MORAb-009 blocks CA125/MUC16-mesothelin interaction. (A) FACS analysis of A431-K5-TEM cells reacted with no mAb, anti-FRa mAb, anti-TEM1 mAb, or MORAb-009. Equivalent positive staining was associated with the expression of cognate proteins (TEM-1 and mesothelin) but not with FRa, which is not expressed in these cells. (B) Fluorescently-labeled A431-K5-TEM cells were reacted with no mAb, anti-FRa mAb (CT IgG), anti-TEM1 mAb, or MORAb-009, and seeded on a monolayer of CA125/MUC16 positive OVCAR-3 cells (first four bars). Cell adhesion was completely blocked by MORAb-009 compared to the other treatments. (C) Same as in B, whereby MORAb-009 concentration ranged from 1 ng/mL to 100 µg/mL. Blockade of CA125/MUC16-mesothelin interaction was seen with concentrations as low as 10 ng/mL.