Kathy Lik, ND
Due to the fact that prevention remains the best approach in reducing the incidence of skin cancer, there has been a significant increase in research looking at natural agents that exhibit photo-protective and anti-neoplastic effects in skin. The data is vast yet in its preliminary stages, as it spans across mostly in vitro and animal models. Although we now understand more about mechanisms of action of various natural agents, we continue to extrapolate when it comes to best modes of administration, dosages and overall clinical relevance.
A continuous source of controversy is the topic of antioxidants
For instance, a continuous source of controversy is the topic of antioxidants. Most studies support topical use of various antioxidants, including vitamins C and E, beta carotene and selenium to protect against UV skin damage and subsequent development of skin cancers. However, the oral use of vitamins E and A, and various carotenoids is highly controversial. Study outcomes vary dramatically depending on the specific forms of vitamins used, the type of study and whether the researchers looked at cell lines, animals or humans. It is hypothesized that the contradictory findings are likely due to the presence and interactions of other, still unknown, dietary factors. Future research is needed to determine guidelines for the use of antioxidants with skin cancers.
Silybum marianum
Another agent that has shown efficacy in protecting us from UV radiation is Silybum marianum. Although I am more accustomed to thinking of milk thistle for gastrointestinal and renal disorders, I was surprised to discover its photo-protective effects. A number of in vivo animal studies have demonstrated that its flavonoid component, silymarin, exerts an array of epidermal anti-carcinogenic effects, including upregulation of tumor-suppressor genes, leading to inhibition of abnormal cell proliferation and apoptosis. It was also found to inhibit epidermal growth factor and insulin-like growth factor receptor signaling, as well as prevent immune suppression induced by UV light.
Genistein
A significant correlation between the serum/plasma level of genistein and the incidence of gender-based cancers in Asian, European and American populations suggests that genistein may also reduce the risk of skin tumor formation. It has been shown that genistein inhibits DNA replication and repair in cancer cells via inhibition of tyrosine kinase receptor protein. It can also arrest cell growth and proliferation along with invasion and angiogenesis. The challenge with genistein remains its biphasic bioactivity (inhibition at high concentration and activation at low), making it difficult to determine proper therapeutic doses.
Green tea
Green tea has been shown to have anti-cancer activity in many types of tumors, and skin cancers are no exception. The research looks at a wide range of forms and components of green tea, including beverage and solids consumption; epigallocatechin gallate (EGCG), orally and topically; polyphenols; and caffeine. Both whole tea and evaluated components have been shown to reduce UV-induced erythema, tumor incidence, multiplicity and growth. These effects are achieved through immune stimulation, DNA repair, induction of apoptosis, cell cycle arrest in damaged cells and reduction of angiogenesis. Interestingly, caffeine has been shown to reduce the dermal fat pad, which is highly associated with tumor multiplicity as well.
Dr. Lik is a second-year resident at the Midwestern Regional Medical Center – Cancer Treatment Centers of America. She graduated from NCNM in 2007.
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