BRCA1 and 53BP1 regulate reprogramming efficiency by mediating DNA repair pathway choice at replication-associated double-strand breaks.

Reprogramming to pluripotency is associated with DNA damage and requires the functions of the BRCA1 tumor suppressor. Here, we leverage separation-of-function mutations in BRCA1/2 as well as the physical and/or genetic interactions between BRCA1 and its associated repair proteins to ascertain the relevance of homology-directed repair (HDR), stalled fork protection (SFP), and replication gap suppression (RGS) in somatic cell reprogramming. Surprisingly, loss of SFP and RGS is inconsequential for the transition to pluripotency. In contrast, cells deficient in HDR, but proficient in SFP and RGS, reprogram with reduced efficiency. Conversely, the restoration of HDR function through inactivation of 53bp1 rescues reprogramming in Brca1-deficient cells, and 53bp1 loss leads to elevated HDR and enhanced reprogramming in mouse and human cells. These results demonstrate that somatic cell reprogramming is especially dependent on repair of replication-associated double-strand breaks (DSBs) by the HDR activity of BRCA1 and BRCA2 and can be improved in the absence of 53BP1.

Lack of SPNS1 results in accumulation of lysolipids and lysosomal storage disease in mouse models.

Accumulation of sphingolipids, especially sphingosines, in the lysosomes is a key driver of several lysosomal storage diseases. The transport mechanism for sphingolipids from the lysosome remains unclear. Here, we identified SPNS1, which shares the highest homology to SPNS2, a sphingosine-1-phosphate (S1P) transporter, functions as a transporter for lysolipids from the lysosome. We generated Spns1-KO cells and mice and employed lipidomic and metabolomic approaches to reveal SPNS1 ligand identity. Global KO of Spns1 caused embryonic lethality between E12.5 and E13.5 and an accumulation of sphingosine, lysophosphatidylcholines (LPC), and lysophosphatidylethanolamines (LPE) in the fetal livers. Similarly, metabolomic analysis of livers from postnatal Spns1-KO mice presented an accumulation of sphingosines and lysoglycerophospholipids including LPC and LPE. Subsequently, biochemical assays showed that SPNS1 is required for LPC and sphingosine release from lysosomes. The accumulation of these lysolipids in the lysosomes of Spns1-KO mice affected liver functions and altered the PI3K/AKT signaling pathway. Furthermore, we identified 3 human siblings with a homozygous variant in the SPNS1 gene. These patients suffer from developmental delay, neurological impairment, intellectual disability, and cerebellar hypoplasia. These results reveal a critical role of SPNS1 as a promiscuous lysolipid transporter in the lysosomes and link its physiological functions with lysosomal storage diseases.

MFSD7c functions as a transporter of choline at the blood-brain barrier.

Mutations in the orphan transporter MFSD7c (also known as Flvcr2), are linked to Fowler syndrome. Here, we used Mfsd7c knockout (Mfsd7c-/-) mice and cell-based assays to reveal that MFSD7c is a choline transporter at the blood-brain barrier (BBB). We performed comprehensive metabolomics analysis and detected differential changes of metabolites in the brains and livers of Mfsd7c-/-embryos. Particularly, we found that choline-related metabolites were altered in the brains but not in the livers of Mfsd7c-/- embryos. Thus, we hypothesized that MFSD7c regulates the level of choline in the brain. Indeed, expression of human MFSD7c in cells significantly increased choline uptake. Interestingly, we showed that choline uptake by MFSD7c is greatly increased by choline-metabolizing enzymes, leading us to demonstrate that MFSD7c is a facilitative transporter of choline. Furthermore, single-cell patch clamp analysis showed that the import of choline by MFSD7c is electrogenic. Choline transport function of MFSD7c was shown to be conserved in vertebrates, but not in yeasts. We demonstrated that human MFSD7c is a functional ortholog of HNM1, the yeast choline importer. We also showed that several missense mutations identified in patients exhibiting Fowler syndrome had abolished or reduced choline transport activity. Mice lacking Mfsd7c in endothelial cells of the central nervous system suppressed the import of exogenous choline from blood but unexpectedly had increased choline levels in the brain. Stable-isotope tracing study revealed that MFSD7c was required for exporting choline derived from lysophosphatidylcholine in the brain. Collectively, our work identifies MFSD7c as a choline exporter at the BBB and provides a foundation for future work to reveal the disease mechanisms of Fowler syndrome.

Physiological cell bioprinting density in human bone-derived cell-laden scaffolds enhances matrix mineralization rate and stiffness under dynamic loading.

Human organotypic bone models are an emerging technology that replicate bone physiology and mechanobiology for comprehensive in vitro experimentation over prolonged periods of time. Recently, we introduced a mineralized bone model based on 3D bioprinted cell-laden alginate-gelatin-graphene oxide hydrogels cultured under dynamic loading using commercially available human mesenchymal stem cells. In the present study, we created cell-laden scaffolds from primary human osteoblasts isolated from surgical waste material and investigated the effects of a previously reported optimal cell printing density (5 × 106 cells/mL bioink) vs. a higher physiological cell density (10 × 106 cells/mL bioink). We studied mineral formation, scaffold stiffness, and cell morphology over a 10-week period to determine culture conditions for primary human bone cells in this microenvironment. For analysis, the human bone-derived cell-laden scaffolds underwent multiscale assessment at specific timepoints. High cell viability was observed in both groups after bioprinting (>90%) and after 2 weeks of daily mechanical loading (>85%). Bioprinting at a higher cell density resulted in faster mineral formation rates, higher mineral densities and remarkably a 10-fold increase in stiffness compared to a modest 2-fold increase in the lower printing density group. In addition, physiological cell bioprinting densities positively impacted cell spreading and formation of dendritic interconnections. We conclude that our methodology of processing patient-specific human bone cells, subsequent biofabrication and dynamic culturing reliably affords mineralized cell-laden scaffolds. In the future, in vitro systems based on patient-derived cells could be applied to study the individual phenotype of bone disorders such as osteogenesis imperfecta and aid clinical decision making.

BRCA2 promotes genomic integrity and therapy resistance primarily through its role in homology-directed repair.

Tumor suppressor BRCA2 functions in homology-directed repair (HDR), the protection of stalled replication forks, and the suppression of replicative gaps, but their relative contributions to genome integrity and chemotherapy response are under scrutiny. Here, we report that mouse and human cells require a RAD51 filament stabilization motif in BRCA2 for fork protection and gap suppression but not HDR. In mice, the loss of fork protection/gap suppression does not compromise genome stability or shorten tumor latency. By contrast, HDR deficiency increases spontaneous and replication stress-induced chromosome aberrations and tumor predisposition. Unlike with HDR, fork protection/gap suppression defects are also observed in Brca2 heterozygous cells, likely due to reduced RAD51 stabilization at stalled forks/gaps. Gaps arise from PRIMPOL activity, which is associated with 5-hydroxymethyl-2'-deoxyuridine sensitivity due to the formation of SMUG1-generated abasic sites and is exacerbated by poly(ADP-ribose) polymerase (PARP) inhibition. However, HDR proficiency has the major role in mitigating sensitivity to chemotherapeutics, including PARP inhibitors.

Bariatric Surgery and Longitudinal Cancer Risk: A Review.

Importance: Cancer is one of the leading causes of death in the United States, with the obesity epidemic contributing to its steady increase every year. Recent cohort studies find an association between bariatric surgery and reduced longitudinal cancer risk, but with heterogeneous findings. Observations: This review summarizes how obesity leads to an increased risk of developing cancer and synthesizes current evidence behind the potential for bariatric surgery to reduce longitudinal cancer risk. Overall, bariatric surgery appears to have the strongest and most consistent association with decreased incidence of developing breast, ovarian, and endometrial cancers. The association of bariatric surgery and the development of esophageal, gastric, liver, and pancreas cancer is heterogenous with studies showing either no association or decreased longitudinal incidences. Conversely, there have been preclinical and cohort studies implying an increased risk of developing colon and rectal cancer after bariatric surgery. A review and synthesis of the existing literature reveals epidemiologic shortcomings of cohort studies that potentially explain incongruencies observed between studies. Conclusions and Relevance: Studies examining the association of bariatric surgery and longitudinal cancer risk remain heterogeneous and could be explained by certain epidemiologic considerations. This review provides a framework to better define subgroups of patients at higher risk of developing cancer who would potentially benefit more from bariatric surgery, as well as subgroups where more caution should be exercised.

Paediatric radiotherapy in the United Kingdom: an evolving subspecialty and a paradigm for integrated teamworking in oncology.

Many different malignancies occur in children, but overall, cancer in childhood is rare. Survival rates have improved appreciably and are higher compared with most adult tumour types. Treatment schedules evolve as a result of clinical trials and are typically complex and multi-modality, with radiotherapy an integral component of many. Risk stratification in paediatric oncology is increasingly refined, resulting in a more personalized use of radiation. Every available modality of radiation delivery: simple and advanced photon techniques, proton beam therapy, molecular radiotherapy, and brachytherapy, have their place in the treatment of children's cancers. Radiotherapy is rarely the sole treatment. As local therapy, it is often given before or after surgery, so the involvement of the surgeon is critically important, particularly when brachytherapy is used. Systemic treatment is the standard of care for most paediatric tumour types, concomitant administration of chemotherapy is typical, and immunotherapy has an increasing role. Delivery of radiotherapy is not done by clinical or radiation oncologists alone; play specialists and anaesthetists are required, together with mould room staff, to ensure compliance and immobilization. The support of clinical radiologists is needed to ensure the correct interpretation of imaging for target volume delineation. Physicists and dosimetrists ensure the optimal dose distribution, minimizing exposure of organs at risk. Paediatric oncology doctors, nurses, and a range of allied health professionals are needed for the holistic wrap-around care of the child and family. Radiographers are essential at every step of the way. With increasing complexity comes a need for greater centralization of services.

Evaluation of the microbiological efficacy of cleaning agents for tracheostomy inner cannulas.

PURPOSE: Biofilms are a significant cause of morbidity in patients with indwelling medical devices. Biofilms pose a potential risk with reusable inner cannulas by increasing the risk of infections. Effective decontamination is thus vital in decreasing bioburden. The current guidelines for cleaning inner cannulas are varied, with multiple techniques being recommended, which are not supported by strong evidence. This randomized, controlled, cross-over study attempted to enumerate the bacterial count of inner cannulas used in tracheostomy patients (n = 60) pre-and post-decontamination with detergent (A) or sterile water (B). MATERIALS AND METHODS: The patients were randomly allocated to sequence A > B or B > A in 1:1 fashion. The saline flushing of the inner cannulas was plated on trypticase soy agar with 5 % sheep blood to enumerate the bacterial count. RESULTS: The mean ratio [Log (CFU)post/Log (CFU)pre]A/[Log (CFU)post/Log (CFU)pre]B based on 53 samples was 0.918 ± 0.470, two-sided 90 % confidence interval (CI) 0.812, 1.024. The equivalence criterion was met as the mean ratio after cleaning fell within the equivalence region of 0.8 and 1.25. CONCLUSION: This study demonstrated the microbiological efficacy of both detergent and sterile water in the decontamination of inner cannulas, and that sterile water was not less effective than detergent in reducing the bacterial load for safe re-use of inner cannulas. This has the potential to promote cost savings for patients with tracheostomy, both in the hospital and the community. The study findings may also be relevant in formulating tracheostomy care policies.

Cellular and molecular overview of gestational diabetes mellitus: Is it predictable and preventable?

BACKGROUND: In contrast to overt diabetes mellitus (DM), gestational DM (GDM) is defined as impaired glucose tolerance induced by pregnancy, which may arise from exaggerated physiologic changes in glucose metabolism. GDM prevalence is reported to be as high as 20% among pregnancies depending on the screening method, gestational age, and the population studied. Maternal and fetal effects of uncontrolled GDM include stillbirth, macrosomia, neonatal diabetes, birth trauma, and subsequent postpartum hemorrhage. Therefore, it is essential to find the potential target population and associated predictive and preventive measures for future intensive peripartum care. AIM: To review studies that explored the cellular and molecular mechanisms of GDM as well as predictive measures and prevention strategies. METHODS: The search was performed in the Medline and PubMed databases using the terms "gestational diabetes mellitus," "overt diabetes mellitus," and "insulin resistance." In the literature, only full-text articles were considered for inclusion (237 articles). Furthermore, articles published before 1997 and duplicate articles were excluded. After a final review by two experts, all studies (1997-2023) included in the review met the search terms and search strategy (identification from the database, screening of the studies, selection of potential articles, and final inclusion). RESULTS: Finally, a total of 79 articles were collected for review. Reported risk factors for GDM included maternal obesity or overweight, pre-existing DM, and polycystic ovary syndrome. The pathophysiology of GDM involves genetic variants responsible for insulin secretion and glycemic control, pancreatic ß cell depletion or dysfunction, aggravated insulin resistance due to failure in the plasma membrane translocation of glucose transporter 4, and the effects of chronic, low-grade inflammation. Currently, many antepartum measurements including adipokines (leptin), body mass ratio (waist circumference and waist-to-hip ratio], and biomarkers (microRNA in extracellular vesicles) have been studied and confirmed to be useful markers for predicting GDM. For preventing GDM, physical activity and dietary approaches are effective interventions to control body weight, improve glycemic control, and reduce insulin resistance. CONCLUSION: This review explored the possible factors that influence GDM and the underlying molecular and cellular mechanisms of GDM and provided predictive measures and prevention strategies based on results of clinical studies.

What do you think of when you hear the word 'feedback'? A reflective thematic analysis study of interviews.

PURPOSE: Although most teaching around feedback focuses on the delivery, one must consider that the word 'feedback' is not a neutral word. It inflicts a range of emotions that, when used, may influence the effectiveness of the feedback process. A more profound understanding of health professions educators' perceptions regarding the word 'feedback' can help explain discrepancies between the provision, reception and acceptance of feedback. METHODS: This is a qualitative inductive, reflective thematic analysis study. The authors interviewed 22 health professions educators participating in an online workshop to develop their feedback giving skills on their initial perspectives of the word 'feedback'. RESULTS: We found four major themes: (1) Can I tell you a little story about my feedback experience? (2) It is probably going to be negative. (3) There is always something to learn if you are willing to hear the message. (4) It is like getting a report card. From the data, we suggest one key antecedent and two practical approaches one could take when giving feedback. CONCLUSION: In this article, the authors highlight barriers during the feedback process due to the mere perception of the nature of feedback and the connotations associated with the term itself and suggest approaches that can refocus conversations towards a shared meaning and purpose of improvement, despite the preconceptions of the word 'feedback'.

A Systematic Review of Non-Seriously Ill Community-Dwelling Asians' Views on Advance Care Planning.

OBJECTIVES: To systematically synthesize the views of community-dwelling Asians on Advance care planning and to summarize the factors and reasons affecting their uptake of ACP. DESIGN: Mixed-methods systematic review (PROSPERO: CRD42018091033). SETTING AND PARTICIPANTS: Asian adults (≥18 years old) living in the community globally. METHODS: Medline (Ovid), Web of Science, CINAHL (EBSCO), Open Grey, and Google Scholar were searched from inception to June 30, 2022. Qualitative, quantitative, or mixed-methods studies reporting on the views of non-seriously ill community-dwelling Asian adults on ACP or the factors influencing their ACP uptake were included. Secondary research, studies not published in English, or studies not available as full text were excluded. Two independent teams of researchers extracted data, assessed methodologic quality, and performed the data analysis. Data analysis was conducted using the multistep convergent integrated approach based on Joanna Briggs Institute methodology for mixed-methods systematic review. RESULTS: Fifty-eight studies were included. Non-seriously ill community-dwelling Asians were willing to engage in ACP (46.5%-84.4%) although their awareness (3.1%-42.9%) and uptake of ACP remained low (14.0%-53.4%). Background factors (sociodemographic factors, and health status, as well as experience and exposure to information) and underlying beliefs (attitude toward ACP, subjective norm, and perceived behavioral control) were found to affect their uptake of ACP. A conceptual framework was developed to facilitate a proper approach to ACP for this population. CONCLUSIONS AND IMPLICATIONS: A flexible approach toward ACP is needed for non-seriously ill community-dwelling Asians. There is also a need to raise end-of-life and ACP literacy, and to explore ways to narrow the gap in the expectations and implementation of ACP so that trust in its effective execution can be built.

Abnormal Pap smear among pregnant women - Feasibility of opportunistic cervical screening.

Objective: The uptake of cervical cancer screening is poor, especially in developing countries. Thus, pregnancy represents a good opportunity to have the test done. The aim of this study is to determine the prevalence of abnormal Pap smear among pregnant women during their antenatal check-ups. Study design: A prospective study involving five hundred and ninety-six women was recruited over a 1-year duration from 15th January 2018 until 14th January 2019 in a tertiary referral center, in Malaysia. Pap smears were performed on all consented pregnant women using liquid-based cytology and the results were obtained to evaluate the prevalence of abnormal Pap smear during pregnancy. Maternal risk factors associated with abnormal Pap smear were identified and the outcomes of abnormal Pap smear were followed up. Results: A total of 670 participants were approached and 596 participants agreed to participate, giving a response rate of 89.0 %. Therefore, 587 participants were available for analysis. There were nine unsatisfactory smears (1.5 %). The prevalence of premalignant lesions reported on p % ap smear was 0.8 %. Three respondents had atypical squamous cells of undetermined significance (ASCUS) (0.5 %) and two respondents had low-grade squamous intraepithelial lesions (LSIL) (0.3 %). Almost one-third (30.3 %) of respondents had an infection and 24 (4.1 %) smears were reported as reactive changes associated with inflammation. Respondents between the age of 20-30 years old had a significant association with an abnormal pre-cancerous smear (p = 0.000) as well as nulliparity (p = 0.0.40). There was no significant association between height, weight, BMI, sexual partner, age of first intercourse, smoking habit, history of sexually transmitted disease and history of abnormal Pap smear. Conclusion: The prevalence of abnormal pre-cancerous smears during pregnancy is low. However, it is desirable to perform cervical screening as it provides an opportunity to no screening at all.

Evaluation of Plasma Calcitonin Gene-Related Peptide as a Biomarker for Painful Temporomandibular Disorder and Migraine.

Objective: To assess associations of plasma calcitonin gene-related peptide (CGRP) with chronic temporomandibular disorder (TMD) myalgia/arthralgia or frequent/chronic migraine, alone and in combination, and to evaluate relations between the CGRP concentration and clinical, psychological, and somatosensory characteristics of participants. Methods: The cross-sectional study selected four groups of adult volunteers: healthy controls (HCs), TMD without migraine, migraine without TMD, and TMD with migraine. Each group comprised 20 participants, providing 94% power to detect statistically significant associations with CGRP concentration for either TMD or migraine. TMD and headache were classified according to the Diagnostic Criteria for TMD and the International Classification for Headache Disorders, 3rd edition, respectively. Plasma CGRP was quantified with a validated high-sensitivity electrochemiluminescent Meso Scale Discovery assay. Questionnaires and clinical examinations were used to evaluate characteristics of TMD, headache, psychological distress, and pressure pain sensitivity. Univariate regression models quantified associations of the CGRP concentration with TMD, migraine, and their interaction. Univariate associations of the CGRP concentration with clinical, psychological, and pressure pain characteristics were also assessed. Results: Among 80 participants enrolled, neither TMD nor migraine was associated with plasma CGRP concentration (P = 0.761 and P = 0.972, respectively). The CGRP concentration (mean ± SD) was similar in all 4 groups: HCs 2.0 ± 0.7 pg/mL, TMD 2.1 ± 0.8 pg/mL, migraine 2.1 ± 0.9 pg/mL, and TMD with migraine 2.2 ± 0.7 pg/mL. CGRP concentration was positively associated with age (P = 0.034) and marginally with body mass index (P = 0.080) but was unrelated to other participant characteristics. Conclusion: In this well-powered study, interictal plasma concentration of CGRP was a poor biomarker for TMD and migraine.

Perturbations in fatty acid metabolism and collagen production infer pathogenicity of a novel MBTPS2 variant in Osteogenesis imperfecta.

Osteogenesis imperfecta (OI) is a heritable and chronically debilitating skeletal dysplasia. Patients with OI typically present with reduced bone mass, tendency for recurrent fractures, short stature and bowing deformities of the long bones. Mutations causative of OI have been identified in over 20 genes involved in collagen folding, posttranslational modification and processing, and in bone mineralization and osteoblast development. In 2016, we described the first X-linked recessive form of OI caused by MBTPS2 missense variants in patients with moderate to severe phenotypes. MBTPS2 encodes site-2 protease, a Golgi transmembrane protein that activates membrane-tethered transcription factors. These transcription factors regulate genes involved in lipid metabolism, bone and cartilage development, and ER stress response. The interpretation of genetic variants in MBTPS2 is complicated by the gene's pleiotropic properties; MBTPS2 variants can also cause the dermatological conditions Ichthyosis Follicularis, Atrichia and Photophobia (IFAP), Keratosis Follicularis Spinulosa Decalvans (KFSD) and Olmsted syndrome (OS) without skeletal abnormalities typical of OI. Using control and patient-derived fibroblasts, we previously identified gene expression signatures that distinguish MBTPS2-OI from MBTPS2-IFAP/KFSD and observed stronger suppression of genes involved in fatty acid metabolism in MBTPS2-OI than in MBTPS2-IFAP/KFSD; this was coupled with alterations in the relative abundance of fatty acids in MBTPS2-OI. Furthermore, we observed a reduction in collagen deposition in the extracellular matrix by MBTPS2-OI fibroblasts. Here, we extrapolate our observations in the molecular signature unique to MBTPS2-OI to infer the pathogenicity of a novel MBTPS2 c.516A>C (p.Glu172Asp) variant of unknown significance in a male proband. The pregnancy was terminated at gestational week 21 after ultrasound scans showed bowing of femurs and tibiae and shortening of long bones particularly of the lower extremity; these were further confirmed by autopsy. By performing transcriptional analyses, gas chromatography-tandem mass spectrometry-based quantification of fatty acids and immunocytochemistry on fibroblasts derived from the umbilical cord of the proband, we observed perturbations in fatty acid metabolism and collagen production similar to what we previously described in MBTPS2-OI. These findings support pathogenicity of the MBTPS2 variant p.Glu172Asp as OI-causative and highlights the value of extrapolating molecular signatures identified in multiomics studies to characterize novel genetic variants.

A nonstructural protein 1 capture enzyme-linked immunosorbent assay specific for dengue viruses.

Dengue non-structural protein (NS1) is an important diagnostic marker during the acute phase of infection. Because NS1 is partially conserved across the flaviviruses, a highly specific DENV NS-1 diagnostic test is needed to differentiate dengue infection from Zika virus (ZIKV) infection. In this study, we characterized three newly isolated antibodies against NS1 (A2, D6 and D8) from a dengue-infected patient and a previously published human anti-NS1 antibody (Den3). All four antibodies recognized multimeric forms of NS1 from different serotypes. A2 bound to NS1 from DENV-1, -2, and -3, D6 bound to NS1 from DENV-1, -2, and -4, and D8 and Den3 interacted with NS1 from all four dengue serotypes. Using a competition ELISA, we found that A2 and D6 bound to overlapping epitopes on NS1 whereas D8 recognized an epitope distinct from A2 and D6. In addition, we developed a capture ELISA that specifically detected NS1 from dengue viruses, but not ZIKV, using Den3 as the capture antibody and D8 as the detecting antibody. This assay detected NS1 from all the tested dengue virus strains and dengue-infected patients. In conclusion, we established a dengue-specific capture ELISA using human antibodies against NS1. This assay has the potential to be developed as a point-of-care diagnostic tool.

BRCA2 promotes genomic integrity and therapy resistance primarily through its role in homology-directed repair.

Highlights: Gap suppression requires BRCA2 C-terminal RAD51 binding in mouse and human cells Brca2 heterozygosity in mice results in fork protection and gap suppression defects Gap suppression mitigates sensitivity to hmdU, but only when HDR is unperturbedHDR deficiency is the primary driver of chemotherapeutic sensitivity. eTOC blurb: Lim et al . report that gap suppression as well as fork protection require BRCA2 stabilization of RAD51 filaments in human and mouse cells but have minimal impact on genome integrity, oncogenesis, and drug resistance. BRCA2 suppression of PRIMPOL-mediated replication gaps confers resistance to the nucleotide hmdU, incorporation of which leads to cytotoxic abasic sites.This effect is diminished when HDR is abrogated. Summary: Tumor suppressor BRCA2 functions in homology-directed repair (HDR), protection of stalled replication forks, and suppression of replicative gaps. The relative contributions of these pathways to genome integrity and chemotherapy response are under scrutiny. Here, we report that mouse and human cells require a RAD51 filament stabilization motif in BRCA2 for both fork protection and gap suppression, but not HDR. Loss of fork protection and gap suppression do not compromise genome instability or shorten tumor latency in mice or cause replication stress in human mammary cells. By contrast, HDR deficiency increases spontaneous and replication stress-induced chromosome aberrations and tumor predisposition. Unlike with HDR, fork protection and gap suppression defects are also observed in Brca2 heterozygous mouse cells, likely due to reduced RAD51 stabilization at stalled forks and gaps. Gaps arise from PRIMPOL activity, which is associated with sensitivity to 5-hydroxymethyl-2’-deoxyuridine due to the formation of abasic sites by SMUG1 glycosylase and is exacerbated by poly(ADP-ribose) polymerase inhibition. However, HDR deficiency ultimately modulates sensitivity to chemotherapeutics, including PARP inhibitors.

Image guidance and interfractional anatomical variation in paediatric abdominal radiotherapy.

OBJECTIVES: To identify variables predicting interfractional anatomical variations measured with cone-beam CT (CBCT) throughout abdominal paediatric radiotherapy, and to assess the potential of surface-guided radiotherapy (SGRT) to monitor these changes. METHODS: Metrics of variation in gastrointestinal (GI) gas volume and separation of the body contour and abdominal wall were calculated from 21 planning CTs and 77 weekly CBCTs for 21 abdominal neuroblastoma patients (median 4 years, range: 2 - 19 years). Age, sex, feeding tubes, and general anaesthesia (GA) were explored as predictive variables for anatomical variation. Furthermore, GI gas variation was correlated with changes in body and abdominal wall separation, as well as simulated SGRT metrics of translational and rotational corrections between CT/CBCT. RESULTS: GI gas volumes varied 74 ± 54 ml across all scans, while body and abdominal wall separation varied 2.0 ± 0.7 mm and 4.1 ± 1.5 mm from planning, respectively. Patients < 3.5 years (p = 0.04) and treated under GA (p < 0.01) experienced greater GI gas variation; GA was the strongest predictor in multivariate analysis (p < 0.01). Absence of feeding tubes was linked to greater body contour variation (p = 0.03). GI gas variation correlated with body (R = 0.53) and abdominal wall (R = 0.63) changes. The strongest correlations with SGRT metrics were found for anterior-posterior translation (R = 0.65) and rotation of the left-right axis (R = -0.36). CONCLUSIONS: Young age, GA, and absence of feeding tubes were linked to stronger interfractional anatomical variation and are likely indicative of patients benefiting from adaptive/robust planning pathways. Our data suggest a role for SGRT to inform the need for CBCT at each treatment fraction in this patient group. ADVANCES IN KNOWLEDGE: This is the first study to suggest the potential role of SGRT for the management of internal interfractional anatomical variation in paediatric abdominal radiotherapy.

Deep learning based synthetic CT from cone beam CT generation for abdominal paediatric radiotherapy.

Objective. Adaptive radiotherapy workflows require images with the quality of computed tomography (CT) for re-calculation and re-optimisation of radiation doses. In this work we aim to improve the quality of on-board cone beam CT (CBCT) images for dose calculation using deep learning.Approach. We propose a novel framework for CBCT-to-CT synthesis using cycle-consistent Generative Adversarial Networks (cycleGANs). The framework was tailored for paediatric abdominal patients, a challenging application due to the inter-fractional variability in bowel filling and small patient numbers. We introduced to the networks the concept of global residuals only learning and modified the cycleGAN loss function to explicitly promote structural consistency between source and synthetic images. Finally, to compensate for the anatomical variability and address the difficulties in collecting large datasets in the paediatric population, we applied a smart 2D slice selection based on the common field-of-view (abdomen) to our imaging dataset. This acted as a weakly paired data approach that allowed us to take advantage of scans from patients treated for a variety of malignancies (thoracic-abdominal-pelvic) for training purposes. We first optimised the proposed framework and benchmarked its performance on a development dataset. Later, a comprehensive quantitative evaluation was performed on an unseen dataset, which included calculating global image similarity metrics, segmentation-based measures and proton therapy-specific metrics.Main results. We found improved performance for our proposed method, compared to a baseline cycleGAN implementation, on image-similarity metrics such as Mean Absolute Error calculated for a matched virtual CT (55.0 ± 16.6 HU proposed versus 58.9 ± 16.8 HU baseline). There was also a higher level of structural agreement for gastrointestinal gas between source and synthetic images measured using the dice similarity coefficient (0.872 ± 0.053 proposed versus 0.846 ± 0.052 baseline). Differences found in water-equivalent thickness metrics were also smaller for our method (3.3 ± 2.4% proposed versus 3.7 ± 2.8% baseline).Significance. Our findings indicate that our innovations to the cycleGAN framework improved the quality and structure consistency of the synthetic CTs generated.

Predictive liver lipid biomarker signature of Acetyl-coenzyme A carboxylase inhibitor related developmental toxicity in non-pregnant female Han Wistar rats - Lipidomics biomarker discovery and validation.

INTRODUCTION: Acetyl-coenzyme A carboxylase (ACCase) inhibition is an attractive herbicide target. However, issues with fetal developmental toxicity identified at the late stages of the development process can halt progression of previously promising candidates. OBJECTIVES: To select and verify predictive lipid biomarkers of ACCase inhibition activity in vivo using liver samples obtained from early stage 7 day repeat dose studies in non-pregnant female Han Wistar rats that could be translated to developmental toxicity endpoints discovered during late-stage studies to provide an early screening tool. METHODS: Liver samples from eight rat repeat dose studies, exposed to six ACCase inhibitors from three different chemistries and one alternative mode of action (MoA) that also perturbs lipid biochemistry, were analysed using liquid chromatography - high resolution accurate mass - mass spectrometry. Multivariate and univariate data analysis methods were used for biomarker discovery and validation. RESULTS: A biomarker signature consisting of sixteen lipids biomarkers were selected. Verification of the signature as indicative of ACCase inhibition was established by demonstrating consistent perturbations in the biomarkers using two different ACCase inhibitor chemistries and the lack thereof with an alternate MoA. The fold change profile pattern was predictive of which test substance doses would or would not cause developmental toxicity. CONCLUSION: A strategy for selecting and verifying a robust signature of lipid biomarkers for predicting a toxicological end point has been described and demonstrated. Differences in lipidomic profiles correlated with developmental toxicity suggesting that indicators of a molecular initiation event resulting in pup developmental toxicity can be predicted from short term, toxicity studies conducted in non-pregnant adult female Han Wistar rats.

Maternal and fetal outcomes of pregnant women with bacterial vaginosis.

Background: Bacterial vaginosis (BV) is a common infection in women of reproductive age group because of vaginal dysbiosis. The impact of BV during pregnancy is still not well defined. The objective of this study is to assess the maternal-fetal outcome in women with BV. Materials and Methods: A prospective cohort study over one-year duration was conducted from December, 2014 until December, 2015, involving 237 women who presented with abnormal vaginal discharge, preterm labour or preterm prelabour rupture of membrane between 22- and 34-weeks period of gestation. Vaginal swabs were sent for culture and sensitivity, BV® Blue testing and PCR for Gardnerella vaginalis (GV). Results: BV was diagnosed in 24/237 (10.1%) cases. The median gestational age was 31.6 weeks. GV was isolated from 16 out of 24 (66.7%) in the BV positive group. There was a significantly higher preterm birth rate, below 34 weeks (22.7% vs. 6.2%, p = 0.019) in women with BV. There was no statistically significant difference in maternal outcome such as clinical chorioamnionitis or endometritis. However, placental pathology revealed more than half (55.6%) of women with BV had histologic chorioamnionitis. Neonatal morbidity was significantly higher with exposure to BV, with a lower median birth weight, higher rate of neonatal intensive care unit admission (41.7% vs. 19.0%, p = 0.010), increased intubation for respiratory support (29.2% vs. 7.6%, p = 0.004) and respiratory distress syndrome (33.3% vs. 9.0%, p = 0.002). Conclusion: More research is needed to formulate guidelines for prevention, early detection and treatment of BV during pregnancy to reduce intrauterine inflammation and the associated adverse fetal outcomes.