Biology subjects

Gilbert, M. R.

Publications and source records attributed to Gilbert, M. R..

8 recordsLinked to original sources

bioRxiv2024

Targeting the sphingolipid rheostat in IDH1mut glioma alters cholesterol homeostasis and triggers apoptosis via membrane degradation

The cross-regulation of metabolism and trafficking is not well understood for the vital sphingolipids and cholesterol constituents of cellular compartments. While reports are starting to surface on how sphingolipids like sphingomyelin (SM) dysregulate cholesterol levels in different cellular compartments (Jiang et al., 2022), limited research is available on the mechanisms driving the relationship between sphingolipids and cholesterol homeostasis, or its biological implications. Previously, we have identified sphingolipid metabolism as a unique vulnerability for IDH1mut gliomas via a rational drug design. Herein, we show how modulating sphingolipid levels affects cholesterol homeostasis in brain tumors. However, we unexpectedly discovered for the first time that C17 sphingosine and NDMS addition to cancer cells alters cholesterol homeostasis by impacting its cellular synthesis, uptake, and efflux leading to a net decrease in cholesterol levels and inducing apoptosis. Our results reflect a reverse correlation between the levels of sphingosines, NDMS, and unesterified, free cholesterol in the cells. We show that increasing sphingosine and NDMS (a sphingosine analog) levels alter not only the trafficking of cholesterol between membranes but also the efflux and synthesis of cholesterol. We also demonstrate that despite the effort to remove free cholesterol by ABCA1-mediated efflux or by suppressing machinery for the influx (LDLR) and biosynthetic pathway (HMGCR), apoptosis is inevitable for IDH1mut glioma cells. This is the first study that shows how altering sphingosine levels directly affects cholesterol homeostasis in cancer cells and can be used to manipulate this relationship to induce apoptosis in IDH1mut gliomas.

cancer biology↗

bioRxiv2023

Exploiting the therapeutic vulnerability of IDH-mutant gliomas with zotiraciclib

Isocitrate dehydrogenase (IDH)-mutant gliomas have distinctive metabolic and biological traits that may render them susceptible to targeted treatments. Here, by conducting a high-throughput drug screen, we pinpointed a specific susceptibility of IDH-mutant gliomas to zotiraciclib (ZTR). ZTR exhibited selective growth inhibition across multiple IDH-mutant glioma in vitro and in vivo models. Mechanistically, ZTR at low doses suppressed CDK9 and RNA Pol II phosphorylation in IDH-mutant cells, disrupting mitochondrial function and NAD+ production, causing oxidative stress. Integrated biochemical profiling of ZTR kinase targets and transcriptomics unveiled that ZTR-induced bioenergetic failure was linked to the suppression of PIM kinase activity. We posit that the combination of mitochondrial dysfunction and an inability to adapt to oxidative stress resulted in significant cell death upon ZTR treatment, ultimately increasing the therapeutic vulnerability of IDH-mutant gliomas. These findings prompted a clinical trial evaluating ZTR in IDH-mutant gliomas towards precision medicine (NCT05588141). HighlightsO_LIZotiraciclib (ZTR), a CDK9 inhibitor, hinders IDH-mutant glioma growth in vitro and in vivo. C_LIO_LIZTR halts cell cycle, disrupts respiration, and induces oxidative stress in IDH-mutant cells. C_LIO_LIZTR unexpectedly inhibits PIM kinases, impacting mitochondria and causing bioenergetic failure. C_LIO_LIThese findings led to the clinical trial NCT 05588141, evaluating ZTR for IDH-mutant gliomas. C_LI

cancer biology↗

bioRxiv2023

"Tumor Treating Fields" delivered via electromagnetic induction have varied effects across glioma cell lines and electric field amplitudes

Previous studies reported that alternating electric fields (EFs) in the intermediate frequency (100 - 300 kHz) and low intensity (1 - 3 V/cm) regime -- termed "Tumor Treating Fields" (TTFields) -- have a specific, anti-proliferative effect on glioblastoma multiforme (GBM) cells. However, the mechanism(s) of action remain(s) incompletely understood, hindering the clinical adoption of treatments based on TTFields. To advance the study of such treatment in vitro, we developed an inductive device to deliver EFs to cell cultures which improves thermal and osmolar regulation compared to prior devices. Using this inductive device, we applied continuous, 200 kHz electromagnetic fields (EMFs) with a radial EF amplitude profile spanning 0 - 6.5 V/cm to cultures of primary rat astrocytes and several human GBM cell lines -- U87, U118, GSC827, and GSC923 -- for a duration of 72 hours. Cell density was assessed via segmented pixel densities from GFP expression (U87, U118) or from staining (astrocytes, GSC827, GSC923). Further RNA-Seq analyses were performed on GSC827 and GSC923 cells. Treated cultures of all cell lines exhibited little to no change in proliferation at lower EF amplitudes (0 - 3 V/cm). At higher amplitudes (> 4 V/cm), different effects were observed. Apparent cell densities increased (U87), decreased (GSC827, GSC923), or showed little change (U118, astrocytes). RNA-Seq analyses on treated and untreated GSC827 and GSC923 cells revealed differentially expressed gene sets of interest, such as those related to cell cycle control. Up- and down-regulation, however, was not consistent across cell lines nor EF amplitudes. Our results indicate no consistent, anti-proliferative effect of 200 kHz EMFs across GBM cell lines and thus contradict previous in vitro findings. Rather, effects varied across different cell lines and EF amplitude regimes, highlighting the need to assess the effect(s) of TTFields and similar treatments on a per cell line basis.

cancer biology↗

bioRxiv2022

Clinically oriented prediction of patient response to targeted and immunotherapies from the tumor transcriptome

BackgroundPrecision oncology is gradually advancing into mainstream clinical practice, demonstrating significant survival benefits. However, eligibility and response rates remain limited in many cases, calling for better predictive biomarkers. MethodsWe present ENLIGHT, a transcriptomics-based computational approach that identifies clinically relevant genetic interactions and uses them to predict a patients response to a variety of therapies in multiple cancer types, without training on previous treatment response data. We study ENLIGHT in two translationally oriented scenarios: Personalized Oncology (PO), aimed at prioritizing treatments for a single patient, and Clinical Trial Design (CTD), selecting the most likely responders in a patient cohort. FindingsEvaluating ENLIGHTs performance on 21 blinded clinical trial datasets in the PO setting, we show that it can effectively predict a patients treatment response across multiple therapies and cancer types. Its prediction accuracy is better than previously published transcriptomics-based signatures and is comparable to that of supervised predictors developed for specific indications and drugs. In combination with the IFN-{gamma}signature, ENLIGHT achieves an odds ratio larger than 4 in predicting response to immune checkpoint therapy. In the CTD scenario, ENLIGHT can potentially enhance clinical trial success for immunotherapies and other monoclonal antibodies by excluding non-responders, while overall achieving more than 90% of the response rate attainable under an optimal exclusion strategy. ConclusionENLIGHT demonstrably enhances the ability to predict therapeutic response across multiple cancer types from the bulk tumor transcriptome. FundingThis research was supported in part by the Intramural Research Program, NIH and by the Israeli Innovation Authority.

bioinformatics↗

bioRxiv2021

Recurrent fusions in PLAGL1 define a distinct subset of pediatric-type supratentorial ependymoma

Ependymomas encompass a heterogeneous group of central nervous system (CNS) neoplasms that occur along the entire neuroaxis. In recent years, extensive (epi-)genomic profiling efforts have identified several molecular groups of ependymoma that are characterized by distinct molecular alterations and/or patterns. Based on unsupervised visualization of a large cohort of genome-wide DNA methylation data, we identified a highly distinct group of pediatric-type tumors (n = 40) forming a cluster separate from all established CNS tumor types, of which a high proportion were histopathologically diagnosed as ependymoma. RNA sequencing revealed recurrent fusions involving the pleomorphic adenoma gene-like 1 (PLAGL1) gene in 19 of 20 of the samples analyzed, with the most common fusion being EWSR1:PLAGL1 (n = 13). Five tumors showed a PLAGL1:FOXO1 fusion and one a PLAGL1:EP300 fusion. High transcript levels of PLAGL1 were noted in these tumors, with concurrent overexpression of the imprinted genes H19 and IGF2, which are regulated by PLAGL1. Histopathological review of cases with sufficient material (n = 16) demonstrated a broad morphological spectrum of largely ependymoma-like tumors. Immunohistochemically, tumors were GFAP-positive and OLIG2- and SOX10-negative. In 3/16 of the cases, a dot-like positivity for EMA was detected. Consistent with other fusion-positive ependymal groups, all tumors in our series were located in the supratentorial compartment. Median age of the patients at the time of diagnosis was 6.2 years. Analysis of time to progression or recurrence revealed survival times comparable to those of patients with ZFTA:RELA-fused ependymoma. In summary, our findings suggest the existence of a novel group of supratentorial ependymomas that are characterized by recurrent PLAGL1 fusions and enriched for pediatric patients.

cancer biology↗

bioRxiv2021

Cysteine is a limiting factor for glioma proliferation and survival

Nutritional intervention is becoming more prevalent as adjuvant therapy for many cancers in view of the tumor dependence on external sources for some nutrients. We report the dependence of glioma cells on exogenous cysteine/cystine, despite this amino acid being nonessential. 13C-tracing and the analysis of cystathionine synthase and cystathioninase levels revealed the metabolic landscape attributable to cysteine deprivation, and the disconnection between the methionine cycle and the transsulfuration pathway. Therefore, we explored the nutritional deprivation in a mouse model of glioma. Animals subjected to a cysteine/cystine-free diet survived longer, with concomitant reductions in glutathione and cysteine plasma levels. At the end point, however, tumors displayed the ability to synthesize glutathione, although higher levels of oxidative stress were detected. We observed a compensation from the nutritional intervention revealed as the recovery of cysteine-related metabolites in plasma. Our study highlights a time window where cysteine deprivation can be exploited for additional therapeutic strategies.

cancer biology↗

bioRxiv2020

IDH1 Mutations Induce Organelle Defects Via Dysregulated Phospholipids

Cytosolic IDH1 enzyme plays a key, but currently unexplored, role in lipid biosynthesis. Using Raman imaging microscopy, we identified heterogeneous lipid profiles in cellular organelles attributed uniquely to IDH1 mutations. Via organelle lipidomics, we found an increase in saturated and monounsaturated fatty acids in the endoplasmic reticulum of IDH1mut cells compared with IDHWT glioma. We showed that these fatty acids incorporate into phospholipids and induce organelle dysfunctions, with prominent dilation of Golgi apparatus, which can be restored by transient knockdown of stearyl-CoA desaturase or inhibition of D-2-hydroxyglutarate (D-2HG) formation. We validated these findings using tissue from patients with glioma. Oleic acid addition led to increased sensitivity to apoptosis of IDH1mut cells compared with IDHWT. Addition of D-2HG to U251WT cells lead in increased ER and Golgi apparatus dilation. Collectively, these studies provide clinically relevant insights into the functional link between IDH1mut-induced lipid alterations and organelle dysfunction, with therapeutic implications. SignificanceGliomas are devastating tumors, with the most aggressive form--glioblastoma multiforme-- correlated with a mean patient survival of 14.5 months. No curative treatment exists to date. Low-grade glioma (LGG) with the isocitrate dehydrogenase 1 (IDH1) mutation, R132H, provides a survival benefit to patients. Understanding the unique metabolic profile of IDH1mut could provide clues regarding its association with longer survival and information about therapeutic targets. Herein, we identified lipid imbalances in organelles, generated by IDHmut in cells and patient tissue, that were responsible for Golgi dilation and that correlated with increased survival. Addition of oleic acid, which tilted the balance towards elevated levels of monounsaturated fatty acids produced IDH1mut-specific cellular apoptosis. HighlightsO_LISingle-organelle omics revealed unique alterations in lipid metabolism due to IDH1-mutations. C_LIO_LIIDH mutation leads to organelle-wide structural defects. C_LIO_LIIDH1 mutation leads to increased monounsaturated fatty acids levels in glioma cells and oligodendroglioma patient samples. C_LIO_LILipid alterations affect the membrane integrity of the Golgi apparatus. C_LIO_LIIncreased D-2HG induced SCD expression and elevated monounsaturated fatty acids C_LIO_LITilting the balance toward more-abundant monounsaturated fatty acids leads to specific IDH1mut glioma apoptosis. C_LI

cancer biology↗

bioRxiv2020

Whole exome precision oncology targeting synthetic lethal vulnerabilities across the tumor transcriptome

Precision oncology has made significant advances in the last few years, mainly by targeting actionable mutations in cancer driver genes. However, the proportion of patients whose tumors can be targeted therapeutically remains limited. Recent studies have begun to explore the benefit of analyzing tumor transcriptomics data to guide patient treatment, raising the need for new approaches for systematically accomplishing that. Here we show that computationally derived genetic interactions can successfully predict patient response. Assembling a broad repertoire of 32 datasets spanning more than 1,500 patients and including both tumor transcriptomics and response data, we predicted the response in 17 out of 21 targeted and 8 out of 11 checkpoint therapy datasets across 8 different cancer types with considerable accuracy, without ever training on these datasets. Analyzing the recently published multi-arm WINTHER trial, we show that the fraction of patients benefitting from transcriptomic-based treatments could potentially be markedly increased from 15% to about 85% by targeting synthetic lethal vulnerabilities in their tumors. In summary, this is the first computational approach to obtain considerable predictive performance across many different targeted and immunotherapy datasets, providing a promising new way for guiding cancer treatment based on the tumor transcriptomics of cancer patients.

cancer biology↗