CA9 and colorectal cancer: Figure 5 shows the staining obtained with A3 only, because both antibodies performed equally well. As positive control, a commercial polyclonal anti-CA IX antiserum was used. A representative positive and negative control is shown for the LS174T tumour. A strong CA IX staining (green) was detectable in the colorectal cancer models LS174T and HT-29 at a distance of ∼100 μm from tumour blood vessels (red).