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 5

Regulatory subunit PPP2R5A (PP2A-B56α) negatively regulates senescence in MB cells.

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Regulatory subunit PPP2R5A (PP2A-B56α) negatively regulates senescence i...
(A) siRNA screen targeting 20 PP2A subunits (n = 16 regulatory and 2 catalytic) in D425 cells. At 48 hours after transfection, CDKN1A (p21) expression was measured by RT-qPCR and normalized to a nontargeting siRNA control. PP2A subunits are grouped according to structural class. (B) Flow cytometric quantification of SA–β-gal in WT and PP2A-B56α–KO (PPP2R5A-KO) D425 cells. Representative histograms and quantification of the percentage of SA–β-gal–positive cells are shown. (C) RT-qPCR analysis of CDKN1A and IL8 expression in WT and PP2A-B56α–KO cells. (D) WT and PP2A-B56α–KO D425 cells were treated with RTx (10 Gy), and SA–β-gal activity was measured by flow cytometry 48 hours after irradiation. Data are shown as mean ± SEM. Statistical significance was determined using unpaired 2-tailed t tests or 1-way ANOVA followed by Dunnett’s multiple-comparisons test, as appropriate for each panel. P < 0.05 was considered statistically significant. ***P < 0.001, ****P < 0.0001.