PCNA and breast cancer: Furthermore, γ-TmT and individual tocopherols were administered to Sprague-Dawley rats which were induced with NMU carcinogen; treatment with γ-TmT, γ-, and δ-tocopherol decreased PCNA levels while increased the levels of cleaved-caspase 3 in mammary tumors, whereas α-tocopherol was not active [105].