Growth-inhibitory effect of prostasomes on prostatic cancer cell lines in culture

Objectives: Prostasomes, small corpuscular organelles derived from the pros tate gland, were isolated from human seminal plasma for incubation with thr ee human prostatic cancer cell lines: DU145, PC3, and LNCaP. The aim of thi s study was to establish any possible growth-inhibitory effect of prostasom es on prostatic cancer cell lines. Methods: Prostasomes were isolated from human seminal plasma. We determined their growth-inhibitory effect on the prostatic cancer cell lines by a flu orimetric cytotoxic assay technique. The results obtained were presented as survival index, defined as a percentage of control cultures, after compens ation for blank values. Results: The prostasomes exhibited a dose-dependent growth-inhibitory effec t on the cells, cell line DU145 being the most sensitive one displaying a s urvival index (mean I SD) of 46+/-10% at 200 mu g prostasomes (protein)/ml while the other two cell lines displayed survival indices of 93+/-6 and 93/-9%. Heat treatment of the prostasomes abolished their growth-inhibitory e ffect on the cell lines, whereas 24-hour dialysis of the prostasomes did no t affect their activity in this regard. Seminal plasma devoid of prostasome s exhibited less effect on the growth of these cancer cell lines, and heat treatment of the plasma did not influence the result. However, dialysis of the seminal plasma for 24 h abrogated its growth-inhibitory effect. Conclusion: The prostasomal growth-inhibitory effect on the cancer cell lin es was different from that of the prostasome-free seminal plasma. The forme r effect was most probably of a proteinaceous nature while the latter effec t was most likely due to the divalent cation composition of seminal plasma. In this regard, the zinc ion content seemed to be decisive. Copyright (C) 2000 S. Karger AG, Basel.