Biology subjects

Verreault, M.

Publications and source records attributed to Verreault, M..

5 recordsLinked to original sources

bioRxiv2025

Multi-omics characterization of IDH-mutant astrocytoma-derived cell lines reveals NOTCH-regulated plastic quiescent astrocyte-like state

Diffuse IDH-mutant astrocytomas are brain tumors typically diagnosed as low-grade but capable of progressing to higher grades. They exhibit three cellular states resembling astrocytes, oligodendrocytes, and neural progenitor (NPC) cells. Understanding their biology has been challenging due to the lack of relevant in vitro models. Here we established and extensively characterized four astrocytoma cell lines (LGG275, LGG336, LGG85, LGG349) derived from IDH-mutant astrocytoma at different grades, cultured in defined media and analyzed by multi-omics. These lines display growth rates in vitro and in vivo consistent with tumor grade and recapitulate key molecular alterations observed in patient tumors, including IDH1, ATRX, and TP53 mutations, activation of the alternative lengthening of telomeres (ALT) pathway and, in the most aggressive line, amplification of MET and PDGFRA. Single-cell RNA sequencing showed that the 4 astrocytoma lines maintain the three major cellular states observed in patient tumors. A hallmark of higher-grade-derived lines (LGG85, LGG349) is the persistence of NPC-like populations without growth factors, reflecting tumor progression. The LGG275 line most accurately mirrors slow-growing astrocytomas. Using CD44 and GLAST, we isolated astrocyte-like (CD44+/GLAST+) cells from LGG275 that preferentially adopt a quiescent state yet retain remarkable plasticity, generating oligodendrocyte-like cells (CD44-/GLAST-). Transcriptomic and proteomic analyses revealed that astrocyte-like and oligodendrocyte-like cells populations resemble quiescent and activated neural stem (NSC) cells from the adult subventricular zone (SVZ). Finally, we found that NOTCH signaling regulates the balance between astrocytic and oligodendrocytic states, while DLL3, expressed by oligodendrocyte-like cells, modulates both proliferation and phenotype. These cell lines represent valuable resources for dissecting lineage dynamics, heterogeneity, and progression mechanisms in IDH-mutant astrocytomas. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=118 SRC="FIGDIR/small/696808v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@953108org.highwire.dtl.DTLVardef@c6234aorg.highwire.dtl.DTLVardef@3703fcorg.highwire.dtl.DTLVardef@1e6c3a9_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightO_LIWe constituted a richly annotated biobank derived from 4 astrocytomas, showing similar characteristics to those found in patients, providing valuable tools to investigate cellular heterogeneity and plasticity, and link with tumor progression. C_LIO_LIscRNA-sequencing revealed three cell states (oligodendrocyte-like, astrocyte-like, and stem cell-like cells) akin to those found in tumors. C_LIO_LIAstrocyte-like cells are quiescent cells, plastic and similar to quiescent neural stem cell (qNSC) from the sub-ventricular zone (SVZ), while oligodendrocyte-like cells are similar to active NSC (aNSC). C_LIO_LIThe Notch pathway plays a role in cell plasticity, enabling a shift towards an astrocyte-like state. C_LI

cancer biology↗

bioRxiv2025

GLUCURONIDATION: THE LAST DEFENSIVE LINE AGAINST BILEACID TOXICITY DURING CHOLESTASIS.

Glucuronidation is a detoxification reaction for bile acids (BA). The present study evaluates its efficiency to protect liver cells during acute (biliary obstruction, BO) and chronic (primary biliary cholangitis, PBC and primary sclerosing cholangitis, PSC) cholestatic situations. BA-glucuronides (G) were first profiled in sera from control, PBC, PSC and BO donors. An impressive accumulation of BA-Gs, formed from toxic BAs, is observed in sera from BO patients. Liver samples from control, PBC, or PSC donors and human hepatic cells were exposed to BAs, BA-G, agonists of the BA sensors Pregnane X-Receptor (PXR) or Farnesoid X-Receptor (FXR) and were analyzed for the expression of BA-conjugating UDP-glucuronosyltransferase (UGT) enzymes using quantitative RT-PCR and/or immnunoblot. Expression of the BA-conjugating UGT1A3, 1A4, and 2B4 enzymes was increased in hepatocytes exposed to BA levels mimicking BO. PXR activation also induced expression of the 3 UGTs, while FXR agonists only activated the UGT1A4 and 2B4 genes. Gelshift and luciferase transfection assays identified PXR response elements within UGT1A3 and 1A4 gene promoters. Finally, Inflammation markers have been reduced in hepatocytes treated with BA-G instead of BA. ConclusionThe present study identifies glucuronidation as a self-defense mechanism against BA toxicity during cholestasis. While of limited efficiency by itself, this endogenous mechanism is proposed as a novel pharmacological target in the treatment of chronic cholestatic diseases.

pharmacology and toxicology↗

bioRxiv2024

The oncometabolite D-2-hydroxyglutarate promotes DNA hypermethylation at lineage-specific enhancers controlling microglial activation in IDHmut gliomas

Tumor-associated microglia and macrophages (TAMs), the most abundant myeloid populations in gliomas, shape immune responses through transcriptional programs influenced by the tumor microenvironment. Although these programs differ according to tumor IDH status, the underlying epigenetic mechanisms remain poorly understood. Here, we uncover widespread DNA hypermethylation in the myeloid compartment of IDH-mutant gliomas, predominantly at distal enhancers enriched for motifs of core microglial transcription factors (TFs). This remodeled enhancer landscape strongly correlated with reduced activity of TF regulons and coordinated repression of immunomodulatory programs that normally support microglial activation. Using primary human microglia, we show that prolonged exposure to the oncometabolite D-2-hydroxyglutarate (D-2HG) reduces TET activity and increases 5mC/5hmC ratios near TF-binding motifs within enhancers affected ex vivo. Consistent with these epigenetic alterations, D-2HG-treated microglia exhibited transcriptional signatures compatible with blunted proinflammatory responses, whereas pharmacological inhibition of mutant IDH in patients partially restored microglial immune reactivity. Altogether, our findings reveal a chronic D-2HG-driven epigenetic priming mechanism that promotes a hyporesponsive microglial state, providing a rationale for the immunologically cold phenotype of IDH-mutant gliomas and offering insight into how IDH-targeted therapies may reshape microglial immune responses.

cancer biology↗

bioRxiv2024

Circumventing glioblastoma resistance to temozolomide through optimal drug combinations designed by quantitative systems pharmacology and machine learning

Glioblastoma is currently associated to a dismal prognosis despite intensive treatment involving maximal-safe surgery, radiotherapy and temozolomide (TMZ)-based chemotherapy. Disease progression or relapse is often due to initial or acquired resistance to temozolomide, which may be mediated by the over-expression of the repair enzyme MGMT. To design TMZ-based drug combinations circumventing the initial resistance of MGMT-overexpressing cells, a quantitative systems pharmacology (QSP) model representing TMZ cellular pharmacokinetics-pharmacodynamics and their connection to the most altered pathways in GBM was developed. This digital network representation of TMZ cellular pharmacology successfully integrates, in a mechanistic fashion, multi-type time- and dose-resolved datasets, available in control or MGMT-overexpressing cells. In silico target inhibition screening identified an optimal antitumor strategy consisting in priming cancer cells with inhibitors of the base excision repair and of the homologous recombination pathway prior to TMZ exposure. This drug combination was validated in dedicated experiments, thus allowing to re-sensitize cells which were initially resistant to TMZ. Using machine learning, functional signatures of response to such optimal multiagent therapy were derived to assist decision making about administering it to other cancer cell lines or patients. The developed framework can be extended to account for additional patientspecific altered pathways and may be translated towards the clinics by representing the tumor micro-environment and drug whole-body pharmacokinetics. Overall, we successfully demonstrated the relevance of combined QSP and machine learning to design multi-agent pharmacotherapies circumventing initial tumor resistance. One Sentence SummaryAn integrated in vitro-in silico approach allowed to design optimal drug combinations re-sensitizing temozolomide-resistant glioblastoma cells.

cancer biology↗

bioRxiv2021

SLIT2-ROBO signaling in tumor-associated microglia/macrophages drives glioblastoma immunosuppression and vascular dysmorphia

SLIT2 is a secreted polypeptide that guides migration of cells expressing ROBO1&2 receptors. Herein, we investigated SLIT2/ROBO signaling effects in gliomas. In patients with glioblastoma (GBM), SLIT2 expression increased with malignant progression and correlated with poor survival and immunosuppression. Knockdown of SLIT2 in mouse glioma cells and patient derived GBM xenografts reduced tumor growth and synergized with immunotherapy to prolong survival. Tumor cell SLIT2 knockdown inhibited macrophage invasion and promoted a cytotoxic gene expression profile, which improved tumor vessel function and enhanced efficacy of chemotherapy and immunotherapy. Mechanistically, SLIT2 promoted microglia/macrophage chemotaxis and tumor-supportive polarization via ROBO1&2-mediated PI3K{gamma} activation. Macrophage Robo1&2 deletion and systemic SLIT2 trap delivery mimicked SLIT2 knockdown effects on tumor growth and the tumor microenvironment (TME), revealing SLIT2 signaling through macrophage ROBOs as a novel regulator of the GBM microenvironment and a potential immunotherapeutic target for brain tumors.

cancer biology↗