Chun Jae Yeon, Nadiminty Nagalakshmi, Dutt Smitha, Lou Wei, Yang Joy C, Kung Hsing-Jien, Evans Christopher P, Gao Allen C
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.
Clin Cancer Res. 2009 Aug 1;15(15):4815-22. doi: 10.1158/1078-0432.CCR-09-0640. Epub 2009 Jul 28.
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.
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).
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.
These results suggest that IL-6 increases levels of intracrine androgens through enhanced expression of genes mediating androgen metabolism in prostate cancer cells.
前列腺癌患者的标准全身治疗是雄激素剥夺疗法。尽管雄激素剥夺疗法后血清睾酮浓度显著降低，但前列腺内雄激素水平仍能被重复检测到，其浓度足以激活雄激素受体并刺激肿瘤生长，这表明前列腺癌细胞可能通过增加前列腺内自分泌雄激素合成来在雄激素剥夺疗法中存活。然而，调节从头开始的自分泌雄激素合成的因素尚未被确定。白细胞介素-6（IL-6）已被证明与前列腺癌中雄激素受体激活以及生长和分化的调节有关。在本研究中，我们调查IL-6是否调节前列腺癌细胞中前列腺内雄激素的合成。
进行定量逆转录-PCR和蛋白质印迹法以检测类固醇生成酶的表达水平。构建AKR1C3启动子报告基因并分析IL-6介导的AKR1C3转录活性。使用针对IL-6受体和gp130的小干扰RNA敲低IL-6介导的信号传导，并检查对AKR1C3表达的影响。通过酶免疫测定法（睾酮酶免疫分析试剂盒）测量培养的前列腺癌细胞和肿瘤中前列腺内雄激素水平。
我们发现IL-6增加了许多参与雄激素生物合成的类固醇生成酶编码基因的表达，包括HSD3B2和AKR1C3。使用特异性小干扰RNA下调IL-6受体和gp130表达消除了IL-6介导的AKR1C3表达，表明IL-6信号传导负责AKR1C３表达。IL-6增加AKR1C3启动子活性，表明IL-6介导的AKR1C3表达增加部分是在转录水平上。IL-6处理增加了LNCaP细胞中的睾酮水平。在原位接种到去势雄性裸鼠前列腺中的IL-6过表达LNCaP-IL6(+)细胞产生的肿瘤中，检测到肿瘤睾酮水平为378 pg/g。
这些结果表明，IL-6通过增强前列腺癌细胞中介导雄激素代谢的基因表达来增加自分泌雄激素水平。
