Citations

Abstract Description CD8 T cell programming creates a pool of naïve, effector, memory, or exhausted subsets, however the regulation of these trajectories is not expansively elucidated and has serious implications for cancer immunity and immune checkpoint inhibitor (ICI) therapy. We found a significant decrease of Dual Specificity Phosphatase 2 (DUSP2) in CX3CR1+ CD8s, a highly resilient subset, from ICI responders. Thus, we hypothesized that DUSP2 negatively regulates CD8 T cells in responses to ICI therapy. DUSP2 knockdown (KD) statistically improved CD8 cytotoxicity and expression of NKG7, a vital effector molecule. DUSP2 KD also increased SMARCA4 expression, a BRG/BRM-associated factor (BAF) complex ATPase, and increased open chromatin regions of BAF components. BAF complexes are chromatin remodelers implicated in CD8 differentiation pathways. In line with this, we found CD8s from DUSP2 conditional knockout (cKO) mice demonstrated a trend in defective memory generation. DUSP2 cKO CD8s also trended towards decreased PD-1 and increased CX3CR1 expression, demonstrating a more effector like phenotype. DUSP2 cKO mice did not show a significant difference in tumor protection in-vivo, presumably due to skewing of CD8 fates via BAF. Promisingly, DUSP2 KD increased ex-vivo cytotoxic functionality in about 50 percent of tested cancer patient PBMCs. Adjuvant BAF inhibition with DUSP2 KO versus KD in a specific CD8 subset may enhance responses further, providing a novel avenue for improving ICI efficacy. Funding Sources Supported by NCI 1F31CA287495-01 Topic Categories Immune Response Regulation: Molecular Mechanisms (IRM)

Abstract Description Therapies targeting the PD-1/PD-L1 axis are among the leading treatments of cancer, but only a minority of patients benefit. Many therapies focus on preventing PD-L1 from binding to its receptor, PD-1, but do not address PD-L1’s ability to be recycled to the cell surface and any intrinsic functions it may possess. Our lab has developed an antibody (H1A) that binds to PD-L1 and prevents its association with a stabilizing protein, CMTM6, therefore targeting it for lysosomal degradation. Consequently, H1A limits any PD-L1 intrinsic function while also decreasing interactions with PD-1. Here, we use human-derived immune cells to test H1A’s effect on immune responses through flow cytometry, multiplex screening, and cytotoxicity assays. Additionally, we have developed a humanized PD-1/PD-L1 mouse model that allows us to test H1A’s effect on tumor growth inhibition in an immunocompetent host. Our results show that H1A specifically targets human myeloid cells, resulting in increased co-stimulation, antigen presentation, and cytokine secretion. H1A demonstrated enhanced T cell cytotoxicity in a whole PBMC culture. Finally, H1A resulted in greater tumor growth inhibition and survival in our in vivo tumor models. This work highlights the importance of targeting beyond PD-1/PD-L1 ligation and that myeloid cells are instrumental to enhancing the immune response against cancer. H1A is emerging as a new immunotherapy tool to target PD-L1 and CMTM6 in myeloid cells for treatment of cancers. Funding Sources NIH R01 92389022; NIH T32 AI170478; Mayo Clinic Graduate School of Biomedical Sciences Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)

Abstract Description Weakened germinal center responses by the aged immune system result in diminished immunity against pathogens and reduced efficacy of vaccines. Prolonged contacts between activated B cells and CD4+ T cells are crucial to germinal center formation and Tfh differentiation, but it is unclear how aging impacts the quality of this interaction. Peptide immunization confirmed that aged mice have decreased expansion of antigen-specific GC B cells and reduced antibody titers. Aging was associated with accumulated Tfh cells with reduced BCL6 and increased CD39. When activated in vitro by aged antigen-presenting cells, young CD4+ naïve T cells generated reduced numbers of activated cells with upregulated CD40L. To determine the contribution of cell-extrinsic influences on antigen-specific Tfh induction, young, antigen-specific B and CD4+ T cells were transferred into aged hosts prior to immunization. Transferred cells had reduced expansion and differentiation into germinal center B cell and Tfh and reduced antigen-specific antibody titers when compared to young hosts. Young CD4+ T cells transferred into aged hosts differentiated into Tfh cells with reduced PD-1 and BCL6, and increased CD39. Recent studies have focused on immune profiling of CD4 T cells in young and aged mice following immunization. These results highlight the role of the lymphoid microenvironment in modulating CD4+ T cell differentiation, which contributes to impaired initiation and maintenance of germinal centers. Funding Sources Research was supported by NIH/NIA R01 AG080037 and the Mayo Clinic Robert and Arlene Kogod Center on Aging Innovation Award UL1R002377 to J.L. Topic Categories Vaccines and Immunotherapy (VAC)

Abstract Description A durable T cell immunity against cancer is dependent on a continually refilling of effector CD8+ T cells. Thymic output has been correlated with favorable prognosis in cancer patients of advanced ages, suggesting thymus is an important source for refilling T cells that are capable of controlling cancer progression in the periphery. However, it remains unclear how PD-1 signals regulate the cytotoxic potential of CD8+ T cells in thymus before they egress to the periphery to establish durable anti-tumor immunity. Here we report PD-1 signaling prelimits thymic single positive (SP) CD8+ T cells to acquire cytotoxic potential by downregulating Gzmb and Nkg7, which are required for CD8+ T cell-mediated cytotoxicity. Unexpectedly, we found the absence of Pdcd1 also led to upregulation of Tox and Tim3 in thymic SP CD8+ T cells, thereby pre-programming these cells for exhaustion within the tumor. Thus, the absence of PD-1 signals in CD8+ T cells only partially delayed tumor growth in peripheral tissues. To improve therapeutic effects of PD-1 inhibition, we observed that tumor growth in CD8-specific Pdcd1 conditional knockout mice was further suppressed by treatment with a PD-L1 antibody that blocks PD-L1 and CD80 interaction. Our results imply that PD-1 inhibition promotes the expansion of effector cytotoxic CD8+ T cells but also retains T cell exhaustion potential, which can be mitigated by PD-L1 blockade that allows more CD80 to provide costimulatory signals to T cells via CD28. Funding Sources NCI R01CA256927 NCI R01CA261932 NCI P30CA15083 Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)

Abstract Description Background Castration-resistant prostate cancers (CRPC) do not respond to immunotherapy.1,2 Prostate cancer-derived immune factors (IF) like sPD-L1 drive immunosuppression and resistance.3 Circulating tumor-reactive T cells (TTR; CD8+CD11ahigh) and other immune subsets predict progression-free survival in oligometastatic CRPC after radiotherapy.4 A better understanding of the levels and changes in IF in CRPC—a tumor immune “circulome”—may lead to better immunotherapeutic approaches. Methods 79 men with oligometastatic castration-resistant prostate cancer were treated with radiation and blood was collected before and after treatment (NCT02816983). Peripheral blood mononuclear cells (PBMC) were subjected to immunophenotyping, and plasma was subjected to the Olink Explore panel assay measuring levels of 5,416 IFs using a proximity extension assay technology. Results High baseline soluble levels of PD-L1, PD-L2, TIM-3, and other selected immunotherapy-related IFs predicted inferior outcomes, including overall survival. Conversely, high soluble CTLA-4 levels strongly predicted superior outcomes (p < 0.0001). These results additionally correlated with changes in circulating tumor-reactive (TTR) T cells in these patients. Discussion IF influence systemic immunity in CRPC. These results suggest a multifactorial mechanism by which prostate cancers drive systemic immunosuppression and resistance to immunotherapy. Ongoing efforts to address IFs may help overcome CRPC immunotherapy resistance.5 Funding Sources Department of Defense HT9425-24-1-0622, An Atlas of the Tumor Immune Circulome (PI: Orme) Prostate Cancer Foundation Young Investigator Award (PI: Orme) National Cancer Institute K12 CA90628-23 (PI: Orme) Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)

Abstract Description The efficacy of ICI and T cell-based therapies is dependent on sufficient killing of tumor cells by T cells. Thus, it’s critical for effector T cells to maintain their function and overcome metabolic stress within the tumor microenvironment. Our previous work in human resilient CD8+ T cells identified malic enzyme 1 (ME1) as a key enzyme that augments effector CD8+ T cells’ metabolic and functional fitness via increased ATP production and curbed ROS production. To further study ME1’s role in promoting CD8+ T cell resilience in vivo, we produced CD8-specific ME1 conditional knockout and transgenic (ME1 Tg) mouse models. In MC38, ME1 was upregulated in CD8+ T cells in TILs compared to those in spleen and ME1 loss in CD8+ T cells abrogated tumor responses to ICI. In ME1 Tg mice, MC38 had reduced tumor growth, while B16F10 tumors were sensitized to ICI. We observed lower ROS and increased lipid content in CD8+ T cells in the TILs of ME1 Tg mice, underscoring ME1’s role in activating alternative metabolic pathways to fuel mitochondrial respiration while keeping ROS in check. The association of ME1 with 6PGD, a key enzyme in the pentose phosphate pathway (PPP), implies its regulation of redox homeostasis in CD8+ T cells. Importantly, ME1 overexpression in TILs dramatically improved the efficacy of TIL therapy in treatment of established tumors. Overall, ME1 upholds T cell resilience in tumor tissues and provides a new therapeutic target to improve the efficacy of TIL therapy. Funding Sources This work was supported by the Mayo Clinic Center for Biomedical Discovery (to H.D.); the Mayo Clinic Cancer Center’s David F. and Margaret T. Grohne Cancer Immunology and Immunotherapy program (to H.D.); R01 AI095239 (to H.D.), R01 CA200551 (to H.D. and S.S.P.), and R01 CA256927 (to H.D.). Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)

Abstract IDH-wildtype diffuse astrocytic gliomas with lower-grade histological features alongside specific genomic alterations (e.g., TERT promoter mutation, EGFR amplification, gain Chr7/loss Chr10) are presently diagnosed as glioblastoma, IDH-wildtype (GBM) under WHO 2021 criteria. Previous analyses categorized these into “early/evolving” or “surgically undersampled” GBMs. However, it remains unclear whether these tumors share identical clinical and prognostic features with histologic GBM. Data from IDH-wt molecular GBMs across six institutions were aggregated. Astrocytic IDH-wt tumors of any grade that lacked necrosis or microvascular proliferation on initial histopathology yet exhibited molecular alterations consistent with WHO 2021 GBM diagnosis, were included. Recursive partitioning analysis (RPA) was used to categorize patients into risk groups based on overall survival (OS). Among the 264 patients included, the median age was 60 years (IQR: 51-67), with 162 (61%) being male. Additionally, 210 (80%) were diagnosed since 2016, and 216 (82%) received chemoradiation plus adjuvant temozolomide (GBM-SOC). The median follow-up period was 3.9 years (95% CI: 3.4, 4.6). Identified univariate risk factors for worse survival included older age, biopsy-only status, EGFR amplification, absence of initial adjuvant treatment, low post-operative KPS, and tumor histologic grade of 3. RPA divided patients into four distinct survival groups (p<0.0001). The “best” risk group comprised lower grade (<=2) tumors (n=58, median OS (mOS): 40 months (95% CI: 33, NA)). The “second best” group included Grade 3 patients receiving GBM-SOC without steroids during initial RT (n=139, mOS: 25 months (95% CI: 22, 28)). The “second worst” group encompassed Grade 3 patients who were on steroids during initial RT while receiving GBM-SOC (n=38, mOS: 15 months (95% CI: 13, 20)). The “worst” group contained Grade 3 tumors that had not undergone SOC (n=29, mOS: 9 months (95% CI: 4, 26)). These data show that histologic features and treatment are strong indicators of patient outcomes.

Abstract Pontine H3 K27-altered diffuse midline gliomas (DMGs) are rare, fatal pediatric brain tumors resistant to systemic therapies due to the blood-brain barrier (BBB) and efflux transporters (ETs), which actively clear drugs from the brain. Convection-enhanced delivery (CED) bypasses the BBB by directly infusing therapeutics into the tumor, but maintaining adequate drug concentrations remains a challenge. This study explores strategies to enhance drug-tumor residence time and improve treatment efficacy. Using chemical modeling, FDA-approved drugs identified in prior high-throughput screening efforts were classified based on physiochemical properties impacting CED pharmacokinetics, including BBB penetration and ET substrate status. Drug behavior was validated in patient-derived in vitro and in vivo DMG models. The impact of systemic drug co-administration on drug retention and therapeutic efficacy was evaluated using multiple patient-derived orthotopic xenograft (PDOX) models. ET substrate drugs exhibited rapid elimination from the brain post-CED, limiting their therapeutic potential. However, systemic everolimus administration prolonged drug retention and potentiated the effects of efflux substrate drugs delivered via CED (e.g., topotecan, ponatinib). This combinatorial approach significantly enhanced anticancer effects in multiple PDOX models, demonstrating improved tumor control compared to monotherapy. Overall, these findings suggest that pharmacological inhibition of ETs via systemic everolimus administration can enhance drug retention in DMG when combined with CED. The observed synergistic effects highlight a promising strategy to overcome drug clearance limitations and improve treatment outcomes. Further clinical investigation is warranted to validate this approach in patients.

Abstract WSD0922-Fu is an oral, CNS-penetrant, small molecule EGFR inhibitor which potently inhibits EGFR aberrations specific to non-small cell lung cancer (NSCLC) and glioblastoma (GBM). MC1914 (NCT04197934) is a first-in-human phase 1 trial in patients with EGFR aberrant recurrent GBM and NSCLC. After determining the maximum tolerated dose, adults with recurrent GBM were treated in two expansion cohorts: (a) non-surgical cohort (6/12 patients thus far): EGFRvIII mutation, first recurrence; food-effect study included (b) surgical cohort (6/6 patients), any EGFR mutation, any recurrence; window-of-opportunity study (WOO) included. Among these 12 patients, median age = 60 years; 50% female; 58% ECOG 0). All patients received prior radiation and temozolomide. After the WOO or food-effect study, patients were dosed at 120 mg BID (5 days on, 2 days off), and escalated to 160 mg BID (5 days on, 2 days off) based on tolerability. Common adverse events (>40%) are comparable to other EGFR inhibitors (acneiform rash, diarrhea, fatigue, xerosis, pruritis). Treatment-related grade 3+ adverse events were limited to lymphopenia (n = 1). WSD0922-Fu exposure in the fed state exceeded the fasted state (median plasma Cmax and AUC0-24h are 1.6x and 1.3x, respectively) with a delayed Tmax (6.0 vs 1.8 hours). For the WOO, time between last dose administered to tumor collection ranged between 4 - 13.5 hours. Median tumor WSD0922-Fu concentration was 0.76 µg/g; estimated median unbound tumor concentration was 24.9 ng/g and within expectations for pharmacodynamic effect. Median brain/plasma ratio = 0.59; median unbound brain/unbound plasma = 0.88. Enrollment to the non-surgical cohort is ongoing, so formal efficacy data remain immature. However, examples of clinical efficacy will be shown along with data on recurrence patterns. Phase 2 clinical trial development is in progress.

Abstract Background and Aims Patients with catecholaminergic polymorphic ventricular tachycardia (CPVT) are at risk for potentially life-threatening arrhythmic events (AEs) even while treated with β-blockers. The aim was to develop a model for individualized prediction of AEs in patients with RYR2-mediated CPVT on β-blocker monotherapy. Methods The derivation and independent validation cohorts included 743 and 129 patients, respectively. AEs were defined as arrhythmic syncope, appropriate implantable cardioverter–defibrillator shock, sudden cardiac arrest (SCA), and sudden cardiac death. Near-fatal or fatal AEs (nf/fAEs) included all AEs except for arrhythmic syncope. Prediction models using Cox regression were developed and internally and externally validated. Results A total of 102 (13.7%) patients in the derivation cohort and 24 (18.6%) patients in the validation cohort experienced ≥1 AE over a median follow-up of 5.1 [interquartile range (IQR), 7.7] and 2.4 (IQR, 4.4) years, respectively. Predictors of AE were arrhythmic syncope or SCA prior to diagnosis and age at β-blocker initiation. In the derivation and validation cohorts, the optimism-corrected C-indices of the models for AE were 0.67 [95% confidence interval (CI) 0.62–0.72] and 0.59 (95% CI 0.48–0.71), respectively. For nf/fAEs, ventricular arrhythmia severity before β-blocker initiation was a fourth independent predictor, and C-indices of the models in the derivation and validation cohorts were 0.74 (95% CI 0.68–0.80) and 0.60 (95% CI 0.47–0.72), respectively. In the derivation cohort, calibration slopes were 1.00 (95% CI 0.59–1.41) for AE and 1.00 (95% CI 0.69–1.32) for nf/fAE. Conclusions These externally validated risk prediction models using clinical parameters accurately distinguished CPVT patients on β-blocker monotherapy at low and high risk for future AEs while treated with β-blockers. These models provide guidance for implementation of clinical management therapies to prevent AEs in patients with CPVT.