Vitamin E: a dark horse at the crossroad of cancer management

Abstract

It appears that the story on vitamin E and its role in human health remains incomplete. It is apparent that vitamin E supplementation involves many variables, some of which include its uptake from the intestine, the preference for α-tocopherol, transport by tocopherol specific proteins and lipid transporters and the differential metabolism of different vitamin E isoforms. The fundamental differences within population genetics can have significant implications for the effect that dietary supplementation might have on human health. When evaluating the efficacy of vitamin E prophylactic or therapeutic use in previous and future studies, it is critical to consider dosage to be administered, form of vitamin E and source (such as whether from synthetic or purified from natural sources). Further studies are needed to determine the effects of all vitamin E isoforms on cell growth, tumorigenicity, to clarify its possible use as an adjuvant to existing chemotherapeutics. The Alpha-Tocopherol, Beta Carotene (ATBC) Cancer Prevention Study Group and Selenium and Vitamin E Cancer Prevention Trial (SELECT) studies along with the numerous studies of vitamin E should help guide the next chapter of vitamin E research.

Keywords: ABCA1; ATBC; ATP-binding cassette A1; Antioxidant; Cancer prevention; Cancer therapy; HDL; LDL; NPC1L1; NSCLC; Niemann-Pick C1-like 1; PKC; PUFA; ROS; SELECT; SR-BI; TAP; TRF; TTP; Tocopherol; Tocopherol associated protein; Tocotrienol; VLDL; Vitamin E transport proteins; alpha-tocopherol, beta-carotene; high density lipoproteins; low density lipoproteins; non-small cell lung cancer; polyunsaturated fatty acids; protein kinase C; reactive oxygen species; scavenger receptor class B type 1; selenium and vitamin E cancer prevention trial; tocopherol transfer protein; tocotrienol rich fraction; very low density lipoprotein.

Figure 1

Vitamin E isoforms: Methyl groups within the chromonal head determine alpha, beta, and delta status (highlighted). Arrows point to existing chiral centers located in the farnesyl tail (3) and phytl tail (1) of tocopherols and tocotrienols respectively. An unsaturated tail distinguishes the tocotrienols form the saturated tail of the tocopherol vitamin E isoforms.