Biology subjects

Ligat, L.

Publications and source records attributed to Ligat, L..

5 recordsLinked to original sources

bioRxiv2025

SG33, a vaccine strain of myxoma virus with oncolytic potential, exploits macropinocytosis and clathrin-mediated endocytosis for entry into pancreatic cancer cells.

Oncolytic viruses are being investigated as therapeutic agents in cancer, yet their mechanisms of entry into tumor cells remain incompletely understood. We previously showed that SG33, a veterinary vaccinal strain derived from a pathogenous myxoma virus, displays oncolytic activity in preclinical models of pancreatic ductal adenocarcinoma (PDAC). Here, we investigated the entry pathways of SG33 into primary PDAC-derived cultures. We found that macropinocytosis, an endocytic process frequently upregulated in PDAC, contributes to SG33 uptake. Moreover, SG33 infection itself induced macropinocytosis in a subset of primary PDAC cultures. Mechanistic studies revealed that phosphatidylserine exposed on the viral envelope promotes SG33 internalization through apoptotic mimicry. In PDAC cultures lacking detectable macropinocytosis, SG33 employed clathrin-mediated endocytosis as an alternative entry route. These findings provide the first insights into the entry mechanisms of SG33 into PDAC-derived cells and indicate that this virus can utilize distinct endocytic pathways depending on the cellular context. ImportancePancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal cancers, with limited therapeutic options. Oncolytic virotherapy is emerging as a promising strategy to overcome treatment resistance, yet the mechanisms by which candidate viruses enter cancer cells remain poorly defined. Here, we characterize the entry route of SG33, a derivative of myxoma virus with potent oncolytic activity in PDAC models. We show that SG33 exploits multiple endocytic pathways, including macropinocytosis (MPC), induces MPC through apoptotic mimicry, and also uses clathrin-mediated endocytosis (CME). These findings provide the first evidence that SG33 has evolved a flexible cell entry strategy, which could enhance its efficacy in the heterogeneous context of PDAC. Understanding the molecular determinants of viral entry is essential for the rational design of improved oncolytic virotherapies. Our study is aligned with this objective and highlights SG33 as a promising candidate to expand the toolbox of virotherapeutic agents against aggressive cancers.

cancer biology↗

bioRxiv2025

Targeting human M2 macrophages with antibodies in optimized 3D tumor spheroids

Tumor microenvironment (TME) constituents, including tumor-associated macrophages (TAMs), are now well known to have a significant impact on tumor development. TAMs can be predominant cells in the TME, able to promote cancer cell proliferation, resistance to treatments and immunosuppression. Inactivating these TAMs in tumors by their depletion or their repolarization into a specific anti-tumor, inflammatory phenotype constitutes a significant challenge in immuno-oncology. Several tools and methods to target TAMs have been proposed but they often show low specificity for pro-tumoral macrophages and target myeloid cells too broadly. This research area is therefore in full expansion and warrants the development of appropriate study models. Given the current global effort to reduce the use of in vivo approaches, developing in vitro models that mimic the behavior of TAMs in the TME has become a priority. In this study, we focused on targeting pro-tumoral TAMs in a simple in vitro model recapitulating cancer cell proliferation and TAMs specific phenotype. We developed a 3D model consisting of cancer cells and pro-tumoral macrophages, in which these macrophages promote tumor cell proliferation, maintaining an immunosuppressive phenotype. We showed that, in this model, macrophages can be easily targeted and killed with specific antibodies even in the central regions of the spheroid. This model could be a first in vitro approach to screen new TAM depletion or depolarization tools before application in in vivo models.

cancer biology↗

bioRxiv2023

The intrinsically disordered region of the E3 ubiquitin ligase TRIP12 induces the formation of chromatin condensates and interferes with DNA damage response.

Chromatin compaction is crucial for the faithful expression and integrity of the genome. Although largely studied, proteins and mechanisms that control the chromatin compaction are not entirely discovered. We previously showed that the nuclear HECT-type E3 ubiquitin ligase Thyroid hormone Receptor Interacting Protein 12 (TRIP12) is tightly associated to chromatin. As TRIP12 is overexpressed in several types of cancers, we explored herein the consequences of a TRIP12 overexpression on chromatin homeostasis. First, we established the TRIP12 proxisome and unveiled its pleiotropic role in chromatin regulation. Second, we demonstrated that TRIP12 overexpression leads to the formation of chromatin condensates enriched in heterochromatin marks via its intrinsically disordered region (IDR). We further discovered that the formation of TRIP12-mediated chromatin condensates is highly dynamic and driven by a mechanism of phase separation. Chromatin condensate formation depends on the TRIP12 concentration, the length of the TRIP12-IDR and relies on electrostatic interactions. We found that the formation of TRIP12 mediated-condensates alters cell cycle progression, genome accessibility, transcription as well as DNA damage response by inhibiting the accumulation of Mediator of DNA Damage Checkpoint 1 (MDC1). Altogether, this study reveals a novel dynamic role for TRIP12 in chromatin compaction independently of its ubiquitin ligase activity with important consequences on cellular homeostasis. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=155 SRC="FIGDIR/small/556486v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@13b3d90org.highwire.dtl.DTLVardef@46b991org.highwire.dtl.DTLVardef@1410bdeorg.highwire.dtl.DTLVardef@1722197_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2022

Single-cell Spatial Explorer: Easy exploration of spatial and multimodal transcriptomics

The development of single cell technologies yields large datasets of informations as diverse and multimodal as transcriptomes, immunophenotypes, and spatial position from tissue sections in the so-called spatial transcriptomics. Currently however, user-friendly, powerful, and free algorithmic tools for straightforward analysis of spatial transcriptomic datasets are scarce. Here, we introduce Single-Cell Spatial Explorer, an open-source software for multimodal exploration of spatial transcriptomics, examplified with 6 human and murine tissues datasets.

bioinformatics↗

bioRxiv2018

Vasohibin1, a new IRES trans-acting factor for sequential induction of angiogenic factors in hypoxia

Hypoxia, a major inducer of angiogenesis, is known to trigger major changes of gene expression at the transcriptional level. Furthermore, global protein synthesis is blocked while internal ribosome entry sites (IRES) allow specific mRNAs to be translated. Here we report the transcriptome and translatome signatures of (lymph)angiogenic genes in hypoxic HL-1 cardiomyocytes: most genes are not induced at the transcriptome-, but at the translatome level, including all IRES-containing mRNAs. Our data reveal activation of (lymph)angiogenic mRNA IRESs in early hypoxia. We identify vasohibin1 (VASH1) as an IRES trans-acting factor (ITAF) able to activate FGF1 and VEGFD IRESs in hypoxia while it inhibits several IRESs in normoxia. Thus this new ITAF may have opposite effects on IRES activities. These data suggest a generalized process of IRES-dependent translational induction of (lymph)angiogenic growth factors expression in early hypoxia, whose pathophysiological relevance is to trigger formation of new functional vessels in ischemic heart. VASH1 is not always required, indicating that the IRESome composition is variable, thus allowing subgroups of IRESs to be activated under the control of different ITAFs.

cell biology↗