Citations

Abstract Chimeric antigen receptor (CAR) T-cell therapy has emerged as a transformative treatment for hematological malignancies, yet its potential to drive lymphomagenesis poses significant clinical concerns. In this study, we investigated the mechanisms underlying CAR T-cell–associated lymphomagenesis in the gastrointestinal (GI) tract on a single case, focusing specifically on the role of integrin α4β7 expression and a predisposing somatic SH2B3 mutation. We observed oligoclonal CAR T cells homing to, and clonally expanding in, the GI tract, with the dominant expanded clone harboring both a pathogenic SH2B3 mutation and a CAR transgene integration within a TFCP2 locus. The clonal CAR T cells subsequently transitioned beyond the GI tract into the peripheral blood, suggesting a potential pathway for systemic dissemination. We found clinical, histological, and molecular evidence demonstrating the efficacy of cyclosporine in reducing the expanded malignant clone and achieving durable clinical remission for more than a year. Our findings highlight the complex interplay between CAR T-cell therapy, preexisting genetic vulnerabilities, and the GI microenvironment, emphasizing the need for vigilant monitoring and tailored therapeutic strategies to address the risks associated with CAR T-cell lymphomagenesis.

Abstract Description In the tumor microenvironment of glioblastoma, myeloid cells act as a double-edged sword—they are a major cellular component suppressing the immune response while serving as a promising therapeutic target. Our study sheds light on the voltage-gated proton channel Hv1, predominantly expressed in myeloid cells, as a pivotal regulator of their physiological functions. Elevated Hv1 expression correlates strongly with poor prognosis in glioblastoma patients, underscoring its clinical significance. Using a glioma mouse model, we demonstrated that Hv1 depletion markedly extended survival. To overcome the limitations of existing tools, we engineered novel transgenic mouse lines optimized for Hv1 research. Our findings revealed tumor-induced Hv1 upregulation, with glioma-associated macrophages identified as the principal contributors. Crucially, we identified that Hv1 in infiltrating macrophages as the major driver of survival phenotype differences. Through a multi-faceted approach combining in vivo two-photon imaging, spectral flow cytometry, and spatial transcriptomic sequencing, we discovered that Hv1 depletion limits macrophage infiltration and enhances antigen presentation, ultimately fostering a stronger adaptive immune response. These findings establish the Hv1 channel as a crucial new immune regulator within the brain tumor milieu, offering a promising target for reprogramming macrophage function to combat glioblastoma. Funding Sources Supported by NIH R35NS132326 (LJW); Mayo Clinic Cancer Center and Mayo Clinic Center for Biomedical Discovery. Topic Categories Neuroimmunology (NEUR)

Abstract Description Sequencing antigen-specific T cell receptors (TCR) remains a major technologic challenge, requiring labor- and cost-intensive single-cell approaches. We have developed a rapid and economical method for sequencing TCR mRNA from antigen stimulated peripheral blood mononuclear cells using targeted long-read nanopore sequencing with Oxford Nanopore Technologies’ (ONT) Minion sequencer. Targeted PCR amplification of TCR alpha and beta cDNA was performed with a template switching oligo (TSO). Dual unique molecular identifiers (UMI) were used for single cell, oligoclonal, or bulk cell sample specific sequence identification followed by nanopore sequencing. The reads were demultiplexed by UMIs and aligned to germline V,D, and J gene sequences from the IMGT database for identification. Error corrected sequences were then used to determine the non-templated complementarity determining region 3 (CDR3) sequence for the TCRs. From bulk PBMCs, TCR Beta Chain had 796 unique TRBV-TRBJ combination and TCR Alpha Chain had 2053 unique TRAV-TRAJ combinations. Human PBMC samples were spiked with 10% Jurkat cells and sequenced using this method for 12 hours resulting in 200K reads. After read demultiplexing, filtering (Q > 25), and alignment, it was found that 8.8% of TCR beta and 7.0% TCR alpha reads matched the Jurkat TCR sequence in the 10% spiked sample. This method provides a fast and cost-effective approach to generating antigen specific TCR sequences for downstream functional studies. Funding Sources Supported by NIH/NCI 5U01CA281660 Topic Categories Technological Innovations in Immunology (TECH)

Background: Achieving active elbow flexion in children with amyoplasia can greatly improve independence in activities of daily living. This study investigated long-term outcomes of the long head triceps transfer procedure performed for that purpose. Methods: A retrospective review of medical records was performed for all patients with amyoplasia who underwent a long head triceps transfer between January 1, 2008 and December 31, 2019. Patients with follow-up of less than 2 years were excluded. Pre- and postoperative range of motion were recorded, and patient-reported outcome measures included a visual analog scale (VAS) for function (scale 0 to 10), a VAS for overall satisfaction (scale 0 to 10), and the Pediatric Outcomes Data Collection Instrument (PODCI). Pre- and postoperative motion were compared via paired t tests. Results: Seventeen patients (25 extremities) were included. Postoperatively, average active elbow flexion was 78 degrees against gravity and 90 degrees with gravity eliminated. Patients with active elevation of the shoulder ≥90 degrees showed average active elbow flexion with gravity eliminated of 85 degrees. The mean VAS score for improvement of function was 8.3 (range, 4 to 10) from parents and 9.0 (range, 8 to 10) from patients older than 10 years. The mean VAS scores for overall satisfaction were 8.0 (range, 5 to 10) and 8.1 (range, 6 to 10), respectively. Mean PODCI scores ranged from 63 to 73 for upper extremity, 83 to 76 for transfer and basic mobility, 64 to 73 for sports participation, 83 to 95 for pain and comfort, 90 to 97 for happiness, and 74 to 79 for global function. Conclusions: The long head of the triceps transfer is an effective treatment modality for patients with amyoplasia who present with absent active elbow flexion, good passive elbow flexion, and well-defined long head and lateral heads of the triceps muscle. Overall, patients gained an active range of elbow motion with no significant functional elbow contracture and improved quality of life. However, patients with a history of elbow release surgery are at higher risk of flexion contracture and should be screened especially carefully. Level of Evidence: Level IV—case series

We sought to characterize the long-term patency of various graft types in patients undergoing coronary artery bypass grafting. A comprehensive literature search identified 139 studies including 56,827 patients who underwent isolated coronary artery bypass grafting surgery. The mean patient age was 62 years (95% confidence interval: 60–63), and 80% (95% confidence interval: 79–82) were male. Patency outcomes were analyzed for each graft type, and parametric extrapolation was performed based on mean patency and mean follow-up time per conduit. The left internal mammary artery (LIMA) demonstrated the highest mean patency at 96% with a mean follow-up of 3.2 years, followed by the right internal mammary artery (RIMA) at 94% (2.8 years), gastroepiploic artery (GEA) at 93% (1.7 years), and radial artery (RA) at 89% (3.7 years). The saphenous vein graft had the lowest mean patency at 82% with a mean follow-up of 3.5 years. Extrapolated 20-year patency rates were 77% for LIMA, 64% for RIMA, 54% for RA, 42% for GEA, and 33% for saphenous vein graft. Arterial grafts demonstrated superior long-term patency compared to vein grafts. LIMA remains the primary conduit of choice, while RIMA, followed by RA and GEA, may be appropriate secondary arterial conduits depending on patient-specific factors. Vein grafts had the poorest long-term patency.

Abstract Triggering receptor expressed on myeloid cells 2 (TREM2) is a critical modulator of phagocytosis, inflammation, and survival for microglia and other macrophages. In neurodegenerative disorders, microglia expressing TREM2 play a protective role at distinct phases of disease progression, enabling uptake of toxic protein aggregates and dead neurons. TREM2 is also highly expressed on tumor-associated macrophages in a variety of cancers, promoting an immunosuppressive microenvironment. We and others have previously investigated the role of TREM2 in gliomas with confounding results, suggesting TREM2 could be pro-tumorigenic or anti-tumorigenic depending on experimental context (Peshoff, et al. Neuro Oncol. and Zheng, et al. Neuro Oncol.) In this study, we aim to resolve these findings by investigating the role of TREM2 across progression of gliomas with unique genetic drivers using immunocompetent mouse models. We employ syngeneic glioma stem cell lines generated via retroviral vectors expressing a dominant negative p53 along with amplification of human PDGFB or oncogenic HRAS G12V to model proneural and mesenchymal glioblastomas, respectfully. In contrast to our previous results demonstrating enhanced GL261 and CT2A growth in Trem2-/- mice, we demonstrate that Trem2 deficiency results in decreased tumor volume and improved survival when mice are challenged with Ras-driven, but not PDGFB-driven, gliomas. Furthermore, Trem2-/- mice display a more immunostimulatory microenvironment with increased T cell infiltration to mesenchymal-like tumors. We employ an in vitro co-culture system of primary mouse microglia with glioma stem cells to understand how microglia sense and respond to different genetic subtypes. We find that TREM2-mediated processes including microglial phagocytosis, chemotaxis, and survival are impacted by glioma genetic drivers. Together, these results indicate discrepancies in the literature regarding the function of TREM2 in gliomas may be explained by tumor genetics behind the cell lines used, which can provide a framework for understanding subtypes of gliomas that could respond to TREM2-modulating therapy.

Abstract BACKGROUND Mirdametinib is the first FDA-approved MEK1/2 inhibitor for both adults and children ≥2 years with NF1 who have symptomatic PN not amenable to complete resection. We report results from the phase 2b ReNeu trial (NCT03962543), including the LTFU. METHODS In ReNeu, mirdametinib was administered in 3-weeks-on/1-week-off 28-day cycles. Following the 24-cycle treatment phase, patients could continue mirdametinib in an optional LTFU. We report results through June 12, 2024, approximately 9 months from the previous data cutoff. RESULTS Fifty-eight adults and 56 children received mirdametinib. Median (range) duration of treatment was 21.8 (0.4, 54.4) months in adults and 25.4 (1.6, 48.5) months in children. Among LTFU-eligible patients, 26/31 (84%) adults and 32/37 (86%) children entered LTFU. Confirmed objective response rate (ORR, treatment+LTFU phases) was 47% (27/58; 95%CI, 33%, 60%) in adults and 55% (31/56; 95%CI, 42%, 69%) in children. Among confirmed responders, 18 adults and 19 children achieved a deep response (best target PN volume reduction from baseline of >50%). Median (range) best percentage change from baseline in target PN volume was –41% (–90%, 13%) in adults and –43% (–98%, 48%) in children. Median duration of response (DoR) was not reached for either age cohort. Treatment-related adverse events (TRAEs) in ≥25% of patients were dermatitis acneiform, diarrhea, nausea, and vomiting in adults; and diarrhea, dermatitis acneiform, and paronychia in children. Grade ≥3 TRAEs occurred in 17% of adults and 25% of children. Dose interruptions, dose reductions, and discontinuations due to TRAEs occurred in 9%, 17%, and 22%, respectively, of adults, and 14%, 14%, and 9%, respectively, of children. CONCLUSIONS Improved confirmed ORR was observed with longer duration of mirdametinib, with additional deep responses achieved in both adults and children. Mirdametinib continued to be well tolerated with a manageable safety profile and no new safety signals in the LTFU.

Abstract Aberrant vasculature is a hallmark of glioblastoma (GBM), contributing to both blood–brain barrier (BBB) dysfunction and frequent intracranial hemorrhage. Myeloid cells, including microglia and macrophages, are known to co-opt tumor vasculature during tumor progression, but the nature and consequences of their physical interactions with blood vessels require clearer definition. To address this, we characterize vessel-associated myeloid cells in murine gliomas with high spatial and temporal resolution, leveraging in vivo two-photon imaging, MRI, and transgenic mouse lines. To investigate the role of microglia in glioma vasculature, we pretreated glioma-bearing mice with CSF1R inhibitors (PLX3397 & PLX5622) to ablate microglia prior to tumor inoculation. Strikingly, over half of the microglia-depleted mice developed acute, lethal paralysis between days 11–15, whereas control tumor-bearing mice remained asymptomatic. MRI revealed extensive intracranial hemorrhage and edema, and two-photon imaging showed nodular, abnormal vasculature. This vascular dysfunction led to a dramatic reduction in median survival—from 30 days in control glioma-bearing mice to 15 days in PLX-treated mice with gliomas. To identify the protective microglial population involved, we examined vascular–myeloid interactions. We found that the peritumoral region harbored dense capillary networks supporting tumor expansion, along with a marked increase in myeloid cells with somas directly contacting blood vessels. Using TMEM119CreER/+:R26tdTomato/+ mice, we confirmed these vessel-associated cells as brain-resident microglia, not infiltrating macrophages. Quantitatively, ~60% of peritumoral microglia were vessel-associated, compared to ~30% in naïve or contralateral hemispheres. These microglia displayed elongated somata and processes aligned with vessels or wrapping around vessels, which is a phenotype also observed following single-vessel photothrombosis, suggesting a response to impaired blood flow and BBB leakage. Our findings uncover a critical neurovascular role for vessel-associated microglia in maintaining vascular integrity during glioma progression and highlight the importance of preserving, reprogramming, and further investigating this population in GBM therapies.