Biology subjects

Bessette, B.

Publications and source records attributed to Bessette, B..

5 recordsLinked to original sources

bioRxiv2026

Effects of panitumumab on the proteome of treated EGFRvIII glioblastoma cells and on their extracellular vesicles

Glioblastoma (GB) is an aggressive brain tumor for which reliable biomarkers of therapeutic response are still needed. Extracellular vesicles (EVs) can carry molecular components derived from their parent cells, thereby providing information on changes associated with the tumor and treatments. Among potential biomarkers, epidermal growth factor receptor variant III (EGFRvIII), is found in more than 40% of GB patients and is associated with aggressive tumor behavior and therapeutic resistance. EGFRvIII has also been detected on the surface of EVs, suggesting its potential value for monitoring tumor-associated molecular changes. This study investigated the effects of panitumumab, an anti-EGFR monoclonal antibody, on the proteomic profiles of EVs derived from EGFRvIII cells. U87 and U87-EGFRvIII cells and their derived EVs were characterized before and after treatment. EGFRvIII expression in cells and EVs was assessed by Western blotting and flow cytometry. Proteomic analyses were performed on cell lysates and EVs before and after treatment. Our results demonstrate that panitumumab significantly reduced surface EGFRvIII on EVs derived from U87-EGFRvIII cells, whereas no significant decrease was observed in cell lysates. This suggests that treatment may affect EGFRvIII trafficking or its incorporation into EVs. The proteomic analysis highlighted much more changes in EVs than in their parental cells after treatment, particularly in proteins associated with extracellular matrix organization and collagen. Together, these results demonstrate that panitumumab treatment is associated with changes in protein profile from EVs derived from EGFRvIII cells suggesting that the panitumumab treatment might have an impact on cells that could be reflected on EVs released by glioblastoma cells. In conclusion, our results suggest that EVs derived from EGFRvIII cells could serve as a useful circulating biomarker for assessing treatment efficacy and for preventing treatment escape.

cancer biology↗

bioRxiv2023

Repression of exosome secretion by mutated β-catenin contributes to immune escape in hepatocellular carcinoma

Immune checkpoint inhibitors have produced encouraging results in cancer patients. However, the majority of {beta}-catenin-mutated tumors have been described as lacking immune infiltrates and resistant to immunotherapy. The mechanisms by which oncogenic {beta}-catenin affects immune surveillance remain unclear. Herein, we highlighted the involvement of {beta}-catenin in the regulation of the exosomal pathway and, by extension, in immune/cancer cell communication in hepatocellular carcinoma (HCC). We showed that mutated {beta}-catenin represses expression of SDC4 and RAB27A, two main actors in exosome biogenesis, in both liver cancer cell lines and HCC patient samples. Using nanoparticle tracking analysis and live-cell imaging, we further demonstrated that activated {beta}-catenin represses exosome release. Then, we demonstrated in 3D spheroid models that activation of {beta}-catenin promotes a decrease in immune cell infiltration through a defect in exosome secretion. Taken together, our results provide the first evidence that oncogenic {beta}-catenin plays a key role in exosome biogenesis. Our study gives new insight into the impact of {beta}-catenin mutations on tumor microenvironment remodeling, which could lead to the development of new strategies to enhance immunotherapeutic response.

cancer biology↗

bioRxiv2021

Acidity and sulfur oxidation intermediate concentrations controlled by O2-driven partitioning of sulfur oxidizing bacteria in a mine tailings impoundment

Acidification of freshwater in mining impacted areas is a major global environmental problem catalyzed by sulfur-oxidizing bacteria (SOB). To date, little is known about the active bacteria in mine tailings impoundments and their environmental niches. Here, biological sulfur oxidation was investigated over four years in a mine tailings impoundment, integrating sulfur geochemistry, genome-resolved metagenomics and metatranscriptomics. We demonstrated oxygen driven niche partitioning of SOB and their metabolic pathways that explain acidity generation and thiosulfate persistence. Four chemolithoautotrophic SOB, Halothiobacillus, Thiobacillus, Sulfuricurvum and Sediminibacterium comprised 37% to 73% of the analyzed communities. The impoundment waters alternated between the dominance of Halothiobacillus versus a Thiobacillus, Halothiobacillus, Sulfuricurvum and Sediminibacterium consortia. Halothiobacillus dominance was associated with lower pH values ([~]4.3), higher [H+]/[SO42-] and lower [S2O32-], collectively indicative of extensive sulfur oxidation. Halothiobacillus, which couple sulfur oxidation via the Sox pathway to aerobic respiration or NO2- reduction, were present throughout the depth profile, yet their expression of sox genes occurred only in upper highly oxygenated waters. Conversely, when consortia of Thiobacillus, Halothiobacillus, Sulfuricurvum and Sediminibacterium dominated, recycling/disproportionating reactions were more prevalent. Thiobacillus, which dominated deeper micro-oxic/anoxic waters, oxidized sulfur primarily through the rDSR pathway, coupled to NO3-/NO2- reduction, resulting in lower [H+]/[SO42-] and higher [S2O32-] relative to upper waters. These field results mirror the Sox/rDSR-geochemical patterns of experimental SOB enrichments and reveal opportunities for biological treatments of recalcitrant reduced sulfur compounds, as well as gene-based monitoring and in situ RNA detection to predict the onset of problematic geochemistry.

microbiology↗

bioRxiv2021

Radiotherapy induces specific miRNA expression profiles in glioblastoma exosomes

BackgroundGlioblastoma (GBM) is the most aggressive and frequent primary brain tumor during adulthood. One of the major treatments is the association of surgery and a combination of chemo and radiotherapies. Despite its immediate efficiency, it fails to prevent the cancer recurrence in the irradiated area due to radioresistance mechanisms. MicroRNAs (miRNAs or miR) are small non-coding, single strand RNA molecules encoding to various specific genes and able to regulate their expression and induce the tumor cell survival leading to radioresistance. Small extracellular vesicles (EVs), or exosomes released by tumor cells in tumor microenvironment and blood circulation are able to transport and diffuse miRNAs and affect the microenvironment by spreading the miRNAs, which drive radioresistance. AimsO_LITo identify the variations of miRNAs expression induced by irradiation in human glioblastoma U87-MG cells and their secreted exosomes collected in supernatants. C_LIO_LITo analyze the miRNAs variations in EVs-derived from the plasma of patients during radiotherapy, in order to identify a miRNA signature induced by radiotherapy in a liquid biopsy. C_LI Materiel and methodsU87-MG cells were cultured on plates and exposed to irradiation. miRNAs analyzes were performed in cells and in EVs isolated from cell supernatants to determine miRNAs expressions both in cells and in secreted exosomes before and after irradiation. Plasma-derived EVs were collected from 4 glioblastoma patients before and after surgery and radiotherapy treatments. ConclusionThe analysis of miRNAs expression profiles in both GBM cells and their derived EVs revealed that miR profile changes after irradiation. However, the number of similar miR between cells or EVs, following cell irradiation, was restricted to 3 miRs alone suggesting that the irradiation-induced changes in the miR profile in the cells and their EVs are not closely linked. In this context, the miR profile in EVs from patients plasma was investigated to establish a potential link with the miRNAs profile observed in EVs from irradiated cells and to assess its relationship with the response to radiotherapy. Three miRs (different from those identified in cells) were common between EVs derived from cells and patients derived-exosomes. These miRs detected in circulating EVs could provide a specific and reliable signature in response to ionizing radiation, which could be useful for monitoring the effectiveness of radiotherapy. Further experiments on a larger patients population with clinical data could also help to define whether this signature might have a prognostic value on the response to radiotherapy.

cancer biology↗

bioRxiv2018

Fragment-based screening identifies inhibitors of the ATPase activity and of hexamer formation of Cagα from the Helicobacter pylori type IV secretion system

Type IV secretion systems are membrane-bound multiprotein complexes that mediate the translocation of macromolecules across the bacterial cell envelope. In Helicobacter pylori a type IV secretion system is encoded by the cag pathogenicity island that encodes 27 Cag proteins and most of these are essential for bacterial virulence. We here present our work on the identification and characterization of inhibitors of Cag, a hexameric ATPase and member of the family of VirB11-like proteins that is essential for translocation of the CagA cytotoxin into mammalian cells. We conducted fragment-based screening using a differential scanning fluorimetry assay and identified 16 molecules that stabilize the protein during thermal denaturation suggesting that they bind Cag. Several of these molecules affect binding of ADP and four of them inhibit the ATPase enzyme activity of Cag. Analysis of enzyme kinetics suggests that their mode of action is non-competitive, suggesting that they do not bind to the ATPase active site. Cross-linking analysis suggests that the active molecules change the conformation of the protein and gel filtration and transmission electron microscopy show that molecule 1G2 dissociates the Cag hexamer. Analysis by X-ray crystallography reveals that molecule 1G2 binds at the interface between Cag subunits. Addition of the molecule 1G2 inhibits the induction of interleukin-8 production in gastric cancer cells after co-incubation with H. pylori suggesting that it inhibits Cag in vivo. Our results reveal a novel mechanism for the inhibition of the ATPase activity of VirB11-like proteins and the identified molecules have potential for the development into antivirulence drugs.

microbiology↗