YBX1/YB-1 induces partial EMT and tumourigenicity through secretion of angiogenic factors into the extracellular microenvironment

// Shashi K. Gopal 1 , David W. Greening 1 , Rommel A. Mathias 1 , Hong Ji 1 , Alin Rai 1 , Maoshan Chen 1 , Hong-Jian Zhu 2 , Richard J. Simpson 1 1 Department of Molecular Science, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia 2 Department of Surgery, The University of Melbourne, Melbourne, Victoria, Australia Correspondence to: Richard J. Simpson, e-mail: Richard.Simpson@latrobe.edu.au Keywords: YBX1, epithelial-mesenchymal transition, EMT, secretome, tumorigenesis Received: January 26, 2015      Accepted: April 10, 2015      Published: April 23, 2015 ABSTRACT Epithelial-mesenchymal transition (EMT) describes a morphogenetic program which confers mesenchymal cell properties, such as reduced cell-cell contact and increased cell migration and invasion, to epithelial cells. Here we investigate the role of the pleiotropic transcription/splicing factor and RNA-binding protein nuclease-sensitive element-binding protein 1 (YBX1/YB-1) in increasing the oncogenic potential of epithelial MDCK cells. Characterization of MDCK cells expressing YBX1 (MDCK YBX1 cells) revealed a partial EMT phenotype, including cytosolic relocalization of E-cadherin, increased cell scattering, and anchorage-independent growth. Subcutaneous injection of parental MDCK cells into NOD/SCID mice did not form tumours. Critically, MDCK YBX1 cells established viable tumour xenografts, and immuno-histochemical staining indicated murine vascularization by CD31+ endothelial cells. We analysed the total secretome (containing soluble and extracellular vesicles) of MDCK YBX1 cells to investigate regulation of the tumour microenvironment. YBX1 expression elevated release of secreted factors known to enhance angiogenesis (TGF-β, CSF-1, NGF, VGF, ADAM9 and ADAM17), compared to MDCK cells. Importantly, treatment with MDCK YBX1 cell-derived secretome increased recipient 2F-2B endothelial cell motility. This defines YBX1 as an oncogenic enhancer that can regulate tumour angiogenesis via release of secreted modulators into the extracellular microenvironment.