ABSTRACT
BACKGROUND: Prostate cancer is the second leading cause of cancer death in men, and early detection is essential to reduce mortality and increase survival. delta-Catenin is a unique beta-catenin superfamily protein primarily expressed in the brain but is upregulated in human prostatic adenocarcinomas. Despite its close correlation with the disease, it is unclear whether delta-catenin presents the potential in prostate cancer screening because it is an intracellular protein. In this study, we investigated the hypothesis of delta-catenin accumulation in the urine of prostate cancer patients and its potential pathways of excretion into extracellular milieu. METHODS: Prostate cancer cell cultures, human tissue biopsies, and voided urines were characterized to determine extracellular delta-catenin accumulation and co-isolation with exosomes/prostasomes. RESULTS: We identified delta-catenin in culture media and in the stroma of human prostate cancer tissues. In PC-3 cells in culture, delta-catenin was partially co-localized and co-isolated with raft-associated membrane protein caveolin-1 and glycosylphosphatidylinositol-anchored protein CD59, suggesting its potential excretion into extracellular milieu through exosome/prostasome associated pathways. Interference with endocytic pathway using wortmannin did not block prostasome excretion, but delta-catenin overexpression promoted the extracellular accumulation of caveolin-1. delta-Catenin, caveolin-1, and CD59 were all detected in cell-free human voided urine prostasomes. delta-Catenin immunoreactivity was significantly increased in the urine of prostate cancer patients (P < 0.0005). CONCLUSIONS: This study demonstrated, for the first time, the extracellular accumulation of delta-catenin in urine supporting its potential utility for non-invasive prostate cancer detection.
