RRR-alpha-tocopheryl succinate inhibits human prostate cancer cell invasiveness

Vitamin E and prostate cancer: is vitamin E succinate a superior chemopreventive agent?

There is convincing evidence that vitamin E succinate significantly reduces human prostate cancer growth in experimental models compared with alpha-tocopherol or tocopheryl acetate. Its intact delivery to cancer cells is questionable when administered orally; however, a study in transgenic mice showed a synergistic inhibitory effect of dietary vitamin E succinate, selenium, and lycopene on prostate cancer incidence. Clinical trials have yet to confirm this effect.

Diet manipulation and prevention of aging, cancer and autoimmune disease

PURPOSE OF REVIEW

Dietary supplementation and other dietary regimens have become increasingly popular in the US population. Information regarding how different dietary constituents interact when consumed simultaneously is needed. This review examines the recent literature on how different dietary constituents may interact physiologically when consumed in combination. Furthermore, the potential human relevance of calorie restriction and nonclassical function of vitamin E is discussed.

RECENT FINDINGS

Long-term calorie restriction in monkeys has shown similar beneficial effects as has been shown in rodents. Limited calorie restriction studies in humans have shown promise in reducing the incidence of heart disease and breast cancer. The combination of calorie restriction and omega-3 fatty acids may be a more potent antiinflammatory diet than either regimen alone. The type of fiber that is most protective against colon cancer may be dependent on the type of dietary fat consumed simultaneously. Vitamin E derivatives that possess no antioxidant activity may be potent inhibitors of cancer, but not normal, cell growth.

SUMMARY

Dietary modification has shown its greatest beneficial effect when started prior to or immediately after the onset of disease. Also, understanding how the subtypes or isoforms of nutrients function is important since their physiological effects may be drastically different. It is important to understand the entire dietary profile of an individual when making dietary recommendations because one nutrient, or dietary ingredient, may enhance or cancel out the beneficial effects of another dietary ingredient.

Chemistry and biology of vitamin E

Our understanding of the role of vitamin E in human nutrition, health, and disease has broadened and changed over the past two decades. Viewed initially as nature's most potent lipid-soluble antioxidant (and discovered for its crucial role in mammalian reproduction) we have now come to realize that vitamin E action has many more facets, depending on the physiological context. Although mainly acting as an antioxidant, vitamin E can also be a pro-oxidant; it can even have nonantioxidant functions: as a signaling molecule, as a regulator of gene expression, and, possibly, in the prevention of cancer and atherosclerosis. Since the term vitamin E encompasses a group of eight structurally related tocopherols and tocotrienols, individual isomers have different propensities with respect to these novel, nontraditional roles. The particular beneficial effects of the individual isomers have to be considered when dissecting the physiological impact of dietary vitamin E or supplements (mainly containing only the alpha-tocopherol isomer) in clinical trials. These considerations are also relevant for the design of transgenic crop plants with the goal of enhancing vitamin E content because an engineered biosynthetic pathway may be biased toward formation of one isomer. In contrast to the tremendous recent advances in knowledge of vitamin E chemistry and biology, there is little hard evidence from clinical and epidemiologic studies on the beneficial effects of supplementation with vitamin E beyond the essential requirement.

Inhibition of the Akt, cyclooxygenase-2, and matrix metalloproteinase-9 pathways in combination with androgen deprivation therapy: Potential therapeutic approaches for prostate cancer

Prostate cancer cells are generally dependent on androgen stimulation mediated by the androgen receptor (AR) for growth and survival, and, therefore, hormonal manipulation, such as castration and/or the use of AR antagonists, results in a regression of the cancer. However, this treatment very rarely leads to the "cure" of advanced disease, and cancers eventually become androgen-independent. A number of genes/pathways have been reported to be activated in prostate cancer, most of which are possibly associated with disease progression. In this article, among them, we focus on Akt (also known as protein kinase B), cyclooxygenase (COX)-2, and matrix metalloproteinase (MMP)-9, whose activities or expressions have been found to be regulated by androgens/AR. Previous studies by us and others, with androgen-sensitive prostate cancer cell lines, have demonstrated that androgen deprivation results in activation/overexpression of Akt, COX-2, and MMP-9 in cells. This suggests that androgen deprivation in clinical settings activates the Akt, COX-2, and MMP-9 pathways in prostate cancer, which may increase cell growth and in turn promote the transition to the androgen-independent state. We hypothesize that androgen deprivation, in combination with inhibition of the Akt, COX-2, and MMP-9 pathways, delays the androgen-independent transition and has more beneficial effects than hormonal therapy alone.