethodsWe performed a retrospective analysis of our institution's database of patients having been treated for high-grade glioma between 2005 and 2017. Inclusion criteria were defined as follows: patients older than 18 years, histopathological, and molecularly defined IDH wild-type glioma, major tumor mass (at least 2/3) invading the corpus callosum in the sagittal plane with a uni- or bilateral infiltration of the adjacent lobules. Surgical therapy (resection vs. biopsy), extent of resection according to the remaining tumor volume and adjuvant treatment as well as overall survival and functional outcome using the Karnofsky Performance Score (KPS) were analyzed.ResultsFifty-five patients were included in the study, from which the mean age was 64 years and men (n = 34, 61.8%) were more often affected than women (n = 21, 38.2%). Thirty (54.5%) patients were treated with stereotactic biopsy alone, while 25 patients received tumor resection resulting in 14.5% (n = 8) gross-total resections and 30.9% (n = 17) partial resections. The 2-year survival rate after resection was 30% compared to 7% after biopsy (p = 0.047). The major benefit was achieved in the group with gross-total resection, while partial resection failed to improve survival. Neurological outcome measured by KPS did not differ between both groups either pre- or postoperatively.ConclusionsOur study suggests that in patients with corpus callosum glioblastoma, gross-total resection prolongs survival without negatively impacting neurological outcome as compared to biopsy.

Project description:Isocitrate dehydrogenase 1 (IDH1) is the most commonly mutated metabolic enzyme in human malignancy. A heterozygous genetic alteration, arginine 132, promotes the conversion of ?-ketoglutarate to D-2-hydroxyglutarate (2-HG). Although pharmacologic inhibitors of mutant IDH1 are promising, resistance mechanisms to targeted therapy are not understood. Additionally, the role of wild-type IDH1 (WT.IDH1) in cancer requires further study. Recently, it was observed that the regulatory RNA-binding protein, HuR (ELAVL1), protects nutrient-deprived cancer cells without IDH1 mutations, by stabilizing WT.IDH1 transcripts. In the present study, a similar regulatory effect on both mutant (Mut.IDH1) and WT.IDH1 transcripts in heterozygous IDH1-mutant tumors is observed. In ribonucleoprotein immunoprecipitation assays of IDH1-mutant cell lines, wild-type and mutant IDH1 mRNAs each bound to HuR. Both isoforms were profoundly downregulated at the mRNA and protein levels after genetic suppression of HuR (siRNAs or CRISPR deletion) in HT1080 (R132C IDH1 mutation) and BT054 cells (R132H). Proliferation and invasion were adversely affected after HuR suppression and metabolomic studies revealed a reduction in Pentose Phosphate Pathway metabolites, nucleotide precursors, and 2-HG levels. HuR-deficient cells were especially sensitive to stress, including low glucose conditions or a mutant IDH1 inhibitor (AGI-5198). IDH1-mutant cancer cells were rescued by WT.IDH1 overexpression to a greater extent than Mut.IDH1 overexpression under these conditions. This study reveals the importance of HuR's regulation of both mutant and wild-type IDH1 in tumors harboring a heterozygous IDH1 mutation with implications for therapy. IMPLICATIONS: This study highlights the HuR-IDH1 (mutant and wild-type IDH1) regulatory axis as a critical, actionable therapeutic target in IDH1-mutated cancer, and incomplete blockade of the entire HuR-IDH1 survival axis would likely diminish the efficacy of drugs that selectively target only the mutant isoenzyme.

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Nuclear FABP7 regulates cell proliferation of wild-type IDH1 glioma through caveolae formation.

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