Citations

Abstract Salvage combination therapy including radiotherapy and immunotherapy has been used to reduce tumor burden and tumor-related symptoms in patients with advanced cancer that is refractory to ICI monotherapy. Among those patients who experienced significant tumor regression in responses to combination therapy, we identified a rebound of effector CD8+ T cells with high cytotoxic capacity and metabolic fitness. We use the term T cell resilience to explain the rebound of cytotoxic CD8+ T cells in response to combination therapy and examine the underlying mechanisms of T cell resilience. Resilient T cells are enriched in CX3CR1+ CD8+ T cells with low mitochondrial membrane potential, accumulate less reactive oxygen species (ROS), and express more malic enzyme 1 (ME1). We found ME1 overexpression enhanced the cytotoxicity and expansion of effector CD8+ T cells partially via the type I interferon pathway. ME1 also increased mitochondrial respiration while maintaining the redox state balance. Importantly, ME1 increased the cytotoxicity of peripheral lymphocytes from patients with advanced cancers and improve the efficacy of tumor-infiltrating lymphocytes (TIL) therapy in animal models. Our results demonstrate the presence of resilient T cells in patients, suggest that T cell resiliency is attributed to their metabolic reprogram mediated by ME1, which is a new T cell-intrinsic therapeutic target for T cell-based immunotherapy. Citation Format: Haidong Dong, Joanina K Gicobi. Discovery of resilient T cells from patients in responses to combination immunotherapy and their metabolic features [abstract]. In: Proceedings of the AACR IO Conference: Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2025 Feb 23-26; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(2 Suppl):Abstract nr A061.

Abstract Addressing the limited responsiveness to immune checkpoint blockade (ICB) in human cancers remains a critical challenge. Efforts over the past two decades have primarily focused on enhancing CD8 T cell function and preventing their exhaustion. However, less attention has been given to understanding the molecular mechanisms that contribute to the immunosuppressive tumor microenvironment (TME), which impedes CD8 T cell infiltration and fosters ICB resistance. The TME in ICB-resistant tumors is characterized by Transforming Growth Factor beta (TGF-β) cytokine signaling, leading to a fibrotic extracellular matrix (ECM) and the accumulation of immunosuppressive fibroblasts and myeloid cells. These features hinder CD8 T cell penetration, thereby promoting immune escape. The immune checkpoint molecule B7-H3, overexpressed in ICB-resistant cancers, has been linked to impaired CD8 T cell infiltration and poor prognosis. However, the molecular mechanisms governing B7-H3 function remain poorly understood. We investigated the relationship between B7-H3 gene expression and ICB response using transcriptomic data from two randomized phase 3 trials (IMvigor010 and IMvigor210). Bulk RNAseq data, tissue staining, and spectral flow cytometry were used to characterize the TME composition of B7-H3 high and low tumors. Multi-omic profiling of tumor cell lines with manipulated B7-H3 expression was performed to identify downstream targets of B7-H3. Syngeneic mouse tumor models were used to assess the impact of B7-H3 on tumor growth and antitumor immunity. High B7-H3 expression was associated with shorter overall survival in both IMvigor010 (HR=0.48, 95% CI: 0.33-0.70, p<0.0001) and IMvigor210 trials (HR=0.68, 95% CI: 0.51-0.92, p=0.01). In ICB-refractory cancers, B7-H3 expression correlated with high levels of fibroblasts, collagen deposits, and M2 macrophages. Gene set enrichment analysis revealed a positive association between B7-H3 and TGF-β signaling. Genetic deletion of B7-H3 in tumor cells reduced the surface expression of MMP14, a metalloprotease that activates TGF-β. Pan-cancer analysis identified MMP14 as the gene most correlated with B7-H3 (Pearson r=0.69, p<0.0001). TGF-β activation was reduced by 70% in B7-H3 knockout cells compared to wild-type. Loss of B7-H3 led to MMP14 accumulation in lysosomes, resulting in its degradation. We generated a B7-H3 inhibitor, 5D10, which promotes MMP14 degradation and inhibits TGF-β activation. In humanized B7-H3 mouse models, 5D10 significantly reduced TGF-β activation, enhancing CD8 T cell infiltration and impairing tumor growth. Our research identifies B7-H3 as a driver of immune exclusion and ICB resistance. We describe a novel, receptor-independent mechanism where B7-H3 promotes TGF-β activation via stabilization of MMP14. Targeting B7-H3 represents a strategy to modulate the TME, transforming immune-excluded tumors into immune-inflamed states that may respond better to ICB. Citation Format: Fabrice Lucien, Roxane Lavoie, Jack Korleski, Yohan Kim, Bharath Wootla, Liguo Wang, Ava Farrell, Kelly Harper, Martine Charbonneau, Claire Dubois, Igor Frank, Sounak Gupta, John Cheville, Jacob Orme, Stephen Boorjian, Parash Shah, Eugene Kwon, Sean Park, Haidong Dong. The immune checkpoint molecule B7-H3 is a driver of tumor immune exclusion by mediating TGF-β activation [abstract]. In: Proceedings of the AACR IO Conference: Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2025 Feb 23-26; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(2 Suppl):Abstract nr B034.

Backgrounds and Aims: HBV-related liver disease ranks as the seventh leading cause of mortality. Despite advances in prevention and treatment, global disparities in the burden of primary liver cancer (PLC) persist. We evaluate global trends in the prevalence, incidence, and death of HBV-related liver disease. Approach and Results: Data from the Global Burden of Disease Study 2021 evaluated acute HBV infection, HBV-related cirrhosis, and HBV-related liver cancer prevalence, incidence, and death. In 2021, there were 7.30 million cases of acute HBV, 283.64 million cases of HBV-related cirrhosis, and 288,110 cases of HBV-related PLC. HBV-related PLC accounted for 39% of the global incidence of PLC; Western Pacific had the highest rates for HBV-related PLC, with an incidence of 5.24 and a death rate of 4.38 per 100,000 population. Between 2000 and 2021, age-standardized incidence, prevalence, and death rates from HBV-related liver disease decreased; however, the incidence of HBV-related PLC rose in 65 countries from 2000 to 2021. In parallel, age-standardized prevalent rates from HBV-related PLC increased in Europe (annual percent change: 0.77%, 95% CI: 0.72%–0.81%) and the Americas (annual percent change: 1.05%, 95% CI: 1.00%–1.10%). Conclusions: From 2000 to 2021, decreases in HBV-related liver disease incidence and prevalence were observed; however, more than one-third of countries showed an increase in the incidence of HBV-related PLC. These findings highlight the need for strengthened HBV treatment efforts to reduce the risk of liver cancer.

Background and Aims: Cholangiocarcinoma (CCA) is an aggressive malignancy arising from the biliary epithelium with limited therapeutic options and poor long-term survival rates. To address the limitations of CCA treatment, we investigated cell-targeted nanovesicles as a delivery platform for transcriptome-targeting therapeutics. Approach and Results: Milk-derived nanovesicles were loaded with short interfering RNAs targeting Yes-associated protein (YAP), the downstream effector of the Hippo pathway; LCK, an upstream regulator of YAP; and tafazzin, a protein critical for the integrity of the inner mitochondrial membrane. These transcriptome-targeting nanovesicles were decorated with a lipid-coupled RNA aptamer to epithelial cell adhesion molecule, including a tracking fluorophore. In vitro studies were conducted using multiple CCA cell lines. In vivo studies were performed using C57BL/6 and non-obese diabetic/severe combined immunodeficient mice to evaluate delivery and efficacy in both an immunocompetent syngeneic murine and a patient-derived xenograft model. We demonstrated that transcriptome-targeting nanovesicles were selectively taken up by liver tumor cells, which was augmented by the incorporation of a targeting aptamer, and that milk-derived nanovesicles loaded with short interfering RNA effectively downregulated target gene expression, both in vitro and in vivo. Downstream effects of target gene inhibition were observed, including downregulation of YAP-TEAD target genes and an increase in reactive oxygen species production at the mitochondrial level. Administration of transcriptome-targeting nanovesicles targeting YAP, LCK, and tafazzin inhibited CCA growth and further synergized with chemotherapy in 2 preclinical CCA models. Conclusions: Herein, we show that aptamer-directed, nanovesicle-mediated targeting of YAP, LCK, and tafazzin potentiates chemosensitivity in 2 CCA models when delivered using aptamer-guided milk-derived nanovesicles.

Background/Objectives: Stereotactic body radiation therapy (SBRT) for skull base reirradiation is particularly challenging, as patients have already received substantial radiation doses to the region, and nearby normal organs may have approached their tolerance limit from prior treatments. In this study, we reviewed the characteristics and capabilities of four advanced external beam radiation delivery systems and four modern treatment planning systems and evaluated the treatment plan quality of each technique using skull base reirradiation patient cases. Methods: SBRT plans were generated for sixteen skull base reirradiation patients using four modalities: the GK plan for the Elekta Leksell Gamma Knife Perfexion/ICON, the CyberKnife (CK) plan for the Accuray CyberKnife, the intensity-modulated proton therapy (IMPT) plan for the Hitachi ProBeat-FR proton therapy machine, and the volumetric-modulated arc therapy (VMAT) plan for the Varian TrueBeam STx. These plans were evaluated and compared using two novel gradient indices in addition to traditional dosimetry metrics for targets and organs at risk (OARs). The steepest border gradient quantified the percent prescription dose fall-off per millimeter at the boundary between the target and adjacent critical structures. This gradient index highlighted the system’s ability to spare nearby critical OARs. The volume gradient assessed the extent of dose spread outside the target toward the patient’s body. Results: All plans achieved comparable target coverage and conformity, while IMPT and VMAT demonstrated significantly better uniformity. The GK plans exhibited the highest border gradient, up to 20.9%/mm, followed by small-spot-size IMPT plans and CK plans. Additionally, IMPT plans showed the benefit of reduced dose spread in low-dose regions and the lowest maximum and mean doses to the brainstem and carotid artery. Conclusions: The advanced external beam radiotherapy modalities evaluated in this study are well-suited for SBRT in skull base reirradiation, which demands precise targeting of tumors with highly conformal doses and steep dose gradients to protect nearby normal structures.

Abstract Background: ASXL1 is one of the three most frequently mutated genes in age-related clonal hematopoiesis (CH), with the others being DNMT3A and TET2. CH frequently progresses to myeloid malignancies including chronic monomyelocytic leukemia (CMML), and is also strongly associated with inflammatory cardiovascular disease and all-cause mortality in humans. DNMT3A and TET2 regulate DNA methylation and demethylation pathways respectively, and loss-of-function mutations of both genes reduce DNA methylation in heterochromatin. In contrast, the mechanisms that connect mutant ASXL1 and CH are not yet fully understood. ASXL1 is a regulatory component of the ASXL1-BAP1 deubiquitinase complex, which removes ubiquitin from mono-ubiquitinated H2A lysine 119 (H2AK119Ub). Recurrent frameshift and nonsense ASXL1 mutations in CH and CMML generate C-terminally truncated proteins that improve BAP1 enzymatic activity. Methods: To relate ASXL1 mutations to CH, we performed the protein immunoprecipitation followed by a mass spectrum to identify proteins interacting with mutant ASXL1. Utilizing a heterozygous Asxl1 mutant knock-in mouse model to recapitulate ASXL1-driven clonal hematopoiesis, we characterized alterations in histone modifications within expanded myeloid populations using CUT&RUN, with Drosophila S2 cells as spike-ins for normalization. Differential gene expression and transposable elements (TEs) activity were quantified in ASXL1-mutant chronic myelomonocytic leukemia (CMML) patients using RNA sequencing (RNA-seq) to assess the broader impact of ASXL1 mutations on transcriptional regulation. Results: Here we show that ASXL1 mutant proteins interact with the EHMT1-EHMT2 methyltransferase complex, which generates H3K9me1 and me2, the latter a repressive modification in constitutive heterochromatin. Compared to cells from age-matched wildtype mice, we found that expanded myeloid cells from old Asxl1 mutant mice display genome-wide decreases of H3K9me2, H3K9me3 and H2AK119Ub as well as an associated increase in expression of transposable elements (TEs) and satellite repeats. Increased TE expression was also observed in monocytes from ASXL1-mutant CMML patients compared to monocytes from healthy controls. Our data suggest that mutant ASXL1 proteins compromise the integrity of both constitutive and facultative heterochromatin in an age-dependent manner, by reducing the levels of H3K9me2/3 and H2AK119Ub. This increase in TE expression correlated with increased expression of nearby genes, including many interferon-inducible (inflammation-associated) genes (ISGs). Conclusion: Our findings provide new insights into how ASXL1 gain-of-function mutations might contribute mechanistically to the progression of CH and myeloid malignancies in aging. We show that even heterozygous expression of truncated ASXL1 proteins can lead to reduced levels of heterochromatin-associated histone modifications, weakening heterochromatin integrity and promoting increased expression of transposable elements that are normally silenced in heterochromatin. Citation Format: Zhen Dong, Hugo Sepulveda, Leo Josue Arteaga Vazquez, Mrinal Patnaik, Samuel A Myers, Anjana Rao. A mutant ASXL1-EHMT complex contributes to heterochromatin dysfunction in clonal hematopoiesis and chronic monomyelocytic leukemia [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: DNA Methylation, Clonal Hematopoiesis, and Cancer; 2025 Feb 1-4; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2025;85(3 Suppl):Abstract nr B001.