Background: To assess the antioxidant effects of gamma-oryzanol on human prostate cancer cells. Materialsand Methods: Cytotoxic activity of gamma-oryzanol on human DU145 and PC3 prostate cancer cells wasdetermined by proliferation assay using 3-(4, 5-dimethylthiazol, 2-yl)-2, 5-diphenyl tetrazolium bromide (MTT)reagent. mRNA levels of genes involved in the intracellular antioxidant system, superoxide dismutase (SOD),catalase (CAT), glutathione peroxidase (GPX) and glutathione reductase (GSR) were determined by reversetranscription-polymerase chain reaction (RT-PCR). Cancer cell lysates were used to measure lipid peroxidationusing thiobarbituric acid reactive substance (TBARS). Glutathione contents of the cell lysates were estimatedby the reaction between sulfhydryl group of 5, 5’-dithio (bis) nitrobenzoic acid (DTNB) to produce a yellowcolorof 5-thio-2-nitrobenzoic acid using colorimetric assay. Catalase activity was also analysed by examiningperoxidative function. Protein concentration was estimated by Bradford’s assay. Results: All concentrationsof gamma-oryzanol, 0.1-2.0mg/ml, significantly inhibited cell growth in a dose- and time-dependent fashionin both prostate cancer cell lines, DU145 and PC3. Gene expression of catalase in DU145 and PC3 exposed togamma-orizanol at 0.5mg/ml for 14 days was down regulated, while mRNA of GPX was also down regulated inPC3. The MDA and glutathione levels including catalase activity in the cell lysates of DU145 and PC3 treatedwith gamma-oryzanol 0.1 and 0.5mg/ml were generally decreased. Conclusions: This study highlighted effectsof gamma-oryzanol via the down-regulation of antioxidant genes, catalase and GPX, not cytotoxic roles. Thismight be interesting for adjuvant chemotherapy to make prostate cancer cells more sensitive to free radicals. Itmight be useful for the reduction of cytotoxic agents and cancer chemoprevention.
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