Human myeloma cells shed ADAM-9. (A) Flow cytometric analysis of ADAM-9 expression on the surface of RPMI-8226 myeloma cells. (B) Flow cytometric analysis of ADAM-9 expression on the surface of RPMI-8226 myeloma cells incubated in the presence of PMA. (C) Comparison of mean fluorescence values (±95% CI) from cells incubated in the presence or absence of PMA demonstrated a reduction in ADAM-9 expression in PMA-treated cells. (D) Western blot analysis of ADAM-9 in media conditioned by RPMI-8226 cells incubated in the presence or absence of PMA and/or proteinase inhibitors. PMA stimulated an increase in the 44-kDa product that was blocked with proteinase inhibitors.