It is rare for a natural molecule to garner the attention of medical researchers for two completely different cancer-fighting properties, but the compound psoralen has done just that. Found in figs, celery and other fruits and vegetables, psoralen is already used to treat lymphoma—as well as skin conditions such as psoriasis—based on its ability to stop DNA from copying itself and triggering cell death when combined with UV light.

Now researchers at Duke University have found that UV light activation of psoralen also has the ability to kill breast cancer cells that overproduce the protein HER2. About one-third of breast tumors are HER2-positive, along with stomach, ovarian, and other types of cancer. HER2-positive breast cancer is considered one of the most aggressive forms of the disease, because the HER2 protein encourages cancer cells’ unchecked growth. The most promising drugs for HER2-positive cancer, such as lapatinib and trastuzumab, can block the function of HER2 on the surface of cells, but they can’t recognize HER2 deep within the cells. Over time, the tumors can become resistant to these drugs. In contrast, psoralen activated with UV light can block all the HER2 in cells, eventually leading to their death.

(Source: PLoS ONE, 2014; 9: e88983.)