Routine Venous Thromboembolism Prophylaxis May Be Inadequate in the Hypercoagulable State of Severe Coronavirus Disease 2019.

OBJECTIVES: The aim of this study was to determine the frequency of venous thromboembolism in critically ill coronavirus disease 2019 patients and associate a degree of inflammatory marker elevation to venous thromboembolism development. DESIGN: An observational study that identified patients with severe coronavirus disease 2019 between March 12, 2020, and March 31, 2020. Data reported are those available through May 6, 2020. SETTING: A multicenter study including three Indianapolis area academic hospitals. PATIENTS: Two-hundred forty consecutive patients with confirmed severe acute respiratory syndrome coronavirus 2 infection were admitted to one of three hospitals. One-hundred nine critically ill coronavirus disease 2019 patients admitted to the ICU were included in the analysis. INTERVENTIONS: All patients received routine subcutaneous chemical venous thromboembolism prophylaxis. MEASUREMENTS AND MAIN RESULTS: The primary outcome of this study was to determine the frequency of venous thromboembolism and the degree of inflammatory and coagulation marker elevation associated with venous thromboembolism development. Descriptive statistics outlined the frequency of venous thromboembolism at any time during severe coronavirus disease 2019. Clinical course and laboratory metrics were compared between patients that developed venous thromboembolism and patients that did not develop venous thromboembolism. Hypercoagulable thromboelastography was defined as two or more hypercoagulable parameters. MAIN RESULTS: One-hundred nine patients developed severe coronavirus disease 2019 requiring ICU care. The mean (± SD) age was 61 ± 16 years and 57% were male. Seventy-five patients (69%) were discharged home, 7 patients (6%) remain in the hospital, and 27 patients (25%) died. Venous thromboembolism was diagnosed in 31 patients (28%) 8 ± 7 days after hospital admission, including two patients diagnosed with venous thromboembolism at presentation to the hospital. Elevated admission D-dimer and peak D-dimer were associated with venous thromboembolism development (p < 0.05). D-dimer greater than 2,600 ng/mL predicted venous thromboembolism with an area under the receiver operating characteristic curve of 0.760 (95% CI, 0.661-0.858; p < 0.0001), sensitivity of 89.7%, and specificity of 59.5%. Twelve patients (11%) had thromboelastography performed and 58% of these patients had a hypercoagulable study. The calculated coagulation index was hypercoagulable in 50% of patients with thromboelastography. CONCLUSIONS: These data show that coronavirus disease 2019 results in a hypercoagulable state. Routine chemical venous thromboembolism prophylaxis may be inadequate in preventing venous thromboembolism in severe coronavirus disease 2019.

Deep Learning Localizes and Identifies Polyps in Real Time With 96% Accuracy in Screening Colonoscopy.

BACKGROUND & AIMS: The benefit of colonoscopy for colorectal cancer prevention depends on the adenoma detection rate (ADR). The ADR should reflect the adenoma prevalence rate, which is estimated to be higher than 50% in the screening-age population. However, the ADR by colonoscopists varies from 7% to 53%. It is estimated that every 1% increase in ADR lowers the risk of interval colorectal cancers by 3%-6%. New strategies are needed to increase the ADR during colonoscopy. We tested the ability of computer-assisted image analysis using convolutional neural networks (CNNs; a deep learning model for image analysis) to improve polyp detection, a surrogate of ADR. METHODS: We designed and trained deep CNNs to detect polyps using a diverse and representative set of 8,641 hand-labeled images from screening colonoscopies collected from more than 2000 patients. We tested the models on 20 colonoscopy videos with a total duration of 5 hours. Expert colonoscopists were asked to identify all polyps in 9 de-identified colonoscopy videos, which were selected from archived video studies, with or without benefit of the CNN overlay. Their findings were compared with those of the CNN using CNN-assisted expert review as the reference. RESULTS: When tested on manually labeled images, the CNN identified polyps with an area under the receiver operating characteristic curve of 0.991 and an accuracy of 96.4%. In the analysis of colonoscopy videos in which 28 polyps were removed, 4 expert reviewers identified 8 additional polyps without CNN assistance that had not been removed and identified an additional 17 polyps with CNN assistance (45 in total). All polyps removed and identified by expert review were detected by the CNN. The CNN had a false-positive rate of 7%. CONCLUSION: In a set of 8,641 colonoscopy images containing 4,088 unique polyps, the CNN identified polyps with a cross-validation accuracy of 96.4% and an area under the receiver operating characteristic curve of 0.991. The CNN system detected and localized polyps well within real-time constraints using an ordinary desktop machine with a contemporary graphics processing unit. This system could increase the ADR and decrease interval colorectal cancers but requires validation in large multicenter trials.

Early treatment with fluvoxamine, bromhexine, cyproheptadine, and niclosamide to prevent clinical deterioration in patients with symptomatic COVID-19: a randomized clinical trial.

Background: Repurposed drugs with host-directed antiviral and immunomodulatory properties have shown promise in the treatment of COVID-19, but few trials have studied combinations of these agents. The aim of this trial was to assess the effectiveness of affordable, widely available, repurposed drugs used in combination for treatment of COVID-19, which may be particularly relevant to low-resource countries. Methods: We conducted an open-label, randomized, outpatient, controlled trial in Thailand from October 1, 2021, to June 21, 2022, to assess whether early treatment within 48-h of symptoms onset with combinations of fluvoxamine, bromhexine, cyproheptadine, and niclosamide, given to adults with confirmed mild SARS-CoV-2 infection, can prevent 28-day clinical deterioration compared to standard care. Participants were randomly assigned to receive treatment with fluvoxamine alone, fluvoxamine + bromhexine, fluvoxamine + cyproheptadine, niclosamide + bromhexine, or standard care. The primary outcome measured was clinical deterioration within 9, 14, or 28 days using a 6-point ordinal scale. This trial is registered with ClinicalTrials.gov (NCT05087381). Findings: Among 1900 recruited, a total of 995 participants completed the trial. No participants had clinical deterioration by day 9, 14, or 28 days among those treated with fluvoxamine plus bromhexine (0%), fluvoxamine plus cyproheptadine (0%), or niclosamide plus bromhexine (0%). Nine participants (5.6%) in the fluvoxamine arm had clinical deterioration by day 28, requiring low-flow oxygen. In contrast, most standard care arm participants had clinical deterioration by 9, 14, and 28 days. By day 9, 32.7% (110) of patients in the standard care arm had been hospitalized without requiring supplemental oxygen but needing ongoing medical care. By day 28, this percentage increased to 37.5% (21). Additionally, 20.8% (70) of patients in the standard care arm required low-flow oxygen by day 9, and 12.5% (16) needed non-invasive or mechanical ventilation by day 28. All treated groups significantly differed from the standard care group by days 9, 14, and 28 (p < 0.0001). Also, by day 28, the three 2-drug treatments were significantly better than the fluvoxamine arm (p < 0.0001). No deaths occurred in any study group. Compared to standard care, participants treated with the combination agents had significantly decreased viral loads as early as day 3 of treatment (p < 0.0001), decreased levels of serum cytokines interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and interleukin-1 beta (IL-1ß) as early as day 5 of treatment, and interleukin-8 (IL-8) by day 7 of treatment (p < 0.0001) and lower incidence of post-acute sequelae of COVID-19 (PASC) symptoms (p < 0.0001). 23 serious adverse events occurred in the standard care arm, while only 1 serious adverse event was reported in the fluvoxamine arm, and zero serious adverse events occurred in the other arms. Interpretation: Early treatment with these combinations among outpatients diagnosed with COVID-19 was associated with lower likelihood of clinical deterioration, and with significant and rapid reduction in the viral load and serum cytokines, and with lower burden of PASC symptoms. When started very soon after symptom onset, these repurposed drugs have high potential to prevent clinical deterioration and death in vaccinated and unvaccinated COVID-19 patients. Funding: Ped Thai Su Phai (Thai Ducks Fighting Danger) social giver group.

Association between antidepressant use and ED or hospital visits in outpatients with SARS-CoV-2.

Antidepressants have previously been associated with better outcomes in patients hospitalized with COVID-19, but their effect on clinical deterioration among ambulatory patients has not been fully explored. The objective of this study was to assess whether antidepressant exposure was associated with reduced emergency department (ED) or hospital visits among ambulatory patients with SARS-CoV-2 infection. This retrospective cohort study included adult patients (N = 25 034) with a positive SARS-CoV-2 test performed in a non-hospital setting. Logistic regression analyses tested associations between home use of antidepressant medications and a composite outcome of ED visitation or hospital admission within 30 days. Secondary exposures included individual antidepressants and antidepressants with functional inhibition of acid sphingomyelinase (FIASMA) activity. Patients with antidepressant exposure were less likely to experience the primary composite outcome compared to patients without antidepressant exposure (adjusted odds ratio [aOR] 0.89, 95% CI 0.79-0.99, p = 0.04). This association was only observed with daily doses of at least 20 mg fluoxetine-equivalent (aOR 0.87, 95% CI 0.77-0.99, p = 0.04), but not with daily doses lower than 20 mg fluoxetine-equivalent (aOR 0.94, 95% CI 0.80-1.11, p = 0.48). In exploratory secondary analyses, the outcome incidence was also reduced with exposure to selective serotonin reuptake inhibitors (aOR 0.87, 95% CI 0.75-0.99, p = 0.04), bupropion (aOR 0.70, 95% CI 0.55-0.90, p = 0.005), and FIASMA antidepressant drugs (aOR 0.87, 95% CI 0.77-0.99, p = 0.03). Antidepressant exposure was associated with a reduced incidence of emergency department visitation or hospital admission among SARS-CoV-2 positive patients, in a dose-dependent manner. These data support the FIASMA model of antidepressants' effects against COVID-19.

Antidepressant Use and Its Association with 28-Day Mortality in Inpatients with SARS-CoV-2: Support for the FIASMA Model against COVID-19.

To reduce Coronavirus Disease 2019 (COVID-19)-related mortality and morbidity, widely available oral COVID-19 treatments are urgently needed. Certain antidepressants, such as fluvoxamine or fluoxetine, may be beneficial against COVID-19. We included 388,945 adult inpatients who tested positive for SARS-CoV-2 at 36 AP−HP (Assistance Publique−Hôpitaux de Paris) hospitals from 2 May 2020 to 2 November 2021. We compared the prevalence of antidepressant use at admission in a 1:1 ratio matched analytic sample with and without COVID-19 (N = 82,586), and assessed its association with 28-day all-cause mortality in a 1:1 ratio matched analytic sample of COVID-19 inpatients with and without antidepressant use at admission (N = 1482). Antidepressant use was significantly less prevalent in inpatients with COVID-19 than in a matched control group of inpatients without COVID-19 (1.9% versus 4.8%; Odds Ratio (OR) = 0.38; 95%CI = 0.35−0.41, p < 0.001). Antidepressant use was significantly associated with reduced 28-day mortality among COVID-19 inpatients (12.8% versus 21.2%; OR = 0.55; 95%CI = 0.41−0.72, p < 0.001), particularly at daily doses of at least 40 mg fluoxetine equivalents. Antidepressants with high FIASMA (Functional Inhibitors of Acid Sphingomyelinase) activity seem to drive both associations. These treatments may reduce SARS-CoV-2 infections and COVID-19-related mortality in inpatients, and may be appropriate for prophylaxis and/or COVID-19 therapy for outpatients or inpatients.

Promyelocytic leukemia nuclear bodies behave as DNA damage sensors whose response to DNA double-strand breaks is regulated by NBS1 and the kinases ATM, Chk2, and ATR.

The promyelocytic leukemia (PML) nuclear body (NB) is a dynamic subnuclear compartment that is implicated in tumor suppression, as well as in the transcription, replication, and repair of DNA. PML NB number can change during the cell cycle, increasing in S phase and in response to cellular stress, including DNA damage. Although topological changes in chromatin after DNA damage may affect the integrity of PML NBs, the molecular or structural basis for an increase in PML NB number has not been elucidated. We demonstrate that after DNA double-strand break induction, the increase in PML NB number is based on a biophysical process, as well as ongoing cell cycle progression and DNA repair. PML NBs increase in number by a supramolecular fission mechanism similar to that observed in S-phase cells, and which is delayed or inhibited by the loss of function of NBS1, ATM, Chk2, and ATR kinase. Therefore, an increase in PML NB number is an intrinsic element of the cellular response to DNA damage.

Unprovoked serotonin syndrome-like presentation of SARS-CoV-2 infection: A small case series.

Clinicians and researchers have reported an array of neurological abnormalities in coronavirus disease 2019 (COVID-19), and while serotonin excess has been observed we are unaware of reports of central nervous system serotonin toxicity in COVID-19. We present two cases that resemble serotonin syndrome in COVID-19, but without identifiable inciting medications. A 54-year-old with multiple sclerosis and diabetes mellitus presented with altered mental status. His altered sensorium was attributed to diabetic ketoacidosis, but his condition quickly deteriorated with fever to 105 degrees Fahrenheit, rigidity in all extremities, inducible clonus, and hyperreflexia. He was intubated and was treated for possible meningitis and seizure. Neurologic workup was negative for acute pathology. Despite acetaminophen, his core temperature remained elevated to 105 degrees Fahrenheit. He was treated with external cooling and cyproheptadine and within 48 h, his fever, rigidity, hyperreflexia, and clonus resolved. He was extubated and discharged home on day 14. A 72-year-old with hyperlipidemia was admitted with tremors, 4 days after testing positive for COVID-19. His symptoms rapidly worsened, and he was transferred to the Intensive Care Unit on day 3 in extremis, febrile to 104.4 degrees Fahrenheit, heart rate of 180 beats per minute, and apparent whole body myoclonus. He was intubated and developed fever refractory to acetaminophen requiring external cooling. Extensive neurologic workup was negative. He received cyproheptadine and slowly improved. He was extubated and discharged to rehab on day 11. These cases represent a unique presentation in COVID-19 that must be considered and requires a high index of suspicion.

Targeting homologous recombination using imatinib results in enhanced tumor cell chemosensitivity and radiosensitivity.

RAD51 is a key protein in the homologous recombination (HR) pathway of DNA double-strand break repair, and HR represents a novel target for cancer therapy. Because imatinib (Gleevec) has been reported to reduce RAD51 protein levels, we tested the clonogenic survival for RT112, H1299, PANC1, and PC3 tumor cell lines of varying p53 status and normal GM05757 normal fibroblasts after exposure to single agent imatinib (0-20 micromol/L; 0-72 hours). We also combined imatinib with DNA damaging agents that are toxic to RAD51-deficient cells, including ionizing radiation, gemcitabine, and mitomycin C. We observed decreased nuclear expression and chromatin binding of RAD51 protein following imatinib treatment. Imatinib also resulted in decreased error-free HR as determined by a flow cytometry-based integrated direct repeat-green fusion protein reporter system; this correlated to reduced RAD51 expression. Clonogenic survival experiments revealed increased cell kill for imatinib-treated cells in combination with ionizing radiation, gemcitabine, and mitomycin C, due in part to mitotic catastrophe. In experiments using imatinib and gemcitabine, tumor cell lines were sensitized to a greater extent than normal fibroblasts. This preservation of the therapeutic ratio was confirmed in vivo using PC3 xenograft growth delay and intestinal crypt cell clonogenic assays. HR inhibition may be an additional mechanism of action for the chemosensitization and radiosensitization of solid tumors with imatinib with preservation of the therapeutic ratio.

Single-center experience demonstrating low adverse events and high efficacy with self-expandable metal esophageal and biliary stents for pseudocyst and walled off necrosis drainage.

Background and study aims Lumen-apposing metal stents (LAMS) have been designed as proprietary stents for the management of pseudocysts (PC)/walled off necrosis (WON). There has been concern about adverse events (AEs) with LAMS including bleeding, buried stent syndrome and migration. Prior to LAMS becoming available, fully-covered self-expandable metal esophageal and biliary stents (FCSEMSs) were used off-label for management of PC/WON with many centers demonstrating low rates of AEs. The primary aim of this study was to study the safety and efficacy of FCSEMS for the management of pseudocysts/WON. Patients and methods This was a retrospective review of all endoscopic ultrasound (EUS)-guided placement of FCSEMSs for drainage of PC/WON cases performed at our institution over 4-year period. The primary outcomes studied were technical success, AEs, PC/WON resolution, and salvage surgical/radiologic intervention. Results Technical success achieved in 65 of 65 (100 %) study patients. An AE occurred 0 of 25 patients (0 %) with PC, and in 10 of 40 patients (25 %) with WON: bleeding (3 %), migration (5 %) and stent dysfunction/infection (18 %). There was resolution in 25 of 25 patients (100 %) with a PC and 31 of 40 patients (78 %) with a WON. Salvage therapy by interventional radiology or surgery was performed in nine of 40 patients (22 %). Conclusions This single-center 4-year experience in the pre-LAMS era showed that FCSEMS was safe and effective in all patients with PC and over 75 % of patients with WON. Given the large cost differential between LAMS and FCSEMS and the efficacy and safety shown with FCSEMS, we believe that FCSEMS should still be considered a first-line option for patients with pancreatic fluid collections, particularly in patients with PCs.

WTp53 induction does not override MTp53 chemoresistance and radioresistance due to gain-of-function in lung cancer cells.

New molecular cancer treatment strategies aim to reconstitute wild-type p53 (WTp53) function in mutant p53 (MTp53)-expressing tumors as a means of resensitizing cells to chemotherapy or radiotherapy. The success of this approach may depend on whether MTp53 proteins are acting in a dominant-negative or independent gain-of-function mode. Herein, we describe an isogenic, temperature-sensitive p53 model (p53(A138V)) in p53-null human H1299 lung cancer cells in which WTp53 can be selectively coexpressed with a temperature-sensitive MTp53 allele (A138V) during initial DNA damage and subsequent DNA repair. Cells expressing MTp53 alone or coexpressing induced WTp53 and MTp53 were tested for p53 transcription, G(1) and G(2) cell cycle checkpoints, apoptosis, and long-term clonogenic survival following DNA damage. Transient transfection of WTp53 into H1299 cells, or shift-down of H1299-p53(A138V) stable transfectants to 32 degrees C to induce WTp53, led to increased p21(WAF1) expression and G(1) and G(2) arrests following DNA damage but did not increase BAX expression or apoptosis. In contrast, both transient and stable expression of the p53(A138V) mutant in p53-null H1299 cells (e.g. testing gain-of-function) at 37 degrees C blocked p21(WAF1) induction following DNA damage. Cell death was secondary to mitotic catastrophe and/or tumor cell senescence. Overexpression of WTp53 did not resensitize resistant MTp53-expressing cells to ionizing radiation, cisplatinum, or mitomycin C. Our results suggest that human MTp53 proteins can lead to resistant phenotypes independent of WTp53-mediated transcription and checkpoint control. This should be considered when using p53 as a prognostic factor and therapeutic target.

A novel poly(ADP-ribose) polymerase inhibitor, ABT-888, radiosensitizes malignant human cell lines under hypoxia.

The chemo- and radioresponse of tumor cells can be determined by genetic factors (e.g., those that modify cell cycle arrest, DNA damage repair or cell death) and microenvironmental factors, such as hypoxia. Poly(ADP-ribose) polymerase (PARP) is a nuclear enzyme that rapidly recognizes and binds to DNA breaks to facilitate DNA strand break repair. Pre-clinical data suggest that PARP inhibitors (PARPi) may potentiate the effects of radiotherapy and chemotherapy. However, it is unclear as to whether PARPi are effective against hypoxic cells. We therefore tested the role for a novel PARPi, ABT-888, as a radiosensitizing agent under hypoxic conditions. Using human prostate (DU-145, 22RV1) and non-small cell lung (H1299) cancer cell lines, we observed that ABT-888 inhibited both recombinant PARP activity and intracellular PARP activity (86% to 92% decrease in all 3 cells lines following 2.5 microM treatment). ABT-888 was toxic to both oxic and hypoxic cells. When ABT-888 was combined with ionizing radiation (IR), clonogenic radiation survival was decreased by 40-50% under oxic conditions. Under acute hypoxia, ABT-888 radiosensitized malignant cells to a level similar to oxic radiosensitivity. To our knowledge, this is the first study to demonstrate that inhibition of PARP activity can sensitize hypoxic cancer cells and the combination of IR-PARPi has the potential to improve the therapeutic ratio of radiotherapy.

Homologous recombination and prostate cancer: a model for novel DNA repair targets and therapies.

Using elegant targeting techniques such as IMRT, radiation oncology has improved the therapeutic ratio of prostate cancer radiotherapy through increased physical precision (e.g. increased local control through dose-escalation without increased normal tissue toxicity). The therapeutic ratio might be further improved by the addition of "biologic precision and escalation" pertaining to the use of molecular inhibitors of DNA damage sensing and repair. Indeed, proteins involved in the ATM-p53 damage signaling axis and the homologous (HR) and non-homologous end-joining (NHEJ) pathways of DNA double-strand break (DNA-dsb) rejoining pathways may be attractive candidates to elucidate cancer risk, prognosis, prediction of response and to develop sensitizers towards oxic and hypoxic prostate tumor cells. This review highlights DNA-dsb in prostate cancer research in terms of novel molecular inhibitors, the role of the microenvironment in DNA-dsb repair and potential DNA-dsb biomarkers for clinical trials.

Evidence for the direct binding of phosphorylated p53 to sites of DNA breaks in vivo.

Despite a clear link between ataxia-telangiectasia mutated (ATM)-dependent phosphorylation of p53 and cell cycle checkpoint control, the intracellular biology and subcellular localization of p53 phosphoforms during the initial sensing of DNA damage is poorly understood. Using G0-G1 confluent primary human diploid fibroblast cultures, we show that endogenous p53, phosphorylated at Ser15 (p53Ser15), accumulates as discrete, dose-dependent and chromatin-bound foci within 30 minutes following induction of DNA breaks or DNA base damage. This biologically distinct subpool of p53Ser15 is ATM dependent and resistant to 26S-proteasomal degradation. p53Ser15 colocalizes and coimmunoprecipitates with gamma-H2AX with kinetics similar to that of biochemical DNA double-strand break (DNA-dsb) rejoining. Subnuclear microbeam irradiation studies confirm p53Ser15 is recruited to sites of DNA damage containing gamma-H2AX, ATM(Ser1981), and DNA-PKcs(Thr2609) in vivo. Furthermore, studies using isogenic human and murine cells, which express Ser15 or Ser18 phosphomutant proteins, respectively, show defective nuclear foci formation, decreased induction of p21WAF, decreased gamma-H2AX association, and altered DNA-dsb kinetics following DNA damage. Our results suggest a unique biology for this p53 phosphoform in the initial steps of DNA damage signaling and implicates ATM-p53 chromatin-based interactions as mediators of cell cycle checkpoint control and DNA repair to prevent carcinogenesis.

Defective DNA strand break repair after DNA damage in prostate cancer cells: implications for genetic instability and prostate cancer progression.

Together with cell cycle checkpoint control, DNA repair plays a pivotal role in protecting the genome from endogenous and exogenous DNA damage. Although increased genetic instability has been associated with prostate cancer progression, the relative role of DNA double-strand break repair in malignant versus normal prostate epithelial cells is not known. In this study, we determined the RNA and protein expression of a series of DNA double-strand break repair genes in both normal (PrEC-epithelial and PrSC-stromal) and malignant (LNCaP, DU-145, and PC-3) prostate cultures. Expression of genes downstream of ATM after ionizing radiation-induced DNA damage reflected the p53 status of the cell lines. In the malignant prostate cell lines, mRNA and protein levels of the Rad51, Xrcc3, Rad52, and Rad54 genes involved in homologous recombination were elevated approximately 2- to 5-fold in comparison to normal PrEC cells. The XRCC1, DNA polymerase-beta and -delta proteins were also elevated. There were no consistent differences in gene expression relating to the nonhomologous end-joining pathway. Despite increased expression of DNA repair genes, malignant prostate cancer cells had defective repair of DNA breaks, alkali-labile sites, and oxidative base damage. Furthermore, after ionizing radiation and mitomycin C treatment, chromosomal aberration assays confirmed that malignant prostate cells had defective DNA repair. This discordance between expression and function of DNA repair genes in malignant prostate cancer cells supports the hypothesis that prostate tumor progression may reflect aberrant DNA repair. Our findings support the development of novel treatment strategies designed to reinstate normal DNA repair in prostate cancer cells.

Loss of Brca2 and p53 synergistically promotes genomic instability and deregulation of T-cell apoptosis.

BRCA2 is a breast cancer susceptibility gene of which the product is thought to be involved in monitoring genome integrity and cell cycle progression. Brca2-null mice have a defect in embryonic cellular proliferation and die in utero. Here we report the generation of T-cell lineage-specific Brca2-deficient (tBrca2(-/-)) mice using the Cre-loxP system. Mice with a flanked by loxP allele of Brca2 were crossed to transgenic mice bearing Cre recombinase driven by the T cell-specific promoter Lck. Thymic cellularity and distribution of subset populations were normal in tBrca2(-/-) mutants. Thymocytes from tBrca2(-/-) mice underwent normal apoptosis in response to a variety of stimuli, and activated tBrca2(-/-) T cells had normal proliferative capacity. tBrca2(-/-) T cells were more likely than wild-type cells to undergo spontaneous apoptosis, but apoptosed normally in response to restimulation or DNA-damaging stress signals. Examination of metaphase spreads of tBrca2(-/-) T cells revealed that the chromosomes often exhibited aberrations such as breaks and tri-radial structures. The level of chromosomal abnormalities was enhanced in T cells from tBrca2(-/-); p53(-/-) double-mutant mice. However, tBrca2(-/-); p53(-/-) T cells did not show the enhanced level of spontaneous apoptosis demonstrated by tBrca2(-/-) T cells, a difference that likely accounts for an increase in cell number and (3)[H]thymidine incorporation of double-mutant T cells in culture compared with either single mutant. Despite this increased T-cell number, the onset of T-cell lymphomas was only marginally accelerated in tBrca2(-/-); p53(-/-) mice compared with p53(-/-) mice. Our results support a role for Brca2 in repairing spontaneous DNA lesions, and suggest that loss of Brca2 enhances the susceptibility of mouse T-lineage cells to chromosomal aberrations and deregulation of apoptosis in the absence of p53.

Bleeding Risk of Stent Removal After EUS-Guided Cystgastrostomy and Metal Stent Placement for Drainage of a Pancreatic Fluid Collection.

Endoscopists are keenly aware of bleeding risks during and immediately after cystgastrostomy and reduce this risk by endoscopic ultrasound guidance to avoid manipulation near major vessels. Bleeding risk associated with cystgastrostomy stent removal after resolution of a pancreatic fluid collection, however, is less evident. We present our experience with bleeding during cystgastrostomy stent removal in a patient with resolved walled-off necrosis and will discuss the significance of unexplained spontaneous upper gastrointestinal bleeding in this setting, which may serve as a warning sign for possible stent erosion into major vessels.