Extracellular vesicle tetraspanin-8 level predicts distant metastasis in non-small cell lung cancer after concurrent chemoradiation

Non-small cell lung cancer (NSCLC) is the most commonly diagnosed cancer and the leading cause of cancer death worldwide. More than half of patients with NSCLC die after developing distant metastases, so rapid, minimally invasive prognostic biomarkers are needed to reduce mortality. We used proteomics to identify proteins differentially expressed on extracellular vesicles (EVs) of nonmetastatic 393P and metastatic 344SQ NSCLC cell lines and found that tetraspanin-8 (Tspan8) was selectively enriched on 344SQ EVs. NSCLC cell lines treated with EVs overexpressing Tspan8 also exhibited increased Matrigel invasion. Elevated Tspan8 expression on serum EVs of individuals with stage III premetastatic NSCLC tumors was also associated with reduced distant metastasis-free survival, suggesting that Tspan8 levels on serum EVs may predict future metastasis. This result suggests that a minimally invasive blood test to analyze EV expression of Tspan8 may be of potential value to guide therapeutic decisions for patients with NSCLC and merits further study.