Stressors alter intercellular communication and exosome profile of nasopharyngeal carcinoma cells

Background: Head and neck cancers comprise the sixth most common cancer type worldwide. One of the most remarkable malignancies of the head and neck is the cancer of the nasopharynx, with a strong metastatic tendency already in the early stage. Besides the conventional pathways of metastasis formation, the information content of exosomes produced by the cancer cells may play a key role in metastatic transformation. The aim of this study was to investigate how stressors alter the characteristic of tumor derived exosomes. Methods: In our experimental model, we compared the quantity and content of exosomes produced by a nasopharyngeal carcinoma cell line (5-8F) under conventional (chemotherapy) and alternative (Ag–TiO₂-catalyzed reactive oxygen species generation) cytostatic treatment. After isolation, exosomes were identified by atomic force microscopy and quantified with Nanosight NS500 device. MicroRNA content of them was analyzed using SOLiD 5500xl technology. The sequences were annotated in CLC Genomics Workbench version 5.5.1. Results: Beyond the classic chemotherapeutic agent (doxorubicin), Ag–TiO₂ in a photo-catalytic process also showed cytostatic activity. Tumor cell damage induced by the cytostatic treatments significantly altered the number of released exosomes and led to the predominance of tumor suppressors in the exosomal miRNA profile. Conclusions: Our results suggest that the intercellular communication between tumor cells and surrounding stroma cells can be altered by microenvironment which increased quantity of exosomes and diversity of miRNAs in this study. Imbalance of oncogenic and tumor suppressor miRNAs caused by cytostatic treatments may influence the antiproliferative and metastasis inhibitory effect of cytostatic agents.