Figure 11. Diagram showing urinary PCA3 (lower arrow) vs serum PSA (upper arrow). Whereas PSA is a glycoprotein that may enter the bloodstream, PCA3 is a gene that exists in the nuclear material of prostate epithelial cells which may be shed into the urine. Those cells, if cancerous, over-express the gene. That over-expression, which may be many times that found in benign prostate cells, is detected by the assay. Importantly, PCA3 expression is normalized against a background of prostate-specific nuclear material (PSAmRNA), yielding a PCA3 score. The PCA3 score is much more cancer-specific than serum PSA levels, which are confounded by factors such as prostate volume, age, trauma, and certain drugs.