Tekur S, Lau K M, Long J, Burnstein K, Ho S M
Division of Urology, Department of Surgery, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
Mol Carcinog. 2001 Jan;30(1):1-13. doi: 10.1002/1098-2744(200101)30:1<1::aid-mc1008>3.0.co;2-x.
RET fused gene (RFG)/ELE1alpha/androgen receptor-associated protein 70(ARA70) was first found to be involved in the activation of the RET proto-oncogene in thyroid neoplasm and has recently been shown to be a ligand-dependent transcriptional coregulator for androgen receptor (AR). The functionality of RFG/ELE1alpha/ARA70 remains controversial, and little is known about factors regulating its expression in the prostate. Of significant interest is whether this molecule is involved in prostate carcinogenesis. Using reverse transcriptase-polymerase chain reaction semiquantitation, we compared RFG/ELE1alpha/ARA70 mRNA levels in four prostate cancer cell lines (LNCaP, TSU-Pr1, DU-145, and PC-3) with those found in primary cultures of normal prostatic epithelial cells (PrECs). In addition, we examined the effects of androgen and antiandrogen, estrogen and antiestrogen, and a demethylating agent on RFG/ELE1alpha/ARA70 mRNA expression levels in AR- and AR+ PC-3 cells. Reduced levels of RFG/ELE1alpha/ARA70 message were observed in all four prostate cancer cell lines when compared with normal PrECs in primary cultures. RFG/ELE1alpha/ARA70 mRNA levels in PC-3 cells, which express both estrogen receptor subtypes, were upregulated by 17beta-estradiol and inhibited by the antiestrogen ICI-182780. In PC-3(AR+) cells, which were genetically engineered to express AR, exposure to androgen upregulated RFG/ELE1alpha/ARA70 mRNA expression, whereas treatment with 4-hydroxyflutamide lowered expression of this transcript. Furthermore, treatment of DU-145 cells, which did not express RFG/ELE1alpha/ARA70 transcripts, with a demethylating agent reactivated transcription of this gene. Polymerase chain reaction analyses of monochromosomal human-rodent hybrid panels localized a putative RFG/ELE1alpha/ARA70 isoform on human chromosome 5q31.1-31.2. In summary, we identified sex hormones and DNA hypermethylation as regulators of RFG/ELE1alpha/ARA70 expression in prostate cancer cells. In addition, we found reduced levels of RFG/ELE1alpha/ARA70 expression in prostate cancer cell lines when compared with expression levels in normal PrECs in culture. These findings suggest that RFG/ELE1alpha/ARA70 may be involved prostate carcinogenesis and that it may serve as a key mediator of estrogen-androgen synergism.
RET融合基因（RFG）/ELE1α/雄激素受体相关蛋白70（ARA70）最初被发现参与甲状腺肿瘤中RET原癌基因的激活，最近已被证明是雄激素受体（AR）的配体依赖性转录共调节因子。RFG/ELE1α/ARA70的功能仍存在争议，关于调节其在前列腺中表达的因素知之甚少。一个重要的问题是该分子是否参与前列腺癌的发生。我们使用逆转录聚合酶链反应半定量法，比较了四种前列腺癌细胞系（LNCaP、TSU-Pr1、DU-145和PC-3）中RFG/ELE1α/ARA70 mRNA水平与正常前列腺上皮细胞（PrECs）原代培养物中的水平。此外，我们研究了雄激素和抗雄激素、雌激素和抗雌激素以及一种去甲基化剂对AR阳性和AR阴性PC-3细胞中RFG/ELE1α/ARA70 mRNA表达水平的影响。与原代培养的正常PrECs相比，在所有四种前列腺癌细胞系中均观察到RFG/ELE1α/ARA70信使水平降低。在同时表达两种雌激素受体亚型的PC-3细胞中，RFG/ELE1α/ARA70 mRNA水平被17β-雌二醇上调，并被抗雌激素ICI-182780抑制。在经过基因工程改造以表达AR的PC-3（AR阳性）细胞中，暴露于雄激素会上调RFG/ELE1α/ARA70 mRNA表达，而用4-羟基氟他胺处理则会降低该转录本的表达。此外，用去甲基化剂处理不表达RFG/ELE1α/ARA70转录本的DU-145细胞可重新激活该基因的转录。对单染色体人-啮齿动物杂交细胞系的聚合酶链反应分析将一种假定的RFG/ELE1α/ARA70异构体定位在人类染色体5q31.1-31.2上。总之，我们确定性激素和DNA高甲基化是前列腺癌细胞中RFG/ELE1α/ARA70表达的调节因子。此外，我们发现与培养的正常PrECs中的表达水平相比，前列腺癌细胞系中RFG/ELE1α/ARA70的表达水平降低。这些发现表明RFG/ELE1α/ARA70可能参与前列腺癌的发生，并且它可能是雌激素-雄激素协同作用的关键介质。
