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 3

PP2Ac deficiency promotes tumor cell senescence and prolongs survival in MB models.

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PP2Ac deficiency promotes tumor cell senescence and prolongs survival in...
(A) Kaplan-Meier survival curves of mice intracranially implanted with 3 × 104 WT or PP2Ac-KO MB cells. Left: nude mice bearing D425 tumors (n = 8–9 per group). Right: C57BL/6J mice bearing #2416 tumors (n = 30–31 per group). (B) Representative immunofluorescence images and quantification of SA-β-gal in D425 tumors collected at endpoint. SA-β-gal (green) and nuclei (DAPI, blue). Quantification was performed from multiple ROIs per tumor. Small colored dots indicate individual ROIs nested within each biological replicate, and the larger dot indicates the mean for each tumor. Statistical analysis was performed on tumor-level means. Scale bar: 100 μm. (C) Representative immunofluorescence images and quantification of p-p65 in D425 tumors at endpoint. p-p65 (purple) and nuclei (DAPI, blue). Quantification and statistical analysis were conducted as in B. Scale bar: 100 μm. (D) Kaplan-Meier analysis of overall survival in patients with MB from the GSE85217 dataset stratified into senescence-high and senescence-low groups using an unbiased cutoff determined by maximally selected rank statistics (cut point = 0.1350506). All patients with available survival data were included in the analysis. Survival differences were assessed using the log-rank test. Cox proportional hazards analysis demonstrated a reduced risk of death in the senescence-high group (HR = 0.67; 95% CI 0.48–0.93). Numbers at risk are indicated below the plot. 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 < 0.001.