Knockdown of K-Ras was achieved by transfecting HCT 116 cells with K-Ras specific validated siRNA (Silencer® select Product # s7940). Western blot analysis (Fig a) was performed using whole cell extracts from K-Ras knockdown cells (Lane 3), non-specific scrambled siRNA transfected cells (Lane 2) and untransfected cells (Lane 1). The blot was probed with Anti-K-Ras Recombinant Rabbit Monoclonal Antibody (Product # 703345, 1:5000 dilution) and Goat anti-Rabbit IgG (H+L) Superclonal™ Secondary Antibody, HRP conjugate (Product # A27036, 0.25 µg/mL, 1:4000 dilution). Densitometric analysis of this Western blot is shown in the histogram (Fig b). Loss of signal upon siRNA mediated knockdown confirms that antibody is specific to K-Ras.