Radiation alters the cargo of exosomes released from cancer cells

Radiation is a highly efficient therapy in squamous head and neck carcinoma (HNSCC) treatment. However, local recurrence and metastasis are common complications. Recent evidence shows that cancer-cell-derived exosomes modify tumour cell movement and metastasis. In this study, researchers from Helmholtz Zentrum München link radiation-induced changes of exosomes to their ability to promote migration of recipient HNSCC cells. The researchers demonstrate that exosomes isolated from irradiated donor cells boost the motility of the HNSCC cells BHY and FaDu. Molecular data identified enhanced AKT-signalling, manifested through increased phospho-mTOR, phospho-rpS6 and MMP2/9 protease activity, as underlying mechanism. AKT-inhibition blocked the pro-migratory action, suggesting AKT-signalling as key player in exosome-mediated migration. Proteomic analysis of exosomes isolated from irradiated and non-irradiated BHY donor cells identified 39 up- and 36 downregulated proteins. In line with the observed pro-migratory effect of exosomes isolated from irradiated cells protein function analysis assigned the deregulated exosomal proteins to cell motility and AKT-signalling.

Functional and molecular comparison of exosomes released from 6 Gy irradiated and non-irradiated head and neck cancer cells. Exosomes isolated from irradiated BHY cells induce migration and chemotaxis by activating AKT-signalling and extracellular MMPs. In the same line radiation-induced changes of exosomal proteins predict effects on migration, chemotaxis and AKT-signalling.

Together, these findings demonstrate that exosomes derived from irradiated HNSCC cells confer a migratory phenotype to recipient cancer cells. This is possibly due to radiation-regulated exosomal proteins that increase AKT-signalling. The research team concludes that exosomes may act as driver of HNSCC progression during radiotherapy and are therefore attractive targets to improve radiation therapy strategies