**5. Anticancer effects of tocotrienols**

The results of various studies in cell lines and animals indicated that the damage incurred by free radicals could be prevented by antioxidants. However, the

#### *Palm Oil Tocotrienols in Cancer Chemoprevention and Treatment DOI: http://dx.doi.org/10.5772/intechopen.98199*

conclusions derived from observational studies in humans are mixed, due to the diverse difference in human genetics, general health and metabolic capability of our bodies [21]. Many diseases (including cancer) are strongly related to oxidative stress conditions [10]. Oxidative stress has always been associated with the process of carcinogenesis and the adverse effects of cancer management i.e., radiotherapy and chemotherapy [56]. Therefore, it was once postulated that similar to the tocopherols, the major actions of tocotrienols in preventing cancer is through their antioxidant and free radical scavenging activities [45].

Several important signalling pathways are activated by the presence of oxidative stress in the cell. These pathways could facilitate tumour development through deregulation of cellular proliferation, angiogenesis, and metastasis [56]. It was noted, however, that consumption of a diet rich in antioxidants e.g., vitamin E and vitamin C, has been beneficial in preventing cancer [57–60]. A study on the pattern of human food consumption had inferred that the intake of foods rich in antioxidants is correlated with decreased breast cancer incidence within the population [61].

A lot of research has been published since the 1980s on the anticarcinogenic effects of tocotrienols. This has led to an accumulation of numerous works of literature on the anticancer activity of tocotrienols, especially on breast cancer. Apart from breast malignancy, other cancers in which tocotrienols intervention had been postulated to be beneficial are liver, prostate, pancreatic, cervical, colorectal, and skin cancers. From the year 2000 onwards, it had become very clear that the anticancer mechanisms of tocotrienols goes way beyond their antioxidant and free radical scavenging properties. Apart from inhibiting the growth of cancer, tocotrienols are able to initiate apoptosis in cancerous cells. The anticancer effects of tocotrienols are manifested through the inhibition of angiogenesis and tumour cell progression [2, 62]. An isomer of tocotrienols i.e., delta-tocotrienol, was found to inhibit the expansion of cancerous cells and initiated the process of apoptosis significantly in an in vitro study using human colon cancer cell lines [63]. Using animal models, delta-tocotrienol was shown to reduce the incidence of colon cancer and initiated apoptosis in rats [63]. Delta-tocotrienol was able to halt the rate of proliferation of cancerous pancreatic cells without affecting normal pancreatic cells [63]. The growth of colorectal cancer cells was found to be prevented by administering tocotrienols supplementation to mice [63]. Studies using cancerous stem cells indicated that melanoma can be treated and prevented with delta-tocotrienol [64].
