Curcumin restores glutathione-S-transferase activity for LNCaP prostate cancer cells

Prostate cancer is a leading cause of death in males aged fifty and over. Glutathione transferase (GST) activity is depressed in prostate cancer cells. The aim of this study was to assess GST reactivation in LNCaP prostate cancer cells treated with curcumin or 5-azacitidine (5-Aza) which is a known hypomethylation agent. GST activity was determined using monochlorobimane (MCB). Cell viability was assessed with resazurin (Vision blue TM) or 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-di-phenyltetrazolium- bromide (MTT). From the results, treatment with >5 μM of curcumin or 5-Aza for 3 or 6 days depressed LNCaP cell viability. The concentrations of curcumin leading to 50% reduction of LNCaP cell viability (IC50) was 10-25 μM or 2-3 μM for 3 days or 6 days of treatment, respectively. The IC50 with 5-Aza was 17-23 μM (3 days) or 50-52 μM (6 days).Combination treatment using curcumin and 5-Aza showed complimentary interactions affecting cell viability. Low levels of curcumin or 5-Aza had no effect on GST activity. By contrast, cytotoxic doses of curcumin or 5-Aza increased GST activity by 450-750 % (3days) or 161-2800 % (6days). In conclusion, GST reactivation was feasible but only when LNCaP prostate cancer cells were treated with cytotoxic doses of curcumin or 5-azacytidne.