Phytotherapy and Nutritional Supplements on Breast Cancer 用于乳腺癌治疗的植物疗法和营养补充剂

4.2.3. Vitamin E

Vitamin E is a liposoluble vitamin that exhibits different pharmacological properties such as antioxidant, anti-inflammatory, and inhibition of protein kinase C [391]. It can be acquired from some dietary sources (e.g., nuts, seeds, vegetal oils, green leafy vegetables, and fortified cereals) or as a supplement. Among its different chemical forms, the alpha-tocopherol is the main and most active form achieved in human plasma and studied in clinical trials.

The supplementation with vitamin E in breast cancer patients has also different outcomes. Some of the effects of vitamin E in breast cancer have been explored previously with the coadministration of other antioxidant vitamins (e.g., vitamin C). Other studies have shown that long-term uptake of vitamin E could have a negative effect on breast cancer patients [114, 131]. The HOPE-TOO trial revealed no effects of long-term vitamin E supplementation (7.1 years) on individual rates of breast cancer [409]. Nagel and collaborators did not find any association between long-term dietary intake vitamin E (8.8 years) and risk of breast cancer development [109]. Alpha-tocopherol acetate (400 mg) supplementation increased biomarkers of estrogen-stimulation in 5 out of 7 breast cancer patients while taking tamoxifen suggesting that vitamin E supplements may decrease the antiproliferative effect of tamoxifen [132].

Tam et al. verified that alpha-tocopheryl succinate, a synthetic derivative of alpha-tocopherol, improved the cells’ sensitivity to doxorubicin (anticancer agent) which reduced the cell viability in cancerous breast tissue samples [410]. This combination, using vitamin E or its analogue in a supplementation regimen, is promising for the treatment of cancer. Random placebo-controlled trials showed that the association of pentoxifylline and vitamin E after radiotherapy in breast cancer women may be used to prevent radiation-induced side effects [133, 134].

In another study, the intracardiac injection of Trolox inhibited osteolysis bone metastasis caused by breast cancer in an experimental metastasis model [411]. Despite this, vitamin E analogue did not have any effect in the mammary fat pad model; it suppressed breast cancer cell-induced osteoclast differentiation and the invasive behaviour of cancer cells via prostaglandin E2- (PGE2-) dependent and PGE2-independent mechanisms.