Tepper Clifford G, Boucher David L, Ryan Philip E, Ma Ai-Hong, Xia Liang, Lee Li-Fen, Pretlow Thomas G, Kung Hsing-Jien
Division of Basic Sciences, University of California Davis Cancer Center and Department of Biological Chemistry, University of California, Davis School of Medicine, Sacramento, California 95817, USA.
Cancer Res. 2002 Nov 15;62(22):6606-14.
CWR22 has been a valuable xenograft model for the study of prostate cancer progression from an androgen-dependent tumor to one that grows in castrated animals. Herein, we report the identification and characterization of a novel androgen receptor (AR) mutation occurring in a relapsed tumor (CWR22R-2152) and in the CWR22Rv1 cell line established from it. The mutation was not detected in the original, hormone-dependent CWR22 xenograft, indicating that this change occurred during the progression to androgen independence. It is characterized by an in-frame tandem duplication of exon 3 that encodes the second zinc finger of the AR DNA-binding domain. Accordingly, immunoblot analyses demonstrated the expression of an AR species having an approximately 5-kDa increase in size relative to the LNCaP AR. This was accompanied by a COOH-terminally truncated AR species migrating with a relative mass of 75-80 kDa, referred to as ARDeltaLBD because it lacks the ligand-binding domain. By recreating the exon 3 duplication mutation in a wild-type AR expression construct, the generation of ARDeltaLBD could be recapitulated. Whereas ARDeltaLBD exhibited constitutive nuclear localization and DNA binding, these functions in the full-length AR remained androgen dependent. The CWR22Rv1 AR repertoire displayed dose-dependent, androgen-responsive transcriptional transactivation in reporter assays, albeit to a lesser extent in comparison with LNCaP. This cell line also expressed low levels of prostate-specific antigen mRNA and did not express or secrete detectable levels of prostate-specific antigen protein in androgen-depleted medium or in response to physiological androgenic stimulation. In summary, the CWR22Rv1 cell line displays both androgen-responsive and androgen-insensitive features due, at least in part, to a novel insertional mutation of the AR.
CWR22一直是一种有价值的异种移植模型，用于研究前列腺癌从雄激素依赖肿瘤发展为在去势动物中生长的肿瘤。在此，我们报告了在复发肿瘤（CWR22R - 2152）及其建立的CWR22Rv1细胞系中发现并鉴定的一种新型雄激素受体（AR）突变。在原始的激素依赖型CWR22异种移植中未检测到该突变，表明这种变化发生在向雄激素非依赖的进展过程中。其特征是编码AR DNA结合域第二个锌指的外显子3发生框内串联重复。相应地，免疫印迹分析表明，与LNCaP AR相比，一种大小增加约5 kDa的AR物种表达。同时还伴有一个COOH末端截短的AR物种，其相对分子质量为75 - 80 kDa，因其缺乏配体结合域而被称为ARDeltaLBD。通过在野生型AR表达构建体中重现外显子3重复突变，可以再现ARDeltaLBD的产生。虽然ARDeltaLBD表现出组成型核定位和DNA结合，但全长AR中的这些功能仍依赖雄激素。在报告基因检测中，CWR22Rv1 AR库显示出剂量依赖性的雄激素反应性转录激活，尽管与LNCaP相比程度较小。该细胞系还表达低水平的前列腺特异性抗原mRNA，并且在雄激素缺乏的培养基中或对生理性雄激素刺激无反应时，不表达或分泌可检测水平的前列腺特异性抗原蛋白。总之，CWR22Rv1细胞系至少部分由于AR的一种新型插入突变而表现出雄激素反应性和雄激素不敏感性特征。
