The mice received the BAPs for two weeks before UVB exposure began, followed by 24 weeks of increasing UVB exposure according to a standardized schedule.
The researchers then counted the number of tumors in the treatment and control groups and calculated their size.
Animals exposed only to UVB developed an average of 8.5 skin tumors. The animals fed the lower and the higher dose of BAPs developed an average of 4.7 and 3.7 tumors respectively. Of those given the topical treatment, the lower and higher doses developed 3.4 and 4.6 tumors respectively.
In terms of tumor volume, the animals fed BAPs at the lower and higher doses had tumors that were 34 percent and 40 percent smaller than those in animals exposed to UVB alone. Of those given the topical treatment, the lower and higher dose animals had tumors that were 27 percent to 43 percent smaller than animals exposed to UVB alone.
In addition, the researchers compared the groups for 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 for cell proliferation rates.
Animals treated with BAPs showed lower levels of both COX-2 and prostaglandin E2.
The researchers found that the dietary BAPs reduced COX-2 activity by 74-82 percent, and that the topical BAPs reduced it by 66-82 percent. They also measured lower rates of cell proliferation in BAP-treated animals.
"Both the oral and topical BAP treatment reduced COX-2 and prostaglandin E2 cell proliferation levels in the skin," Stoner says, "which corresponds with fewer tumors and small tumors in the treated animals."