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Tryptophan metabolism is inversely regulated in the tumor and blood of patients with glioblastoma.

ABSTRACT: Tryptophan (Trp)-catabolic enzymes (TCEs) produce metabolites that activate the aryl hydrocarbon receptor (AHR) and promote tumor progression and immunosuppression in glioblastoma. As therapies targeting TCEs or AHR become available, a better understanding of Trp metabolism is required. Methods: The combination of LC-MS/MS with chemical isobaric labeling enabled the simultaneous quantitative comparison of Trp and its amino group-bearing metabolites in multiple samples. We applied this method to the sera of a cohort of 43 recurrent glioblastoma patients and 43 age- and sex-matched healthy controls. Tumor volumes were measured in MRI data using an artificial neural network-based approach. MALDI MSI visualized Trp and its direct metabolite N-formylkynurenine (FK) in glioblastoma tissue. Analysis of scRNA-seq data was used to detect the presence of Trp metabolism and AHR activity in different cell types in glioblastoma. Results: Compared to healthy controls, glioblastoma patients showed decreased serum Trp levels. Surprisingly, the levels of Trp metabolites were also reduced. The decrease became smaller with more enzymatic steps between Trp and its metabolites, suggesting that Trp availability controls the levels of its systemic metabolites. High tumor volume associated with low systemic metabolite levels and low systemic kynurenine levels associated with worse overall survival. MALDI MSI demonstrated heterogeneity of Trp catabolism across glioblastoma tissues. Analysis of scRNA-seq data revealed that genes involved in Trp metabolism were expressed in almost all the cell types in glioblastoma and that most cell types, in particular macrophages and T cells, exhibited AHR activation. Moreover, high AHR activity associated with reduced overall survival in the glioblastoma TCGA dataset. Conclusion: The novel techniques we developed could support the identification of patients that may benefit from therapies targeting TCEs or AHR activation.

SUBMITTER: Panitz V

PROVIDER: S-EPMC8490504 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND:Depression in patients with brain tumors is associated with impaired quality of life and shorter survival. Altered metabolism of tryptophan to serotonin and kynurenine metabolites may play a role in tumor-associated depression. Our recent studies with alpha[(11)C]methyl-L-tryptophan (AMT)-PET in brain tumor patients indicated abnormal tryptophan metabolism not only in the tumor mass but also in normal-appearing contralateral brain. In the present study, we explored if tryptophan metabolism in such brain regions is associated with depression. METHODS:Twenty-one patients (mean age: 57 years) with a brain tumor (10 meningiomas, 8 gliomas, and 3 brain metastases) underwent AMT-PET scanning. MRI and AMT-PET images were co-registered, and AMT kinetic parameters, including volume of distribution (VD', an estimate of net tryptophan transport) and K (unidirectional uptake, related to tryptophan metabolism), were measured in the tumor mass and in unaffected cortical and subcortical regions contralateral to the tumor. Depression scores (based on the Beck Depression Inventory-II [BDI-II]) were correlated with tumor size, grade, type, and AMT-PET variables. RESULTS:The mean BDI-II score was 12?±?10 (range: 2-33); clinical levels of depression were identified in seven patients (33 %). High BDI-II scores were most strongly associated with high thalamic AMT K values both in the whole group (Spearman's rho?=?0.63, p?=?0.004) and in the subgroup of 18 primary brain tumors (r?=?0.68, p?=?0.004). Frontal and striatal VD' values were higher in the depressed subgroup than in non-depressed patients (p?<?0.05); the group difference was even more robust when moderately/severely depressed patients were compared to patients with no/mild depression (frontal: p?=?0.005; striatal: p?<?0.001). Tumor size, grade, and tumor type were not related to depression scores. CONCLUSIONS:Abnormalities of tryptophan transport and metabolism in the thalamus, striatum, and frontal cortex, measured by PET, are associated with depression in patients with brain tumor. These changes may indicate an imbalance between the serotonin and kynurenine pathways and serve as a molecular imaging marker of brain tumor-associated depression. TRIAL REGISTRATION:ClinicalTrials.gov NCT02367469.

Project description:Abstract OBJECTIVE Glioblastoma (GBM) patients with high intratumoral IDO1 mRNA levels have an associated decrease in survival (Zhai et al., 2017; CCR). IDO1 is an immunosuppressive mediator that metabolizes tryptophan (Trp), and through its associated enzyme activity, has long been recognized to increase immunosuppressive CD4+CD25+FoxP3+ Tregs. Accordingly, we previously showed that the genetic knockdown of IDO1 in murine glioma cells, suppresses intratumoral Treg recruitment and increases animal subject survival. Unexpectedly, however, IDO1 knockdown has no effect on intratumoral Trp metabolism (Zhai et al., 2017; BBI). Further surprisingly, we recently demonstrated that, although IDO1 overexpression increases Treg levels in brain tumors, the pharmacological inhibition of IDO1 metabolism has no effect on Treg accumulation (Ladomersky et al., 2018; CCR). These novel data led us to question the requirement for IDO1 enzyme activity to regulate Tregs in malignant glioma. METHODS Lentiviral vectors encoding: (i) vector control-, (ii) wild-type (WT)-, or (iii) enzyme-null-IDO1, were created by site-directed mutagenesis in a plasmid containing WT, murine, IDO1-GFP cDNA. IDO1-deficient glioma cells from transgenic mice [(ERT2)GFAP→Cre;pTENfl/fl;p53fl/fl;Rbfl/fl;IDO1-/-] were transduced with the modified plasmids. RT-PCR, Western blotting and HPLC confirmed IDO1 expression and enzyme activity, in vitro. Syngeneic IDO1-/- mice were intracranially-engrafted with 2 × 105 modified glioma cells and studied for intratumoral Treg levels. RESULTS The substitution of IDO1 histidine 350, to an alanine (H350A), decreases IDO1 enzyme activity by 90%. Syngeneic mice with intracranial, IDO1 enzyme null (H350A) glioma, have similar intratumoral Treg levels as IDO1 WT glioma, at 25% and 26%, respectively, and is significantly increased as compared to the 5.8% Tregs in vector control glioma (P=0.015). CONCLUSIONS Our data challenge current dogma explaining how IDO1 causes Treg accumulation, and are in-line with the recent IDO1 enzyme inhibitor-focused Phase III clinical trial failure [NCT02752074]. We are now focused on revealing the mechanism underlying IDO1-mediated immunosuppression in malignant glioma.

Project description:Background and objective200 kHz tumor treating fields (TTFields) is clinically approved for newly-diagnosed glioblastoma (nGBM). Because its effects on conventional surveillance MRI brain scans are equivocal, we investigated its effects on perfusion MRI (pMRI) brain scans.MethodsEach patient underwent institutional standard pMRI: dynamic contrast-enhanced (DCE) and dynamic susceptibility contrast (DSC) pMRI at three time points: baseline, 2-, and 6-months on-adjuvant therapy. At each timepoint, the difference between T1 pre- versus post-contrast tumor volume (ΔT1) and these pMRI metrics were evaluated: normalized and standardized relative cerebral blood volume (nRCBV, sRCBV); fractional plasma volume (Vp), volume of extravascular extracellular space (EES) per volume of tissue (Ve), blood-brain barrier (BBB) permeability (Ktrans), and time constant for gadolinium reflux from EES back into the vascular system (Kep). Between-group comparisons were performed using rank-sum analysis, and bootstrapping evaluated likely reproducibility of the results.ResultsAmong 13 pMRI datasets (11 nGBM, 2 recurrent GBM), therapies included temozolomide-only (n = 9) and temozolomide + TTFields (n = 4). No significant differences were found in patient or tumor characteristics. Compared to temozolomide-only, temozolomide + TTFields did not significantly affect the percent-change in pMRI metrics from baseline to 2 months. But during the 2- to 6-month period, temozolomide + TTFields significantly increased the percent-change in nRCBV (+26.9% [interquartile range 55.1%] vs -39.1% [37.0%], p = 0.049), sRCBV (+9.5% [39.7%] vs -30.5% [39.4%], p = 0.049), Ktrans (+54.6% [1768.4%] vs -26.9% [61.2%], p = 0.024), Ve (+111.0% [518.1%] vs -13.0% [22.5%], p = 0.048), and Vp (+98.8% [2172.4%] vs -24.6% [53.3%], p = 0.024) compared to temozolomide-only.ConclusionUsing pMRI, we provide initial in-human validation of pre-clinical studies regarding the effects of TTFields on tumor blood volume and BBB permeability in GBM.

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Tryptophan metabolism is inversely regulated in the tumor and blood of patients with glioblastoma.

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