Normal prostate cells and prostate cancer cells produce prostate-specific antigen (PSA): thus, it is frequently increased in non-malignant conditions such as prostatitis and benign prostatic hyperplasia. Indeed, PSA is an excellent biomarker to monitor disease progression. The low diagnostic specificity of PSA leads to many false-positive and a large number of biopsies. These well-recognized limitations of PSA suggest that new prostate cancer biomarkers could play a useful role in reducing the number of unnecessary biopsies.