Characterization of a novel androgen receptor mutation in a relapsed CWR22 prostate cancer xenograft and cell line.
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.
Tepper
Clifford G
CG
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. cgtepper@ucdavis.edu
Boucher
David L
DL
Ryan
Philip E
PE
Ma
Ai-Hong
AH
Xia
Liang
L
Lee
Li-Fen
LF
Pretlow
Thomas G
TG
Kung
Hsing-Jien
HJ
D000728:Androgens / Q000172:deficiency / Q000502:physiology; D000818:Animals; D001483:Base Sequence; D005091:Exons; D020440:Gene Duplication; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009368:Neoplasm Transplantation; D009376:Neoplasms, Hormone-Dependent / Q000235:genetics; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011944:Receptors, Androgen / Q000096:biosynthesis / Q000235:genetics*; D013739:Testosterone / Q000494:pharmacology; D014162:Transfection; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
D000728:Androgens; D012333:RNA, Messenger; D011944:Receptors, Androgen; D013739:Testosterone