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Currently, there is increasing interest in the in vivo protective effects of natural antioxidants found in dietary plants against oxidative damage caused by free radical species. Oxidative stress has been invoked as a causative agent in cancer and epidemiological data suggest that the consumption of fruits and vegetables may be associated with a lower incidence of cancer. The fruit of the Olea europaea L. and olive oil contain hundreds of phytochemicals and its extracts have recently been shown to exhibit antioxidant properties, due to the action of oleuropein. In view of these considerations, in this study, we investigated the effects of oleuropein on LNCaP and DU145 prostate cancer cell lines and on BPH-1 non-malignant cells. Oleuropein reduces cell viability and induces thiol group modifications, γ-glutamylcysteine synthetase, reactive oxygen species, pAkt and heme oxygenase-1. Exposing cell cultures to oleuropein induces an antioxidant effect on BPH-1 cells and a pro-oxidant effect on cancer cells. Our results confirm the beneficial properties of olive oil and oleuropein, suggesting its possible use as an adjuvant agent in the treatment of prostatitis, in order to prevent the transformation of hypertrophic to cancerous cells.

Benign prostate hypertrophy (BPH) and prostate cancer (PC) are prostate chronic diseases that require a long period for development from a small lesion to clinical manifestation. PC is the most common cancer in men in Europe and the Americas. Tumor growth and metastasis depend upon the development of neovasculature around the tumor. This process, called angiogenesis, may be regulated by NO, and thus modulation of NO production could play an important role in tumor progression. Recent studies report the involvement of DDAH, an enzyme which metabolizes the endogenous NOS inhibitor ADMA, in the development of tumor vasculature. The aim of the present study was to verify the involvement of the DDAH/NOS pathway in the progression of prostate cancer. The effect of the NOS inhibitor L-NAME was evaluated in the human prostate cancer cell line LnCap and in BPH-1 cells which represent benign prostatic hypertrophy. Higher DDAH-2, eNOS, iNOS and VEGF expression was found in LnCap cells compared to BPH-1 cells. L-NAME treatment of LnCap cells resulted in a reduction in VEGF, iNOS and eNOS expression. VEGF, iNOS and eNOS inhibition is a promising approach for targeting tumor vasculature and certain NOS inhibitors could potentially serve as experimental agents for treatment of certain chemoresistant tumors, including prostate tumors. Moreover, since in our experimental conditions L-NAME was unable to reduce DDAH activity and expression, it is plausible to hypothesize the development of a targeted polypharmacological approach by developing dual and specific inhibitors of DDAH and NOS to better control NO biosynthesis.