Radiothérapie « flash » à très haut débit de dose : un moyen d'augmenter l'indice thérapeutique par minimisation des dommages aux tissus sains [Ultrahigh dose-rate, "flash" irradiation minimizes the side-effects of radiotherapy].

PURPOSE: Pencil beam scanning and filter free techniques may involve dose-rates considerably higher than those used in conventional external-beam radiotherapy. Our purpose was to investigate normal tissue and tumour responses in vivo to short pulses of radiation. MATERIAL AND METHODS: C57BL/6J mice were exposed to bilateral thorax irradiation using pulsed (at least 40Gy/s, flash) or conventional dose-rate irradiation (0.03Gy/s or less) in single dose. Immunohistochemical and histological methods were used to compare early radio-induced apoptosis and the development of lung fibrosis in the two situations. The response of two human (HBCx-12A, HEp-2) tumour xenografts in nude mice and one syngeneic, orthotopic lung carcinoma in C57BL/6J mice (TC-1 Luc+), was monitored in both radiation modes. RESULTS: A 17Gy conventional irradiation induced pulmonary fibrosis and activation of the TGF-beta cascade in 100% of the animals 24-36 weeks post-treatment, as expected, whereas no animal developed complications below 23Gy flash irradiation, and a 30Gy flash irradiation was required to induce the same extent of fibrosis as 17Gy conventional irradiation. Cutaneous lesions were also reduced in severity. Flash irradiation protected vascular and bronchial smooth muscle cells as well as epithelial cells of bronchi against acute apoptosis as shown by analysis of caspase-3 activation and TUNEL staining. In contrast, the antitumour effectiveness of flash irradiation was maintained and not different from that of conventional irradiation. CONCLUSION: Flash irradiation shifted by a large factor the threshold dose required to initiate lung fibrosis without loss of the antitumour efficiency, suggesting that the method might be used to advantage to minimize the complications of radiotherapy

J022 Effecteurs du récepteur Notch3 dans la cellule musculaire lisse des petites artères

Notch3 code pour un récepteur transmembranaire dont l’expression est fortement restreinte aux cellules musculaires lisses (CML) des petites artères. Des études génétiques chez l’homme et la souris ont démontré que Notch3 était un acteur clé dans la physiologie normale et la pathologie des petites artères. Chez l’homme, des mutations dominantes de Notch3 sont responsables de la maladie CADASIL, une forme héréditaire de maladie des petites artères cérébrales. Chez la souris, Notch3 est requis pour la maturation postnatale des petites artères, en contrôlant l’identité artérielle et le remodelage du cytosquelette des CML. Notch3 joue également un rôle clé dans la fonction normale des petites artères, en contrôlant les réponses myogéniques à la pression artérielle. L’activation de Notch3, dans la voie canonique, induit, par clivage protéolytique, la libération de son domaine intracellulaire qui se lie dans le noyau à RBP-Jk, favorisant la formation d’un complexe activateur de la transcription.Notre objectif est d’identifier et de caractériser les effecteurs de Notch3 dans les petites artères.Par une approche combinant transcriptome et Q-PCR sur des artères de souris Notch3KO et WT, nous avons identifié 11 gènes candidats. Leur niveau d’expression est significativement diminué dans les artères de souris Notch3KO, à un stade où il n’existe pas encore de lésions cellulaires visibles, et, cette diminution est corrigée par la réintroduction spécifiquement dans les CML d’une protéine Notch3WT mais pas par celle d’une protéine mutée défective pour la signalisation RBP-Jk. Les 6 gènes dont nous avons pu étudier le patron d’expression sont tous exprimés dans les CML artérielles. De façon remarquable, l’expression vasculaire est artérielle prédominante pour les 6 gènes et « petite artère » préférentielle pour 4 d’entre eux. De plus, chacun de ces gènes a un profil d’expression unique au niveau de l’arborisation artérielle et capillaire, mais, la superposition des différents profils recouvre celui de Notch3.Les travaux en cours ont pour but de déterminer si les gènes candidats identifiés sont ou non des cibles primaires, RBPJk-dépendantes, et de caractériser histologiquement et fonctionnellement les mutants souris perte-de-fonction de ces gènes

Caffeic Acid Phenethyl Ester (CAPE), a natural polyphenol to increase the therapeutic window for lung adenocarcinomas

BACKGROUND AND PURPOSE: Lung cancers are highly resistant to radiotherapy, necessitating the use of high doses, which leads to radiation toxicities such as radiation pneumonitis and fibrosis. Caffeic Acid Phenethyl Ester (CAPE) has been suggested to have anti-proliferative and pro-apoptotic effects in tumour cells, while radioprotective anti-inflammatory and anti-oxidant effects in the normal tissue. We investigated the radiosensitizing and radioprotective effects of CAPE in lung cancer cell lines and normal tissue in vitro and ex vivo, respectively. MATERIALS AND METHODS: The cytotoxic and radiosensitizing effects of CAPE in lung cancer were investigated using viability and clonogenic survival assays. The radioprotective effects of CAPE were assessed in vitro and ex vivo using precision cut lung slices (PCLS). Potential underlying molecular mechanisms of CAPE focusing on cell cycle, cell metabolism, mitochondrial function and pro-inflammatory markers were investigated. RESULTS: Treatment with CAPE decreased cell viability in a dose-dependent manner (IC 57.6±16.6µM). Clonogenic survival assays showed significant radiosensitization by CAPE in lung adenocarcinoma lines (p<0.05), while no differences were found in non-adenocarcinoma lines (p=0.13). Cell cycle analysis showed an increased S-phase (p<0.05) after incubation with CAPE in the majority of cell lines. Metabolic profiling showed that CAPE shifted cellular respiration towards glycolysis (p<0.01), together with mitochondrial membrane depolarization (p<0.01). CAPE induced a decrease in NF-?B activity in adenocarcinomas and decreased pro-inflammatory gene expression in PCLS. CONCLUSION: The combination of CAPE and radiotherapy may be a potentially effective approach to increase the therapeutic window in lung cancer patients

Les promesses du haut débit de dose en radiothérapie [Hopes of high dose-rate radiotherapy]

In this review, we present the synthesis of the newly acquired knowledge concerning high dose-rate irradiations and the hopes that these new radiotherapy modalities give rise to. The results were presented at a recent symposium on the subject

Ultrahigh dose-rate FLASH irradiation increases the differential response between normal and tumor tissue in mice.

In vitro studies suggested that sub-millisecond pulses of radiation elicit less genomic instability than continuous, protracted irradiation at the same total dose. To determine the potential of ultrahigh dose-rate irradiation in radiotherapy, we investigated lung fibrogenesis in C57BL/6J mice exposed either to short pulses (≤ 500 ms) of radiation delivered at ultrahigh dose rate (≥ 40 Gy/s, FLASH) or to conventional dose-rate irradiation (≤ 0.03 Gy/s, CONV) in single doses. The growth of human HBCx-12A and HEp-2 tumor xenografts in nude mice and syngeneic TC-1 Luc(+) orthotopic lung tumors in C57BL/6J mice was monitored under similar radiation conditions. CONV (15 Gy) triggered lung fibrosis associated with activation of the TGF-β (transforming growth factor-β) cascade, whereas no complications developed after doses of FLASH below 20 Gy for more than 36 weeks after irradiation. FLASH irradiation also spared normal smooth muscle and epithelial cells from acute radiation-induced apoptosis, which could be reinduced by administration of systemic TNF-α (tumor necrosis factor-α) before irradiation. In contrast, FLASH was as efficient as CONV in the repression of tumor growth. Together, these results suggest that FLASH radiotherapy might allow complete eradication of lung tumors and reduce the occurrence and severity of early and late complications affecting normal tissue