Is single fraction the future of stereotactic body radiation therapy (SBRT)? A critical appraisal of the current literature

Stereotactic Body Radiation Therapy (SBRT) is a standard of care for many localizations but the question of the optimal fractionation remains a matter of concern. If single fraction sessions are routinely used for intracranial targets, their utilization for mobile extracranial lesions is a source of debate and apprehension. Single session treatments improve patient comfort, provide a medico-economic benefit, and have proven useful in the context of the SARS-CoV 2 pandemic. However, both technical and radiobiological uncertainties remain. Experience from intracranial radiosurgery has shown that the size of the target, its proximity to organs at risk, tumor histology, and the volume of normal tissue irradiated are all determining factors in the choice of fractionation. The literature on the use of single fraction for extracranial sites is still scarce. Only primary and secondary pulmonary tumors have been evaluated in prospective randomized trials, allowing the integration of these fractionation schemes in daily practice, for highly selected cases and in trained teams. The level of evidence for the other organs is mainly based on dose escalation or retrospective trials and calls for caution, with further studies being needed before routine use in clinical practice.

Long term operation of a 30 kW Beryllium target at IPHI

Following tests of low power bulk Beryllium targets in 2016–2020, a high power target was designed, built and tested at the High Intensity Proton Injector (IPHI) at CEA Paris–Saclay. The design of the target and the results of the tests will be described.

Ion irradiation induced strain and structural changes in LiTaO3perovskite

LiTaO₃crystals irradiated with 3 MeV and 1.162 GeV Au ions were studied by single crystal x-ray diffraction and Raman scattering measurements. The maximum lattice strains after 3 MeV Au ion irradiation to a fluence of 1.2 × 10¹³ cm^-2were 1.2% and 0.6% along thec- anda-/b-axes, respectively. Two effects were observed in 1.162 GeV Au ion irradiated samples: (i) the (0006) and (1120) Bragg peaks were split into doublets, which suggested a subtle structural change due to slight modification of chemical composition; and (ii) the pre-damaged 1.2% lattice strain along thec-axis was relaxed to 0.9% after subsequent irradiation with 1.162 GeV Au ions, while relaxation along thea- orb-axis was not obvious. A distinct change in the Raman spectrum of the 〈0001〉 oriented LiTaO₃crystals was observed after 1.162 GeV Au ion irradiation, but no obvious change was observed in the 〈1120〉 oriented samples or in 3 MeV Au ion irradiated samples. Strain and structural changes in crystalline LiTaO₃, with or without pre-existing defects, upon ion irradiation are delineated in its responding to inelastic ionization and elastic nuclear collisions.

A Unique and Scalable Model for Increasing Research Engagement, STEM Persistence, and Entry into Doctoral Programs

Low persistence in science majors and limited participation in high-impact research experiences contribute to the nationwide underrepresentation of minorities in the science workforce, particularly jobs requiring a graduate degree. The Program for Excellence in Education and Research in the Sciences (PEERS) is an academic support program at the University of California, Los Angeles (UCLA) that supports first- and second-year science majors from underrepresented and underserved backgrounds to maximize student success and science, technology, engineering, and mathematics (STEM) persistence. Here, we evaluate the success of PEERS through data from the UCLA registrar, student surveys, and longitudinal tracking of student outcomes. Results show that PEERS students have significantly higher participation rates in undergraduate research, despite PEERS having no formal research component. Importantly, PEERS students were seven times as likely to enroll in PhD programs, and twice as likely to enroll in MD programs compared with propensity-matched controls. Combined results show that increased success of PEERS students in their first 2 years as science majors resulted in improved outcomes later in their undergraduate studies and had tangible impacts on subsequent educational trajectories that will increase participation of underrepresented groups in high-skill STEM careers.

First steps toward the development of SONATE, a Compact Accelerator driven Neutron Source

Facilities providing bright thermal neutron beams are of primary importance for various research topics such as condensed matter experiments, neutron-imaging or medical applications. Currently these are mainly spallation sources and nuclear reactors. However, these later facilities are ageing and the political context does not favor the building of new ones. This is the case in CEA-Saclay (France), where the Orphee reactor is planned to shutdown in 2019. Therefore, another local facility, affordable by one country, able to provide high brilliance neutron beams has to be built. At CEA-Saclay, a compact accelerator driven neutron source, SONATE, is investigated in taking advantage of the IPHI accelerator able to deliver a 3 MeV proton beam with an intensity up to 100 mA. In the future, SONATE is foreseen to operate with 20 MeV protons to increase the neutron brightness. In addition to the difficulties to operate such high intensity accelerators, the other challenges regard the target-moderator-reflector (TMR) design which is crucial to maximize the neutron flux at the detector location. At CEA-Saclay, several experiments were performed between 2016 and 2019 with the IPHI accelerator. Geant4 simulations were also developed. They demonstrate the feasibility of such concept and enable to find the best TMR configuration for the future SONATE facility. These developments are reported in this article.

Implementation of a Learning Assistant Program Improves Student Performance on Higher-Order Assessments

Learning assistant (LA) programs have been implemented at a range of institutions, usually as part of a comprehensive curricular transformation accompanied by a pedagogical switch to active learning. While this shift in pedagogy has led to increased student learning gains, the positive effect of LAs has not yet been distinguished from that of active learning. To determine the effect that LAs would have beyond a student-centered instructional modality that integrated active learning, we introduced an LA program into a large-enrollment introductory molecular biology course that had already undergone a pedagogical transformation to a highly structured, flipped (HSF) format. We used questions from a concept test (CT) and exams to compare student performance in LA-supported HSF courses with student performance in courses without LAs. Students in the LA-supported course did perform better on exam questions common to both HSF course modalities but not on the CT. In particular, LA-supported students' scores were higher on common exam questions requiring higher-order cognitive skills, which LAs were trained to foster. Additionally, underrepresented minority (URM) students particularly benefited from LA implementation. These findings suggest that LAs may provide additional learning benefits to students beyond the use of active learning, especially for URM students.

Down-regulation of the cancer/testis antigen 45 (CT45) is associated with altered tumor cell morphology, adhesion and migration

Background

Due to their restricted expression in male germ cells and certain tumors, cancer/testis (CT) antigens are regarded as promising targets for tumor therapy. CT45 is a recently identified nuclear CT antigen that was associated with a severe disease score in Hodgkin’s lymphoma and poor prognosis in multiple myeloma. As for many CT antigens, the biological function of CT45 in developing germ cells and in tumor cells is largely unknown.

Methods

CT45 expression was down-regulated in CT45-positive Hodgkin’s lymphoma (L428), fibrosarcoma (HT1080) and myeloma (U266B1) cells using RNA interference. An efficient CT45 knock-down was confirmed by immunofluorescence staining and/or Western blotting. These cellular systems allowed us to analyze the impact of CT45 down-regulation on proliferation, cell cycle progression, morphology, adhesion, migration and invasive capacity of tumor cells.

Results

Reduced levels of CT45 did not coincide with changes in cell cycle progression or proliferation. However, we observed alterations in cell adherence, morphology and migration/invasion after CT45 down-regulation. Significant changes in the distribution of cytoskeleton-associated proteins were detected by confocal imaging. Changes in cell adherence were recorded in real-time using the xCelligence system with control and siRNA-treated cells. Altered migratory and invasive capacity of CT45 siRNA-treated cells were visualized in 3D migration and invasion assays. Moreover, we found that CT45 down-regulation altered the level of the heterogeneous nuclear ribonucleoprotein syncrip (hnRNP-Q1) which is known to be involved in the control of focal adhesion formation and cell motility.

Conclusions

Providing first evidence of a cell biological function of CT45, we suggest that this cancer/testis antigen is involved in the modulation of cell morphology, cell adherence and cell motility. Enhanced motility and/or invasiveness of CT45-positive cells could contribute to the more severe disease progression that is correlated to CT45-positivity in several malignancies.

The pluripotency factor-bound intron 1 of Xist is dispensable for X chromosome inactivation and reactivation in vitro and in vivo

X chromosome inactivation (XCI) is a dynamically regulated developmental process with inactivation and reactivation accompanying the loss and gain of pluripotency, respectively. A functional relationship between pluripotency and lack of XCI has been suggested, whereby pluripotency transcription factors repress the master regulator of XCI, the noncoding transcript Xist, by binding to its first intron (intron 1). To test this model, we have generated intron 1 mutant embryonic stem cells (ESCs) and two independent mouse models. We found that Xist's repression in ESCs, its transcriptional upregulation upon differentiation, and its silencing upon reprogramming to pluripotency are not dependent on intron 1. Although we observed subtle effects of intron 1 deletion on the randomness of XCI and in the absence of the antisense transcript Tsix in differentiating ESCs, these have little relevance in vivo because mutant mice do not deviate from Mendelian ratios of allele transmission. Altogether, our findings demonstrate that intron 1 is dispensable for the developmental dynamics of Xist expression.

[Congenital hepatic fibrosis in children. Report of 9 cases and review of the literature]

Congenital hepatic fibrosis is a recessive autosomic disease with two major risks: gastrointestinal haemorrhage caused by portal hypertension and cholangitis related to bacterial infection of dilated intrahepatic bile ducts.. The aim of our study is to define epidemiological features, the presenting symptoms, the diagnosis, the evolution and the management of this disease. Between January 1990 and December 2000, we reported the cases of nine children with this disease at children hospital of Tunis. Three were male and six female. The mild age was three years and six months. Consanguinity was present in five cases and similar cases were found in six cases. The FHC was revealed by portal hypertension in five cases, angiocholitis in one case and by portal hypertension and angiocholitis in three cases. Liver biopsy was done in seven children. Ultrasound examination of the liver and kidney revealed caroli syndrome in five cases and polykystose renal in two cases The intravenous pyelography was performed in four cases showing precalicial canalicular ectasia in four cases. Eosophageal endoscopy had shown oesophageal varices in six patients. The follow up had shown that three patients had gastrointestinal bleeding, three had angiocholitis. One patient died with multivisceral failure. The treatment of acute bleeding has needed blood transfusion in four cases. Primary prevention of bleeding was done by endoscopic sclerosis alone in one case and associated to betablokers in two cases. Secondary prevention of varices bleeding was done by sclerotherapic in two cases, by beta blokers alone in one case and by betablokers associated to elastic ligation of oesophageal varices in one case.