Abstract 2608: EGF signaling activates a TAZ-driven oncogenic program in glioblastoma

Glioblastoma multiforme (GBM) is the most aggressive and lethal primary brain tumor in humans. Hyperactivation of the signaling pathway driven by the epidermal growth factor (EGF) and its receptor (EGFR) are commonly occurring in GBM. The oncogenic transcriptional program driven by EGF signaling is still incompletely understood in GBM. Here, we found that EGF induces the upregulation and nuclear translocation of TAZ, an oncogenic transcriptional co-activator. TAZ and its paralog gene YAP are commonly known as downstream mediators of the Hippo signaling pathway. TAZ has been found as a driver of mesenchymal transition in GBM cells and promotes GBM radioresistance. Our results support that EGF induces TAZ transcription and the activation of TAZ gene targets, through the signaling axis including EGFR, STAT3 and ERK. EGFRvIII is the most frequently occurring EGFR mutation in GBM causing constitutively active EGFR. We found that EGFRvIII causes EGF-independent activation of TAZ and its downstream oncogenic targets. Next, we used next-generation sequencing to establish a genome-wide map of TAZ gene targets in GBM cells after EGF stimulation. The results suggest that EGF signaling activates a TAZ-driven oncogenic program including autocrine and paracrine factors that promote GBM growth, angiogenesis, stemness and immunoescape. Moreover, we found that TAZ targeting by shRNAs or the FDA-approved drug Verteporfin effectively inhibits the TAZ-driven oncogenic program activated by EGF stimulation or the EGFRvIII mutant. TAZ targeting also inhibits GBM cell growth and xenograft formation. In contrast, enforced TAZ induces the TAZ-driven oncogenic program and promotes GBM cell growth and xenograft formation. In conclusion, our results reveal a novel TAZ-driven oncogenic program that is activated by EGF signaling in GBM. Our discoveries strongly support TAZ as a therapeutic target for GBM and likely other human cancer with hyperactivation of EGF signaling. Our preclinical studies also provide a clinically translatable strategy for GBM therapy based on using the FDA-approved drug Verteporfin. Citation Format: Minling Gao, Yi Fu, Laterra John, Mingyao Ying. EGF signaling activates a TAZ-driven oncogenic program in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2608.