Comment modéliser les événements de la fibrose cutanée ?

Classiquement, les fibroses cutanées sont considérées comme l’étape ultime d’un processus inflammatoire chronique et persistant, qui pérennise l’hyperplasie et la différenciation fibroblastique ainsi que l’accumulation de matrice extracellulaire. Le retentissement clinique de ces fibroses s’exprime tant au niveau esthétique que fonctionnel, et se révèle d’autant plus problématique qu’il n’existe à ce jour ni régression spontanée, ni thérapeutique antifibrosante efficace et sûre. Le développement et le maintien de la fibrose cutanée impliquent les différents composants cellulaires de la peau ainsi que plusieurs médiateurs paracrines, qui activent différentes voies de signalisation intracellulaires : ce réseau d’interaction est complexe et difficile à modéliser. Cette revue présente les modèles cellulaires et expérimentaux permettant de modéliser la fibrose cutanée, et expose leurs apports dans la compréhension des mécanismes physiopathologiques de fibrogenèse cutanée. Ces modèles constituent des outils performants pour tester de nouvelles hypothèses mécanistiques et thérapeutiques.Skin fibrosis is classically seen as the consequence of chronic inflammation and altered healing response that is characterized by the differentiation of fibroblasts into secretory myofibroblasts and accumulation of connective tissue. Although fibrosis severely affects organ function and causes esthetic defects, no effective therapy is currently available to attenuate the fibrogenic process probably because the fibrogenic process is more complex than previously thought. Indeed, it might involve several interacting and mutually dependent cell types (fibroblasts, keratinocytes, endothelial cells, inflammatory cells), numerous paracrine factors, bio-active molecules and micro-environmental stimuli (growth factors, vasoactive peptides, balance between pro- and anti-inflammatory cytokines, coagulation system, reactive oxygen species, extracellular matrix…). In this perspective, the traditional approach that model individual cell response in simple cell culture system is probably inadequate and too simplistic. This article reviews the new models used to study skin fibrosis in vitro, in organotypic culture systems and in vivo and examines how these different models might be used to identify new molecular pathways involved in fibrogenesis. The monolayer cultures allow the study of fibrogenic signals induced by a single factor on a single cell type. Isolation of cells from fibrotic tissue allows to define the fibrogenic differentiation acquired in vivo. The organotypic models allow cell to cell and cell to matrix interaction and the experimental models in pigs and mice allowed studies in integrated physiological systems. These various and complementary models would also provide new tools to develop and test new drugs and treatments

Lung Cancer Stem Cell: New Insights on Experimental Models and Preclinical Data

Lung cancer remains the leading cause of cancer death. Understanding lung tumors physiopathology should provide opportunity to prevent tumor development or/and improve their therapeutic management. Cancer stem cell (CSC) theory refers to a subpopulation of cancer cells, also named tumor-initiating cells, that can drive cancer development. Cells presenting these characteristics have been identified and isolated from lung cancer. Exploring cell markers and signaling pathways specific to lung CSCs may lead to progress in therapy and improve the prognosis of patients with lung cancer. Continuous efforts in developing in vitro and in vivo models may yield reliable tools to better understand CSC abilities and to test new therapeutic targets. Preclinical data on putative CSC targets are emerging by now. These preliminary studies are critical for the next generation of lung cancer therapies

Emerging Opportunities of Radiotherapy Combined With Immunotherapy in the Era of Breast Cancer Heterogeneity

The association of radiotherapy and immunotherapy has recently emerged as an exciting combination that might improve outcomes in many solid tumor settings. In the context of breast cancer, this opportunity is promising and under investigation. Given the heterogeneity of breast cancer, it might be meaningful to study the association of radiotherapy and immunotherapy distinctly among the various breast cancer subtypes. The use of biomarkers, such as tumor infiltrating lymphocytes, which are also associated to breast cancer heterogeneity, might provide an opportunity for tailored studies. This review highlights current knowledge of the association of radiotherapy and immunotherapy in the setting of breast cancer and attempts to highlight the therapeutic opportunities among breast cancer heterogeneity

A new mouse model of radiation-induced liver disease reveals mitochondrial dysfunction as an underlying fibrotic stimulus.

Background & Aims High-dose irradiation is an essential tool to help control the growth of hepatic tumors, but it can cause radiation-induced liver disease (RILD). This life-threatening complication manifests itself months following radiation therapy and is characterized by fibrosis of the pericentral sinusoids. In this study, we aimed to establish a mouse model of RILD to investigate the underlying mechanism of radiation-induced liver fibrosis. Methods Using a small animal image-guided radiation therapy platform, an irradiation scheme delivering 50 Gy as a single dose to a focal point in mouse livers was designed. Tissues were analyzed 1 and 6 days, and 6 and 20 weeks post-irradiation. Irradiated livers were assessed by histology, immunohistochemistry, imaging mass cytometry and RNA sequencing. Mitochondrial function was assessed using high-resolution respirometry. Results At 6 and 20 weeks post-irradiation, pericentral fibrosis was visible in highly irradiated areas together with immune cell infiltration and extravasation of red blood cells. RNA sequencing analysis showed gene signatures associated with acute DNA damage, p53 activation, senescence and its associated secretory phenotype and fibrosis. Moreover, gene profiles of mitochondrial damage and an increase in mitochondrial DNA heteroplasmy were detected. Respirometry measurements of hepatocytes in vitro confirmed irradiation-induced mitochondrial dysfunction. Finally, the highly irradiated fibrotic areas showed markers of reactive oxygen species such as decreased glutathione and increased lipid peroxides and a senescence-like phenotype. Conclusions Based on our mouse model of RILD, we propose that irradiation-induced mitochondrial DNA instability contributes to the development of fibrosis via the generation of excessive reactive oxygen species, p53 pathway activation and a senescence-like phenotype. Lay summary Irradiation is an efficient cancer therapy, however, its applicability to the liver is limited by life-threatening radiation-induced hepatic fibrosis. We have developed a new mouse model of radiation-induced liver fibrosis, that recapitulates the human disease. Our model highlights the role of mitochondrial DNA instability in the development of irradiation-induced liver fibrosis. This new model and subsequent findings will help increase our understanding of the hepatic reaction to irradiation and to find strategies that protect the liver, enabling the expanded use of radiotherapy to treat hepatic tumors

Updates on radiotherapy-immunotherapy combinations: Proceedings of 6(th) annual ImmunoRad conference

Focal radiation therapy (RT) has attracted considerable attention as a combinatorial partner for immunotherapy (IT), largely reflecting a well-defined, predictable safety profile and at least some potential for immunostimulation. However, only a few RT-IT combinations have been tested successfully in patients with cancer, highlighting the urgent need for an improved understanding of the interaction between RT and IT in both preclinical and clinical scenarios. Every year since 2016, ImmunoRad gathers experts working at the interface between RT and IT to provide a forum for education and discussion, with the ultimate goal of fostering progress in the field at both preclinical and clinical levels. Here, we summarize the key concepts and findings presented at the Sixth Annual ImmunoRad conference

Novel Anti-Metastatic Action of Cidofovir Mediated by Inhibition of E6/E7, CXCR4 and Rho/ROCK Signaling in HPV+ Tumor Cells

Cervical cancer is frequently associated with HPV infection. The expression of E6 and E7 HPV oncoproteins is a key factor in its carcinogenicity and might also influence its virulence, including metastatic conversion. The cellular mechanisms involved in metastatic spread remain elusive, but pro-adhesive receptors and their ligands, such as SDF-1α and CXCR4 are implicated. In the present study, we assessed the possible relationship between SDF-1α/CXCR4 signaling, E6/E7 status and the metastatic process. We found that SDF-1α stimulated the invasion of E6/E7-positive cancer cell lines (HeLa and TC-1) in Matrigel though CXCR4 and subsequent Rho/ROCK activation. In pulmonary metastatic foci generated by TC-1 cells IV injection a high proportion of cells expressed membrane-associated CXCR4. In both cases models (in vitro and in vivo) cell adhesion and invasion was abrogated by CXCR4 immunological blockade supporting a contribution of SDF-1α/CXCR4 to the metastatic process. E6 and E7 silencing using stable knock-down and the approved anti-viral agent, Cidofovir decreased CXCR4 gene expression as well as both, constitutive and SDF-1α-induced cell invasion. In addition, Cidofovir inhibited lung metastasis (both adhesion and invasion) supporting contribution of E6 and E7 oncoproteins to the metastatic process. Finally, potential signals activated downstream SDF-1α/CXCR4 and involved in lung homing of E6/E7-expressing tumor cells were investigated. The contribution of the Rho/ROCK pathway was suggested by the inhibitory effect triggered by Cidofovir and further confirmed using Y-27632 (a small molecule ROCK inhibitor). These data suggest a novel and highly translatable therapeutic approach to cervix cancer, by inhibition of adhesion and invasion of circulating HPV-positive tumor cells, using Cidofovir and/or ROCK inhibition

[How to model the events in cutaneous fibrosis?]

Skin fibrosis is classically seen as the consequence of chronic inflammation and altered healing response that is characterized by the differentiation of fibroblasts into secretory myofibroblasts and accumulation of connective tissue. Although fibrosis severely affects organ function and causes esthetic defects, no effective therapy is currently available to attenuate the fibrogenic process probably because the fibrogenic process is more complex than previously thought. Indeed, it might involve several interacting and mutually dependent cell types (fibroblasts, keratinocytes, endothelial cells, inflammatory cells), numerous paracrine factors, bio-active molecules and micro-environmental stimuli (growth factors, vasoactive peptides, balance between pro- and anti-inflammatory cytokines, coagulation system, reactive oxygen species, extracellular matrix...). In this perspective, the traditional approach that model individual cell response in simple cell culture system is probably inadequate and too simplistic. This article reviews the new models used to study skin fibrosis in vitro, in organotypic culture systems and in vivo and examines how these different models might be used to identify new molecular pathways involved in fibrogenesis. The monolayer cultures allow the study of fibrogenic signals induced by a single factor on a single cell type. Isolation of cells from fibrotic tissue allows to define the fibrogenic differentiation acquired in vivo. The organotypic models allow cell to cell and cell to matrix interaction and the experimental models in pigs and mice allowed studies in integrated physiological systems. These various and complementary models would also provide new tools to develop and test new drugs and treatments

Towards clinical translation of FLASH radiotherapy

The ultimate goal of radiation oncology is to eradicate tumours without toxicity to non-malignant tissues. FLASH radiotherapy, or the delivery of ultra-high dose rates of radiation (>40 Gy/s), emerged as a modality of irradiation that enables tumour control to be maintained while reducing toxicity to surrounding non-malignant tissues. In the past few years, preclinical studies have shown that FLASH radiotherapy can be delivered in very short times and substantially can widen the therapeutic window of radiotherapy. This ultra-fast radiation delivery could reduce toxicity and thus enable dose escalation to enhance antitumour efficacy, with the additional benefits of reducing treatment time and organ motion-related issues, eventually increasing the number of patients who can be treated. At present, FLASH is recognized as one of the most promising breakthroughs in radiation oncology, standing at the crossroads between technology, physics, chemistry and biology; however, several hurdles make its clinical translation difficult, including the need for a better understanding of the biological mechanisms, optimization of parameters and technological challenges. In this Perspective, we provide an overview of the principles underlying FLASH radiotherapy and discuss the challenges along the path towards its clinical application

Molecular aspects of intestinal radiation-induced fibrosis

Radiation therapy is a key component of the management of various pelvic tumors, including prostate, gynecological, and anorectal carcinomas. Unfortunately, normal tissues located in the vicinity of target organs are radiosensitive, and long-term cancer survivors may develop late treatment-related injury, most notably radiation-induced fibrosis (RIF) of the small bowel. The cellular mediators of intestinal fibrosis are mesenchymal cells (i.e. myofibroblasts, fibroblasts and smooth muscle cells) which, when activated, serve as the primary collagen-producing cells, and are responsible for excess deposition of extracellular matrix components, eventually leading to intestinal loss of function. For decades, the underlying mechanisms involved in chronic activation of myofibroblasts within the normal tissues were unknown, and the fibrotic process, which ensued, was considered irreversible. Recent advances in the pathogenesis of RIF have demonstrated prolonged upregulation of fibrogenic cytokines, such as Transforming growth factor-beta1 (TGF-beta1) and its main downstream effector, Connective tissue growth factor (CTGF), in the myofibroblasts of irradiated small bowel. TGF-beta1-mediated activation of CTGF gene expression is controlled by Smads, but recently Rho/ROCK signaling has emerged as an alternative pathway involved in the control of CTGF expression in intestinal fibrosis. This article underlines the clinical relevance of RIF as it relates to damage to the small bowel, provides insight to its molecular biology, and finally unveils the potential role of Rho-ROCK inhibitors as emerging strategies to promote RIF reversal