Effects of tamoxifen, an antiestrogen, on rat prostate carcinogenesis by 3,2'-dimethyl-4-aminobiphenyl and testosterone do not support an estrogen role in testosterone promotion.
BACKGROUND
Our previous data suggest that estrogen plays an important role in rat prostate carcinogenesis, particularly in promotion by testosterone. Therefore, in the present experiment, effects of an antiestrogen, tamoxifen (TAM), were investigated.


METHODS
Male F344 rats initially received 3,2'-dimethyl-4-aminobiphenyl (DMAB) at 50 mg/kg bw every 2 weeks for 20 weeks and then TAM in Silastic tubes was subcutaneously given alone or together with testosterone propionate (TP) for 40 weeks.


RESULTS
TAM significantly suppressed prostate weights, suggesting an estrogenic action, but the development of preneoplastic and/or neoplastic lesions of the prostate or seminal vesicles in rats given DMAB alone or DMAB and TP was not altered. TAM reversed the suppression of development of ventral atypical hyperplasias by TP.


CONCLUSIONS
These findings suggest that estrogen, which is derived from testosterone by the action of aromatase, is not involved in the strong promotion by TP of DMAB prostate carcinogenesis.
Miyata
E
E
First Department of Pathology, Nagoya City University Medical School, Japan.
Kawabe
M
M
Sano
M
M
Takesada
Y
Y
Takahashi
S
S
Shirai
T
T
D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D002273:Carcinogens; D002461:Cell Line, Transformed; D004965:Estrogen Antagonists / Q000494:pharmacology*; D008297:Male; D009929:Organ Size / Q000187:drug effects; D011467:Prostate / Q000187:drug effects / Q000473:pathology; D011470:Prostatic Hyperplasia / Q000139:chemically induced; D011471:Prostatic Neoplasms / Q000139:chemically induced*; D051381:Rats; D012669:Seminal Vesicles / Q000187:drug effects / Q000473:pathology; D013629:Tamoxifen / Q000494:pharmacology*; D013739:Testosterone / Q000633:toxicity*; D014407:Tumor Cells, Cultured
D002273:Carcinogens; D004965:Estrogen Antagonists; D013629:Tamoxifen; D013739:Testosterone; D015127:9,10-Dimethyl-1,2-benzanthracene