Objective: To study effects of estrogens on endothelin-1 (ET-1) mRNA expression in the androgen-sensitive LNCaP-FGC cell line and its androgen-resistant derivative LNCaP-r. Further, if effects of estrone sulfate (E1S) are mediated via conversion to estradiol-17beta (E2). Estrogens have been shown to down-regulate ET-1, a mediator of the osteoblastic response of bone to metastatic prostate cancer.
Methods: Cells were grown in steroid-depleted medium and incubated for 2-4 and 48 hours with 0, 1, 10, and 100 nM of either E1S or E2. mRNA levels were measured with an RT-PCR technique. Estrogen metabolism by LNCaP-FGC cells was studied by incubation with estrone (E1) and E1S at the same conditions, followed by determination of E1 and E2.
Results: ET-1 mRNA expression in LNCaP-FGC cells was significantly suppressed by E2 and E1S following incubation for 2-4h but after 48 h only by E2 at 1 and 10nM and in LNCaP-r cells only by E2 at 100 nM following 2-4h of incubation. ET-1 mRNA expression was significantly higher in untreated LNCaP-r than in untreated LNCaP-FGC cells. E1 was efficiently transformed into E2 by LNCaP-FGC cells but very little to E1 and no E2 was formed from E1S.
Conclusion: ET-1 mRNA expression in LNCaP-FGC can be inhibited by E2, but also by its prehormone E1S. The lack of formation of E2 from E1S suggests a mode of action not related to classical steroid receptors. The higher level of ET-1 mRNA expression found in LNCaP-r cells may reflect the capability of a hormone refractory tumor to maintain activity on its own, independently of known regulatory mechanisms such as sex steroids.