Abstract 1811: A PEAK1/GATA2 signaling axis controls VEGFR2 expression to mediate angiogenesis

Abstract

Abstract Formation of new blood vessels (angiogenesis) is crucial for proper development, but can also contribute to many diseases including cancer. Vascular endothelial growth factor receptor 2 (VEGFR2) is a receptor tyrosine kinase that mediates angiogenesis in developing vertebrates and is frequently upregulated in many human cancers. However, the underlying mechanisms that regulate VEGFR2 expression in normal and diseased cells are poorly understood. Here we demonstrate that pseudopodium-enriched atypical kinase 1 (PEAK1) mediates developmental and tumor-induced angiogenesis by modulating VEGFR2 expression and downstream signaling. Knockout of peak1 in zebrafish using TALEN technology (Transcription Activator-Like Effector Nucleases) or knockdown by specific peak1 morpholinos (MO) induced severe pericardial edema, blood-pooling defects, and inhibited formation of intersegmental (ISV) and subintestinal vessels (SIV). In Peak1 knockout mice, neonatal retinal vessel development was severely delayed, and the ex vivo angiogenic ability of adult thoracic aorta was greatly reduced. Intravital time-lapse imaging of ISV formation in peak1 knockout zebrafish revealed major defects in endothelial cell migration and proliferation. Similarly, PEAK1 knockdown or overexpression in HUVECs modulated endothelial cell migration, proliferation, and vessel sprouting in vitro. Biochemical studies and quantitative proteomic profiling of PEAK1 knockdown HUVECs revealed a dramatic loss of VEGFR2 mRNA and protein expression, which attenuated downstream signaling to Akt and ERK, leading to loss of VEGF-mediated vessel formation. PEAK1 specifically regulated VEGFR2 levels and did not alter VEGFR1 expression, and reconstitution of PEAK1 knockdown cells with PEAK1 restored VEGFR2 mRNA and protein expression. Mechanistic studies revealed that PEAK1 specifically regulates VEGFR2 mRNA transcription by modulating expression of the transcription factor GATA2. Re-expression of GATA2 in PEAK1 depleted cells restored VEGFR2 mRNA and protein expression as well as downstream signaling, indicating that GATA2 is a necessary downstream component in this response. Also, introduction of gata2 mRNA into PEAK1 knockdown zebrafish restored normal ISV formation and vegfr2 mRNA expression in these animals. Finally, bioinformatics and interrogation of the TCGA RNAseq database revealed significant Pearson’s correlations between PEAK1 and VEGFR2 expression in 17 of 32 different human cancers. Collectively, our findings indicate that PEAK1 regulates developmental and tumor-induced angiogenesis by regulating GATA2-dependent VEGFR2 expression and its downstream signals. Citation Format: Richard L. Klemke. A PEAK1/GATA2 signaling axis controls VEGFR2 expression to mediate angiogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1811. doi:10.1158/1538-7445.AM2017-1811