Long-term exposure of tumor necrosis factor alpha causes hypersensitivity to androgen and anti-androgen withdrawal phenomenon in LNCaP prostate cancer cells.
BACKGROUND
One of the mechanisms through which prostate cancers relapse during anti-androgen therapy may involve adaptation to low concentrations of androgen induced by anti-androgen therapies. Recent studies from our laboratory have reported that tumor necrosis factor-alpha (TNFalpha) is secreted from prostate cancer epithelial cells and LNCaP cells. We hypothesized that TNFalpha changes androgen-sensitivity in LNCaP cells.


METHODS
We cultured LNCaP cells for more than 3 months in the presence of 50 ng/ml TNFalpha and established TNFalpha-resistant LNCaP cells (LN-TR2). Sensitivity to androgen was examined by the cell proliferation assay. We also transfected LNCaP and LN-TR2 cells with a luciferase reporter plasmid driven by prostate-specific antigen (PSA) promoter and compared PSA promoter activity. Nuclear localization of AR protein that binds to target genes was also examined by Western blotting.


RESULTS
LN-TR2 cells had increased sensitivity to dihydrotestosterone (DHT) (i.e., proliferation and PSA promoter activation) than LNCaP cells. Total AR mRNA and AR protein levels were decreased in LN-TR2 cells. However, LN-TR2 cells demonstrated increased levels of nuclear AR compared to LNCaP cells. At 1 nM DHT, the anti-androgen bicalutamide stimulated LN-TR2 and inhibited LNCaP proliferation.


CONCLUSIONS
Long-term exposure of TNFalpha causes hypersensitivity to DHT in LNCaP and this was associated with increased nuclear AR protein. Furthermore, hypersensitivity to androgen caused anti-androgen withdrawal phenomenon in the presence of DHT although bicalutamide itself did not stimulate LNCaP proliferation without androgen. This result may be one possible mechanism for the anti-androgen withdrawal phenomenon.
Department of Urology, University of Occupational & Environmental Health, Kitakyushu, Japan.
S
S
Harada
E T
ET
Keller
N
N
Fujimoto
K
K
Koshida
M
M
Namiki
T
T
Matsumoto
A
A
Mizokami
D000726:Androgen Antagonists / Q000494:pharmacology*; D000813:Anilides / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D015152:Blotting, Northern; D015153:Blotting, Western; D013196:Dihydrotestosterone / Q000378:metabolism*; D006801:Humans; D008156:Luciferases / Q000032:analysis; D008297:Male; D009570:Nitriles; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D013997:Time Factors; D014105:Tosyl Compounds; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D000726:Androgen Antagonists; D000813:Anilides; D000970:Antineoplastic Agents; D009570:Nitriles; D014105:Tosyl Compounds; D014409:Tumor Necrosis Factor-alpha; D013196:Dihydrotestosterone; C053541:bicalutamide; D008156:Luciferases