Coordinating Etk/Bmx activation and VEGF upregulation to promote cell survival and proliferation

Cindy H. Chau, Kai Yun Chen, Hong Tao Deng, Kwang Jin Kim, Ken Ichi Hosoya, Tetsuya Terasaki, Hsiu Ming Shih, David K. Ann

Research output: Contribution to journalArticlepeer-review

49 Citations (Scopus)

Abstract

Etk/Bmx, a member of the Tec family of non-receptor tyrosine kinase, is characterized by an N-terminal PH domain and has recently been shown to be involved in the regulation of various cellular processes, including proliferation, differentiation, motility and apoptosis. Since VEGF and the activation of its signaling pathway have been implicated in modulating a variety of biological responses, we characterized the role of Etk-dependent signaling pathways involved in the upregulation of VEGF expression, and explored the functional implications of this enhancement in sustaining cell proliferation and survival. Using Northern and Western analyses, transient transfections, and pharmacological agents, we demonstrate that Etk activation alone is sufficient to transcriptionally induce VEGF expression, independent of the previously identified hypoxia response element (HRE), in both Pa-4 epithelial and TR-BBB endothelial cells under normoxia. In addition, Etk utilizes both MEK/ERK and PI3-K/Pak1 signaling pathways in concert to activate VEGF transcription. Functionally, Etk activation elicits a profound stimulatory effect on TR-BBB cell proliferation and formation of capillary-like networks in Matrigel containing reduced levels of growth factors. Finally, antisense oligonucleotides against either endogenous VEGF or Etk abrogate the proliferation of Etk-activated TR-BBB cells, and exogenous VEGF treatment stimulates endogenous Etk tyrosine phosphorylation in HUVECs. Taken together, these results indicate that VEGF is both an Etk downstream target gene and an Etk upstream activator, constituting a reciprocal Etk-VEGF autoregulatory loop. These findings, to our knowledge, are the first delineation of a network of positive feedforward signaling pathways that converge on the Etk-VEGF axis, causally associating Etk-mediation of VEGF induction with enhanced cellular processes in both epithelial and endothelial cells.

Original languageEnglish
Pages (from-to)8817-8829
Number of pages13
JournalOncogene
Volume21
Issue number57
DOIs
Publication statusPublished - 2002 Dec 12

Keywords

  • Autocrine
  • Etk
  • Proliferation
  • Survival
  • VEGF

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cancer Research

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