Selenomethionine does not affect PSA secretion independent of its effect on LNCaP cell growth

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Abstract
BACKGROUND Individuals supplemented with selenium have reduced incidence of prostate cancer. This study determines whether selenomethionine specifically affects the secretion of prostate specific antigen (PSA) in vitro. METHODS LNCaP cells were supplemented with selenomethionine for 7 days. PSA secretion was determined by ELISA. Cell proliferation was assessed by enumeration of trypan blue excluding cells. Colony formation was determined in soft agar. Cell cycle distribution was determined by FACS analysis of propidium iodide stained cells. RESULTS Selenomethionine at ≥ 70 μM inhibited LNCaP cell growth and colony formation. 0–100 μM selenomethionine did not affect the secretion of PSA by LNCaP cells in cell culture supernatants when normalized to the number of cells in culture. At supra-nutritional concentrations of selenomethionine, LNCaP cells had longer G0/G1 phase in agreement with the inhibitory effects on cell growth. CONCLUSIONS PSA secretion is not specifically inhibited by concentrations of selenomethionine corresponding to plasma selenium concentrations found in individuals supplemented with chemopreventive concentrations of selenized yeast. These data suggest that changes in serum PSA levels in individual patients during selenium supplementation is not an effect specific for PSA secretion, but rather may be a useful indicator for changes in disease progression in individual patients. Prostate 54: 315–321, 2003.