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Updated: May 26, 2025
A Rapid Screening Workflow to Identify Potential Combination Therapy for GBM using Patient-Derived Glioma Stem Cells
Published on: March 28, 2021
PRMT5 inhibition sensitizes glioblastoma tumor models to temozolomide
Shumpei Onishi1, Sridharan Jayamohan2, Ashis Chowdhury1
1NINDS, NIH.
Background:
Despite multi-model therapy of maximal surgical resection, radiation, chemotherapy, and tumor-treating fields, glioblastoma patients show dismal prognosis. Protein Arginine Methyltransferase 5 (PRMT5) is overexpressed in glioblastoma and its inhibition imparts an anti-tumor effect. Even though Temozolomide (TMZ) is the standard chemotherapeutic agent in the treatment of glioblastoma, tumor cells invariably develop resistance to TMZ. However, the mechanistic role of PRMT5 in glioblastoma therapy resistance is unknown.
Methods:
Patient-derived primary glioblastoma neurospheres (GBMNS), treated with PRMT5 inhibitor (LLY-283) or transfected with PRMT5 target-specific siRNA were treated with TMZ and subjected to in vitro functional and mechanistic studies. The intracranial mouse xenograft model was used to test the in vivo antitumor efficacy of combination treatment.
Results:
We found that PRMT5 inhibition increased the cytotoxic effect and caspase 3/7 activity of TMZ in GBMNS suggesting that apoptosis is the potential mode of cell death in the combination treatment. PRMT5 inhibition abrogated the TMZ-induced G2/M cell cycle arrest. Unbiased transcriptomic studies indicate that PRMT5 inhibition negatively enriches DNA damage repair genes. Importantly, combination therapy increased DNA double-strand breaks (H2AX foci) and enhanced the DNA damage (comet assay), suggesting that the combination treatment increases the TMZ-induced DNA damage. Specifically, the LLY-283 treatment blocked homologous recombination repair in GBMNS. In vivo, LLY-283 and TMZ combination significantly curbed the tumor growth and prolonged the survival of tumor-bearing mice.
Conclusion:
Concomitant treatment of LLY-283 and TMZ has significantly greater antitumor efficacy, suggesting that PRMT5 inhibition and TMZ combination could be a new therapeutic strategy for glioblastoma.
Insights
Combining PRMT5 inhibition with Temozolomide (TMZ) enhances glioblastoma treatment by increasing DNA damage and apoptosis. This novel therapeutic strategy overcomes TMZ resistance and improves outcomes in preclinical models.
Area of Science:
- Neuro-oncology
- Cancer Therapeutics
- Molecular Biology
Background:
- Glioblastoma (GBM) remains a challenging brain tumor with poor prognosis despite standard treatments.
- Protein Arginine Methyltransferase 5 (PRMT5) is overexpressed in GBM and shows anti-tumor potential.
- Tumor resistance to Temozolomide (TMZ), the standard chemotherapy, is a significant clinical hurdle.
Purpose of the Study:
- To investigate the mechanistic role of PRMT5 in glioblastoma resistance to Temozolomide (TMZ).
- To evaluate the therapeutic efficacy of combining a PRMT5 inhibitor (LLY-283) with TMZ in glioblastoma.
- To explore the impact of PRMT5 inhibition on TMZ-induced DNA damage and cell death pathways.
Main Methods:
- Patient-derived glioblastoma neurospheres (GBMNS) were treated with LLY-283 and/or TMZ.
- In vitro studies assessed cytotoxicity, apoptosis (caspase 3/7 activity), cell cycle progression, and DNA damage.
- An intracranial mouse xenograft model was utilized for in vivo efficacy assessment of combination therapy.
Main Results:
- PRMT5 inhibition potentiated TMZ's cytotoxic effects and induced apoptosis in GBMNS.
- Combination therapy abrogated TMZ-induced G2/M cell cycle arrest and enhanced DNA double-strand breaks.
- LLY-283 blocked homologous recombination repair, increasing TMZ-induced DNA damage; combination therapy curbed tumor growth and prolonged survival in vivo.
Conclusions:
- PRMT5 inhibition sensitizes glioblastoma cells to TMZ by increasing DNA damage and blocking repair.
- The combination of LLY-283 and TMZ demonstrates significant antitumor efficacy in preclinical glioblastoma models.
- Targeting PRMT5 alongside TMZ represents a promising new therapeutic strategy for glioblastoma treatment.
