The relationship between nanoscale genome organization and gene expression in mouse embryonic stem cells during pluripotency transition

During early development, gene expression is tightly regulated. However, how genome organization controls gene expression during the transition from naïve embryonic stem cells to epiblast stem cells is still poorly understood. Using single-molecule microscopy approaches to reach nanoscale resolution, we show that genome remodeling affects gene transcription during pluripotency transition. Specifically, after exit from the naïve pluripotency state, chromatin becomes less compacted, and the OCT4 transcription factor has lower mobility and is more bound to its cognate sites. In epiblast cells, the active transcription hallmark, H3K9ac, decreases within the Oct4 locus, correlating with reduced accessibility of OCT4 and, in turn, with reduced expression of Oct4 nascent RNAs. Despite the high variability in the distances between active pluripotency genes, distances between Nodal and Oct4 decrease during epiblast specification. In particular, highly expressed Oct4 alleles are closer to nuclear speckles during all stages of the pluripotency transition, while only a distinct group of highly expressed Nodal alleles are in close proximity to Oct4 when associated with a nuclear speckle in epiblast cells. Overall, our results provide new insights into the role of the spatiotemporal genome remodeling during mouse pluripotency transition and its correlation with the expression of key pluripotency genes.

Prematurity and congenital malformations differ according to the type of pregestational diabetes

BACKGROUND

Diabetes mellitus (DM) is the most common metabolic disorder in pregnancy. Women with Type 2 DM seems to have no better perinatal outcomes than those with Type 1 DM.

METHODS

Single-center prospective cohort observational study. Pregnant women with diabetes (141 with Type 1 DM and 124 with Type 2 DM) that were followed in the university hospital between 2009 and 2021 were included in this study. Clinical data and obstetric and perinatal outcomes were collected.

RESULTS

As expected, women with Type 1 DM were younger and had a longer duration of diabetes than women with Type 2 DM. Obesity and chronic hypertension were higher in the group of women with Type 2 DM and their value of HbA1c in the second and third trimesters were lower than in Type 1 DM. No differences in prematurity were found, but more extreme prematurity was observed in Type 2 DM, as well as a higher rate of congenital malformations. The frequency of hypoglycemia and the weight of the newborn was higher in Type 1 DM. The maternal independent factors related to the weight of the newborn were: the glycemic control at the third trimester, the weight gain during pregnancy, and pregestational BMI.

CONCLUSIONS

Newborns born to mothers with Type 1 DM were larger and had a higher frequency of hypoglycemia, while congenital malformations and precocious preterm was more associated to Type 2 DM. Metabolic control, weight gain and pregestational weight were important determinants of both obstetric and neonatal complications.

[Arthritis and osteomyelitis in childhood and adolescence-Bacterial and nonbacterial]

Bacterial arthritis and osteomyelitis are usually acute diseases, which in this way differ from the often insidious course of nonbacterial osteomyelitis; however, there is often an overlap both in less acute courses of bacterial illnesses and also in nonbacterial osteitis. The overlapping clinical phenomena can be explained by similar pathophysiological processes. In bacteria-related illnesses the identification of the pathogen and empirical or targeted anti-infectious treatment are prioritized, whereas no triggering agent is known for nonbacterial diseases. The diagnostics are based on the exclusion of differential diagnoses, clinical scores and magnetic resonance imaging (MRI). An activity-adapted anti-inflammatory treatment is indicated.

Catastrophic Streptococcus pyogenes Disease: A Personalized Approach Based on Phenotypes and Treatable Traits

Streptococcal toxic shock syndrome (STTS) is a critical medical emergency marked by high morbidity and mortality, necessitating swift awareness, targeted treatment, and early source control due to its rapid symptom manifestation. This report focuses on a cohort of 13 patients admitted to Vall d'Hebron University Hospital Intensive Care Unit, Barcelona, from November 2022 to March 2023, exhibiting invasive Streptococcus pyogenes infections and meeting institutional sepsis code activation criteria. The primary infections were community-acquired pneumonia (61.5%) and skin/soft tissue infection (30.8%). All patients received prompt antibiotic treatment, with clinical source control through thoracic drainage (30.8%) or surgical means (23.1%). Organ support involved invasive mechanical ventilation, vasopressors, and continuous renal replacement therapy as per guidelines. Of note, 76.9% of patients experienced septic cardiomyopathy, and 53.8% required extracorporeal membrane oxygenation (ECMO). The study identified three distinct phenotypic profiles-hyperinflammatory, low perfusion, and hypogammaglobulinemic-which could guide personalized therapeutic approaches. STTS, with a mean SOFA score of 17 (5.7) and a 53.8% requiring ECMO, underscores the need for precision medicine-based rescue therapies and sepsis phenotype identification. Integrating these strategies with prompt antibiotics and efficient source control offers a potential avenue to mitigate organ failure, enhancing patient survival and recovery in the face of this severe clinical condition.

Error traps in the perioperative management of children with type 1 diabetes

Patients with type 1 diabetes mellitus (T1D) require insulin administration at all times to maintain euglycemia and metabolic stability. Insulin administration in the perioperative period is complicated by fasting requirements and perioperative stressors that can change the patient's insulin needs. In addition, many anesthesia providers are not familiar with insulin dosing strategies and technology, such as insulin pumps and continuous glucose monitors (CGMs), that are commonly used by patients with T1D. Errors in perioperative insulin administration can lead to hypoglycemia, hyperglycemia, and diabetic ketoacidosis. This article reviews common errors of associated with the perioperative management of patients with T1D, including failure to assess and coordinate patient care preoperatively; failure to understand diabetes management and technology; failure to monitor blood glucose and recognize dysglycemia; and failure to appropriately administer basal insulin.

Implementing systematic melanoma risk assessment and risk-tailored surveillance in a skin cancer focussed dermatology clinic: A qualitative study of feasibility and acceptability to patients and clinic staff

BACKGROUND

International bodies recommend that melanoma risk assessment should be integrated into skin cancer care provision, but evidence to support implementation is lacking.

AIM

To explore the acceptability and feasibility of implementing personalised melanoma risk assessment and tailored patient education and skin surveillance within routine clinical care.

METHODS

This prospective qualitative implementation study was informed by the Theoretical Framework of Acceptability (TFA). Personalised, systematic melanoma risk assessment was implemented in the dermatology clinic at the Melanoma Institute Australia, Sydney, Australia February-May 2021. Pre- and post-implementation observations and semi-structured interviews with patients and staff were conducted (September 2020-March 2021). Observational notes and interview transcript data were analysed thematically using the TFA as a classifying framework.

RESULTS

A total of 37 h of observations were made, and 29 patients and 12 clinic staff were interviewed. We found that the delivery of personalised melanoma risk estimates did not impact on patient flow through the clinic. Dermatologists reported that the personalised risk information enhanced their confidence in assessing patient risk and recommending tailored surveillance schedules. Most patients reported that the risk assessment and tailored information were a beneficial addition to their care. Among patients whose risk deviated from their expectations, some reported feeling worried, confused or mistrust in the risk information, including those at lower risk who were recommended to decrease surveillance frequency.

CONCLUSIONS

It is feasible and acceptable to patients and clinic staff to calculate and deliver personalised melanoma risk information and tailored surveillance as part of routine clinical care within dermatology clinics.

Vitamin C deficiency in critically ill COVID-19 patients admitted to intensive care unit

Objectives

To determine vitamin C plasma kinetics, through the measurement of vitamin C plasma concentrations, in critically ill Coronavirus infectious disease 2019 (COVID-19) patients, identifying eventually the onset of vitamin C deficiency.

Design

Prospective, observational, single-center study.

Setting

Intensive Care Unit (ICU), Vall d'Hebron University Hospital, Barcelona. Study period from November 12th, 2020, to February 24th, 2021.

Patients

Patients who had a severe hypoxemic acute respiratory failure due to COVID-19 were included.

Interventions

Plasma vitamin C concentrations were measured on days 1, 5, and 10 of ICU admission. There were no vitamin C enteral nor parenteral supplementation. The supportive treatment was performed following the standard of care or acute respiratory distress syndrome (ARDS) patients.

Measurement

Plasma vitamin C concentrations were analyzed using an ultra-performance liquid chromatography (UPLC) system with a photodiode array detector (wavelength set to 245 nm). We categorized plasmatic levels of vitamin C as follows: undetectable: < 1,5 mg/L, deficiency: <2 mg/L. Low plasma concentrations: 2-5 mg/L; (normal plasma concentration: > 5 mg/L).

Main results

Forty-three patients were included (65% men; mean age 62 ± 10 years). The median Sequential Organ Failure Assessment (SOFA) score was 3 (1-4), and the Acute Physiology and Chronic Health disease Classification System (APACHE II) score was 13 (10-22). Five patients had shock. Bacterial coinfection was documented in 7 patients (16%). Initially all patients required high-flow oxygen therapy, and 23 (53%) further needed invasive mechanical ventilation during 21 (± 10) days. The worst PaO2/FIO2 registered was 93 (± 29). ICU and hospital survival were 77 and 74%, respectively. Low or undetectable levels remained constant throughout the study period in the vast majority of patients.

Conclusion

This observational study showed vitamin C plasma levels were undetectable on ICU admission in 86% of patients with acute respiratory failure due to COVID-19 pneumonia requiring respiratory support. This finding remained consistent throughout the study period.

[Prospective controlled study evaluating teleconsultation and tele-semiology for the management of renal colic]

INTRODUCTION

Physical examination appears to be a limiting factor of teleconsultation (TC). We evaluated the feasibility of self-percussion of the lumbar fossae (sPLF) and TC for simple renal colic (SRC) in comparison with a face-to-face consultation (FC).

MATERIAL AND METHODS

We performed a comparative prospective study in two steps. First: evaluation of the quality of an sPLF on a standardized patient in TC, without and with tutorial. Secondarily: evaluation of a TC and a FC for a SRC with a standardized patient in real conditions. Evaluation using objective clinical scores and qualitative scales by an observer, the standardized patient and the practitioner himself.

RESULTS

Forty-two practitioners were included in the study. In the absence of a tutorial, the sPLF was most often "poorly done". The tutorial led to a significant improvement in the quality of sPLF. There was no difference in diagnostic and therapeutic performance among senior physicians between TC and FC. The therapeutic performances of the interns were significantly lower in TC without his being aware of it. The qualitative scores were significantly lower in TC vs FC according to the practitioners, the standardized patient and the observer.

CONCLUSION

An sPLF is feasible but its practice should be taught. Unlike interns, senior physicians were able to perform a TC comparable to FC for the management of SRC. TC and telesemiology therefore require dedicated training and an experienced practitioner.

LEVEL OF EVIDENCE: 2

A survey of patients with facial angiofibromas associated with tuberous sclerosis complex: Short-, medium- and long-term efficacy and safety of topical rapamycin

AIMS

Topical rapamycin is used to reduce facial angiofibromas in patients with tuberous sclerosis (TSC). In the absence of a commercially available preparation, numerous formulations have been tested clinically, although only in the short term.

METHODS

The pharmacy at Angers University Hospital (France) produced a cream formulation that was administered to people presenting this genetic disease. We conducted a questionnaire-based survey among 79 patients with TSC about their perceptions regarding the short-, medium- and long-term efficacy and safety of a topical rapamycin preparation in relation to facial angiofibromas.

RESULTS

This formulation was very well tolerated and its efficacy was sustained over the long term with a mean treatment duration of 33 months (extremes 1-60). Efficacy was rated ≥ 8/10 by 67.1% of patients while safety was rated ≥ 8/10 by 84.8% of patients.

CONCLUSION

This survey supports the safety and efficacy of topical rapamycin in the short-, medium- and long-term in the treatment of facial angiofibromas in a cohort of 79 patients with TSC.

Factors associated with diagnostic ultrasound for midgut volvulus and relevance of the non-diagnostic examination

BACKGROUND

Few reports explore the frequency and factors associated with diagnostic ultrasound (US) for midgut volvulus.

OBJECTIVE

To evaluate predictive factors for diagnostic US for midgut volvulus and clinical outcomes of patients with non-diagnostic US.

MATERIALS AND METHODS

This retrospective study included infants imaged for midgut volvulus with US. Exams were rated as diagnostic (midgut volvulus present or absent) or non-diagnostic by a pediatric radiologist, and in cases of disagreement with the original report, an additional pediatric radiologist was the tie-breaker. For each exam, the following were recorded: age, weight, respiratory support, exam indication, sonographer experience, and gaseous dilated bowel loops on radiography. Logistic regression models with "stepwise" variable selection were used to investigate the association of diagnostic US for midgut volvulus with each of the independent variables.

RESULTS

One hundred nineteen patients were imaged. US was diagnostic in 74% (88/119) of patients. In subsets of patients presenting with bilious emesis or age <28 days, US was diagnostic in 92% (22/24) and 90% (53/59), respectively. Logistic regression suggested that symptom type (bilious vs other) was the best predictor of diagnostic US (type 3 P=0.02). Out of 26 patients with available radiographs, US was diagnostic in 92% (12/13) of patients without bowel dilation on radiographs compared to 62% (8/13) of patients with bowel dilation (P=0.16). Weight, respiratory support, and sonographer experience did not differ between groups. Two sick neonates, ages 2 days and 30 days, in whom the primary clinical concern was dropping hematocrit and sepsis, respectively, had non-diagnostic ultrasounds in the setting of bowel dilation on radiography. Both were found to have midgut volvulus at surgery and both expired.

CONCLUSION

US was most frequently diagnostic in patients with bilious emesis or age less than 28 days. Non-diagnostic US for midgut volvulus must prompt a predetermined follow-up strategy, such as an additional imaging study (e.g., upper GI series), particularly in a sick child, as non-diagnostic US may miss midgut volvulus.

Observation of the effect of gravity on the motion of antimatter

Einstein's general theory of relativity from 19151 remains the most successful description of gravitation. From the 1919 solar eclipse2 to the observation of gravitational waves3, the theory has passed many crucial experimental tests. However, the evolving concepts of dark matter and dark energy illustrate that there is much to be learned about the gravitating content of the universe. Singularities in the general theory of relativity and the lack of a quantum theory of gravity suggest that our picture is incomplete. It is thus prudent to explore gravity in exotic physical systems. Antimatter was unknown to Einstein in 1915. Dirac's theory4 appeared in 1928; the positron was observed5 in 1932. There has since been much speculation about gravity and antimatter. The theoretical consensus is that any laboratory mass must be attracted6 by the Earth, although some authors have considered the cosmological consequences if antimatter should be repelled by matter7-10. In the general theory of relativity, the weak equivalence principle (WEP) requires that all masses react identically to gravity, independent of their internal structure. Here we show that antihydrogen atoms, released from magnetic confinement in the ALPHA-g apparatus, behave in a way consistent with gravitational attraction to the Earth. Repulsive 'antigravity' is ruled out in this case. This experiment paves the way for precision studies of the magnitude of the gravitational acceleration between anti-atoms and the Earth to test the WEP.

Frontal Alpha Asymmetry in Posttraumatic Stress Disorder: Group Differences Among Individuals With and Without PTSD During an Inhibitory Control Task

The current study examined frontal alpha asymmetry (FAA) as a marker of approach- and avoidance-related prefrontal activity in participants with and without trauma exposure and posttraumatic stress disorder (PTSD). We investigated FAA in an inhibitory control paradigm (threatening vs nonthreatening cues) under 2 levels of cognitive demand (baseline: images constant within a block of trials; vs filtering: images varied randomly within a block) in 3 groups of participants: individuals with PTSD (n = 16), exposed to trauma but without PTSD (n = 14), and a control group without PTSD or trauma exposure (n = 15). Under low demand (baseline), both PTSD and trauma-exposed participants exhibited significantly greater relative left than right frontal brain activity (approach) to threatening than to nonthreatening images. Under high demand (filtering), no FAA differences were found between threatening and nonthreatening images, but PTSD participants revealed more relative left than right FAA, whereas trauma-exposed participants showed reduced left relative right FAA. In all conditions, healthy controls exhibited reduced left relative to right FAA and no differences between threatening and nonthreatening images. Study findings suggest dysfunctional prefrontal mechanisms of emotion regulation in PTSD, but adaptive prefrontal regulation in trauma-exposed individuals without PTSD.

Factors associated with early relapse of infantile haemangioma in children treated for at least six months with oral propranolol: A case-control study using the 2014-2021 French Ouest DataHub

BACKGROUND

The factors associated with early relapse of infantile haemangioma (IH) after a first course of treatment with oral propranolol for at least six months (initiated after the marketing authorization had been granted) have not previously been investigated.

OBJECTIVES

To identify factors associated with the risk of early relapse in children with IH treated with oral propranolol according to the current prescribing guidelines.

METHODS

We performed a multicentre, retrospective, case-control study, using the Ouest Data Hub database. All children treated for at least 6 months with oral propranolol for IH between 31 June 2014 and 31 December 2021, and with a follow-up visit at least three months after treatment discontinuation were included. A case was defined as relapse of IH within three months of treatment discontinuation; each case was matched for age at treatment initiation and for centre, with four (relapse-free) controls. The association between relapse and treatment or IH characteristics was expressed as an odds ratio (OR) from univariate and multivariate conditional logistic regressions.

RESULTS

A total of 225 children were included. Of these, 36 (16%) relapsed early. In a multivariate analysis, a deep IH component was a risk factor for early relapse [OR = 8.93; 95%CI: 1.0-78.9, p = 0.05]. A propranolol dosage level of less than 3 mg/kg/day protected against early relapse [OR = 0.11; 95%CI: 0.02-0.7, p = 0.02]. Tapering before propranolol discontinuation was not associated with a lower risk of early relapse.

CONCLUSION

The risk factors for late and early relapse are probably different. Investigation of the risk factors for early vs. late IH relapse is now warranted.

Skin lesions by Scedosporium apiospermum and Nocardia pulmonary infection in an oncologic patient: a case report

BACKGROUND

Fungal infections, other than candidiasis and aspergillosis, are an uncommon entity. Despite this, emerging pathogens are a growing threat. In the following case report, we present the case of an immunocompromised patient suffering from two serious opportunistic infections in the same episode: the first of these, Nocardia multilobar pneumonia; and the second, skin infection by Scedosporium apiospermum. These required prolonged antibacterial and antifungal treatment.

CASE PRESENTATION

This case is a 71-year-old oncological patient admitted for recurrent pneumonias that was diagnosed for Nocardia pulmonary infection. Nervous system involvement was discarded and cotrimoxazole was started. Haemorrhagic skin ulcers in the lower limbs appeared after two weeks of hospital admission. We collected samples which were positive for Scedosporium apiospermum and we added voriconazole to the treatment. As a local complication, the patient presented a deep bruise that needed debridement. We completed 4 weeks of intravenous treatment with slow improvement and continued with oral treatment until the disappearance of the lesions occurs.

CONCLUSIONS

Opportunistic infections are a rising entity as the number of immunocompromised patients is growing due to more use of immunosuppressive therapies and transplants. Clinicians must have a high suspicion to diagnose and treat them. A fluid collaboration with Microbiology is necessary as antimicrobial resistance is frequent.

Dexamethasone administration to improve patient recovery in ambulatory vaginal reconstructive surgery: a randomized prospective trial

INTRODUCTION AND HYPOTHESIS

Dexamethasone is a potent glucocorticoid that may improve quality of recovery (QoR). We hypothesized that standard administration of dexamethasone at induction may improve QoR compared to placebo in subjects undergoing ambulatory vaginal reconstructive surgeries.

METHODS

This was a randomized prospective clinical trial on subjects scheduled for ambulatory vaginal reconstructive surgery for prolapse and/or urinary incontinence. Intervention arm subjects were administered dexamethasone and the control group, a placebo (normal saline). Timing of administration, anesthesia medications, postoperative pain medications, and antiemetics were standardized. Primary outcome was difference in QoR (QoR-40) scores 24-48 h after surgery. Power analysis estimated that 27 subjects were required in each group to detect a difference in QoR-40 scores with 80% power and an alpha of 0.05.

RESULTS

Fifty-one subjects were enrolled and randomized. 4 withdrew, 1 was excluded, and 46 were analyzed. For the primary outcome, there was no difference in the QoR-40 between the dexamethasone and placebo group (--13.5 vs -19.6, p=0.24). Postoperative nausea vomiting intensity scores were not different (8.33 vs 9.09, p=1). Pain scores were similar in the two groups (6.0 vs 4.7, p=0.12). Although not statistically significant, surgical satisfaction at 6 weeks was better with dexamethasone (23.5 vs 26.9, p=0.09).

CONCLUSION

Based on this study, a single dose of dexamethasone at the time of induction prior to ambulatory vaginal reconstructive surgery was not associated with improved QoR. Standardized anesthesia protocols may play a role in postoperative nausea, pain control, and thereby QoR in patients undergoing ambulatory vaginal reconstructive surgeries.

Clinical Performance of Lateral Flow Assay for Cryptosporidium spp. Diagnosis

Cryptosporidium spp. is an apicomplexan protozoan parasite associated with gastroenteritis in humans. In 2018, Spain showed 1511 confirmed cases, with a growing trend since 2014. Despite this fact, Cryptosporidium spp. is not usually routinely examined when a parasitological study is ordered, although accurate diagnosis is fundamental to prevent the spread of the illness. The main objectives of the present work is to demonstrate the circulation and to study the epidemiology of cryptosporidiosis in patients who were being tested for the presence of Cryptosporidium spp. parasites in the faeces in the Metropolitan North Area of Barcelona, Maresme, and Vallés Occidental using a two-step algorithm. The stool samples were analysed using the Cryptosporidium/Giardia spp. immunochromatographic test; the positive samples were visualised under a microscope using auramine staining. The proportion of Cryptosporidium spp. cases was around 2% in the studied patients, with a pronounced seasonal incidence peak in late summer-early autumn. In our cohort, weight loss was the main symptom related to confirmed cases. The mean age of confirmed patients was 19 years old, and they were younger than the unconfirmed group. Cryptosporidium spp. is one of the parasites that currently circulate in many areas in Europe. Prevalence must be taken into account for active searching.

The relationship between cognitive reserve and outcome after controlling for psychological status and sex following mild traumatic brain injury

OBJECTIVE

Cognitive reserve is the brain's ability to optimize performance by differentially recruiting brain networks. It is easily measured and is reportedly associated with post-concussion symptom (PCS) reporting in the post-acute period after mild traumatic brain injury (mTBI). Past studies have not examined whether this relationship exists when the influence of psychological status is removed, despite this factor being strongly associated with symptom reporting. This study investigated whether cognitive reserve predicts PCS reporting or cognitive complaint in the post-acute period after mTBI, independently from psychological status and sex.

METHOD

Ninety-four pre-morbidly healthy adults were assessed on three measures of cognitive reserve, as well as measures of post-concussion symptoms, cognitive complaint, and psychological status.

RESULTS

Bivariate analyses revealed significant relationships between measures of cognitive reserve and both PCS reporting (p < 0.01) and cognitive complaint (<.05). After removing the influence of psychological distress and sex, however, no measure of cognitive reserve significantly predicted any type of symptom reporting.

CONCLUSION

These findings indicate that cognitive reserve does not independently predict symptom reporting 9 weeks after mTBI, and clinicians should not incorporate this factor into their decision-making regarding likelihood of ongoing symptom reporting and the consequent need for intervention in the post-acute period after mTBI.

Hippocampal blood flow rapidly and preferentially increases after a bout of moderate-intensity exercise in older adults with poor cerebrovascular health

Over the course of aging, there is an early degradation of cerebrovascular health, which may be attenuated with aerobic exercise training. Yet, the acute cerebrovascular response to a single bout of exercise remains elusive, particularly within key brain regions most affected by age-related disease processes. We investigated the acute global and region-specific cerebral blood flow (CBF) response to 15 minutes of moderate-intensity aerobic exercise in older adults (≥65 years; n = 60) using arterial spin labeling magnetic resonance imaging. Within 0-6 min post-exercise, CBF decreased across all regions, an effect that was attenuated in the hippocampus. The exercise-induced CBF drop was followed by a rebound effect over the 24-minute postexercise assessment period, an effect that was most robust in the hippocampus. Individuals with low baseline perfusion demonstrated the greatest hippocampal-specific CBF effect post-exercise, showing no immediate drop and a rapid increase in CBF that exceeded baseline levels within 6-12 minutes postexercise. Gains in domain-specific cognitive performance postexercise were not associated with changes in regional CBF, suggesting dissociable effects of exercise on acute neural and vascular plasticity. Together, the present findings support a precision-medicine framework for the use of exercise to target brain health that carefully considers age-related changes in the cerebrovascular system.

Abstract 6186: Patient-derived tumor organoids with p53 mutations, and not wild-type p53, demonstrate synergistic sensitivity to treatment with temozolomide in combination with talazoparib PARP inhibitor

Mutations in the TP53 gene can be found in more than 50% of tumors. We recently showed in 2D breast cancer cell lines that mutant p53 (mtp53) proteins tightly associate with replicating DNA, chromatin and Poly (ADP-ribose) polymerase (PARP) protein. In addition, missense mtp53 R273H causes an increase in the chromatin association of replication proteins including PARP, and mini-chromosome maintenance complex 2-7 (MCM2-7). The expression of mtp53 R273H enhances overall MCM2 levels, promotes cell proliferation, and improves the synergistic cytotoxicity of treatment with the alkylating agent temozolomide in combination with the PARP inhibitor (PARPi) talazoparib. Currently, PARPis are indicated for patients that present BRCA1/2 mutations, but there might be patients with other alterations associated with DNA damage repair that could benefit from PARPi treatment; this includes expression of mtp53. Patient-derived Tumor Organoids (PDTO) are 3D culture models that retain cell-cell and cell-matrix interactions and are shown to reproduce drug responses observed in patients. Here, we evaluated the sensitivity of wild-type BRCA1/2 breast and lung PDTO with either mtp53 or wild-type p53 (wtp53) to the combination of DNA damaging agent temozolomide plus the PARPi talazoparib. First, we tested the sensitivity of the organoids to talazoparib and temozolomide individually. To determine if there was synergy between the two treatments, the organoids were treated with an inhibitor matrix to evaluate multiple combinatorial concentrations. Three breast cancer and two lung cancer PDTO with mtp53 presented synergistic cytotoxicity of the combination treatment. Two breast organoid lines with wtp53 showed no synergistic interaction between the two drugs, and the same was observed in a wtp53 lung organoid line. We analyzed wtp53 and mtp53 PDTO cell extracts by western blot to assess the activation of downstream p53 effectors and DNA damage markers after treatment with temozolomide and/or talazoparib. Combination of talazoparib and temozolomide induced higher DNA double-strand breaks in mtp53 organoids as shown by increased gamma-H2AX expression. The results obtained demonstrated that in mtp53 PDTO synergism is achieved with combined talazoparib-temozolomide treatment supporting the idea that tumors expressing mtp53 may be potential candidates for this combination PARPi treatment.

Citation Format: Florencia P. Madorsky Rowdo, Gu Xiao, Melissa B. Davis, Laura Martin, Olivier Elemento, Jill Bargonetti. Patient-derived tumor organoids with p53 mutations, and not wild-type p53, demonstrate synergistic sensitivity to treatment with temozolomide in combination with talazoparib PARP inhibitor. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6186.