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International audience; Evaluer la réponse thérapeutique tumorale : intérêt d’une approche bimodale en IRM CEST et imagerie nucléaire. Roxane Autissier1,2,3, Guilhem Pagés2,3, Erwan Boutault1, Jean-Marie Bonny2,3, Sébastien Schmitt1, Philippe Auzeloux1, Emmanuel Moreau1, Aurélie Dutour4, Elisabeth Miot-Noirault1, Leslie Mazuel1,2,3.1 Université Clermont Auvergne, Inserm, IMoST, F-63000 Clermont-Ferrand, France INRAe, 2 UR QuaPA, F-63122 Saint-Genès-Champanelle, France3AgroResonance, INRAe, 2018. Nuclear Magnetic Resonance Facility for agronomy, food and health, https://doi.org/10.15454/1.5572398324758228E123,44Team Cell Death and Pediatric Cancer, Cancer Initiation and Tumor Cell Identity Department, INSERM1052, CNRS5286, Cancer Research Center of Lyon, F-69008 Lyon, FranceObjectifs : Le chondrosarcome (CHS), tumeur maligne du cartilage, dispose d’un microenvironnement caractérisé par une matrice extracellulaire (MEC) riche en glycosaminoglycanes (GAGs) et par un cœur hypoxique. Ces deux caractéristiques sont identifiables par une stratégie d’acquisitions bimodales par IRM CEST et imagerie nucléaire [1]. Dans ce contexte, nous souhaitons évaluer la pertinence de cette stratégie pour déceler les modifications ayant lieu au sein de la tumeur en réponse à une thérapie ciblant la MEC (acide zolédronique) ou l’hypoxie (TH-302). Matériels et Méthodes : Les rats SD OFA implantés en paratibial avec un fragment de CHS (SWARM) sont traités ensuite par 2 injections/semaine d’acide zolédronique (0,1mg/kg, sc, J5-J36) ou 5 injections/semaine de TH-302 (Evofosphamide) (50mg/kg, ip, J11-J22) ou de sérum physiologique. Les animaux sont imagés hebdomadairement jusqu’à J40 par IRM à 11,7T. Un repérage anatomique puis une séquence RARE comprenant un module de préparation CEST (B1=1,5µT, tsat=4 s, Δω=50Hz sur  2500 Hz) est réalisée sur une coupe axiale passant par le centre de la tumeur. Une carte B0 est enregistrée à l’aide d’une WASSR (B1=0,1µT, tsat=1s, Δω=20Hz sur 1000Hz). Des imageries TEMP (99mTc-NTP15-5, 30MBq/animal, 30min pi) et TEP (18F-FMISO, 20MBq/animal, 4h pi) sont réalisées sur les mêmes animaux pour caractériser les GAGs et l’hypoxie, respectivement. Les tumeurs prélevées sont étudiées par histologie, immunofluorescence et dosage des GAGs.Résultats : L’approche bimodale a permis de mettre en évidence la réponse du CHS SWARM au traitement TH-302 avec une réduction significative de 75% du volume tumoral (p

International audience; An increasing number of studies concerning solid cancers, including prostate cancer, are tending to demonstrate the predominant role of the interactions of tumor cells with their microenvironment, and underlining the relevance of therapeutic approaches co-targeting these two components. Artificial in vitro 3D culture models, such as spheroids, are therefore being designed to allow intercellular interactions between tumor cells and the matrix, under hypoxic conditions mimicking a microtumor. This project aims to develop and characterize a multicellular tumor spheroid (MCTS) model of human prostate cancer cells expressing PSMA, for in vitro drug screening. To this end, 1,000 cells/well were seeded in 100 µl of culture medium with 0.5% of methylcellulose in 96-well, non-adherent, V-shaped bottom plates. Bioluminescent imaging of the spheroids enabled the measurement of spheroid growth. From Day 7 of growth, immunofluorescence studies showed cellular proliferation (Ki-67), mainly located in the periphery of the spheroid section, associated with the formation of an apoptotic core (TUNEL). Scanning electron microscopy and fluorescent imaging (Lox-1 probe) showed the presence of an extracellular matrix and the installation of an oxygen gradient leading to the formation of a hypoxic area during growth. This hypoxia was correlated with increased VEGF excretion. Drug sensitivity was assessed on 2D and 3D cultures. The LNCaP-Luc spheroids are more resistant to docetaxel and TH-302, a hypoxia-activated prodrug, compared with cells grown in a monolayer. For docetaxel, this resistance increased with the spheroid growth stage, whereas the activity of TH-302 was potentiated by the hypoxic environment. In conclusion, the development of LNCaP-Luc cell MCTS provides a simple model mimicking a microtumor; it appears to be particularly well-suited to the validation of new therapeutic approaches targeting proliferation and the microenvironment.

International audience; Background99mTc-NTP 15-5 is a SPECT radiotracer targeting proteoglycans (PG), components of the cartilaginous extracellular matrix. Imaging of PGs would be useful for the early detection of cartilage disorders (osteoarthritis, arthritis and chondrosarcoma, Aromatase Inhibitor associated arthralgia (AIA) in breast cancer), and the follow-up of patients under treatment. According to preclinical study results, 99mTc-NTP 15-5, is a good candidate for a specific functional molecular imaging of joints. We intend to initiate a first in-human study to confirm and quantify 99mTc-NTP 15-5 uptake in healthy joints.MethodsAs the clinical development of this radiotracer would be oriented toward the functional imaging of joint pathologies, we have chosen to include patients with healthy joints (unilateral osteoarthritis of the knee or breast cancer with indication of AI treatment). This phase I study will be an open-label, multicenter, dose-escalation trial of a radiopharmaceutical orientation to determine the recommended level of activity of 99mTc-NTP 15-5 to obtain the best joint tracer contrasts on images, without dose limiting toxicity (DLT). The secondary objectives will include the study of the pharmacology, biodistribution (using planar whole body and SPECT-CT acquisitions), toxicity, and dosimetry of this radiotracer. The dose escalation with 3 activity levels (5, 10, and 15 MBq/kg), will be conditioned by the absence at the previous level of DLT and of a visualized tracer accumulation on more than 80% of healthy joints as observed on scintigraphy performed at ≤ 2 h post-injection.DiscussionThis first in-human phase I trial will be proof-of-concept of the relevance of 99mTc-NTP 15-5 as a cartilage tracer, with the determination of the optimal methodology (dose and acquisition time) to obtain the best contrast to provide a functional image of joints with SPECT-CT.Trial registration numberClinicaltrials.gov: NCT04481230. Identifier in French National Agency for the Safety of Medicines and Health Products (ANSM): N°EudraCT 2020-000495-37.

International audience

International audience

International audience; INTRODUCTION: Chondrosarcoma (CHS) is a malignant cartilaginous tumor representing the most common primary bone cancer in adults.[1] Due to its dense chondrogenic extracellular matrix and hypoxic environment, CHS is highly resistant to conventional chemotherapy and radiation.[2] Development of multimodal imaging to characterize and map in vivo CHS microenvironment is fundamental for specific diagnosis and personalized therapy. In this work, we proposed to combine the resolution of chemical exchange saturation transfer (CEST) MRI with nuclear imaging sensitivity to improve CHS microenvironment understanding.[3]METHODS: Swarm rat CHSs were implanted subcutaneously in NMRI nude mice (n=10). When tumors were measurable (12-16 days post-transplant), mice were imaged by CEST MRI.[4] Proteoglycans, the main component of chondrogenic extracellular matrix, were quantified by GAG CEST contrast. Guanidyl-and APT CEST contrasts were combined to characterize acidic pH, as hypoxia reflect. These two features, proteoglycans and hypoxia, were assessed in parallel by nuclear imaging with 99m Tc-NTP 15-5 SPECT imaging [5] and 18F-FMISO PET imaging [6], respectively. Data were also completed by ex vivo analyses of proteoglycans (Alcian blue stain and biochemical assay with dimethylmethylene blue) and hypoxia (pimonidazole immunofluorescence).RESULTS/DISCUSSION: For extracellular matrix assessment, a proteoglycan concentration-related map was established with GAG CEST contrast showing more intense areas in the tumor than in the muscle (AUC =27.29 ± 8.38 vs 2.15 ± 1.88, respectively; P < 0.0001) (Fig 1). Similarly, a significant (P < 0.0001) radiotracer uptake was observed by nuclear imaging with 99mTc-NTP 15-5 within tumoral tissue (179.38 ± 38.39 kBq/mL) as opposed to muscle (35.07 ± 5.17 kBq/mL). These results were supported by biochemical assay (6.33 ± 1.60 μg/mg vs 0.41 ± 0.09 μg/mg, respectively; P < 0.0001). Considering hypoxia, a small discrepancy was observed between CHS and muscle with 18F-FMISO PET imaging. Interestingly, with Guanidyl and APT contrast, the weakly hypoxic status of the CHS was explained by a heterogeneous acidic pH distribution within the tumoral tissue (Fig 1). Moreover, immunofluorescence with pimonidazole evidenced a weak staining within tumor mainly localized in the center of CHS lobules.CONCLUSION: The results from CEST MRI, nuclear imaging and ex vivo analyses were in agreement and highlighted a rich proteoglycan extracellular matrix and a heterogeneous hypoxic tumoral microenvironment for Swarm rat CHS xenograft in mice. This study emphasizes the role of multimodal imaging to characterize tumor phenotypes resistant to treatments and allows a better understanding of the relationship between tumor cells and their environment.