Prostasome Modulation of Blood Cascade System and Phosphoprotein Reactions with Focus on Prostate Cancer

Abstract: Prostasomes are extracellularly occurring submicron, membrane-surrounded organelles produced by the epithelial cells of the prostate and present in semen. Their precise physiological role is not known, although some of their properties assign them to important physiological and patho-physiological functions. In this thesis, some new properties of seminal and malignant cell line (DU145, PC-3 and LNCaP) prostasomes have been identified. Differences in the expressions and activities of prostasomal CD59, ATPase, protein kinases and tissue factor (TF) have been characterized. The transfer of prostasomal CD59 to CD59-deficient erythrocytes (rabbit and human PNH erythrocytes) has been established. CD59, protein kinases and TF were overexpressed by malignant cell prostasomes. ATPase activity was highest on seminal prostasomes with minimal expression by malignant cell prostasomes resulting in more residual ATP available for phosphorylation reactions. Several proteins were phosphorylated by prostasomal protein kinases, viz. complement component C3, fibrinogen, vitronectin and E-cadherin. Furthermore, TF was identified as the main endogenous phosphorylation substrate on prostasomes. In addition, prothrombotic effects of prostasomes were established. DU145 and PC-3-derived prostasomes exerted a higher clotting effect on whole blood and plasma compared to LNCaP and seminal prostasomes.In conclusion, malignant cell prostasomes showed higher ability to interact with the biological system in favor of prostate cancer cell promotion and survival. The roles played by prostasomes in this context may improve the understanding of the mechanisms that help the prostate cancer cells to avoid the complement attack (CD59 transfer and phosphorylation of C3), to promote angiogenesis (TF) and to metastasize. It may also provide a better understanding of some of the complications usually seen in some terminal prostate cancer patients like thrombotic events and tendency to develop disseminated intravascular coagulation.