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.

中文翻译：

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Betacellulin可驱动胶质母细胞瘤的治疗抵抗力。

背景技术转录因子信号转导子和转录激活因子3（STAT3）驱动胶质母细胞瘤（GBM）的进展，提示STAT3作为治疗靶点。然而令人惊讶的是，GBM细胞通常显示出对STAT3阻断的主要抗性。方法使用人类胶质母细胞瘤细胞系LN229，U87，SF767和U373以及患者源异种移植物（PDXs）GBM8和GBM43评估STAT3抑制过程中的表皮生长因子受体（EGFR）激活。在STAT3抑制剂处理的细胞上进行了蛋白质和基因表达实验，蛋白质稳定性测定，细胞因子阵列，磷酸酪氨酸阵列和EGFR配体蛋白质阵列。为了评估抗肿瘤活性，我们单独和与STAT3抑制联合施用了β细胞素（BTC）中和抗体。BTC是EGFR配体。因此，我们使用第三代EGFR抑制剂osimertinib（具有或不具有STAT3抑制功能）对原位异种移植小鼠进行了治疗。结果我们证明，小分子抑制剂和STAT3的敲低均导致EGFR配体BTC的表达和分泌，从而导致EGFR活化和随后的核因子-κB（NF-κB）下游磷酸化。抗BTC的中和抗体可消除STAT3的抑制作用，从而消除EGFR和NF-κB的激活；STAT3和BTC的联合阻断可诱导GBM细胞凋亡。一起阻断EGFR和STAT3可以抑制肿瘤的生长，提高体内原位携带GBM PDX的小鼠的存活率。结论这些数据揭示了STAT3，EGFR，