Staining controls were performed on a) benign prostate cells, which are negative for ERG (Figure S4C, left image); b) endothelial cells and lymphocytes, which stain positive for ERG [50] and constitute an internal staining control (example in Figure S4C, right image); and c) cell lines representing ERG+ (VCAP) or ERG− (Du145) prostate cancer (Figure S4D). This evidence concerns the gene ERG and prostate cancer.