Transient PP2A inhibition alleviates normal tissue stem cell susceptibility to cell death during radiotherapy

Abstract Unintended outcomes of cancer therapy include ionizing radiation (IR)-induced stem cell depletion, diminished regenerative capacity, and accelerated aging. Stem cells exhibit attenuated DNA damage response (DDR) and are hypersensitive to IR, as compared to differentiated non-stem cells. We performed genomic discovery research to compare stem cells to differentiated cells, which revealed Phosphoprotein phosphatase 2A (PP2A) as a potential contributor to susceptibility in stem cells. PP2A dephosphorylates pATM, γH2AX, pAkt etc. and is believed to play dual role in regulating DDR and apoptosis. Although studied widely in cancer cells, the role of PP2A in normal stem cell radiosensitivity is unknown. Here we demonstrate that constitutively high expression and radiation induction of PP2A in stem cells plays a role in promoting susceptibility to irradiation. Transient inhibition of PP2A markedly restores DNA repair, inhibits apoptosis, and enhances survival of stem cells, without affecting differentiated non-stem and cancer cells. PP2Ai-mediated stem cell radioprotection was demonstrated in murine embryonic, adult neural, intestinal, and hematopoietic stem cells

Evolution of the Illegal Substances Market and Substance Users' Social Situation and Health during the COVID-19 Pandemic.

The outbreak of the COVID-19 pandemic and the measures taken for tackling it had the potential to lead to deep modifications in the supply of illegal drugs and to impact substance users' health and social situation. To investigate this, we used mixed methods, i.e., quantitative data collected with a brief questionnaire from substance users receiving opioid agonist treatment in a treatment centre in Switzerland (N = 49), and qualitative data obtained using semi-structured phone interviews among a sub-group of participants (N = 17). We repeated data collection twice over four weeks to investigate trends over time (N = 51 and 14 at wave 2). Findings consistently showed the limited impact of the COVID-19 outbreak on the illegal substance market. Over the two waves, the supply, price and purity of three main illegal substances did not significantly vary. Substance use was estimated as usual by most, trending toward a decrease. The impact of the pandemic on participants' social situation and health was appraised as low to medium. Nevertheless, a minority of participants reported higher impact and multivariate analyses showed a more important impact for those who were female, younger, and not using multiple substances. This process was implemented quickly and provided an understanding of the short-term impact of the pandemic on drug markets and users

Analysis of residual content of used syringes collected from low threshold facilities in Lausanne, Switzerland.

For the first time in Switzerland, an analysis of residual contents from used syringes collected from low threshold facilities was performed. This preliminary study is part of a wider project aiming to understand patterns of injecting drug use over time. Among the 100,000 syringes exchanged annually by the ABS foundation (Accueil Bas Seuil), 113 were collected following a purposive sampling method and analysed by gas chromatography coupled with mass spectrometry (GC-MS). Four syringes (4% of the sample population) contained no substances take into consideration the limit of the method. Cocaine was the most commonly observed compound and was detected in 77 syringes (68%), whilst users reported syringes with cocaine among those analysed in this study. Heroin was detected in 49 syringes (43%) and reported by 53 users returning syringes; midazolam was detected in 31 syringes (27%) and reported as the medicine Dormicum(®) in 22 occurrences. No new or unusual illicit drug was detected in the sample. The results show the presence of cocaine in more than half of the sample, an absence of new or unusual illicit drugs, as well as very few traces of methadone, which suggests that this substitution drug is rarely injected. This preliminary study also demonstrates the potential of this developed methodology for monitoring purposes. An ongoing and more systematic approach could allow to detect modifications in drug use patterns among the target population as well as the appearance of new and hazardous substances. Such systematic and timely results could allow an adaptation of harm reduction interventions

Histone H3 lysine 9 acetylation obstructs ATM activation and promotes ionizing radiation sensitivity in normal stem cells

Dynamic spatiotemporal modification of chromatin around DNA damage is vital for efficient DNA repair. Normal stem cells exhibit an attenuated DNA damage response (DDR), inefficient DNA repair, and high radiosensitivity. The impact of unique chromatin characteristics of stem cells in DDR regulation is not yet recognized. We demonstrate that murine embryonic stem cells (ES) display constitutively elevated acetylation of histone H3 lysine 9 (H3K9ac) and low H3K9 tri-methylation (H3K9me3). DNA damage-induced local deacetylation of H3K9 was abrogated in ES along with the subsequent H3K9me3. Depletion of H3K9ac in ES by suppression of monocytic leukemia zinc finger protein (MOZ) acetyltransferase improved ATM activation, DNA repair, diminished irradiation-induced apoptosis, and enhanced clonogenic survival. Simultaneous suppression of the H3K9 methyltransferase Suv39h1 abrogated the radioprotective effect of MOZ inhibition, suggesting that high H3K9ac promoted by MOZ in ES cells obstructs local upregulation of H3K9me3 and contributes to muted DDR and increased radiosensitivity

Multipoint temperature monitoring of microwave thermal ablation in bones through fiber bragg grating sensor arrays

Bones are a frequent site of metastases that cause intolerable cancer-related pain in 90% of patients, making their quality of life poor. In this scenario, being able to treat bone oncology patients by means of minimally invasive techniques can be crucial to avoid surgery-related risks and decrease hospitalization times. The use of microwave ablation (MWA) is gaining broad clinical acceptance to treat bone tumors. It is worth investigating temperature variations in bone tissue undergoing MWA because the clinical outcomes can be inferred from this parameter. Several feasibility studies have been performed, but an experimental analysis of the temperature trends reached into the bone during the MWA has not yet been assessed. In this work, a multi-point temperature study along the bone structure during such treatment is presented. The study has been carried out on ex vivo bovine femur and tibia, subjected to MWA. An overall of 40 measurement points covering a large sensing area was obtained for each configuration. Temperature monitoring was performed by using 40 fiber Bragg grating (FBGs) sensors (four arrays each housing 10 FBGs), inserted into the bones at specific distances to the microwave antenna. As result, the ability of this experimental multi-point monitoring approach in tracking temperature variations within bone tissue during MWA treatments was shown. This study lays the foundations for the design of a novel approach to study the effects of MWA on bone tumors. As consequence, the MWA treatment settings could be optimized in order to maximize the treatment effects of such a promising clinical application, but also customized for the specific tumor and patient

Unique epigenetic influence of H2AX phosphorylation and H3K56 acetylation on normal stem cell radioresponses

Normal tissue injury resulting from cancer radiotherapy is often associated with diminished regenerative capacity. We examined the relative radiosensitivity of normal stem cell populations compared with non–stem cells within several radiosensitive tissue niches and culture models. We found that these stem cells are highly radiosensitive, in contrast to their isogenic differentiated progeny. Of interest, they also exhibited a uniquely attenuated DNA damage response (DDR) and muted DNA repair. Whereas stem cells exhibit reduced ATM activation and ionizing radiation–induced foci, they display apoptotic pannuclear H2AX-S139 phosphorylation (γH2AX), indicating unique radioresponses. We also observed persistent phosphorylation of H2AX-Y142 along the DNA breaks in stem cells, which promotes apoptosis while inhibiting DDR signaling. In addition, down-regulation of constitutively elevated histone-3 lysine-56 acetylation (H3K56ac) in stem cells significantly decreased their radiosensitivity, restored DDR function, and increased survival, signifying its role as a key contributor to stem cell radiosensitivity. These results establish that unique epigenetic landscapes affect cellular heterogeneity in radiosensitivity and demonstrate the nonubiquitous nature of radiation responses. We thus elucidate novel epigenetic rheostats that promote ionizing radiation hypersensitivity in various normal stem cell populations, identifying potential molecular targets for pharmacological radioprotection of stem cells and hopefully improving the efficacy of future cancer treatment