Research Article
Abstract
Medulloblastoma (MB) is the most common malignant pediatric brain tumor. Current therapies are associated with substantial morbidity, and prognosis remains poor in high-risk subgroups, particularly those with TP53 mutations or relapsed disease. Cellular senescence is a tumor-suppressive program implicated in MB, but its role in antitumor immunity remains incompletely understood. We found that protein phosphatase 2A (PP2A) regulated immunogenic senescence in MB. Genetic ablation of the PP2A catalytic subunit PP2Ac or depletion of the regulatory subunit PP2A-B56α induced senescence in MB models. PP2Ac-deficient senescent cells exhibited increased MHC class I expression and enhanced immunogenicity. In syngeneic orthotopic models, PP2Ac loss prolonged survival in an immune- and CD8+ T cell–dependent manner. Analysis of patient datasets showed that senescence-associated gene signatures correlated with improved survival. Single-cell transcriptomic analysis further revealed that senescent MB cells were heterogeneous and that reduced PP2A activity was associated with an immunogenic senescence state. Because the PP2A inhibitor LB-100 has limited potency and off-target effects, we developed a lipid nanoparticle (LNP) platform to deliver siRNA targeting PPP2CA. LNP–small-interfering PP2Ac efficiently silenced PP2Ac in vitro and, when delivered locally in vivo, prolonged survival in a CD8+ T cell–dependent manner. Together, these findings identify PP2A as a regulator of immunogenic senescence in MB and support PP2Ac targeting as a therapeutic strategy.
Authors
Winson S. Ho, Isha Mondal, Jingjing Liu, Raymond Sun, Jiawei Huo, Chao Gao, Oishika Das, Daren Tieu, Jingqi Sun, Hanchen Lin, Peng Zhang, Jiyang Yu, Rongze Olivia Lu
Abstract
Gene therapy–based biological pacemakers have been proposed as an alternative to their hardware-based counterparts. In this context, short-term ectopic expression of the T-box transcription factor 18 (TBX18) in the ventricle has been reported to generate potent, short-term pacemaker function in various animal models. Here, we investigated the impact of adeno-associated virus–mediated (AAV-mediated), long-term expression of TBX18 and compared the outcomes with those of the pacemaker ion channel hyperpolarization-activated cyclic nucleotide-gated potassium and sodium channel 2 (Hcn2). Our findings revealed that CMV-driven ectopic TBX18 expression in mouse hearts led to severe cardiac fibrosis. At lower, nonfibrogenic levels, TBX18 maintained its transcriptional function but failed to induce pacemaker phenotypes. TBX18-expressing cells showed suppressed expression of key working myocardial genes, but the pacemaker gene program was not induced. Electrophysiological studies showed abnormal automaticity in TBX18-expressing cells, combined with prolonged repolarization and various current changes. However, no hyperpolarization-activated funny current was detected. In a complete atrioventricular block rat model, AAV-mediated Hcn2 expression induced robust ectopic pacemaker activity in the presence of isoproterenol, whereas TBX18 expression neither generated such activity nor augmented Hcn2-mediated pacing. In conclusion, at functionally nonfibrogenic levels, TBX18 is neither sufficient nor necessary to induce pacemaker activity. In contrast, Hcn2 generates reliable pacing, making it a more viable candidate for biological pacemaker development.
Authors
Jianan Wang, Mathilde R. Rivaud, Mischa Klerk, Arie R. Boender, Ruud N. Visser, Rinske Sparrius, Hee Young Lee, Karel van Duijvenboden, Huiling Zhou, Yuting Yang, Emiel J.M. Kramer, Kyung Ho Park, Larry C. Park, Silke Schrödel, Christian Thirion, Eric Ehrke-Schulz, Anja Ehrhardt, Osne F. Kirzner, Klaus Neef, Hanno L. Tan, Arie O. Verkerk, Vincent M. Christoffels, Gerard J.J. Boink
Abstract
Tregs expressing forkhead box P3 (FOXP3) play crucial roles in maintaining immune tolerance and tissue integrity. EZH2, a histone H3 lysine 27 (H3K27) methyltransferase, is known as a key regulator of Treg identity and suppressive function upon activation. Here, we demonstrate that the H3K27 lysine demethylase KDM6B, which catalyzes the opposing reaction to EZH2, is also required for Treg identity and function after activation. Treg-specific deletion of Kdm6b impaired tissue Treg fate and function. KDM6B was upregulated after T cell antigen receptor signaling in Tregs and contributed to the regulation of Treg-associated gene expression through both direct and indirect mechanisms. A subset of Treg functional genes were direct targets of KDM6B and were co-occupied by FOXP3 at cis-regulatory regions, where KDM6B recruitment limited H3K27me3 accumulation. More broadly, KDM6B-dependent H3K27 demethylation facilitated Treg gene expression programs that supported tissue Treg homeostasis.
Authors
Minghong He, Beisi Xu, Pria G. Bose, Morgan J. McCullough, Rani S. Sellers, Xinying Zong, Wenjie Qi, Brianna L. Banten, Miriya K. Tune, Matthew P. Zimmerman, Genevieve Mullins, Brian C. Miller, J. Justin Milner, Jason K. Whitmire, Ageliki Tsagaratou, Karl B. Shpargel, Claire M. Doerschuk, Yong-Dong Wang, Jacob A. Steele, Shondra M. Pruett-Miller, Yongqiang Feng, Jason R. Mock
Abstract
We previously identified a muscular dystrophy caused by biallelic variants in JAGGED2 (JAG2), whose protein product, JAG2, is a canonical NOTCH ligand. However, the disease mechanism remains unclear, particularly with respect to muscle stem cell (muscle satellite cell/MuSC) function and muscle regeneration. We examined the consequences of JAG2 deficiency and modeled pathogenic JAG2 variants in vitro and in vivo, the latter in mouse and fly models and with particular attention to the MuSC–muscle endothelial cell (MuEC) niche. We found that both Jag2 deficiency and overexpression of pathogenic JAG2 variants impaired NOTCH signaling and myogenic self-renewal and differentiation. Hypomorphic Jag2 mutant (Jag2sm) mice displayed depleted MuSCs, corresponding with impaired muscle regeneration in those mice. Coculture experiments and the examination of cell type–specific Jag2 conditional knockout mice demonstrated that MuEC-specific Jag2 knockout resulted in reduced MuSC self-renewal, while MuSC-specific Jag2 knockout resulted in reduced myogenic differentiation. Human reference JAG2, but not human pathogenic variants of JAG2, rescued the deficiency of Serrate, the Drosophila ortholog of JAG2. Therefore, pathogenic variants in JAG2 impair muscle development and regeneration through disrupted cell-autonomous cis-inhibition and nonautonomous trans-activation involving NOTCH signaling dysfunction. Our findings indicate that optimizing JAG2-mediated NOTCH signaling is a potential therapeutic approach for JAG2-related muscular dystrophy.
Authors
Minoru Tanaka, Nam Chul Kim, Isabelle Draper, Hannah R. Littel, Mekala Gunasekaran, Johnnie Turner, Natalya M. Wells, Qasim Mujteba, Yoko Asakura, Peter B. Kang, Atsushi Asakura
Abstract
Cancers reflect aberrant growth and differentiation of normal cell populations. Biological understanding of small intestine neuroendocrine tumors (SI-NETs) is hampered because their closest normal counterparts, enteroendocrine cells (EECs), constitute tiny fractions of intestinal epithelium. Recent characterization of adult human EEC ontogeny from intestinal stem cells can help overcome that limitation. Transient expression of the transcription factor gene ASCL1 normally ensures proper timing and fidelity of well-differentiated EECs, which express NEUROD1. Here, we report that SI-NETs resembled mature enterochromaffin cells; however, individual tumor cells coexpressed stem/progenitor genes, harboring each differentiation state along the EEC trajectory except ASCL1+ precursors. We found that enhancers normally active, and others inactive, during EEC differentiation underlie aberrant SI-NET gene activity. SI-NETs uniformly expressed NEUROD1 but lacked ASCL1, owing to inaccessible chromatin and repressive H3K27me3 marking at the ASCL1 locus. Multiple cyclin-dependent kinase inhibitor (CDKi) genes were similarly silenced, other than CDKN1B, the only gene recurrently mutated in SI-NETs. Deletion of CDKN1B altered cell cycle kinetics during human EEC differentiation, and deletions of ASCL1 or CDKN1B activated certain genes that are expressed in SI-NETs but not in the normal EEC trajectory. We propose that a limited CDKi repertoire and absence of ASCL1-dependent constraints on EEC maturation together explain unique SI-NET characteristics.
Authors
Pratik N.P. Singh, Elsa Hadj Bachir, James R. Howe, Andrew M. Bellizzi, Paloma Cejas, Shariq Madha-Krause, Charles B. Epstein, Jennifer A. Chan, Bradley Bernstein, Matthew H. Kulke, Qiao Zhou, Ramesh A. Shivdasani
Abstract
Cellular plasticity is a hallmark of cancer, enabling tumor cells to alter identity and evade therapeutic pressure. In invasive mucinous adenocarcinoma of the lung (IMA), NK2 homeobox 1 (NKX2-1) loss triggers a pulmonary to gastric switch marked by aberrant activation of hepatocyte nuclear factor 4 alpha (HNF4α), a master regulator of gastrointestinal/hepatic differentiation. We show that HNF4α promoted IMA growth and activated a gastric pit cell–like program. Loss of HNF4α enabled forkhead box A1 and A2 (FoxA1/2) transcription factors to bind de novo sites and activate alternative, nongastric identities in IMA. HNF4α also established a mucinous program associated with tolerance to KRAS blockade, and loss of HNF4α enhanced response to KRASG12D inhibition. Mechanistically, HNF4α blocked cell-cycle exit in drug-tolerant persister cells and promoted activity of the antioxidant transcription factor nuclear factor erythroid 2–related factor 2 (NRF2). NRF2 activation partially rescued the effects of Hnf4a deletion on KRASG12D inhibition, whereas NRF2 inhibition enhanced sensitivity to KRASG12D blockade. Thus, HNF4α is a key regulator of growth, identity, and primary response to KRASG12D inhibition in IMA.
Authors
Headtlove Essel Dadzie, Yangsook Song Green, Soledad A. Camolotto, Henry U. Arnold, Matthew Gumbleton, Minzhe Guo, Mari Mino-Kenudson, Yutaka Maeda, Benjamin T. Spike, Eric L. Snyder
Abstract
The global prevalence of metabolic dysfunction–associated steatohepatitis (MASH) is rising, driven by a complex interplay of metabolic disturbances, inflammation, and fibrosis, yet effective treatment options remain limited. This study examined the relationships among intestinal microbial dysbiosis, ammonia production, and hepatic CD8+ T cell activity in MASH, then assessed the therapeutic potential of DT-109, a glycine-based tripeptide. We investigated the gut/liver axis across human cohorts and both nonhuman primate and mouse MASH models. Multiomics approaches were used to characterize ileal microbiota, ammonia levels, and hepatic immune and metabolic pathways. Causality was verified through microbiota transplantation, C. perfringens NirA-knockout mutants, and functional validation in vitro and in vivo. The efficacy of DT-109 was evaluated in nonhuman primates and mice. Our results revealed a significant increase in the ammonia-producing gut bacterium C. perfringens, which led to elevated intestinal ammonia and disruption of the intestinal barrier in MASH. Elevated ammonia levels triggered FosB-mediated upregulation of CCL5 in CD8+ T cells, which in turn drove T cell cytotoxicity in the liver. Notably, DT-109 effectively lowered C. perfringens abundance, reduced intestinal ammonia, restored intestinal barrier integrity, and alleviated CD8+ T cell dysregulation in MASH. These results identify a distinct mechanism in which gut-derived ammonia drives CD8+ T cell–mediated MASH and demonstrate that DT-109 effectively targets this axis by inhibiting C. perfringens and reducing ammonia, ultimately ameliorating MASH.
Authors
Pengxiang Qu, Shusi Ding, Yanru Zhang, Yang Zhao, Erfei Song, Liangshuo Hu, Ruike Ding, Wenbin Cao, Yiting Hou, Jia Qi, Juan Zhao, Chenjing Duan, Shuangqing Liu, Chong Shen, Ying Zhao, Yanhong Guo, Zuowen Zheng, Shiwei Luo, Huizhong Hu, Liang Bai, Sihai Zhao, Bo Wang, Shuixiang He, Yi Wu, Xuelian Xiong, Qiutong Wu, Weiwang Gu, Oren Rom, Aimin Xu, Lemin Zheng, Jifeng Zhang, Enqi Liu, Y. Eugene Chen
Abstract
Dysfunctional intestinal fibrosis is an irreversible complication of Crohn’s disease (CD). The complex heterogeneity of intestinal mesenchymal cells makes it difficult to understand the pathogenesis of intestinal fibrosis. Previously, we identified Meflin as a marker of fibroblast subsets. This study aimed to explore the role of Meflin-positive fibroblasts in intestinal fibrogenesis and investigate the potential of pharmacological control of Meflin expression as a treatment for patients with CD. Our results indicated that Meflin expression was upregulated in fibroblasts at the early stage of fibrosis but was downregulated in established fibrosis in both patients with CD and 2 different mouse models, which are the chronic dextran sodium sulfate (DSS) model and an IL-10–deficient model that spontaneously develops intestinal inflammation. Meflin-deficient mice exacerbated intestinal fibrosis with dysregulated expression of noncanonical Wnt ligand WNT5A and its receptor ROR2. Pharmacologically induced Meflin expression through the administration of a synthetic retinoid reversed intestinal fibrosis in the DSS model and suppressed profibrotic protein secretion in fibroblasts isolated from patients with CD. Our findings indicate that Meflin-positive fibroblasts represent a functional subpopulation that suppresses intestinal fibrosis. Augmentation of Meflin expression shows antifibrotic effects and holds promise as a therapeutic approach for intestinal fibrosis in patients with CD.
Authors
Jingxi Mu, Keiko Maeda, Tadashi Iida, Shinji Mii, Nobutoshi Esaki, Yukihiro Shiraki, Yasuyuki Mizutani, Masanao Nakamura, Takeshi Yamamura, Tsunaki Sawada, Eri Ishikawa, Kentaro Murate, Takashi Hirose, Kazuhiro Furukawa, Akina Oishi, Haruhiko Suzuki, Takayoshi Kishida, Goro Nakayama, Mitsuhiro Fujishiro, Hiroki Kawashima, Atsushi Enomoto
Abstract
Lymphatic valves are essential for maintaining tissue fluid homeostasis, and their dysfunction leads to lymphedema, a morbid and disfiguring disease without a cure. Mechanical forces due to lymph flow are required for proper lymphatic valve development, yet it remains unclear how lymphatic endothelial cells (LECs) sense and decode mechanical signals. In this study, we identify the cell guidance semaphorin receptor plexin D1 (PLXND1) as a lymphatic mechanosensor required for lymphatic valve morphogenesis. Conditional genetic ablation of Plxnd1 in LECs caused major defects in lymphatic valve development in 2 different lymphatic vascular beds. Mechanistically, PLXND1 acted as a mechanosensor within a lymphatic mechanocomplex, initiating distinct mechanical signals and activating the lymphatic valve transcriptional program through an unconventional pathway. Screening of patients with primary lymphedema identified PLXND1 missense variants, and functional analysis established 2 pathogenic variants that selectively disrupt the ligand versus mechanosensing functions of this receptor. Variants associated with lymphedema in members of the mechanocomplex disrupted its formation, underscoring the central role of this complex in lymphatic valve biology. Our work uncovers a mechanosensing mechanism guiding lymphatic valve development, and has profound implications for the understanding and treatment of primary lymphedema in humans.
Authors
Kar-Lai Pang, Vedanta Mehta, Claire Aitken, Sara E. Dobbins, Jing Yu, Gabriele Bonetti, Adam N. Keen, Feiran Zhang, Amélie Sabine, Tatiana V. Petrova, Paul R. Riley, E. Yvonne Jones, Sandro Michelini, Matteo Bertelli, John S. Reader, Pia Ostergaard, Ellie Tzima
Abstract
MDM2 is transcriptionally activated by the ST-MYCL-Tip60 complex in virus-positive Merkel cell carcinoma (MCC). MDM2 suppresses p53 and is a rational therapeutic target. MDM2 inhibitors face an intrinsic limitation: p53 activation induces MDM2 transcription, creating a feedback loop that blunts inhibitor efficacy. We demonstrate that MDM2 degraders KTX-049 and KT-253 overcome this limitation by collapsing the p53/MDM2 negative feedback loop. KTX-049 was >100-fold more potent than the MDM2 inhibitor DS-3032 across WT p53 MCC cell lines, and this superior potency was quantitatively supported by mechanistic mathematical modeling. In vivo, KT-253 produced deep and durable tumor regressions, including complete responses in patient-derived xenograft models. Acquired resistance was strongly associated with acquisition of TP53 mutations, confirming on-target pathway pressure. These findings establish feedback architecture as a critical determinant of therapeutic response and position MDM2 degradation as a qualitatively distinct strategy that produces more durable pathway engagement than MDM2 inhibition, providing a preclinical rationale for prioritizing MDM2 degraders in WT TP53 MCC.
Authors
Varsha Ananthapadmanabhan, Simone Bruno, Leonard Vonk, Yu-Chen Cheng, Abeba Teshager, Benjamin K. Eschle, Charles L. Howarth, Joana S. Rodrigues, Julia Schnabel, Ananya Kodali, Prafulla C. Gokhale, Rujuta Kshirsagar, Susanne B. Breitkopf, Kirti Sharma, Joao A. Paulo, Yvonne Li, Andrew D. Cherniack, Franziska Michor, Yogesh Chutake, Joyoti Dey, James A. DeCaprio
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ISSN: 0021-9738 (print), 1558-8238 (online)