Citations

Abstract PAX5 is genetically altered in over 30% of B-ALL cases, with point mutations representing the second most common type of alteration. These point mutations are highly enriched in the DNA binding (paired) domain and have been recognized as founder events in PAX5 P80R and PAX5alt B-ALL subtypes, which account for over 12% of B-ALL. However, the molecular features and underlying mechanisms of these mutations in B-ALL remain largely undefined, limiting the development of targeted therapies and resulting in poor outcomes, especially in adult patients. We systematically investigated the functional roles and oncogenic mechanisms of PAX5 paired domain mutations. Integrated CRISPR screening and genomic profiling revealed that the paired domain is critical for PAX5 function. Disruptions in this region significantly reduced cell viability in B-ALL cell lines, and analysis of 2,955 B-ALL samples showed that recurrent PAX5 missense mutations are highly enriched in this domain, further underscoring its functional importance. Functional analysis of knock-in mice with PAX5 mutations revealed that R38H and R140L severely impair DNA binding and block B-cell differentiation, while P34L and P80R retain binding ability but alter binding specificity and gene regulation. Mice carrying homozygous (P34L, R38H, P80R, R140L) or heterozygous (R38H, P80R) mutations developed spontaneous B-ALL within one year. To model co-occurring mutations observed in patients, Pax5 R38H/P34L and R38H/R140L mice were generated. These compound mutations exhibited greater leukemogenic potential than single mutants. Transcriptomic analysis of leukemia samples showed consistent up-regulation of metabolic pathways and Myc target genes. Notably, biallelic PAX5 alterations and additional genetic lesions in signaling pathways were detected in all PAX5R38H/+ and PAX5P80R/+ leukemias, faithfully recapitulating the genetic alteration features of patient B-ALL driven by PAX5 mutations. Among Pax5-mutant mouse strains, Pax5P80R/+ mice develop B-ALL with short latency and complete penetrance, making them an ideal model to study the mutational evolution and leukemogenesis of B-ALL. To characterize the stepwise leukemogenesis process, we performed serial bone marrow aspirations in the same Pax5P80R/+ mice. In all 17 mice analyzed, we identified early preleukemic clones with only Pax5 WT deletions, followed by the emergence of leukemic clones harboring Jak1/3 mutations. Single-cell RNA/BCR-seq revealed that Pax5 WT allele deletions relieve metabolic constraints, thereby promoting clonal expansion of preleukemic B cells blocked at the pre-B stage. These changes coincide with downregulation of metabolic checkpoint genes and upregulation of glycolytic enzymes, promoting genetic instability and facilitating malignant transformation. Clinically, PAX5 P80R patients have better outcomes than PAX5alt cases. Using our mouse models, we observed that leukemic cells driven by the PAX5 P80R mutation exhibit greater sensitivity to dexamethasone compared to the ones carrying other PAX5 mutations in PAX5alt subtype, potentially due to their heightened dependence on glucose uptake and glycolysis, suggesting that metabolic rewiring driven by PAX5 mutants may influence therapeutic response. Interestingly, we found that an aberrant isoform of MEGF10 (aMEGF10) is highly and specifically expressed in PAX5 P80R B-ALL. This N-terminal truncated isoform encodes a protein that retains the intracellular immunoreceptor tyrosine-based activation motifs (ITAMs). Using CUT&Tag, we showed that PAX5 P80R directly binds to the aMEGF10 promoter. By engineering human CD34⁺ cells, we established a humanized PAX5 P80R leukemia model that recapitulates the gene expression profile of patient samples, including robust activation of aMEGF10. Functionally, aMEGF10 binds to and activates SYK, thereby promoting leukemic cell proliferation. Importantly, this oncogenic effect depends on intact ITAM motifs and SYK signaling, revealing a novel targetable vulnerability in PAX5 P80R leukemias. Overall, the study establishes that PAX5 DNA binding domain mutations contribute to leukemogenesis through stepwise loss of PAX5 WT alleles and acquisition of signaling pathway mutations, involving impaired differentiation, metabolic deregulation, and novel oncogene activation. These findings not only deepen the understanding of PAX5-driven leukemias but also highlight aMEGF10–SYK signaling as a promising therapeutic target.

Background/Objectives: Coronavirus disease 2019 (COVID-19) is associated with gastrointestinal (GI) symptoms. Small intestinal bacterial overgrowth (SIBO) is emerging as a significant GI sequela post-COVID-19 infection. This study aimed to evaluate the prevalence and incidence of SIBO post-COVID-19 infection across different age groups and to identify associated risk factors in a global cohort. Methods: A retrospective study utilized the TriNetX database and included adult patients (≥18 years) diagnosed with SIBO following COVID-19 infection (1 January 2022–30 May 2024). A propensity score matching (1:1) was used to adjust for demographics and SIBO risk factors. Kaplan–Meier survival analysis assessed the SIBO incidence within 12 months. Results: Among 1,660,092 COVID-19 patients and 42,322,017 controls, SIBO was diagnosed in 353 COVID-19 patients without hydrogen breath tests (BT) and 78 with BT, compared to 3368 controls without BT and 871 with BT. Age-specific analysis demonstrated a clear, progressive increase in the SIBO incidence, becoming distinctly significant by 6 months and highest at 12 months post-infection. The highest risks were noted in ages 60–69 (0.011% vs. 0.004%, OR 2.6, p = 0.0003) and 70–79 (0.011% vs. 0.005%, OR 2.0, p = 0.0004), with younger age groups (30–49 years) also showing significantly increased risks. The medication analysis revealed strong associations with chronic opioid, proton pump inhibitor, and antidiarrheal medication. Conclusions: COVID-19 significantly increased the risk of SIBO, particularly within the first 12 months post-infection, across various age groups and, notably, in association with certain chronic medications. Clinical vigilance and targeted management strategies are recommended to mitigate long-term GI consequences.

Background: Studies suggest circulating iron levels play a role in the pathophysiology of abdominal aortic aneurysms (AAAs). Low iron levels lead to medial degeneration and VSMC dysfunction while elevated iron levels promote oxidative stress. Hepcidin is a major iron regulatory hormone that binds ferroportin to reduce serum iron levels, and its removal in VSMCs has been shown to exacerbate AAAs; however, the role of sex in this mechanism remains understudied. The goal of the current study is to investigate the potential role of sex in iron metabolism in AAAs. Methods: Male and female C57BL/6 wild-type (WT/WT), heterozygous hepcidin knock-out (WT/KO) and hepcidin KO (KO/KO) underwent peri-adventitial application of porcine pancreatic elastase on the infrarenal aorta (n=10-19/group). At day 14, the aortas were measured using video micrometry and harvested for immunohistochemistry. In separate studies, male and female hepcidin WT/WT and KO/KO underwent elastase application and systemic b-aminopropionitrile (BAPN, 0.02%) administration and were harvested at 28 days. Finally, male and female LysM Cre Ferroportin flx/flx mice and their controls underwent elastase application and harvested at 14 days (n=5-10/group). Results: Hepcidin WT/KO and KO/KO male mice had dose dependent protection of aneurysm formation compared with controls (WT/WT: 145.5±33.8% vs WT/KO: 110.7±34.8% vs KO/KO: 53.7±13.7%, p=0.0001 by ANOVA). Female Hepcidin WT/KO and KO/KO mice exhibited increased AAA size compared with their controls (KO/KO: 119.0±23.5% vs WT/KO: 101.6 ±28.6% vs WT/WT: 71.2±22.0%, p =.0011 by ANOVA). In the elastase + BAPN model, Hepcidin KO/KO male mice had less aortic dilation compared to controls (KO/KO: 196.0 ±31.9% vs WT/WT: 476.8±82.2%, p =.0002 by Mann-Whitney) while female KO/KO mice exhibited greater aortic dilation (WT/WT: 186.7±26.0% vs. KO/KO: 406.9±62.2%, p=0.006). Male LysM Cre Ferroportin flx/flx mice had decreased aortic dilation (WT/WT: 132.5±19.3% vs flx/flx: 53.5±7.8%, p=0.001). Conclusion: Elimination of hepcidin in AAA formation exhibited protective effects in male and deleterious effects in female mice. This data suggests targeting of hepcidin using drug-based therapies could have gender-specific clinical implications.

Importance The clinical effects of risankizumab (a monoclonal antibody that selectively targets the p19 subunit of IL-23) for the treatment of ulcerative colitis are unknown. Objective To evaluate the efficacy and safety of risankizumab when administered as an induction and a maintenance therapy for patients with ulcerative colitis. Design, Setting, and Participants Two phase 3 randomized clinical trials were conducted. The induction trial was conducted at 261 clinical centers (in 41 countries) and enrolled 977 patients from November 5, 2020, to August 4, 2022 (final follow-up on May 16, 2023). The maintenance trial was conducted at 238 clinical centers (in 37 countries) and enrolled 754 patients from August 28, 2018, to March 30, 2022 (final follow-up on April 11, 2023). Eligible patients had moderately to severely active ulcerative colitis; a history of intolerance or inadequate response to 1 or more conventional therapies, advanced therapies, or both types of therapies; and no prior exposure to risankizumab. Interventions For the induction trial, patients were randomized 2:1 to receive 1200 mg of risankizumab or placebo administered intravenously at weeks 0, 4, and 8. For the maintenance trial, patients with a clinical response (determined using the adapted Mayo score) after intravenous treatment with risankizumab were randomized 1:1:1 to receive subcutaneous treatment with 180 mg or 360 mg of risankizumab or placebo (no longer receiving risankizumab) every 8 weeks for 52 weeks. Main Outcomes and Measures The primary outcome was clinical remission (stool frequency score ≤1 and not greater than baseline, rectal bleeding score of 0, and endoscopic subscore ≤1 without friability) at week 12 for the induction trial and at week 52 for the maintenance trial. Results Among the 975 patients analyzed in the induction trial (aged 42.1 [SD, 13.8] years; 586/973 [60.1%] were male; and 677 [69.6%] were White), the clinical remission rates at week 12 were 132/650 (20.3%) for 1200 mg of risankizumab and 20/325 (6.2%) for placebo (adjusted between-group difference, 14.0% [95% CI, 10.0%-18.0%], P < .001). Among the 548 patients analyzed in the maintenance trial (aged 40.9 [SD, 14.0] years; 313 [57.1%] were male; and 407 [74.3%] were White), the clinical remission rates at week 52 were 72/179 (40.2%) for 180 mg of risankizumab, 70/186 (37.6%) for 360 mg of risankizumab, and 46/183 (25.1%) for placebo (adjusted between-group difference for 180 mg of risankizumab vs placebo, 16.3% [97.5% CI, 6.1%-26.6%], P < .001; adjusted between-group difference for 360 mg of risankizumab vs placebo, 14.2% [97.5% CI, 4.0%-24.5%], P = .002). No new safety risks were detected in the treatment groups. Conclusion and Relevance Compared with placebo, risankizumab improved clinical remission rates in an induction trial and in a maintenance trial for patients with moderately to severely active ulcerative colitis. Further study is needed to identify benefits beyond the 52-week follow-up. Trial Registration ClinicalTrials.gov Identifiers: NCT03398148 and NCT03398135

TPS8076 Background: Light chain (AL) amyloidosis is a progressive and typically fatal disorder caused by misfolded AL protein produced by plasma cells. Birtamimab is a monoclonal antibody designed to neutralize circulating soluble and deposited insoluble amyloid, thus promoting phagocytic clearance. In 2018, the phase 3 VITAL study in newly diagnosed, treatment-naive patients was terminated based on futility analysis of the primary endpoint (time to all-cause mortality [ACM] or time to cardiac hospitalization > 90 days after first study drug infusion); the final hazard ratio (HR) numerically favored birtamimab + standard of care (SOC) over placebo + SOC (0.835 [95% CI: 0.5799, 1.2011]; p = 0.330). Post-hoc analysis of ACM over 9 months revealed a substantial survival benefit (HR = 0.413 [95% CI: 0.191, 0.895]; p = 0.025) in patients at high risk for early death (Mayo Stage IV). Post-hoc analyses of secondary endpoints in this subgroup indicated meaningful improvements in health-related quality of life (assessed with 36-Item Short Form Health Survey version 2; SF-36v2) and 6-minute walk test (6MWT) distance with birtamimab + SOC (p < 0.05) at 9 months. Methods: The phase 3, double-blind, placebo-controlled AFFIRM-AL study (NCT04973137) will enroll up to 150 Mayo Stage IV patients with newly diagnosed, untreated AL amyloidosis. Patients will be randomized (2:1) to 24 mg/kg intravenous birtamimab or placebo every 28 days. Both arms will receive concomitant chemotherapy with a first-line bortezomib-containing regimen, with or without daratumumab (D), at the discretion of the investigator. Patients will be stratified at randomization based on their 6MWT distance ( < 300 vs ≥300 meters) and initiation of D. The primary efficacy endpoint is time to ACM. Secondary endpoints are change from baseline to month 9 in the physical component summary of the SF-36v2 and 6MWT distance. This trial is powered at a significance level of 0.1 under a Special Protocol Assessment (SPA) with the U.S. Food and Drug Administration (FDA). Given the > 50% relative risk reduction for ACM observed in the post-hoc analysis of VITAL for patients with Mayo Stage IV disease, the AFFIRM-AL study is designed to confirm this effect of birtamimab. Approximately 130 global sites are planned; site initiation and patient randomization are underway. Conclusion: Treatments that improve survival in AL amyloidosis are needed, particularly for patients with advanced cardiac involvement, as median overall survival for those with Mayo Stage IV disease is ̃6–9 months. The AFFIRM-AL study is designed to confirm the survival benefit observed in the VITAL study in patients with Mayo Stage IV AL amyloidosis. Clinical trial information: NCT04973137.

The zebrafish has emerged as an excellent model for cardiovascular research thanks to its ex-utero and rapid embryonic development, its embryonic transparent nature, and its capacity to survive in the absence of a functional cardiovascular system during the first week of development, which enables functional characterization of mutations that would otherwise induce lethality in traditional murine models. The aim of this project is to identify and characterize novel genes involved in zebrafish cardiovascular development using mutagenic gene trapping, a technique that generates random insertional mutations across the genome. We use the well-defined RP2 gene-breaking transposon system, which not only mutates, but also fluorescently tags the trapped gene product(s) (Clark, Nat Methods, 2011). RP2 also introduces loxP sites into the mutant locus, which can be used for Cre-mediated phenotype rescue by microinjection of Cre recombinase, or by crossing to tissue-specific Cre lines. From over 3000 RP2-injected embryos, 141 fish showed germline transmission. Among them, 51 expressed strong fluorescence in different tissues, including the heart, vessels, notochord, central nervous system (CNS), and eyes. Three cardiovascular lines were selected for phenotypic characterization and functional studies. RP2#C2 strain expressed fluorescence in the heart valves, CNS, eyes and pectoral fin buds. Inverse PCR in RP2#C2 demonstrated a trapped gene at meis4.1a, which encodes a homeobox transcription factor that has not been previously studied in zebrafish. RP2#121 strain expressed strong fluorescence in cardiac and skeletal muscles. RP2#91 strain showed expression in the vasculature and demonstrated a trapped gene at pdgfra. Homozygous RP2#91 mutants showed severe defects in the heart, blood flow, and other body parts including the head and musculature. We are currently creating a panel of tissue-specific Cre lines targeting tissues such as cardiomyocytes, endothelial cells and smooth muscle cells for spatiotemporal rescuing of the mutant phenotype. The generated zebrafish protein-trap lines are invaluable tools to annotate gene function, dissect the molecular mechanisms of cardiovascular development, and potentially serve as disease models.

Abstract Background: Tumor infiltrating lymphocytes (TILs) play an important, but incompletely understood role in chemotherapy response and prognosis. In breast cancer, there appear to be distinct immune responses by subtype, but most studies have used limited numbers of protein markers or bulk sequencing of RNA to characterize immune response, in which spatial organization cannot be assessed. Methods: To identify immune phenotypes of Basal-like vs. Luminal breast cancer we used the GeoMx® (NanoString) platform to perform digital spatial profiling (DSP) of immune-related proteins in tumor whole sections and tissue microarrays (TMA). Visualization of CD45, CD68, or pan-Cytokeratin by immunofluorescence was used to select regions of interest (ROIs) in formalin-fixed paraffin embedded tissue sections. 44 antibodies representing stromal markers and multiple immune cell types were applied to quantify the tumor microenvironment. Results: In whole tumor slides, immune hot spots (CD45+) had increased expression of many immune markers, suggesting a diverse and robust immune response. In epithelium-enriched areas, immune signals were also detectable and varied by subtype, with Regulatory T cell (Treg) markers (CD4, CD25, FOXP3) being higher in Basal-like vs. Luminal breast cancer. Extending these findings to TMAs with more patients (n=75), we confirmed subtype-specific immune profiles, including enrichment of Treg markers in Basal-likes. Conclusion: This work demonstrated that immune responses can be detected in epithelium-rich tissue, and that TMAs are a viable approach for obtaining important immunoprofiling data. In addition, we found that immune marker expression is associated with BC subtype, suggesting possible prognostic or targetable differences. Citation Format: Andrea Walens, Linnea T. Olsson, Xiaohua Gao, Alina M. Hamilton, Erin L. Kirk, Stephanie M. Cohen, Bentley R. Midkiff, Yongjuan Xia, Mark E. Sherman, Nana Nikolaishvili-Feinberg, Katherine A. Hoadley, Melissa A. Troester, Benjamin C. Calhoun. Protein-based immune profiles of basal-like vs luminal breast cancers [abstract]. In: Proceedings of the AACR Virtual Special Conference on Tumor Heterogeneity: From Single Cells to Clinical Impact; 2020 Sep 17-18. Philadelphia (PA): AACR; Cancer Res 2020;80(21 Suppl):Abstract nr PO-090.

AbstractThe mainstream approach to antiviral drugs against COVID‐19 is to focus on key stages of the SARS‐CoV‐2 life cycle. The vast majority of candidates under investigation are repurposed from agents of other indications. Understanding protein–inhibitor interactions at the molecular scale will provide crucial insights for drug discovery to stop this pandemic. In this article, we summarize and analyze the most recent structural data on several viral targets in the presence of promising inhibitors for COVID‐19 in the context of the perspective of modes of action (MOA) to unravel insightful mechanistic features with atomistic resolution. The targets include spike glycoprotein and various host proteases mediating the entry of the virus into the cells, viral chymotrypsin‐ and papain‐like proteases, and RNA‐dependent RNA polymerase. The main purpose of this review is to present detailed MOA analysis to inspire fresh ideas for both de novo drug design and optimization of known scaffolds to combat COVID‐19.

AbstractThe mainstream approach to antiviral drugs against COVID‐19 is to focus on key stages of the SARS‐CoV‐2 life cycle. The vast majority of candidates under investigation are repurposed from agents of other indications. Understanding protein–inhibitor interactions at the molecular scale will provide crucial insights for drug discovery to stop this pandemic. In this article, we summarize and analyze the most recent structural data on several viral targets in the presence of promising inhibitors for COVID‐19 in the context of the perspective of modes of action (MOA) to unravel insightful mechanistic features with atomistic resolution. The targets include spike glycoprotein and various host proteases mediating the entry of the virus into the cells, viral chymotrypsin‐ and papain‐like proteases, and RNA‐dependent RNA polymerase. The main purpose of this review is to present detailed MOA analysis to inspire fresh ideas for both de novo drug design and optimization of known scaffolds to combat COVID‐19.