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Updated: Jan 18, 2026
Genome-wide RNAi Screening to Identify Host Factors That Modulate Oncolytic Virus Therapy
Published on: April 3, 2018
MicroRNA-138 regulation promotes the efficacy of oncolytic herpes virus G47Δ for malignant brain tumor therapy
Seisaku Kanayama1, Takeshi Haraguchi2, Hideo Iba2
1Division of Innovative Cancer Therapy and Department of Surgical Neuro-Oncology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
Abstract:
G47Δ, a third-generation oncolytic herpes simplex virus type 1, is a promising therapeutic agent for malignant glioma. We investigated whether inhibition of host microRNA-138 (miR-138), a regulator of the viral immediate-early protein ICP0, could enhance its efficacy. In vitro, miR-138 suppression increased viral protein expression, progeny virus production, and cytotoxicity in human glioblastoma and murine Neuro2a cells, whereas overexpression suppressed these effects. Neuro2a cells stably silenced for miR-138 showed tumor regression in 9 of 13 syngeneic mice, but not in athymic mice or following CD8+ T cell depletion, indicating dependence on adaptive immunity. Mechanistically, miR-138 directly targeted signal transducer and activator of transcription 1 (STAT1) mRNA: Its inhibition increased STAT1 and enhanced MHC class I expression. In bilateral subcutaneous tumors, miR-138 inhibition suppressed growth on the treated side, but contralateral tumor suppression required combination with G47Δ, suggesting systemic antitumor immunity involvement. In vivo electroporation-mediated miR-138 inhibition in subcutaneous tumors elevated STAT1 and suppressed growth. G47Δ combined with in vivo miR-138 inhibition significantly augmented efficacy compared with G47Δ alone. These findings identify miR-138 as both an antiviral regulator and immune modulator, and demonstrate that its inhibition potentiates G47Δ efficacy, providing rationale for a novel therapeutic strategy for malignant brain tumors.
Insights
Inhibiting microRNA-138 (miR-138) enhances the oncolytic virus G47Δ efficacy against malignant glioma by boosting viral replication and adaptive immunity. This strategy shows promise for brain tumor treatment.
Area of Science:
- Virology
- Immunology
- Oncology
Background:
- Oncolytic herpes simplex virus type 1 (G47Δ) shows potential for treating malignant glioma.
- MicroRNA-138 (miR-138) regulates viral immediate-early protein ICP0 and influences host-pathogen interactions.
Purpose of the Study:
- To investigate if inhibiting miR-138 can enhance the therapeutic efficacy of G47Δ against malignant glioma.
- To elucidate the mechanisms underlying miR-138's role in viral replication and anti-tumor immunity.
Main Methods:
- In vitro studies using human glioblastoma and murine Neuro2a cells to assess viral replication and cytotoxicity following miR-138 manipulation.
- In vivo studies in mice using genetically modified cells and direct in vivo miR-138 inhibition (electroporation) in combination with G47Δ.
- Analysis of STAT1 and MHC class I expression to understand immune modulation.
Main Results:
- miR-138 suppression increased G47Δ viral protein expression, progeny production, and cancer cell killing in vitro.
- Stable miR-138 silencing in Neuro2a cells led to tumor regression in mice, dependent on CD8+ T cells and adaptive immunity.
- miR-138 inhibition increased STAT1 expression and MHC class I presentation, enhancing anti-tumor immune responses.
- Combination therapy of G47Δ and in vivo miR-138 inhibition significantly improved tumor suppression compared to G47Δ alone.
Conclusions:
- miR-138 acts as a negative regulator of G47Δ oncolytic virus efficacy and an immune modulator.
- Inhibiting miR-138 potentiates G47Δ-mediated anti-glioma effects through enhanced viral replication and adaptive immunity.
- Targeting miR-138 presents a novel therapeutic strategy to improve outcomes for malignant brain tumors.
