CD9 and osteosarcoma: We compared our sEV isolate derived from 143B human osteosarcoma cells (fractions 1 through 4 from the qEV2) or an equivalent volume of our low particle count, high protein fractions from the same preparation (5 through 10) for expression of the sEV surface markers CD81 and CD9 and the cellular contamination marker GM130 via Western blot analysis.