Evidence for a novel mechanism of androgen resistance in the human prostate cancer cell line, PC-3.
Progression to hormone-refractory disease is a common outcome of human prostate cancer. In this study, we have investigated the basis of androgen insensitivity in the human prostate cancer cell line, PC-3, which was derived from a bone metastasis of a hormone-refractory prostate cancer. PC-3 cells with virtually undetectable (PC-3AR-) or low (PC-3AR+) levels of androgen receptor (AR) RNA expression were examined. RNase protection assays demonstrated that the level of AR RNA in PC-3AR+ cells was similar to that in a normal androgen-responsive genital skin fibroblast cell strain. Quantitative immunocytochemical staining of AR in PC-3AR+ cells using antibodies directed against the amino and carboxyl termini of the receptor revealed staining in 30% of cells with either antibody. Furthermore, the level of AR staining in PC-3AR+ cells was higher than in the androgen-responsive breast cancer cell lines ZR-75-1, T47-D, and MCF-7. Despite the expression of AR RNA and protein, PC-3AR+ cell proliferation was unaffected by the presence of 0.1-10 nM mibolerone. Scatchard analysis demonstrated a complete absence of specific [3H]dihydrotestosterone ([3H]DHT) binding to PC-3AR+ cytosolic extracts, which could not be explained by structural alterations in the AR gene. The sizes of individual AR exons amplified from genomic DNA derived from PC-3AR+ cells were identical to those amplified from normal human cells. Furthermore, sequence analysis did not reveal a mutation in the DNA- or hormone-binding domains of the AR gene in PC-3AR+ cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Tilley
W D
WD
Department of Surgery, School of Medicine, Flinders University of South Australia, Bedford Park.
Bentel
J M
JM
Aspinall
J O
JO
Hall
R E
RE
Horsfall
D J
DJ
D000728:Androgens / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D004351:Drug Resistance; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D012334:RNA, Neoplasm / Q000096:biosynthesis*; D011869:Radioligand Assay; D011944:Receptors, Androgen / Q000235:genetics*; D014407:Tumor Cells, Cultured
D000728:Androgens; D009363:Neoplasm Proteins; D012334:RNA, Neoplasm; D011944:Receptors, Androgen