Abstract 1018: Epithelial-to-mesenchymal transition (EMT) alters vesiculation of cancer cells expressing oncogenic epidermal growth factor receptor (EGFR): Implications for the aggressive, procoagulant and proangiogenic properties

Abstract

Abstract Cancer cells release elevated amounts of membrane-derived organelles containing complex molecular cargo, and known as extracellular vesicles (EVs). This process (vesiculation) is implicated in intercellular communication, as well as in cancer invasion, metastasis, angiogenesis and activation of the coagulation system. We have previously demonstrated a link between oncogenic transformation mediated by mutant K-ras, epidermal growth factor receptor (EGFR) as well as other genetic lesions and the intensity of cancer cell vesiculation. In the present study we interrogate vesiculation during the superimposed processes of de-differentiation and epithelial-to-mesenchymal transition (EMT). In the EGFR-driven epidermoid cancer cell line A431, EMT can be induced by stimulation with EGFR ligands coupled with blockade of the E-cadherin. Of note, A431 cells express high levels of the Tissue Factor (TF) receptor which renders them procoagulant, and is required for the efficient tumor initiation and proangiogenic signalling. A431 cells emit heterogeneous population of EVs, including subsets containing TF, and EGFR. We observed that induction of EMT in A431 cells is associated with a global increase in vesiculation, as revealed by nanoparticle tracking analysis (NTA/Nanosight). At the same time, EGFR and TF are relocated from the plasma membrane to distinct subcellular microdomains, and this change is associated with a rearrangement in the proteome of EVs emitted by cancer cells, including a significant increase in TF content. Tumor cell-derived, TF-containing EVs are readily taken up by endothelial cells and trigger their procoagulant conversion and angiogenic responses. While forming tumors in vivo A431 cells spontaneously undergo multilineage differentiation and generate EMT-like subpopulations, which release into the circulation a subset of EVs with a distinct molecular signature. Thus, EMT-like processes not only modulate intrinsic cellular properties (cell shape, differentiation), but also trigger a shift in cellular vesiculation that may be detected in EV preparations isolated from peripheral blood. Moreover, EVs that emanate from cancer cells upon their entry into the EMT pathway may acquire the ability to modify the extracellular and vascular milieu, and possibly facilitate tumor initiation, invasion and metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1018. doi:1538-7445.AM2012-1018