RNA interference-mediated silencing of the S100A10 gene attenuates plasmin generation and invasiveness of Colo 222 colorectal cancer cells.

S100A10 is a key plasminogen receptor of the extracellular cell surface that is overexpressed in many cancer cells. Typically, S100A10 is thought to be anchored to the plasma membrane via the phospholipid-binding sites of its binding partner, annexin A2. Here, using the potent and highly sequence-specific mechanism of RNA interference (RNAi), we have stably silenced the expression of the S100A10 gene in colorectal (CCL-222) cancer cells. We show that siRNA expression mediated by the pSUPER vector causes efficient, stable, and specific down-regulation of S100A10 gene expression. The siRNA-mediated down-regulation of S100A10 gene expression resulted in a major decrease in the appearance of extracellular S100A10 protein and correlated with a 45% loss of plasminogen binding, a 65% loss in cellular plasmin generation and a complete loss in plasminogen-dependent cellular invasiveness. We also observed that the CCL-222 cells do not express annexin A2 on their extracellular surface. Thus, the data show that annexin A2 is not required by S100A10 for its association with the plasma membrane, for its colocalization with uPAR, or for its binding and activation of plasminogen.