Plasma-derived Exosomes Reverse Epithelial-to-Mesenchymal Transition after Photodynamic Therapy of Patients with Head and Neck Cancer

Marie-Nicole Theodoraki 1,2*, Saigopalakrishna S. Yerneni 3*, Cornelia Brunner 2, Joannis Theodorakis 4, Thomas K. Hoffmann 2, Theresa L. Whiteside 1,5

1 Department of Pathology, University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, PA 15213, USA

2 Department of Otorhinolaryngology, Head and Neck Surgery, University of Ulm, Germany

3 Department of Biomedical Engineering, College of Engineering, Carnegie Mellon University, Pittsburgh, PA 15217, USA

4 Department of Urology, Geniki Kliniki, Thessaloniki, Greece

5 Departments of Immunology and Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA

* These authors contributed equally to the manuscript

Correspondence to:

Theresa L. Whiteside, email: whitesidetl@upmc.edu

Keywords: plasma-derived exosomes; exosome-mediated reprogramming; epithelial-to-mesenchymal transition, head and neck cancer; photodynamic therapy

Received: April 06, 2018 Accepted: April 21, 2018 Published: April 29, 2018


Photodynamic therapy (PDT) is a palliative treatment option for head and neck squamous cell carcinoma (HNSCC) patients which induces local inflammation and alters tumor cell morphology. We show that exosomes in plasma of HNSCC patients undergoing PDT reprogram tumor cells towards an epithelial phenotype. Nine HNSCC patients were treated with PDT and plasma was collected prior to and at three timepoints after therapy. Exosome levels of E-Cadherin, N-Cadherin and TGF-β1 were tested by flow cytometry. Exosomes were co-incubated with cancer cells, and changes in expression of EMT markers were evaluated as were proliferation, migration, chemotaxis and invasiveness of tumor cells. Exosomes harvested preand 24h after PDT were enriched in N-Cadherin and TGF-β1. They induced the mesenchymal phenotype and up-regulated Vimentin and transcripts for Snail, Twist, α-SMA, Slug and ZEB1 in epithelial tumor cells. These exosomes also enhanced tumor proliferation, migration and invasion. In contrast, exosomes obtained on day 7 or 4-6 weeks after PDT carried E-cadherin, restored epithelial morphology and EpCAM expression in tumor cells, down-regulated expression of mesenchymal genes and inhibited proliferation, migration and invasion. The PDT-mediated conversion from the mesenchymal to epithelial tumor phenotype was mediated by exosomes, which also served as non-invasive biomarkers of this transition.

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