Researchers from the University of Colorado Cancer Center have reported that a compound in milk thistle kills skin cells mutated by UVA radiation and protects skin cells from the UVB damage. The research team, led by Rajesh Agarwal, PhD, a professor at the Skaggs School of Pharmacy and Pharmaceutical Sciences and co-program leader of Cancer Prevention and Control at the CU Cancer Center, published two studies on silibinin, one in Photochemistry and Photobiology and one in Molecular Carcinogenesis.
The first study worked with human skin cells subjected to UVA radiation, which makes up about 95% of the sun’s radiation that reaches Earth. The Agarwal Lab treated these UVA-affected cells with silibinin. With silibinin, the rate at which these damaged cells died increased dramatically.
“When you take human [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,” Agarwal said in a university press release. Therefore, the mutated cells that can cause skin cancer and photo-aging are removed. Specifically, the study shows that pretreatment 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 shows that instead of beneficially killing cells damaged by UVA radiation, treatment with silibinin protects human skill cells from damage by UVB radiation, which comprises the other 5% of the sun’s radiation reaching Earth. In this study, silibinin increases cells’ expression of the protein interleukin-12, working to quickly repair damaged cells.
“It has been 20 years of work with this compound, silibinin,” Agarwal noted. “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.”
Agarwal and colleagues continue to test the effectiveness of silibinin in cancer prevention and treatment in cell lines and mouse models, and are working toward human trials of silibinin-based therapeutics.