Protein phosphatase 2A regulates senescence and immunogenicity in medulloblastoma models
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
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
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Research Article Immunology Oncology

Protein phosphatase 2A regulates senescence and immunogenicity in medulloblastoma models

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

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Figure 6

PP2Ac deficiency enhances immunogenic senescence in MB tumors.

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PP2Ac deficiency enhances immunogenic senescence in MB tumors. (A) GSEA ...
(A) GSEA plots demonstrating enrichment of type I and type II IFN response signatures in PP2Ac-KO versus WT D425 and #2416 cells. (B) Flow cytometric quantification of MHC-I surface expression in WT and PP2Ac-KO D425 and #2416 cells. Representative histograms and quantification of MFI are shown. (C) D425 cells were treated with 5 Gy RTx, and MHC-I expression was measured 48 hours later in SA-β-gal–positive and SA-β-gal–negative populations by flow cytometry. (D) Immunofluorescence analysis of CD8+ T cell infiltration in #2416 tumors. CD8 (green), tumor cells (RFP, red), and nuclei (DAPI, blue). Quantification was performed from multiple ROIs per tumor. Small colored dots represent individual ROIs nested within each biological replicate, and the larger dot represents the mean value for each tumor. Statistical analysis was performed using tumor-level means. Scale bar: 20 μm. (E) Kaplan-Meier survival analysis of nude mice bearing intracranial #2416 tumors derived from WT or PP2Ac-KO cells. (F) Kaplan-Meier survival analysis of C57BL/6J mice bearing intracranial #2416 tumors treated with anti-CD8 antibody (clone 2.43) or isotype control. Treatment was initiated on day 3 after implantation (250 μg/mouse i.p., twice weekly). Data are shown as mean ± SEM. Statistical significance was determined using unpaired 2-tailed t tests or the log-rank test, as appropriate for each panel. P < 0.05 was considered statistically significant. *P < 0.05, **P < 0.01, ****P < 0.0001. FOV, field of view; GO, Gene Ontology; NES, normalized enrichment score.