 ARSB activity was lower in malignant than normal prostate tissue, and immunostaining of prostate tissue microarrays showed not only decreasing ARSB staining in prostate cancer tissue of a higher Gleason score, but also lower staining in patients with recurrent compared to non-recurrent cancer.ARSB staining was a greater predictor of recurrence than Prostate-specific antigen (PSA) test, indicating possible future role of ARSB as a prognostic biomarker of prostate cancer.Further evidence of ARSB as a tumor suppressor was determined by molecular studies in cell cultures where ARSB was silenced by siRNA.