Activating antiviral immune responses potentiates immune checkpoint inhibition in glioblastoma models
Deepa Seetharam, … , Defne Bayik, Ashish H. Shah
Deepa Seetharam, … , Defne Bayik, Ashish H. Shah
Published March 17, 2025
Citation Information: J Clin Invest. 2025;135(6):e183745. https://doi.org/10.1172/JCI183745.
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Research Article Oncology Virology

Activating antiviral immune responses potentiates immune checkpoint inhibition in glioblastoma models

Abstract

Viral mimicry refers to the activation of innate antiviral immune responses due to the induction of endogenous retroelements (REs). Viral mimicry augments antitumor immune responses and sensitizes solid tumors to immunotherapy. Here, we found that targeting what we believe to be a novel, master epigenetic regulator, Zinc Finger Protein 638 (ZNF638), induces viral mimicry in glioblastoma (GBM) preclinical models and potentiates immune checkpoint inhibition (ICI). ZNF638 recruits the HUSH complex, which precipitates repressive H3K9me3 marks on endogenous REs. In GBM, ZNF638 is associated with marked locoregional immunosuppressive transcriptional signatures, reduced endogenous RE expression, and poor immune cell infiltration. Targeting ZNF638 decreased H3K9 trimethylation, increased REs, and activated intracellular dsRNA signaling cascades. Furthermore, ZNF638 knockdown upregulated antiviral immune programs and significantly increased PD-L1 immune checkpoint expression in diverse GBM models. Importantly, targeting ZNF638 sensitized mice to ICI in syngeneic murine orthotopic models through innate IFN signaling. This response was recapitulated in recurrent GBM (rGBM) samples with radiographic responses to checkpoint inhibition with widely increased expression of dsRNA, PD-L1, and perivascular CD8 cell infiltration, suggesting that dsRNA signaling may mediate response to immunotherapy. Finally, low ZNF638 expression was a biomarker of clinical response to ICI and improved survival in patients with rGBM and patients with melanoma. Our findings suggest that ZNF638 could serve as a target to potentiate immunotherapy in gliomas.

Authors

Deepa Seetharam, Jay Chandar, Christian K. Ramsoomair, Jelisah F. Desgraves, Alexandra Alvarado Medina, Anna Jane Hudson, Ava Amidei, Jesus R. Castro, Vaidya Govindarajan, Sarah Wang, Yong Zhang, Adam M. Sonabend, Mynor J. Mendez Valdez, Dragan Maric, Vasundara Govindarajan, Sarah R. Rivas, Victor M. Lu, Ritika Tiwari, Nima Sharifi, Emmanuel Thomas, Marcus Alexander, Catherine DeMarino, Kory Johnson, Macarena I. De La Fuente, Ruham Alshiekh Nasany, Teresa Maria Rosaria Noviello, Michael E. Ivan, Ricardo J. Komotar, Antonio Iavarone, Avindra Nath, John Heiss, Michele Ceccarelli, Katherine B. Chiappinelli, Maria E. Figueroa, Defne Bayik, Ashish H. Shah

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Figure 8

ZNF638 knockdown potentiates ICI response in vivo.

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ZNF638 knockdown potentiates ICI response in vivo. (A) Diagram of in viv...
(A) Diagram of in vivo study design with syngeneic murine GBM model. Made in BioRender. (B) Syngeneic GBM murine model with ZNF638 knockdown and PD-L1 inhibition demonstrates significantly improved survival relative to other treatment and control groups (n = 5 per group, P < 0.01). Multiple animals died on the same day in each group making it appear as if there are fewer animals than were included in each group. (C) ZNF638 knockdown and PD-L1 inhibition significantly reduces tumor volume relative to all other groups (1-way ANOVA, ****P < 0.00001, ***P < 0.0001, **P < 0.001, *P < 0.01). (D) ZNF638 knockdown + α-PD-L1 shows decreased expression of ZNF638 and increased expression of RIG-I, TLR3, NFK-β, and MERV (RLTR6) transcripts as measured by qPCR. Additionally, there is significant downregulation of IL-6, TNF-α (performed in biological triplicate, 1-way ANOVA, ****P < 0.00001, ***P < 0.0001, **P < 0.001). (E) ZNF638 knockdown with PD-L1 inhibition significantly increased expression of IFN-α and IFN-γ, as well as decreased expression of TNF-α (performed in biological triplicate, 1-way ANOVA, ****P < 0.0001, ***P < 0.001, **P < 0.01). (F) Proteomic cytokine profiler array with hierarchical clustering depicts distinct cytokine profiles between all treatment/control groups with the greatest difference between CTL+ α-PD-L1 mice and ZNF638 KD + α-PD-L1 mice (1-way ANOVA, *P < 0.05).