Oral or topical administration of chemicals called brown algae polyphenols (BAPs), found in a type of brown marine seaweed, reduced the number and size of skin tumors in mice induced by UVB radiation, the researchers found.

UBS radiation from natural sources such as sunshine and artificial sources such as UV lamps is believed to be the cause of 90 percent of 1.3 million of non-melanoma skin cancer cases in the U.S. each year.

The chemopreventative effect of BAPs against skin cancer was potent, according to the researchers. Both topical application and oral administration of BAPs in hairless mice at fairly low doses reduced the number of skin tumors by up to 60 percent and the size of the tumors by up to 43 percent.

The polyphenols reduced inflammation and might have anticancer properties, Gary D. Stoner, professor emeritus of internal medicine and a cancer chemoprevention researcher from the OSU and colleagues write in their report published in the Dec. 15 2007 issue of the International Journal of Cancer.

In the study, hairless mice in nine groups were randomly fed a diet with 0.1% or 0.5% of BAPs or topically applied with a solution with 3 and 6 mg of BAPs per 0.2 ml and irradiated with UVB for 26 weeks.

The diet with 0.1% and 0.5% of brown algae polyphenols significantly reduced tumor number by 45% and 56%, and tumor volume by 54% and 65% respectively.

Similarly, topical administration at levels of 3 and 6 mg significantly decreased tumor number by 60% and 46%, and tumor volume by 66% and 57%, respectively.

Both dietary feeding and topical administration of the polyphenols also reduced tumor incidence by 6% and 21%, respectively although the results were not significant.

Test results also show that dietary administration and topical application of the brown algae polyphenols drastically reduced skin levels of the enzyme cyclooxygenase-2 (COX-2) and of the hormone-like substance prostaglandin E2, both of which are strong indicators of inflammation and cell proliferation rates.

Specifically, the dietary BAPs reduced COX-2 activity by 74 to 82 percent whereas the topical BAPs reduced it by 66 to 82 percent.

The researchers explained that the brown algae compounds may get to skin cells and neutralize the cancer-causing oxygen radicals that are produced by UV exposure.

The researchers concluded that "These observations show that brown algae polyphenols have an antiphotocarcinogenic effect which may be associated with the prevention of UVB-induced oxidative stress, inflammation, and cell proliferation in the skin."