Estrogens increase the endothelial nitric oxide synthase (ecNOS) mRNA level in LNCaP human prostate carcinoma cells

The endothelial cell-specific form of nitric oxide synthases (ecNOS) may play an important role in vascular development, maintenance of vascular tone, and tumor growth in human prostate cancer. Estrogens have been shown to upregulate ecNOS expression in different human cell culture systems. Estrone sulfate (E1S) is the most abundant circulating estrogen, and may serve as a prehormone for the terminal biologically active estrogen estradiol-17beta (E2) in men.

The effects of E1S and E2 on mRNA expression of ecNOS were studied in the androgen-sensitive LNCaP-FGC cell line and its androgen-resistant derivative, LNCaP-r. The cells were grown in steroid-depleted medium and incubated for 2-4 or 48 hr with 0-100 nM of E1S and E2, respectively. ecNOS mRNA levels were determined using RT-PCR and are expressed as arbitrary units after correction for control HGPRT gene mRNA levels.

Treatment for 48 hr with 10 and 100 nM E1S significantly (P<0.05) increased ecNOS mRNA levels in LNCaP-FGC cells. Significantly higher (P<0.05) ecNOS mRNA levels also were found in LNCaP-FGC cells treated with E2 for 2-4 hr, irrespective of E2 concentration. The level of ecNOS mRNA was significantly lower (P<0.05) in untreated LNCaP-r than in LNCaP-FGC. LNCaP-r cells incubated with 100 nM E2 for 48 hr had a significantly higher (P<0.05) level of ecNOS mRNA than control LNCaP-r cells.

The results indicate that ecNOS mRNA expression in LNCaP-FGC can be induced by E2, but also by its prehormone E1S, probably after conversion to E2. However, the different stimulation patterns observed for E2 and E1S in LNCaP-FGC and LNCaP-r cells also could indicate stimulatory as well as inhibitory effects of estrogens in this model system, and this could depend on time of exposure and the concentration of active estrogen.