Endocrine Abstracts

Somatostatin (SS) receptors (SSR) expression may be modulated by estrogens in breast cancer cells. Aim of this study was to evaluate the effects of estradiol (E₂) on SSR levels in prostate epithelial cells (PEC).

Methods: We investigated the effects of E₂ and SS-analogue SOM230 combined treatment on two PEC lines: EPN that expresses both ERalfa and beta and CPEC, showing no ERalfa and very low ERbeta expression. Cells starved in red phenol-free DMEM and 1% charcoal treated FBS for 5d were treated with 20 mM E₂ or 10⁻⁶ or 10⁻⁸ SOM230 or 20 mM E₂+ SOM230 (10⁻⁸ or +10⁻⁶⁾ for 48 h. Cells were differently harvested for semiquantitative RT-PCR, Western blot or flow cytometry (FACS) analyses.

Results: In EPN E₂ or SOM 10⁻⁶ alone induced apoptosis and decreased slightly proliferation; 20 mM E₂+ SOM230 (10⁻⁸ or 10⁻⁶⁾ combined treatment induced a stronger rate of apoptosis and a greater decrease of proliferation. The synergistic action correlated to: a reduction in S-phase proliferation with an arrest in G0/G1 phase induced by SOM230 and increased by E₂-SOM 230 co-treatment; a caspase-dependent apoptosis induced by SOM230; a reduction of bcl-2 levels induced after addition of E₂; an up-regulation of SSR 1, 2 and 5 mRNA and proteins induced by E₂ that amplified SOM230 effects at lower doses. In CPEC, expressing SSRs 3, 5, and low levels of SSTR1 and 2, SOM230 induced a modest apoptotic effect; moreover, E₂ administration did not influence SSR expression neither SOM230 effects on cell growth.

Conclusion: Of E₂ increases the inhibitory effects of SOM230 in prostate cellsexpressing ERalfa and beta, acting directly on cell growth and cell death control and up-regulating SSRs. The evaluation of ERs and SSRs should be performed preliminarily in order to verify the possible efficiency of E₂-SOM230 combined treatment in prostate cancer.