Interleukin-6 regulates androgen synthesis in prostate cancer cells.
OBJECTIVE
The standard systemic treatment for prostate cancer patients is androgen deprivation therapy. Although serum testosterone concentrations were significantly reduced after androgen deprivation therapy, levels of intraprostatic androgens are reproducibly measured at concentrations sufficient to activate androgen receptor and stimulate tumor growth, suggesting that prostate cancer cells may survive androgen deprivation therapies by increasing intracrine androgen synthesis within the prostate. However, factors that regulate de novo intracrine androgen synthesis have not been identified. Interleukin-6 (IL-6) has been implicated in the modulation of androgen receptor activation and growth and differentiation in prostate cancer. In this study, we investigate whether IL-6 regulates intraprostatic androgen synthesis in prostate cancer cells.


METHODS
Quantitative reverse transcription-PCR and Western blotting were done to detect expression levels of steroidogenic enzymes. AKR1C3 promoter reporter was constructed and analyzed for IL-6-mediated AKR1C3 transcriptional activity. IL-6-mediated signaling was knocked down using small interfering RNA specific to IL-6 receptor and gp130, and the effect on AKR1C3 expression was examined. Intraprostatic androgen levels in prostate cancer cells in culture and in tumors were measured by an enzyme immunoassay (Testosterone EIA kit).


RESULTS
We found that IL-6 increases the expression of genes encoding many steroidogenic enzymes, including HSD3B2 and AKR1C3, involved in androgen biosynthesis. Down-regulation of IL-6 receptor and gp130 expression using specific small interfering RNA abolished IL-6-mediated AKR1C3 expression, suggesting that IL-6 signaling is responsible for AKR1C3 expression. IL-6 increases AKR1C3 promoter activity, indicating that the increase in IL-6-mediated AKR1C3 expression is in part at the transcriptional level. Treatment of IL-6 increased testosterone level in LNCaP cells. The tumor testosterone levels were detected at 378 pg/g in tumors generated from IL-6-overexpressing LNCaP-IL6(+) cells inoculated orthotopically into the prostates of castrated male nude mice.


CONCLUSIONS
These results suggest that IL-6 increases levels of intracrine androgens through enhanced expression of genes mediating androgen metabolism in prostate cancer cells.
Chun
Jae Yeon
JY
Department of Urology, Graduate Program of Pharmacology and Toxicology, and Department of Biological Chemistry, and Cancer Center, University of California at Davis, Sacramento, CA 95817, USA. acgao@ucdavis.edu
Nadiminty
Nagalakshmi
N
Dutt
Smitha
S
Lou
Wei
W
Yang
Joy C
JC
Kung
Hsing-Jien
HJ
Evans
Christopher P
CP
Gao
Allen C
AC
D015096:3-Hydroxysteroid Dehydrogenases / Q000235:genetics; D000074425:Aldo-Keto Reductase Family 1 Member C3; D000728:Androgens / Q000096:biosynthesis*; D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015536:Down-Regulation / Q000235:genetics; D006801:Humans; D006911:Hydroxyprostaglandin Dehydrogenases / Q000235:genetics; D015850:Interleukin-6 / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008819:Mice, Nude; D011375:Progesterone Reductase / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011471:Prostatic Neoplasms / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D019947:Receptors, Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D013739:Testosterone / Q000819:agonists / Q000032:analysis / Q000378:metabolism
D000728:Androgens; D015850:Interleukin-6; D034741:RNA, Small Interfering; D019947:Receptors, Interleukin-6; D013739:Testosterone; D015096:3-Hydroxysteroid Dehydrogenases; D006911:Hydroxyprostaglandin Dehydrogenases; C533068:3 beta-hydroxysteroid dehydrogenase type II; D011375:Progesterone Reductase; C487341:AKR1C3 protein, human; D000074425:Aldo-Keto Reductase Family 1 Member C3