Qiwen Fan1,2, Zhenyi An1,2, Robyn A Wong1,2, Xujun Luo1,2, Edbert D Lu1,2, Albert Baldwin3, Manasi K Mayekar2, Franziska Haderk2, Kevan M Shokat4, Trever G Bivona2, William A Weiss1,2,5,6. 1. Department of Neurology, University of California San Francisco (UCSF), San Francisco, California. 2. Helen Diller Family Comprehensive Cancer Center, San Francisco, California. 3. Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina. 4. Howard Hughes Medical Institute and Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California. 5. Department of Pediatrics, University of California San Francisco, San Francisco, California. 6. Department of Neurological Surgery, University of California San Francisco, San Francisco, California.
Abstract
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.
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:Humanglioblastoma 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.
Authors: Qi-Wen Fan; Christine Cheng; Chris Hackett; Morri Feldman; Benjamin T Houseman; Theodore Nicolaides; Daphne Haas-Kogan; C David James; Scott A Oakes; Jayanta Debnath; Kevan M Shokat; William A Weiss Journal: Sci Signal Date: 2010-11-09 Impact factor: 8.192
Authors: Qi-Wen Fan; Christine K Cheng; W Clay Gustafson; Elizabeth Charron; Petra Zipper; Robyn A Wong; Justin Chen; Jasmine Lau; Christiane Knobbe-Thomsen; Michael Weller; Natalia Jura; Guido Reifenberger; Kevan M Shokat; William A Weiss Journal: Cancer Cell Date: 2013-10-14 Impact factor: 31.743