Biology subjects

Pierron, G.

Publications and source records attributed to Pierron, G..

8 recordsLinked to original sources

bioRxiv2026

The ITCC-P4 PDX platform of pediatric cancers for preclinical testing

Cancer is the leading cause of disease-related deaths among children in high-income countries. Tumor heterogeneity and lack of mechanism-of-action-based therapeutic options are key challenges to overcome in order to improve pediatric cancer patients survival. Here, we report the EU-IMI-2 funded public-private partnership "ITCC-Pediatric Preclinical Proof-of-Concept Platform" (ITCC-P4), which has built a large repertoire of patient-derived xenograft (PDX) models, representing all major solid pediatric cancer types, for in vivo drug testing. Three-hundred-fifty-three PDX models from diagnostic and relapsed pediatric cancers have been established and molecularly characterized, together with matched germline/tumor samples. As proof-of-concept, we present in vivo drug screening data in neuroblastoma and rhabdomyosarcoma models. PDX data, accessible at http://r2platform.com/itcc-p4, allow the selection of models based on oncogenic drivers and/or potential biomarkers for preclinical testing. Operated by a non-profit entity (www.itccp4.com), this sustainable platform aids academic and industrial researchers in developing and prioritizing innovative therapies for pediatric cancer. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/703023v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@195ba30org.highwire.dtl.DTLVardef@f2c2d9org.highwire.dtl.DTLVardef@1d63f4dorg.highwire.dtl.DTLVardef@d60027_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2025

Cytoplasmic roles of HSATIII RNAs in RNA granule assembly and production of actin cytoskeleton-associated repeat-containing proteins

HSATIII architectural lncRNAs are nuclear short-tandem repeat ncRNAs induced upon thermal stress and serve as scaffolding molecules for nuclear stress bodies (nSBs), stress-induced membraneless organelles in the nucleus. We report that HSATIII lncRNAs are exported to the cytoplasm during stress recovery, where they form novel cytoplasmic bodies with nucleocytoplasmic RNA-binding proteins, including PURA, PURB, and m6A reader proteins. Recruitment of ALYREF to nSBs promotes HSATIII RNA export. These HSATIII-based granules, named HERALDs (Heat-removal-associated scaffolds), are transported along microtubules and accumulate at distal cellular regions. We further show that cytoplasmic HSATIII RNAs are translated into MEWNG-rich proteins, which interact with actin filaments and form complexes with HSPA8 and stress granule proteins such as ZC3HAV1 and ATXN2L. Together, these findings reveal previously unrecognized cytoplasmic roles of HSATIII RNAs, functioning both as lncRNAs to scaffold RNA granules and as mRNAs to produce proteins during the late phase of thermal stress recovery.

molecular biology↗

bioRxiv2023

Shell protein composition specified by NEAT1 domains dictates the formation of paraspeckles as distinct membraneless organelles

Many membraneless organelles (MLOs) formed through phase separation play crucial roles in various cellular processes. Although these MLOs co-exist in cells, how they maintain their independence without coalescence or engulfment remains largely unknown. Here, we investigated the molecular mechanism by which paraspeckles with core-shell architecture scaffolded by NEAT1_2 lncRNAs exist as distinct MLOs. We identified NEAT1 deletion mutants that assemble paraspeckles that are incorporated into nuclear speckles. Several paraspeckle proteins, including SFPQ, HNRNPF, and BRG1, prevent this incorporation and thus contribute to the segregation of paraspeckles from nuclear speckles. Shell localization of these proteins in the paraspeckles, which is determined by NEAT1_2 lncRNA domains, is required for this segregation process. Conversely, U2-related spliceosomal proteins are involved in internalizing the paraspeckles into nuclear speckles. This study shows that the paraspeckle shell composition dictates the independence of MLOs in the nucleus, providing insights into the importance of the shell in defining features and functions of MLOs.

cell biology↗

bioRxiv2023

mTOR Inhibition Suppresses Salinomycin-Induced Ferroptosis in Breast Cancer Stem Cells by Ironing Out Mitochondrial Dysfunctions

Ferroptosis constitutes a promising therapeutic strategy against cancer by efficiently targeting the highly tumorigenic and treatment-resistant cancer stem cells (CSCs). We previously showed that the lysosomal iron-targeting drug Salinomycin (Sal) was able to eliminate CSCs by triggering ferroptosis. Here, in a well-established breast CSCs model (human mammary epithelial HMLER CD24low/CD44high), we identified that pharmacological inhibition of mechanistic target of rapamycin (mTOR), suppresses Sal-induced ferroptosis. Mechanistically, mTOR inhibition modulates iron cellular flux and prevents the iron and ROS bursts induced by Sal. Besides, integration of multi-omics data identified mitochondria as a key target of Sal action. We demonstrated that mTOR inhibition prevents Sal-induced mitochondrial functional and structural alteration, and that Sal-induced metabolic plasticity is mainly dependent on the mTOR pathway. Overall, our findings provide experimental evidences on the detailed mechanisms of mTOR as a crucial effector of Sal-induced ferroptosis, and gives proof-of-concept that careful evaluation of such combination therapy (here mTOR and ferroptosis co-targeting) is required for effective treatment. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/539040v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@8b8772org.highwire.dtl.DTLVardef@695e0forg.highwire.dtl.DTLVardef@19e3f83org.highwire.dtl.DTLVardef@5bc0a6_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2021

Sensitive visualization of SARS-CoV-2 RNA with CoronaFISH

The current COVID-19 pandemic is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The positive-sense single-stranded RNA virus contains a single linear RNA segment that serves as a template for transcription and replication, leading to the synthesis of positive and negative-stranded viral RNA (vRNA) in infected cells. Tools to visualize viral RNA directly in infected cells are critical to analyze its replication cycle, screen for therapeutic molecules or study infections in human tissue. Here, we report the design, validation and initial application of fluorescence in situ hybridization (FISH) probes to visualize positive or negative RNA of SARS-CoV-2 (CoronaFISH). We demonstrate sensitive visualization of vRNA in African green monkey and several human cell lines, in patient samples and human tissue. We further demonstrate the adaptation of CoronaFISH probes to electron microscopy (EM). We provide all required oligonucleotide sequences, source code to design the probes, and a detailed protocol. We hope that CoronaFISH will complement existing techniques for research on SARS-CoV-2 biology and COVID-19 pathophysiology, drug screening and diagnostics.

microbiology↗

bioRxiv2021

Interplay between intrinsic reprogramming potential and microenvironment controls neuroblastoma cell plasticity and identity

Two cell identities, noradrenergic and mesenchymal, have been characterized in neuroblastoma cell lines according to their epigenetic landscapes relying on specific circuitries of transcription factors. Yet, their relationship and relative contribution in patient tumors remain poorly defined. Here, we demonstrate that the knock-out of GATA3, but not of PHOX2A or PHOX2B, in noradrenergic cells induces a mesenchymal phenotype. Our results document spontaneous plasticity in several models between both identities and show that plasticity relies on epigenetic reprogramming. We demonstrate that an in vivo microenvironment provides a powerful pressure towards a noradrenergic identity for these models. Consistently, tumor cells with a mesenchymal identity are not detected in a series of PDX models. Further study of the intra-tumor noradrenergic heterogeneity reveals two distinct cell populations exhibiting features of chromaffin-like or sympathoblast-like cells. This work emphasizes that both external cues of the environment and intrinsic factors control plasticity and cell identity in neuroblastoma.

cancer biology↗

bioRxiv2020

Paraspeckles are constructed as block copolymer micelles through microphase separation

Paraspeckles are constructed by NEAT1_2 architectural long noncoding RNAs and possess characteristic cylindrical shapes with highly ordered internal organization, distinct from typical liquid-liquid phase-separated condensates. We experimentally and theoretically investigated how the shape and organization of paraspeckles are determined. We identified the NEAT1_2 RNA domains responsible for shell localization of the NEAT1_2 ends, which determine the characteristic internal organization. We then applied a theoretical framework using soft matter physics to understand the principles that determine the NEAT1_2 organization, shape, number, and size of paraspeckles. By treating paraspeckles as amphipathic block copolymer micelles, we could explain and predict the experimentally observed behaviors of paraspeckles upon NEAT1_2 domain deletions or transcriptional modulation. Thus, we propose that paraspeckles are block copolymer micelles assembled through microphase separation. This work provides an experimentally-based theoretical framework for the concept that ribonucleoprotein complexes (RNPs) can act as block copolymers to form RNA-scaffolding microphase-separated condensates in cells.

molecular biology↗

bioRxiv2018

RNA is a critical element for the sizing and the composition of phase-separated RNA-protein condensates

Liquid-liquid phase separation is thought to be a key organizing principle in eukaryotic cells to generate highly concentrated dynamic assemblies, such as the RNP granules. Numerous in vitro approaches have validated this model, yet a missing aspect is to take into consideration the complex molecular mixture and promiscuous interactions found in vivo. Here we report the versatile scaffold \"ArtiG\" to generate concentration-dependent RNA-protein condensates within living cells, as a bottom-up approach to study the impact of co-segregated endogenous components on phase separation. We demonstrate that intracellular RNA seeds the nucleation of the condensates, as it provides molecular cues to locally coordinate the formation of endogenous high order RNP assemblies. Interestingly, the co-segregation of intracellular components ultimately impacts the size of the phase-separated condensates. Thus, RNA arises as an architectural element that can influence the composition and the morphological outcome of the condensate phases in an intracellular context.

cell biology↗