Alterations of prostate biomarker expression and testosterone utilization in human LNCaP prostatic carcinoma cells by garlic-derived S-allylmercaptocysteine
Jt. Pinto et al., Alterations of prostate biomarker expression and testosterone utilization in human LNCaP prostatic carcinoma cells by garlic-derived S-allylmercaptocysteine, PROSTATE, 45(4), 2000, pp. 304-314
BACKGROUND. This study determined the effects of S-allylmercaptocysteine (S
AMC), a phytoconstituent from garlic, on the expression of androgen-respons
ive biomarkers, prostate specific antigen (PSA), and prostate specific memb
rane antigen (PSMA), in human prostatic carcinoma cells (LNCaP).
METHODS. Secretion of PSA was determined as well as the activity of PSMA me
asured as a function of its ability to hydrolyze poly-gamma -glutamated fol
ate and N-acetylaspartylglutamate (NAAG). Folate hydrolase capacity was als
o determined in SAMC-treated cells grown in charcoal stripped fetal calf se
rum (CS-FCS). In addition, testosterone disappearance was measured from cul
ture media of SAMC-treated LNCaP and PC-3 cells as well as from cell free l
ysates.
RESULTS. PSA secretions were significantly decreased compared to control va
lues at. 1 day (8.4 +/- 2.6 vs. 18.9 +/- 1.7, P < 0.01), 4 days (18.9 +/- 5
.3 vs. 73.8 +/- 4.4, P < 0.001), and 6 days (35.6 +/- 2.1 vs. 96.5 +/- 17.9
ng/10(5) cells, P < 0.01; mean +/- SD). By contrast, PSMA activity measure
d as either folate hydrolase or NAAG dipeptidase (NAALADase) activity incre
ased in cells treated with SAMC. PSMA-folate hydrolase activity in SAMC-tre
ated cells grown in CS-FCS increased beyond that observed in cells grown in
CS-FCS alone. Pre-exposure of LNCaP cells to SAMC resulted in enhanced rat
e of testosterone disappearance from culture media at 6 hr (P < 0.01) and a
t 48 hr (P < 0.001) compared to media from cells not previously exposed to
SAMC. Results similar to these were also observed in androgen-independent P
C-3 cells treated with SAMC. In lysates of SAMC-treated LNCaP cells, the ra
te of testosterone catabolism was twice that from phosphate buffered saline
(PBS)-treated cells. SAMC-treated LNCaP cells grown in media supplemented
with testosterone temporarily exhibited enhanced growth over a 2 day period
but cell numbers declined later to levels similar to those of SAMC treatme
nt.
CONCLUSIONS. These results show that SAMC exhibits differential effects on
recognized biomarkers for LNCaP cells similar to those produced by androgen
deprivation and strongly suggests that this effect may be mediated, in par
t, by diminishing the trophic effects of testosterone, likely by converting
it to metabolites less reactive toward androgen receptors. (C) 2000 Wiley-
Liss, Inc.