Effects of phenylethyl isothiocyanate and its metabolite on cell-cycle arrest and apoptosis in LNCaP human prostate cancer cells

Cruciferous vegetable consumption is associated with decreased risk of several cancers, including prostate cancer. Gluconasturtiin, one of the predominant glucosinolates in cruciferous vegetables, is hydrolyzed to yield phenylethyl isothiocyanate (PEITC). PEITC absorption and metabolism in humans involves glutathione conjugation followed by conversion via the mercapturic acid pathway to an N-acetylcysteine (NAC) conjugate that is excreted in the urine. We observed an inhibitory effect of PEITC and its metabolite, NAC-PEITC, on cancer cell proliferation, cell-cycle progression, and apoptosis in LNCaP human prostate cancer cells. PEITC and NAC-PEITC suppressed LNCaP cell proliferation in a dose-dependent manner, and exposure to 5 mu M PEITC or NAC-PEITC reduced cell proliferation by 25% and 30%, respectively. Cell-cycle analysis revealed that cells treated with 5 mu M PEITC or NAC-PEITC arrested at the G(2)/M phase. In addition, the percentage of cells in the S phase decreased from 46% to 25% following 48 h of incubation with PEITC or NAC-PEITC. The G(2)/M-phase cell-cycle arrest of LNCaP cells grown in the presence of PEITC or NAC-PEITC is correlated with the downregulation of Cdk1 and cyclin B-1 protein expression. Apoptosis was observed at the later stages of 24-h and 48-h treatments with 5 mu M PEITC and NAC-PEITC. In conclusion, PEITC and NAC-PEITC are potential chemopreventive/chemotherapeutic agents against LNCaP human prostate cancer cells.