Is proton radiation more effective than photon radiation at inducing senescence?

https://openworks.mdanderson.org/sumexp21/1158/thumbnail.jp

Multiparametric radiobiological assays show that variation of X-ray energy strongly impacts relative biological effectiveness: comparison between 220 kV and 4 MV

International audienceBased on classic clonogenic assay, it is accepted by the scientific community that, whatever the energy, the relative biological effectiveness of X-rays is equal to 1. However, although X-ray beams are widely used in diagnosis, interventional medicine and radiotherapy, comparisons of their energies are scarce. We therefore assessed in vitro the effects of low- and high-energy X-rays using Human umbilical vein endothelial cells (HUVECs) by performing clonogenic assay, measuring viability/mortality, counting γ-H2AX foci, studying cell proliferation and cellular senescence by flow cytometry and by performing gene analysis on custom arrays. Taken together, excepted for γ-H2AX foci counts, these experiments systematically show more adverse effects of high energy X-rays, while the relative biological effectiveness of photons is around 1, whatever the quality of the X-ray beam. These results strongly suggest that multiparametric analysis should be considered in support of clonogenic assay

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Intérêt d'implémentation de mesures biologiques multiparamétriques pour prédire le risque de complications aux tissus sains après une radiothérapie

Despite the development of radiotherapy (RT), the biological effects on healthy tissue remain poorly studied. To predict radiation-induced biological effects, radiobiologists use the Relative Biological Effectiveness (RBE) concept to compare doses between two ionizing radiations given the same biological effect. RBE is essentially based on clonogenic assay. According to several studies, this assay is insufficient to predict effects on healthy tissues after radiation exposure. Based on the various effects known after irradiation (IR), the aim of this work is therefore to acquire multiparametric biological measures to be integrated in a predictive model to foresee the biological effects of emerging radiation therapy modalities and/or protocols. For single dose, in vitro data show a deleterious effect at the highest dose rate on clonogenic survival, cell morphology, viability, cell cycle, senescence and gene expression signing cell dysfunction. These results were confirmed in vivo on a preclinical mice model of radiation-induced enteropathy. In contrary to ICRP statement, our results show an RBE of photon different from 1 and depending on the dose rate. On the other hand, different fractionated IR protocols highlight in vitro an impact of the dose rate based on a continuum of “effective biological dose” (BED). Different protocols with equivalent BED show different radio-induced response both in vitro and in vivo. This results exhibit certain limits of BED measures for clinical use to compare different fractionated IR protocols. The use of multiparametric biological measures could ultimately allow a better risk prediction related to current and future radiotherapy practices.Malgré l’évolution de la radiothérapie (RT), la toxicité aux tissus sains reste une limite en clinique. Les mesures d’Efficacité Biologique Relative (EBR) permettent de prédire les effets biologiques d’un rayonnement d’intérêt par rapport à celui de référence. Elles sont principalement basées sur le test de survie clonogénique qui ne peut suffire à lui seul à prédire le devenir de tissus sains exposés. Les nouveaux appareils de RT utilisent des débits de dose plus élevés sans que les effets biologiques soient bien connus. Le but de ces travaux est d’acquérir des mesures biologiques multiparamétriques à intégrer dans un futur modèle prédictif pour mieux prédire les effets biologiques des protocoles de RT émergents. Pour les irradiations (IR) en dose unique, la modélisation des données in vitro a mis en évidence un effet plus délétère du débit de dose le plus élevé sur la survie clonogénique, la morphologie, la viabilité et le cycle cellulaire, la sénescence et l’expression de gènes signant une dysfonction cellulaire. Ces résultats ont été confirmés in vivo sur un modèle d’IR intestinale. Contrairement au postulat de la CIPR, l’EBR des photons n’est pas de 1 et dépend du débit de dose. Pour les IR fractionnées selon différents protocoles, un impact du débit de dose sur un continuum de “dose biologique équivalente” (BED) a également été démontré in vitro. En revanche, la réponse in vitro et in vivo est différente pour des protocoles à BED équivalente ce qui montre une limite son utilisation pour comparer des protocoles. L’utilisation de mesures biologiques multiples pourrait permettre à terme de mieux prédire les risques potentiels des pratiques actuelles et futures en RT

Interest of multiparametric radiobiological parameters implementation to predict radiation-induced adverse effects

Malgré l’évolution de la radiothérapie (RT), la toxicité aux tissus sains reste une limite en clinique. Les mesures d’Efficacité Biologique Relative (EBR) permettent de prédire les effets biologiques d’un rayonnement d’intérêt par rapport à celui de référence. Elles sont principalement basées sur le test de survie clonogénique qui ne peut suffire à lui seul à prédire le devenir de tissus sains exposés. Les nouveaux appareils de RT utilisent des débits de dose plus élevés sans que les effets biologiques soient bien connus. Le but de ces travaux est d’acquérir des mesures biologiques multiparamétriques à intégrer dans un futur modèle prédictif pour mieux prédire les effets biologiques des protocoles de RT émergents. Pour les irradiations (IR) en dose unique, la modélisation des données in vitro a mis en évidence un effet plus délétère du débit de dose le plus élevé sur la survie clonogénique, la morphologie, la viabilité et le cycle cellulaire, la sénescence et l’expression de gènes signant une dysfonction cellulaire. Ces résultats ont été confirmés in vivo sur un modèle d’IR intestinale. Contrairement au postulat de la CIPR, l’EBR des photons n’est pas de 1 et dépend du débit de dose. Pour les IR fractionnées selon différents protocoles, un impact du débit de dose sur un continuum de “dose biologique équivalente” (BED) a également été démontré in vitro. En revanche, la réponse in vitro et in vivo est différente pour des protocoles à BED équivalente ce qui montre une limite son utilisation pour comparer des protocoles. L’utilisation de mesures biologiques multiples pourrait permettre à terme de mieux prédire les risques potentiels des pratiques actuelles et futures en RT.Despite the development of radiotherapy (RT), the biological effects on healthy tissue remain poorly studied. To predict radiation-induced biological effects, radiobiologists use the Relative Biological Effectiveness (RBE) concept to compare doses between two ionizing radiations given the same biological effect. RBE is essentially based on clonogenic assay. According to several studies, this assay is insufficient to predict effects on healthy tissues after radiation exposure. Based on the various effects known after irradiation (IR), the aim of this work is therefore to acquire multiparametric biological measures to be integrated in a predictive model to foresee the biological effects of emerging radiation therapy modalities and/or protocols. For single dose, in vitro data show a deleterious effect at the highest dose rate on clonogenic survival, cell morphology, viability, cell cycle, senescence and gene expression signing cell dysfunction. These results were confirmed in vivo on a preclinical mice model of radiation-induced enteropathy. In contrary to ICRP statement, our results show an RBE of photon different from 1 and depending on the dose rate. On the other hand, different fractionated IR protocols highlight in vitro an impact of the dose rate based on a continuum of “effective biological dose” (BED). Different protocols with equivalent BED show different radio-induced response both in vitro and in vivo. This results exhibit certain limits of BED measures for clinical use to compare different fractionated IR protocols. The use of multiparametric biological measures could ultimately allow a better risk prediction related to current and future radiotherapy practices

Intérêt d'implémentation de mesures biologiques multiparamétriques pour prédire le risque de complications aux tissus sains après une radiothérapie

Despite the development of radiotherapy (RT), the biological effects on healthy tissue remain poorly studied. To predict radiation-induced biological effects, radiobiologists use the Relative Biological Effectiveness (RBE) concept to compare doses between two ionizing radiations given the same biological effect. RBE is essentially based on clonogenic assay. According to several studies, this assay is insufficient to predict effects on healthy tissues after radiation exposure. Based on the various effects known after irradiation (IR), the aim of this work is therefore to acquire multiparametric biological measures to be integrated in a predictive model to foresee the biological effects of emerging radiation therapy modalities and/or protocols. For single dose, in vitro data show a deleterious effect at the highest dose rate on clonogenic survival, cell morphology, viability, cell cycle, senescence and gene expression signing cell dysfunction. These results were confirmed in vivo on a preclinical mice model of radiation-induced enteropathy. In contrary to ICRP statement, our results show an RBE of photon different from 1 and depending on the dose rate. On the other hand, different fractionated IR protocols highlight in vitro an impact of the dose rate based on a continuum of “effective biological dose” (BED). Different protocols with equivalent BED show different radio-induced response both in vitro and in vivo. This results exhibit certain limits of BED measures for clinical use to compare different fractionated IR protocols. The use of multiparametric biological measures could ultimately allow a better risk prediction related to current and future radiotherapy practices.Malgré l’évolution de la radiothérapie (RT), la toxicité aux tissus sains reste une limite en clinique. Les mesures d’Efficacité Biologique Relative (EBR) permettent de prédire les effets biologiques d’un rayonnement d’intérêt par rapport à celui de référence. Elles sont principalement basées sur le test de survie clonogénique qui ne peut suffire à lui seul à prédire le devenir de tissus sains exposés. Les nouveaux appareils de RT utilisent des débits de dose plus élevés sans que les effets biologiques soient bien connus. Le but de ces travaux est d’acquérir des mesures biologiques multiparamétriques à intégrer dans un futur modèle prédictif pour mieux prédire les effets biologiques des protocoles de RT émergents. Pour les irradiations (IR) en dose unique, la modélisation des données in vitro a mis en évidence un effet plus délétère du débit de dose le plus élevé sur la survie clonogénique, la morphologie, la viabilité et le cycle cellulaire, la sénescence et l’expression de gènes signant une dysfonction cellulaire. Ces résultats ont été confirmés in vivo sur un modèle d’IR intestinale. Contrairement au postulat de la CIPR, l’EBR des photons n’est pas de 1 et dépend du débit de dose. Pour les IR fractionnées selon différents protocoles, un impact du débit de dose sur un continuum de “dose biologique équivalente” (BED) a également été démontré in vitro. En revanche, la réponse in vitro et in vivo est différente pour des protocoles à BED équivalente ce qui montre une limite son utilisation pour comparer des protocoles. L’utilisation de mesures biologiques multiples pourrait permettre à terme de mieux prédire les risques potentiels des pratiques actuelles et futures en RT

Importance of dosimetry protocol for cell irradiation on a low X-rays facility and consequences for the biological response

International audiencePurpose: The main objective of radiobiology is to establish links between doses and radiation-induced biological effects. In this context, well-defined dosimetry protocols are crucial to the determination of experimental protocols. This work proposes a new dosimetry protocol for cell irradiation in a SARRP and shows the importance of the modification of some parameters defined in dosimetry protocol for physical dose and biological outcomes.Materials and methods: Once all parameters of the configuration were defined, dosimetry measurements with ionization chambers and EBT3 films were performed to evaluate the dose rate and the attenuation due to the cell culture medium. To evaluate the influence of changes in cell culture volume and/or additional filtration, 6-well plates containing EBT3 films with water were used to determine the impact on the physical dose at 80 kV. Then, experiments with the same irradiation conditions were performed by replacing EBT3 films by HUVECs. The biological response was assessed using clonogenic assay.Results: Using a 0.15 mm copper filter lead to a variation of +1% using medium thickness of 0.104 cm to -8% using a medium thickness of 0.936 cm on the physical dose compare to the reference condition (0.313 cm). For the 1 mm aluminum filter, a variation of +8% to -40% for the same medium thickness conditions has been observed. Cells irradiated in the same conditions showed significant differences in survival fraction, corroborating the effects of dosimetric changes on physical dose.Conclusion: This work shows the importance of dosimetry in radiobiology studies and the need of an accurate description of the dosimetry protocol used for irradiation

Variation of 4 MV X-ray dose rate in fractionated irradiation strongly impacts biological endothelial cell response in vitro

International audienceComparisons of X-ray beam dose rates are scarce although these beams are widely used in medical diagnosis or radiotherapy. We have recently demonstrated in vitro and in vivo, that for a single dose of irradiation, the relative biological effectiveness (RBE) deviates from 1 when changing the dose rate of high energy X-ray beams. To further investigate the impact of the dose rate on RBE, in this study we performed in vitro fractionated irradiations by using the same two dose rates (0.63 and 2.5 Gy.min-1) of high-energy X-rays (both at 4 MV) on normal endothelial cells (HUVECs). We studied the viability/mortality, measured cellular senescence by flow cytometry and performed gene analysis on custom arrays. Taken together, these experiments show that the RBE of photons deviates from 1 when varying the dose rate of high-energy X-rays in fractionated irradiations. These results strengthen the interest of multiparametric analysis approaches in providing an accurate evaluation of the outcomes of irradiated cells in support of clonogenic assays, especially when such assays are not feasible

Variation of 4 MV X-ray dose rate strongly impacts biological response both in vitro and in vivo

International audienceBased on classic clonogenic assay, it is accepted by the scientific community that, whatever the energy or the dose rate, the relative biological effectiveness of X-rays is equal to 1. However, although X-ray beams are widely used in diagnosis, interventional medicine and radiotherapy, comparisons of their dose rates are scarce. We therefore assessed in vitro the effects of high-energy X-rays at two dose rates (0.63 and 2.5 Gy/min) using normal endothelial cells (HUVECs) by using clonogenic assay, measuring viability/mortality, studying the cell cycle and cellular senescence by flow cytometry and by performing gene analysis on custom arrays. In order to consolidate these data, we performed localized irradiation of exteriorized small intestine at 0.63 and 2.5 Gy/min. Interestingly, in vivo validation has shown a significantly higher loss of weight at the higher dose when irradiating to 19 Gy a small fragment of exteriorized small intestine of C57Bl6J mice. Nevertheless, no significant differences were observed in lesioned scores between the two dose rates, while bordering epithelium staining indicated twofold greater severe damage at 2.5 Gy/min compared to 0.63 Gy/min at one week post-irradiation. Taken together, these experiments systematically show more adverse effects of high energy X-rays at 2.5 Gy/min, while the relative biological effectiveness of photons is around 1, whatever the quality of the X-ray beam. These results strongly suggest that multiparametric analysis should be considered in support of clonogenic assay

Glutaminase Inhibition Radiosensitizes Non-Small Cell Lung Cancer Cells to X-rays and Protons

https://openworks.mdanderson.org/sumexp21/1035/thumbnail.jp