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Updated: Jan 4, 2026
Live-Cell Imaging Assays to Study Glioblastoma Brain Tumor Stem Cell Migration and Invasion
Published on: August 29, 2018
Betacellulin drives therapy resistance in glioblastoma
Qiwen Fan1,2, Zhenyi An1,2, Robyn A Wong1,2
1Department of Neurology, University of California San Francisco (UCSF), San Francisco, California.
Background:
The transcription factor signal transducer and activator of transcription 3 (STAT3) drives progression in glioblastoma (GBM), suggesting STAT3 as a therapeutic target. Surprisingly however, GBM cells generally show primary resistance to STAT3 blockade.
Methods:
Human glioblastoma cell lines LN229, U87, SF767, and U373, and patient-derived xenografts (PDXs) GBM8 and GBM43 were used to evaluate epidermal growth factor receptor (EGFR) activation during STAT3 inhibition. Protein and gene expression experiments, protein stability assays, cytokine arrays, phospho-tyrosine arrays and EGFR-ligand protein arrays were performed on STAT3 inhibitor-treated cells. To evaluate antitumor activity, we administered a betacellulin (BTC)-neutralizing antibody alone and in combination with STAT3 inhibition. BTC is an EGFR ligand. We therefore treated mice with orthotopic xenografts using the third-generation EGFR inhibitor osimertinib, with or without STAT3 knockdown.
Results:
We demonstrate that both small-molecule inhibitors and knockdown of STAT3 led to expression and secretion of the EGFR ligand BTC, resulting in activation of EGFR and subsequent downstream phosphorylation of nuclear factor-kappaB (NF-κB). Neutralizing antibody against BTC abrogated activation of both EGFR and NF-κB in response to inhibition of STAT3; with combinatorial blockade of STAT3 and BTC inducing apoptosis in GBM cells. Blocking EGFR and STAT3 together inhibited tumor growth, improving survival in mice bearing orthotopic GBM PDXs in vivo.
Conclusion:
These data reveal a feedback loop among STAT3, EGFR, and NF-κB that mediates primary resistance to STAT3 blockade and suggest strategies for therapeutic intervention.
Insights
Glioblastoma cells resist STAT3 blockade due to a STAT3-EGFR-NF-κB feedback loop. Combining STAT3 and EGFR inhibition overcomes this resistance, inducing apoptosis and improving survival in preclinical models.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Therapeutics
Background:
- Signal transducer and activator of transcription 3 (STAT3) is a key driver in glioblastoma (GBM) progression.
- Glioblastoma cells exhibit primary resistance to STAT3 inhibition, posing a therapeutic challenge.
Purpose of the Study:
- To investigate the mechanisms underlying primary resistance to STAT3 blockade in glioblastoma.
- To evaluate combination therapies targeting STAT3 and epidermal growth factor receptor (EGFR) pathways.
Main Methods:
- Utilized human glioblastoma cell lines and patient-derived xenografts (PDXs).
- Assessed EGFR activation upon STAT3 inhibition using molecular and cellular assays.
- Evaluated the efficacy of betacellulin (BTC)-neutralizing antibodies and EGFR inhibitors (osimertinib) in combination with STAT3 inhibition in vitro and in vivo.
Main Results:
- STAT3 inhibition induced expression and secretion of the EGFR ligand betacellulin (BTC).
- BTC activated EGFR, leading to downstream nuclear factor-kappaB (NF-κB) phosphorylation.
- Combined blockade of STAT3 and BTC induced glioblastoma cell apoptosis and inhibited tumor growth in vivo.
Conclusions:
- A STAT3-EGFR-NF-κB feedback loop mediates primary resistance to STAT3 blockade in glioblastoma.
- Targeting this feedback loop by combining STAT3 and EGFR inhibition offers a promising therapeutic strategy for GBM.
