LA JOLLA—Mitochondria, tiny structures present in most cells, are known for their energy-generating machinery. Now, Salk researchers have discovered a new function of mitochondria: they set off molecular alarms when cells are exposed to stress or chemicals that can damage DNA, such as chemotherapy. The results, published online in Nature Metabolism on December 9, 2019, could lead to new cancer treatments that prevent tumors from becoming resistant to chemotherapy.