Ultrasmall AGuIX theranostic nanoparticles for vascular-targeted interstitial photodynamic therapy of glioblastoma

International audienceDespite combined treatments, glioblastoma outcome remains poor with frequent local recurrences, indicating that a more efficient and local therapy is needed. In this way, vascular-targeted photodynamic therapy (VTP) could help tumor eradication by destroying its neovessels. In this study, we designed a polysiloxane-based nanoparticle (NP) combining a magnetic resonance imaging (MRI) contrast agent, a photosensitizer (PS) and a new ligand peptide motif (KDKPPR) targeting neuropilin-1 (NRP-1), a receptor overexpressed by angiogenic endothelial cells of the tumor vasculature. This structure achieves the detection of the tumor tissue and its proliferating part by MRI analysis, followed by its treatment by VTP. The photophysical properties of the PS and the peptide affinity for NRP-1 recombinant protein were preserved after the functionalization of NPs. Cellular uptake of NPs by human umbilical vein endothelial cells (HUVEC) was increased twice compared to NPs without the KDKPPR peptide moiety or conjugated with a scramble peptide. NPs induced no cytotoxicity without light exposure but conferred a photocytotoxic effect to cells after photodynamic therapy (PDT). The in vivo selectivity, evaluated using a skinfold chamber model in mice, confirms that the functionalized NPs with KDKPPR peptide moiety were localized in the tumor vessel wall

Gadolinium-based nanoparticles for the treatment of glioblastoma by MRI-guided photodynamic therapy

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Ultrasmall AGuIX theranostic nanoparticles for vascular-targeted interstitial photodynamic therapy of glioblastoma

International audienceDespite combined treatments, glioblastoma outcome remains poor with frequent local recurrences, indicating that a more efficient and local therapy is needed. In this way, vascular-targeted photodynamic therapy (VTP) is a promising complementary approach to improve tumor eradication1 by destroying its neovessels2. In this study, we designed a polysiloxane-based nanoparticle (NP) combining a magnetic resonance imaging (MRI) contrast agent, a photosensitizer (PS) and a new ligand peptide motif (KDKPPR) targeting neuropilin-1 (NRP-1)3,4, a receptor overexpressed by angiogenic endothelial cells of the tumor vasculature. This structure achieves the detection of the tumor tissue and its proliferating part by MRI analysis, followed by its treatment by VTP. The photophysical properties of the PS and the peptide affinity for NRP-1 recombinant protein were preserved after the functionalization of NPs. Cellular uptake of NPs by human umbilical vein endothelial cells (HUVEC) was increased twice compared to NPs without the KDKPPR peptide moiety or conjugated with a scramble peptide. NPs induced no cytotoxicity without light exposure but conferred a photocytotoxic effect to cells after photodynamic therapy (PDT)5. In vivo, complementary approaches were investigated, combining non-invasive imaging by magnetic resonance or by fluorescence and a tissue assay by ICP-MS to determine gadolinium concentrations, revealing renal and hepatic eliminations. The tumor selectivity of the NPs compared to the healthy brain parenchyma was validated by MRI data. The in vivo selectivity, evaluated using a skinfold chamber model in mice, confirms that the functionalized NPs with KDKPPR peptide moiety were localized in the tumor vessel wall, validating this vascular targeting strategy

AGUIX® theranostic nanoparticles for vascular-targeted interstitial photodynamic therapy of brain tumors

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Human RAD52 stimulates the RAD51-mediated homology search

International audienceHomologous recombination (HR) is a DNA repair mechanism of double-strand breaks and blocked replication forks, involving a process of homology search leading to the formation of synaptic intermediates that are regulated to ensure genome integrity. RAD51 recombinase plays a central role in this mechanism, supported by its RAD52 and BRCA2 partners. If the mediator function of BRCA2 to load RAD51 on RPA-ssDNA is well established, the role of RAD52 in HR is still far from understood. We used transmission electron microscopy combined with biochemistry to characterize the sequential participation of RPA, RAD52, and BRCA2 in the assembly of the RAD51 filament and its activity. Although our results confirm that RAD52 lacks a mediator activity, RAD52 can tightly bind to RPA-coated ssDNA, inhibit the mediator activity of BRCA2, and form shorter RAD51-RAD52 mixed filaments that are more efficient in the formation of synaptic complexes and D-loops, resulting in more frequent multi-invasions as well. We confirm the in situ interaction between RAD51 and RAD52 after double-strand break induction in vivo. This study provides new molecular insights into the formation and regulation of presynaptic and synaptic intermediates by BRCA2 and RAD52 during human HR

Inhibition of CHK 1 (Checkpoint Kinase 1) Elicits Therapeutic Effects in Pulmonary Arterial Hypertension

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Mitochondrial HSP90 Accumulation Promotes Vascular Remodeling in Pulmonary Arterial Hypertension

Rationale: Pulmonary arterial hypertension (PAH) is a vascular remodeling disease with a poor prognosis and limited therapeutic option. Although the mechanisms contributing to vascular remodeling in PAH are still unclear, several features, including hyper-proliferation and resistance to apoptosis of pulmonary artery smooth muscle cells (PASMCs), have led to the emergence of the cancer-like concept. The molecular chaperone heat shock protein 90 (HSP90) is directly associated with malignant growth and proliferation under stress conditions. In addition to be highly expressed in the cytosol, HSP90 exists in a subcellular pool compartmentalized in the mitochondria (mtHSP90) of tumor cells, but not in normal cells, where it promotes cell survival. Objectives: We hypothesized that mtHSP90 in PAH-PASMCs represents a protective mechanism against stress promoting their proliferation and resistance to apoptosis. Measurements and Main Results: We demonstrated that in response to stress HSP90 preferentially accumulates in PAH-PASMC mitochondria (dual immunostaining, immunoblot and immunogold electron microscopy) to ensure cell survival by preserving mitochondrial DNA integrity and bioenergetics functions (Seahorse). Whereas cytosolic HSP90 inhibition displays a lack of absolute specificity for PAH-PASMCs, Gamitrinib, a specific mtHSP90 inhibitor decreased mitochondrial DNA content and repair capacity and bioenergetics functions, thus repressing PAH-PASMC proliferation (Ki67 labeling) and resistance to apoptosis (Annexin V assay) without affecting control cells. In vivo, Gamitrinib improves PAH in two experimental rat models (monocrotaline and Fawn-Hooded rat). Conclusions: Our data show for the first time that accumulation of mtHSP90 is a feature of PAH-PASMCs and key regulator of mitochondrial homeostasis contributing to vascular remodeling in PAH