A novel truncated form of Nephronectin is present in small extracellular vesicles isolated from 66cl4-cells

Extracellular vesicles are quickly emerging as biomarkers in breast cancer. Our recent report suggested that an intracellular granular staining pattern of the extracellular matrix protein Nephronectin (NPNT) in breast tumor sections correlated with poor prognosis. In this study we performed proteomic analysis which reveals that overexpression of NPNT in breast cancer cells alters the cargo of its NPNT-containing small extracellular vesicles, and includes several tumor promoting proteins. We identify three different forms of NPNT at 80, 60 and 20 kDa. We report that the native form of NPNT at 60 kDa gets further glycosylated and is detected as the 80 kDa NPNT, which maybe truncated then by matrix metalloproteinases to a shorter form of around 20 kDa. Although both 80 kDa and 20 kDa NPNT are detected in small extracellular vesicles (sEVs) derived from breast cancer cells, the truncated form of NPNT is concentrated in sEVs, which is a novel finding.