Increased CD59 protein expression predicts a PSA relapse in patients after radical prostatectomy

BACKGROUND: Human protectin (CD59) is a regulator of complement activation that inhibits complement-mediated cell lysis, and thus might confer immune resistance to tumor cells. CD59 expression has been described in a variety of human malignancies, including breast cancer. Since a comprehensive investigation of CD59 expression in prostate cancer has not been conducted yet, we aimed to determine the significance of CD59 expression in prostate cancer. METHODS: Eighty-six primary adenocarcinomas of the prostate were immunostained using a monoclonal CD59 antibody (clone MEM-43) and a standard detection system. The immunoreactivity of the tumor was evaluated as low versus high for statistical analysis. Additionally, CD59 mRNA levels were determined by real-time PCR in matched (tumor/normal) microdissected tissues from 26 cases. RESULTS: Cytoplasmic CD59 immunoreactivity was found in epithelia of prostate cancer, prostatic intraepithelial neoplasia, benign hyperplasia, atrophic, and normal glands. High rates of CD59 expression were noted in 36% of prostate cancer cases and were significantly associated with tumor pT stage (P = 0.043), Gleason grade (P = 0.013) and earlier biochemical (PSA) relapse in Kaplan-Meier analysis (P = 0.0013). On RNA level, we found an upregulation in 19.2% (five cases), although the general rate of CD59 transcript was significantly lower in tumor tissue (P = 0.03). CONCLUSION: CD59 protein is strongly expressed in 36% of adenocarcinomas of the prostate and and is associated with disease progression and adverse patient prognosis.