Overexpression of 5 alpha-reductase type 1 increases sensitivity of prostate cancer cells to low concentrations of testosterone.
BACKGROUND
Conversion of testosterone to dihydrotestosterone (DHT) by the enzymes 5 alpha-reductase types 1 (5 alpha R1) and 2 (5 alpha R2) is important for normal and pathological growth of the prostate. The predominant isoenzyme in normal prostate is 5 alpha R2. However, prostate cancer (PCa) development is accompanied by a decrease in 5 alpha R2 and an increase in 5 alpha R1. The biological significance of increased 5 alpha R1 expression is not fully understood. Therefore, the aim of this study was to determine the effect of overexpression of 5 alpha R1 on growth and prostate-specific antigen (PSA) production in PCa cells.


METHODS
LNGK-9 PCa cells, transiently transfected with pTRE-5 alpha R1 or pTRE alone, were cultured in the presence or absence of testosterone at varying concentrations. Cell growth and PSA secretion were measured after 4-6 days. Cyclin E1, Ki67, and PSA mRNA levels were evaluated using RT-PCR after 24 hr of treatment.


RESULTS
10 pM testosterone increased growth of pTRE-5 alpha R1 transfectants by 54.1% over cells grown in the absence of testosterone, compared to 25.0% in pTRE transfectants (P < 0.01). Likewise, PSA secretion was increased by 56-fold in pTRE-5 alpha R1 transfectants treated with 10 pM testosterone, compared to 26-fold in pTRE transfectants (P < 0.01). At concentrations of testosterone above 10 pM, the stimulatory effect on growth and PSA secretion was not distinguishable between pTRE-5 alpha R1 and pTRE transfectants.


CONCLUSIONS
These results demonstrate that upregulation of 5 alpha R1 enhances the cellular response to low, but not high, concentrations of testosterone. This explains one mechanism by which castration-recurrent PCa can proliferate in the presence of castrate levels of circulating testosterone.
Thomas
Lynn N
LN
Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada. lynn.thomas@dal.ca
Douglas
Robert C
RC
Rittmaster
Roger S
RS
Too
Catherine K L
CK
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000235:genetics*; D045744:Cell Line, Tumor; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D004273:DNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007527:Isoenzymes / Q000235:genetics; D008297:Male; D017430:Prostate-Specific Antigen / Q000235:genetics; D011471:Prostatic Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013739:Testosterone / Q000494:pharmacology*; D014162:Transfection; D015854:Up-Regulation
D017931:DNA Primers; D018076:DNA, Complementary; D004273:DNA, Neoplasm; D007527:Isoenzymes; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D013739:Testosterone; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase; D017430:Prostate-Specific Antigen