Proton minibeam radiation therapy spares normal rat brain: Long-Term Clinical, Radiological and

Proton minibeam radiation therapy (pMBRT) is a novel strategy for minimizing normal tissue damage resulting from radiotherapy treatments. This strategy partners the inherent advantages of protons for radiotherapy with the gain in normal tissue preservation observed upon irradiation with narrow, spatially fractionated beams. In this study, whole brains (excluding the olfactory bulb) of Fischer 344 rats (n = 16) were irradiated at the Orsay Proton Therapy Center. Half of the animals received standard proton irradiation, while the other half were irradiated with pMBRT at the same average dose (25 Gy in one fraction). The animals were followed-up for 6 months. A magnetic resonance imaging (MRI) study using a 7-T small-animal MRI scanner was performed along with a histological analysis. Rats treated with conventional proton irradiation exhibited severe moist desquamation, permanent epilation and substantial brain damage. In contrast, rats in the pMBRT group exhibited no skin damage, reversible epilation and significantly reduced brain damage; some brain damage was observed in only one out of the eight irradiated rats. These results demonstrate that pMBRT leads to an increase in normal tissue resistance. This net gain in normal tissue sparing can lead to the efficient treatment of very radio-resistant tumours, which are currently mostly treated palliatively.

Transfer of Minibeam Radiation Therapy into a cost-effective equipment for radiobiological studies:

Minibeam radiation therapy (MBRT) is an innovative synchrotron radiotherapy technique able to shift the normal tissue complication probability curves to significantly higher doses. However, its exploration was hindered due to the limited and expensive beamtime at synchrotrons. The aim of this work was to develop a cost-effective equipment to perform systematic radiobiological studies in view of MBRT. Tumor control for various tumor entities will be addressable as well as studies to unravel the distinct biological mechanisms involved in normal and tumor tissues responses when applying MBRT. With that aim, a series of modifications of a small animal irradiator were performed to make it suitable for MBRT experiments. In addition, the brains of two groups of rats were irradiated. Half of the animals received a standard irradiation, the other half, MBRT. The animals were followed-up for 6.5 months. Substantial brain damage was observed in the group receiving standard RT, in contrast to the MBRT group, where no significant lesions were observed. This work proves the feasibility of the transfer of MBRT outside synchrotron sources towards a small animal irradiator.

Implementation of planar proton minibeam radiation therapy using a pencil beam scanning system: A

Proton minibeam radiation therapy (pMBRT) is an innovative approach that combines the advantages of minibeam radiation therapy with the more precise ballistics of protons to further reduce the side effects of radiation. One of the main challenges of this approach is the generation of very narrow proton pencil beams with an adequate dose-rate to treat patients within a reasonable treatment time (several minutes) in existing clinical facilities. The aim of this study was to demonstrate the feasibility of implementing pMBRT by combining the pencil beam scanning (PBS) technique with the use of multislit collimators. This proof of concept study of pMBRT with a clinical system is intended to guide upcoming biological experiments.

Proton minibeam radiation therapy widens the therapeutic index for high-grade gliomas.

Proton minibeam radiation therapy (pMBRT) is a novel strategy which has already shown a remarkable reduction in neurotoxicity as to compared with standard proton therapy. Here we report on the first evaluation of tumor control effectiveness in glioma bearing rats with highly spatially modulated proton beams. Whole brains (excluding the olfactory bulb) of Fischer 344 rats were irradiated. Four groups of animals were considered: a control group (RG2 tumor bearing rats), a second group of RG2 tumor-bearing rats and a third group of normal rats that received pMBRT (70 Gy peak dose in one fraction) with very heterogeneous dose distributions, and a control group of normal rats. The tumor-bearing and normal animals were followed-up for 6 months and one year, respectively. pMBRT leads to a significant tumor control and tumor eradication in 22% of the cases. No substantial brain damage which confirms the widening of the therapeutic window for high-grade gliomas offered by pMBRT. Additionally, the fact that large areas of the brain can be irradiated with pMBRT without significant side effects, would allow facing the infiltrative nature of gliomas.

Tumor Control in RG2 Glioma-Bearing Rats: A Comparison Between Proton Minibeam Therapy and Standard

Proton minibeam radiation therapy (pMBRT) is a novel radiation therapy approach that exploits the synergies of proton therapy with the gain in normal tissue preservation observed upon irradiation with narrow, spatially fractionated, beams. The net gain in normal tissue sparing that has been shown by pMBRT may lead to the efficient treatment of very radioresistant tumors, which are currently mostly treated palliatively. The aim of this study was to perform an evaluation of the tumor effectiveness of proton minibeam radiation therapy for the treatment of RG2 glioma-bearing rats.

Team Publications

Team Members

New Approaches in Radiotherapy

Radiotherapy (RT) is one of the most frequently used methods for cancer treatment (above 50% of patients will receive RT). Despite remarkable advancements, the dose tolerances of normal tissues continue being the main limitation in RT. Finding novel approaches that allow increasing normal tissue resistance is of utmost importance. This would make it possible to escalate tumour dose, resulting in an improvement in cure rate. Along this line, the team New Approaches in Radiotherapy (NARA) works on the exploration on novel  RT techniques.  NARA is a team pioneering the conception and development of innovative methods based on the use of the spatial fractionation of the dose. This strategy has already shown a remarkable reduction in side effects of the radiation.

Since we do not believe in frontiers, NARA was born with an interdisplinary and international character.  We work at the interphase between medical physics, computing (Monte Carlo simulations), and radiobiology.

 

image Site YP

Yolanda Prezado, PhD

Unstable genomes promote inflammation.

Chromatin remodeler Fft3 plays a dual role at blocked DNA replication forks.

Here, we investigate the function of fission yeast Fun30/Smarcad1 family of SNF2 ATPase-dependent chromatin remodeling enzymes in DNA damage repair. There are three Fun30 homologues in fission yeast, Fft1, Fft2, and Fft3. We find that only Fft3 has a function in DNA repair and it is needed for single-strand annealing of an induced double-strand break. Furthermore, we use an inducible replication fork barrier system to show that Fft3 has two distinct roles at blocked DNA replication forks. First, Fft3 is needed for the resection of nascent strands, and second, it is required to restart the blocked forks. The latter function is independent of its ATPase activity.

Anna Minello

EZHIP constrains Polycomb Repressive Complex 2 activity in germ cells.

The Polycomb group of proteins is required for the proper orchestration of gene expression due to its role in maintaining transcriptional silencing. It is composed of several chromatin modifying complexes, including Polycomb Repressive Complex 2 (PRC2), which deposits H3K27me2/3. Here, we report the identification of a cofactor of PRC2, EZHIP (EZH1/2 Inhibitory Protein), expressed predominantly in the gonads. EZHIP limits the enzymatic activity of PRC2 and lessens the interaction between the core complex and its accessory subunits, but does not interfere with PRC2 recruitment to chromatin. Deletion of Ezhip in mice leads to a global increase in H3K27me2/3 deposition both during spermatogenesis and at late stages of oocyte maturation. This does not affect the initial number of follicles but is associated with a reduction of follicles in aging. Our results suggest that mature oocytes Ezhip-/- might not be fully functional and indicate that fertility is strongly impaired in Ezhip-/- females. Altogether, our study uncovers EZHIP as a regulator of chromatin landscape in gametes.

MYO1C stabilizes actin and facilitates the arrival of transport carriers at the Golgi complex.

In this study, we aimed to identify the myosin motor proteins that control trafficking at the Golgi complex. In addition to the known Golgi-associated myosins MYO6, MYO18A and MYH9 (myosin IIA), we identified MYO1C as a novel player at the Golgi in a human cell line. We demonstrate that depletion of induces Golgi complex fragmentation and decompaction. MYO1C accumulates at dynamic structures around the Golgi complex that colocalize with Golgi-associated actin dots. depletion leads to loss of cellular F-actin, and Golgi complex decompaction is also observed after inhibition or loss of the actin-related protein 2/3 complex, Arp2/3 (also known as ARPC). We show that the functional consequence of depletion is a delay in the arrival of incoming transport carriers, both from the anterograde and retrograde routes. We propose that MYO1C stabilizes actin at the Golgi complex, facilitating the arrival of incoming transport carriers at the Golgi.This article has an associated First Person interview with the first author of the paper.

Tech Times #2

Tech Times is your newsletter that regularly informs you about the latest updates on the PICT Light-Microscopy.
Have a good reading!

The Cell and Tissue Imaging Platform (PICT) welcomes you for your microscopy projects. PICT is IBiSA certified and is a member of the FranceBioImaging infrastructure.

In short, the PICT light-microscopy is:
  • 55 high-end microscopes
  • 12 experts in microscopy and image analysis
  • 2 locations in Paris and Orsay
  • 4 sites Burg, BDD, Pavillon Pasteur and Orsay buildings

Need advice on the use of light-microscopy ?

Make an appointment with the PICT imaging team closest to your unit, contacts available here.

New engineer: Chloé Guedj
After post-doc with Angela Taddei, Chloé started her first position in 2016 as an engineer on the ImagoSeine platform (IJM). In September she joined the PICT-Lhomond facility bringing her expertise in super-resolution imaging and clearing methods.

New : Live Super-Resolution Confocal Microscopy is arrived on PICT-LM@Orsay!
Super-resolution microscopes are becoming more and more common on imaging platforms. These microscopes allow you to see a level of detail that was previously impossible. The opportunity to see ever smaller components opens up access to new information on the structures of the observed samples.
The Live-SR is based on optically demodulated structured illumination technique with online processing.
Combined with spinning confocal, it enables Super-Resolution to be achieved at high speed and low photo-toxicity, making it the ideal solution for live high resolution cell imaging. Moreover, because of the nature of the light modulation, no line or pattern artifact is created.
The Live-SR process can be run live during acquisition or integrated into an offline routine. Processing is parameter free making it very easy to use. Necessary data for processing are directly read from the acquisition software.

Next Imaging TechWatch events

13 Novembre 2019: Correlative Optical Tweezers – Fluorescence & Label-free Microscopy with Lumicks
4 Decembre 2019: creating your own deep learning model with AIVIA from DRVision

Single-Molecule
Localization Microscopy

Abbelight’s Safe360 microscope will be evaluated on the PICT@Paris in October. Please contact if you are interested.

Questions about microscopy or image analysis ?

On the last Thursday of each month (remember this date) the PICT-photonic organizes an OpenDesk: engineers are gathered to answer your questions, on both microcopy and image processing. Join us on the next one, the 31st of October from 11AM to 12:30PM in Pavillon Pasteur.

CREST demo – 4th au 8th November 2019
The company CrestOpics will join us to present the next generation of X-light spinning disk. We will try to compare this solution with the spinnings we have on our platform, especially on field homogeneity and sensitivity. The particularity of this one is to be able to modulate the size of the pinholes by choosing its disk. This version will be installed on the AZ100 macroscope in the Nikon Center
https://crestopt.com/

NanoLive demo : 12th-14th November 2019
The Nanolive company offers us to test their microscope based on the analysis of the refractive index. No need for dyes no photobleaching anymore. Everything is based on the change/analysis of refractive index that exists between the nucleus, the cytoplasm, membranes… Go check the website https://nanolive.ch/ to find out more but the new solution finally offers to do LiveCell with CO2 & temperature control.

We provide basic and advanced training on image analysis using the ImageJ/Fiji software. Registration for the next training session will be open very soon. A communication will be sent to all researchers of the Institute. Attention! limited number of seats.

Which microscopes are available on the platform?

It is easy, just go to our website.

Need a microscope training ?

Login to the OpenIRIS booking system and make an online training request. The procedure is described in our wiki but in case of problems contact us.

Thank you for your participation in the survey. The results of the survey are available here (pdf file).

The Institut Curie is hosting the Nikon Imaging Centre since 2007. More information here.

You have just published an article with microscopy data…. Congratulations! Don’t forget to thank the PICT-IBiSA platform member of FranceBioImaging  (example of acknowledgements here).

A big thank you to all the researchers, units, labex and institute that funds and/or helps us to finance the platform’s equipment.

“We believe in sharing equipment”.

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Antoine Récanati, PhD

Romain Ménégaux

Asma Nouira

Arthur Imbert

Transcriptional alterations in glioma result primarily from DNA methylation-independent mechanisms.

In cancer cells, aberrant DNA methylation is commonly associated with transcriptional alterations, including silencing of tumor suppressor genes. However, multiple epigenetic mechanisms, including polycomb repressive marks, contribute to gene deregulation in cancer. To dissect the relative contribution of DNA methylation-dependent and -independent mechanisms to transcriptional alterations at CpG island/promoter-associated genes in cancer, we studied 70 samples of adult glioma, a widespread type of brain tumor, classified according to their isocitrate dehydrogenase (IDH1) mutation status. We found that most transcriptional alterations in tumor samples were DNA methylation-independent. Instead, altered histone H3 trimethylation at lysine 27 (H3K27me3) was the predominant molecular defect at deregulated genes. Our results also suggest that the presence of a bivalent chromatin signature at CpG island promoters in stem cells predisposes not only to hypermethylation, as widely documented, but more generally to all types of transcriptional alterations in transformed cells. In addition, the gene expression strength in healthy brain cells influences the choice between DNA methylation- and H3K27me3-associated silencing in glioma. Highly expressed genes were more likely to be repressed by H3K27me3 than by DNA methylation. Our findings support a model in which altered H3K27me3 dynamics, more specifically defects in the interplay between polycomb protein complexes and the brain-specific transcriptional machinery, is the main cause of transcriptional alteration in glioma cells. Our study provides the first comprehensive description of epigenetic changes in glioma and their relative contribution to transcriptional changes. It may be useful for the design of drugs targeting cancer-related epigenetic defects.