Milk thistle extract, Silibinin, protects against UV-induced skin cancer, says a new study.
"When you have a cell affected by UV radiation, you either want to repair it or kill it, so that it cannot go on to cause cancer. We show that silibinin does both," said Rajesh Agarwal, co-programme leader of Cancer Prevention and Control at the Colorado University Cancer Centre.
The first study worked with human skin cells subjected to UVA radiation, which makes up about 95 percent of the sun's radiation that reaches the Earth. The Agarwal Lab treated these UVA-affected cells with silibinin, the journal Photochemistry and Photobiology reports.
"When you take human skin cells - keratinocytes - and treat them with silibinin, nothing happens. It's not toxic. But when you damage these cells with UVA radiation, treatment with silibinin kills the cells," thus removing the mutated cells that can cause skin cancer and photo-aging, Agarwal said, according to a Colorado statement.
Specifically, the study shows that pre-treatment with silibinin resulted in higher release of reactive oxygen species (ROS) within the UVA-exposed cells, leading to higher rates of cell death.
The second study, published by the same authors in the journal Molecular Carcinogenesis, shows that instead of beneficially killing cells damaged by UVA radiation, treatment with silibinin protects human skin cells from damage by UVB radiation, which makes up about five percent of the sun's radiation reaching Earth.
Agarwal's suggestion is that the prevention of UV-induced skin cancer can happen in two ways: by protecting against DNA damage or by killing cells with damaged DNA.
With UVA, silibinin kills; with UVB, it protects, in this case by increasing cells' expression of the protein interleukin-12, which works to quickly repair damaged cells.
"It has been 20 years of work with this compound, silibinin," Agarwal said.
"We first noticed its effectiveness in treating both skin and solid cancers, and we now have a much more complete picture of the mechanisms that allow this compound to work," he added.