MUC16 released from epithelial surfaces by SP168 does not bind to a MUC16 cytoplasmic tail antibody indicating ectodomain release.

<p>HCLE cells were cultured with growth culture filtrate obtained from strain SP168 for 1 hour (SP168), and the resultant media was diluted 1∶3 with DMEM/F12, and subjected to a 10 kDa cutoff concentrator. HCLE cell lysate with intact full-length MUC16 (75 µg) was used as a positive control. Western blot of the resulting concentrate and cell lysate using: <b>A</b>) MUC16CT antibody that recognizes full-length MUC16 at >250 kDa and the cytoplasmic tail between 25–37 kDa, or <b>B</b>) MUC16 extracellular domain (ECD) antibody (M11). The MUC16CT antibody binds to the positive control cell lysate only (arrow), but not to the cell culture supernatants after exposure to SP168 (A). Conversely, M11 antibody binds to a band of appropriate molecular weight in culture supernatants as well as the cell lysate (B). These data indicate that the sheddase releases the MUC16 ectodomain into the cell culture media. Molecular weight standards are on the left in kDa.