Potent inhibitory effect of β-tocopherol on prostate cancer cells cultured in vitro and grown as xenograft tumors in vivo

In the present study, the effects of β-tocopherol (β-T) on growth and apoptosis of human prostate cancer cells were determined and compared with that of Δ-tocopherol (Δ-T), a commonly used form of vitamin E. Treatment of human prostate cancer cells with β-T resulted in strong growth inhibition and apoptosis stimulation, while the effects of Δ-T were modest. The strong effects of β-T on the cells were associated with suppression of androgen receptor (AR) activity and decreased level of prostate specific antigen (PSA) that is a downstream target of the AR signaling. In the in vivo study, we found that β-T had a more potent inhibitory effect on the formation and growth of prostate xenograft tumors than that of Δ-T. Moreover, β-T inhibited proliferation and stimulated apoptosis in the tumors. The present study identified β-T as a better form of vitamin E than Δ-T for future clinical studies of prostate cancer prevention.