Inhibition of telomerase activity and secretion of prostate specific antigen by silibinin in prostate cancer cells.
OBJECTIVE
The androgen sensitive prostate cancer cell line LNCaP is strongly positive for dihydrotestosterone (DHT) dependent telomerase activity, which is an important factor in cellular immortality and carcinogenesis. In this study we determined the potential of silibinin as an anticancer drug that down-regulates telomerase activity and prostate specific antigen (PSA) together with the co-activator of the androgen receptor prostate epithelium specific Ets transcription factor.


METHODS
LNCaP cells were treated with various concentrations of silibinin in the presence or absence of 5alpha-DHT. We used real-time reverse transcriptase-polymerase chain reaction to quantify mRNA expression of PSA, prostate epithelium specific Ets transcription factor and the catalytic subunit of telomerase vs the housekeeping gene porphobilinogen deaminase with gene specific, dual labeled fluorescence probes. PSA secretion from LNCaP cells in conditioned medium was measured with an Elecsys System 2010 (Roche Diagnostics, Mannheim, Germany) and telomerase activity in extracts from LNCaP cells was measured with a TRAP (telomeric repeat amplification protocol) assay.


RESULTS
Silibinin down-regulated PSA mRNA expression and PSA secretion in conditioned medium. Simultaneous stimulation with silibinin and 10(-8) M DHT also resulted in PSA down-regulation, whereas DHT alone increased PSA secretion. Telomerase catalytic subunit mRNA decreased significantly after silibinin stimulation. Telomerase activity was down-regulated by silibinin and stimulated by DHT. The 2 agents in combination resulted in telomerase down-regulation.


CONCLUSIONS
The down-regulation of PSA by silibinin and its counteraction on DHT effects indicate that this compound can interact with the expression of genes that are regulated through the androgen receptor. Silibinin can also inhibit the telomerase activity that mediates cell immortality and carcinogenesis. The 2 effects underline the possible therapeutic use of silibinin as an antiproliferative agent in intervention for prostate cancer.
Thelen
P
P
Department of Urology, Institute of Human Genetics, Georg-August-University, Göttingen, Germany.
Wuttke
W
W
Jarry
H
H
Grzmil
M
M
Ringert
R-H
RH
D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008297:Male; D020944:Silybum marianum; D017430:Prostate-Specific Antigen / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D000077385:Silybin; D012838:Silymarin / Q000494:pharmacology*; D019098:Telomerase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D012838:Silymarin; D000077385:Silybin; D019098:Telomerase; D017430:Prostate-Specific Antigen