The biphasic stimulation of proliferation of Leydig cells by estrogen exposure

Citation
Jw. Du Mond et al., The biphasic stimulation of proliferation of Leydig cells by estrogen exposure, INT J ONCOL, 18(3), 2001, pp. 623-628
Citations number
30
Categorie Soggetti
Onconogenesis & Cancer Research
Journal title
INTERNATIONAL JOURNAL OF ONCOLOGY
ISSN journal
10196439 → ACNP
Volume
18
Issue
3
Year of publication
2001
Pages
623 - 628
Database
ISI
SICI code
1019-6439(200103)18:3<623:TBSOPO>2.0.ZU;2-R
Abstract
In this study, we have examined the influence of diethylstilbestrol (DES) a nd 17 beta -estradiol on the proliferation of TM3 Leydig cells, a normalize d mouse cell line. Cells were treated with seven different concentrations ( 1 pg-1 mug/ml) of DES or 17 beta -estradiol, and cell growth was measured a t 24-, 48-, and 72-h periods. DES treatment resulted in a significant (p < 0.05) stimulation of cell proliferation. We observed two independent peaks of cell proliferation, one at 1 pg/ml DES (186.87%) and the other at 100 ng /ml DES (248.23%). Cytotoxicity was noted at all time periods with 1 <mu>g/ ml DES treatment. 17 beta -estradiol treatment resulted in a significant st imulation of cell proliferation (p < 0.05) with a trend similar in response to that of DES treatment, as peak proliferation was noted with 1 pg/ml 17< beta>-estradiol (125.27%) and 10 ng/ml 17 beta -estradiol (138.31%). Based on these data, it appears that DES is more mitogenic in these Leydig cells compared to 17 beta -estradiol. Furthermore, for the first time, we detecte d that both DES and 17 beta -estradiol were able to stimulate proliferation of Leydig cells in a biphasic fashion. Cell cycle kinetic analysis reveale d that cell entry into the S-phase was higher in the DES treated cells comp ared to the controls, and doubling times of DES exposed cells were signific antly reduced (p < 0.05). Go-administration of tamoxifen at a concentration 1000-fold higher than either DES or 17<beta>-estradiol resulted in complet e inhibition of cell proliferation. Analysis of expression of ER alpha and ER beta by RT-PCR in untreated Leydig cells, as well as Leydig cells expose d to 1 pg/ml DES, revealed that the transcripts of ER alpha and ER beta wer e not detectable even after 40 cycles of amplification. A 100-ng/ml dose of DES induced ER alpha expression by 20-fold. These data suggest that estrog en exposure-mediated increases in cell proliferation, coupled with the decr ease in cell cycle time, may allow greater accumulation of DNA damage to oc cur in the testicular target cells compared to untreated cells under normal cell cycle control. In addition, an unidentified estrogen receptor may be responsible for the mitogenic activity of estrogens at low levels.