Loss of thymocyte competition underlies the tumor suppressive functions of the E2a transcription factor in T-ALL.

T lymphocyte acute lymphoblastic leukemia (T-ALL) is frequently associated with increased expression of the E protein transcription factor inhibitors TAL1 and LYL1. In mouse models, ectopic expression of TAL1 or LYL1 in T cell progenitors, or inactivation of E2A, is sufficient to predispose mice to develop T-ALL. How E2A suppresses thymocyte transformation is currently unknown. Here, we show that early deletion of E2a, prior to the DN3 stage, was required for robust leukemogenesis and was associated with alterations in thymus cellularity, T cell differentiation, and gene expression in immature CD4+CD8+ thymocytes. Introduction of wild-type thymocytes into mice with early deletion of E2a prevented leukemogenesis, or delayed disease onset, and impacted the expression of multiple genes associated with transformation and genome instability. Our data indicate that E2A suppresses leukemogenesis by promoting T cell development and enforcing inter-thymocyte competition, a mechanism that is emerging as a safeguard against thymocyte transformation. These studies have implications for understanding how multiple essential regulators of T cell development suppress T-ALL and support the hypothesis that thymocyte competition suppresses leukemogenesis.

Loss of thymocyte competition underlies the tumor suppressive functions of the E2a transcription factor in T lymphocyte acute lymphoblastic leukemia.

T lymphocyte acute lymphoblastic leukemia (T-ALL) is frequently associated with increased expression of the E protein transcription factor inhibitors TAL1 and LYL1. In mouse models, ectopic expression of Tal1 or Lyl1 in T cell progenitors or inactivation of E2a, is sufficient to predispose mice to develop T-ALL. How E2a suppresses thymocyte transformation is currently unknown. Here, we show that early deletion of E2a , prior to the DN3 stage, was required for robust leukemogenesis and was associated with alterations in thymus cellularity, T cell differentiation, and gene expression in immature CD4+CD8+ thymocytes. Introduction of wild-type thymocytes into mice with early deletion of E2a prevented leukemogenesis, or delayed disease onset, and impacted the expression of multiple genes associated with transformation and genome instability. Our data indicate that E2a suppresses leukemogenesis by promoting T cell development and enforcing inter-thymocyte competition, a mechanism that is emerging as a safeguard against thymocyte transformation. These studies have implications for understanding how multiple essential regulators of T cell development suppress T-ALL and support the hypothesis that thymus cellularity is a determinant of leukemogenesis.

Development and External Validation of a Machine Learning Model for Prediction of Potential Transfer to the PICU.

OBJECTIVES: Unrecognized clinical deterioration during illness requiring hospitalization is associated with high risk of mortality and long-term morbidity among children. Our objective was to develop and externally validate machine learning algorithms using electronic health records for identifying ICU transfer within 12 hours indicative of a child's condition. DESIGN: Observational cohort study. SETTING: Two urban, tertiary-care, academic hospitals (sites 1 and 2). PATIENTS: Pediatric inpatients (age <18 yr). INTERVENTIONS: None. MEASUREMENT AND MAIN RESULTS: Our primary outcome was direct ward to ICU transfer. Using age, vital signs, and laboratory results, we derived logistic regression with regularization, restricted cubic spline regression, random forest, and gradient boosted machine learning models. Among 50,830 admissions at site 1 and 88,970 admissions at site 2, 1,993 (3.92%) and 2,317 (2.60%) experienced the primary outcome, respectively. Site 1 data were split longitudinally into derivation (2009-2017) and validation (2018-2019), whereas site 2 constituted the external test cohort. Across both sites, the gradient boosted machine was the most accurate model and outperformed a modified version of the Bedside Pediatric Early Warning Score that only used physiologic variables in terms of discrimination ( C -statistic site 1: 0.84 vs 0.71, p < 0.001; site 2: 0.80 vs 0.74, p < 0.001), sensitivity, specificity, and number needed to alert. CONCLUSIONS: We developed and externally validated a novel machine learning model that identifies ICU transfers in hospitalized children more accurately than current tools. Our model enables early detection of children at risk for deterioration, thereby creating opportunities for intervention and improvement in outcomes.

Mortality and PICU Hospitalization Among Pediatric Gunshot Wound Victims in Chicago.

Firearm injury accounts for significant morbidity with high mortality among children admitted to the PICU. Understanding risk factors for PICU admission is an important step toward developing prevention and intervention strategies to minimize the burden of pediatric gunshot wound (GSW) injury. OBJECTIVES: The primary objective of this study was to characterize outcomes and the likelihood of PICU admission among children with GSWs. DESIGN SETTING AND PARTICIPANTS: Retrospective cohort study of GSW patients 0-18 years old evaluated at the University of Chicago Comer Children's Hospital Pediatric Trauma Center from 2010 to 2017. MAIN OUTCOMES AND MEASURES: Demographic and injury severity measures were acquired from an institutional database. We describe mortality and hospitalization characteristics for the cohort. We used logistic regression models to test the association between PICU admission and patient characteristics. RESULTS: During the 8-year study period, 294 children experienced GSWs. We did not observe trends in overall mortality over time, but mortality for children with GSWs was higher than all-cause PICU mortality. Children 0-6 years old experienced longer hospitalizations compared with children 13-16 years old (5 vs 3 d; p = 0.04) and greater frequency of PICU admission (83.3% vs 52.9%; p = 0.001). Adjusting for severity of illness, children less than 7 years old were four-fold more likely to be admitted to the PICU than children 13-16 years old (aOR range, 3.9-4.6). CONCLUSIONS AND RELEVANCE: Despite declines in pediatric firearm mortality across the United States, mortality did not decrease over time in our cohort and was higher than all-cause PICU mortality. Younger children with GSWs experience longer hospitalizations and require PICU care more often than older children. Our findings suggest that the youngest victims of firearm-related injury may be particularly at-risk of the long-term sequelae of critical illness and injury.

The transcriptional repressor ID2 supports natural killer cell maturation by controlling TCF1 amplitude.

Gaining a mechanistic understanding of the expansion and maturation program of natural killer (NK) cells will provide opportunities for harnessing their inflammation-inducing and oncolytic capacity for therapeutic purposes. Here, we demonstrated that ID2, a transcriptional regulatory protein constitutively expressed in NK cells, supports NK cell effector maturation by controlling the amplitude and temporal dynamics of the transcription factor TCF1. TCF1 promotes immature NK cell expansion and restrains differentiation. The increased TCF1 expression in ID2-deficient NK cells arrests their maturation and alters cell surface receptor expression. Moreover, TCF1 limits NK cell functions, such as cytokine-induced IFN-γ production and the ability to clear metastatic melanoma in ID2-deficient NK cells. Our data demonstrate that ID2 sets a threshold for TCF1 during NK cell development, thus controlling the balance of immature and terminally differentiated cells that support future NK cell responses.

Cabozantinib Unlocks Efficient In Vivo Targeted Delivery of Neutrophil-Loaded Nanoparticles into Murine Prostate Tumors.

A major barrier to the successful application of nanotechnology for cancer treatment is the suboptimal delivery of therapeutic payloads to metastatic tumor deposits. We previously discovered that cabozantinib, a tyrosine kinase inhibitor, triggers neutrophil-mediated anticancer innate immunity, resulting in tumor regression in an aggressive PTEN/p53-deficient genetically engineered murine model of advanced prostate cancer. Here, we specifically investigated the potential of cabozantinib-induced neutrophil activation and recruitment to enhance delivery of BSA-coated polymeric nanoparticles (BSA-NPs) into murine PTEN/p53-deficient prostate tumors. On the basis of the observation that BSA coating of NPs enhanced association and internalization by activated neutrophils by approximately 6-fold in vitro, relative to uncoated NPs, we systemically injected BSA-coated, dye-loaded NPs into prostate-specific PTEN/p53-deficient mice that were pretreated with cabozantinib. Flow cytometric analysis revealed an approximately 4-fold increase of neutrophil-associated BSA-NPs and an approximately 32-fold increase in mean fluorescent dye uptake following 3 days of cabozantinib/BSA-NP administration, relative to BSA-NP alone. Strikingly, neutrophil depletion with Ly6G antibody abolished dye-loaded BSA-NP accumulation within tumors to baseline levels, demonstrating targeted neutrophil-mediated intratumoral NP delivery. Furthermore, we observed an approximately 13-fold decrease in accumulation of BSA-NPs in the liver, relative to uncoated NPs, post-cabozantinib treatment, suggesting that BSA coating of NPs can significantly enhance cabozantinib-induced, neutrophil-mediated targeted intratumoral drug delivery, while mitigating off-target toxicity. Collectively, we demonstrate a novel targeted nano-immunotherapeutic strategy for enhanced intratumoral delivery of BSA-NPs, with translational potential to significantly augment therapeutic indices of cancer medicines, thereby overcoming current pharmacologic barriers commonly encountered in preclinical/early-phase drug development.