Chemopreventive Activity of Vitamin E in Breast Cancer: A Focus on γ- and δ-Tocopherol

Abstract

Vitamin E consists of eight different variants: α-, β-, γ-, and δ-tocopherols (saturated phytyl tail) and α-, β-, γ-, and δ-tocotrienols (unsaturated phytyl tail). Cancer prevention studies with vitamin E have primarily utilized the variant α-tocopherol. To no avail, a majority of these studies focused on variant α-tocopherol with inconsistent results. However, γ-tocopherol, and more recently δ-tocopherol, have shown greater ability to reduce inflammation, cell proliferation, and tumor burden. Recent results have shown that γ-enriched mixed tocopherols inhibit the development of mammary hyperplasia and tumorigenesis in animal models. In this review, we discuss the possible differences between the variant forms, molecular targets, and cancer-preventive effects of tocopherols. We recommend that a γ-enriched mixture, γ- and δ-tocopherol, but not α-tocopherol, are promising agents for breast cancer prevention and warrant further investigation.

Keywords

• vitamin E
• tocopherols
• breast cancer
• estrogen receptor (ER)
• peroxisome proliferator activated receptor γ (PPARγ)
• nuclear factor (erythroid-derived 2)-like 2 (Nrf2)
• anti-inflammatory
• cell proliferation
• apoptosis
• case-control studies