The Telomeres and Telomerase Group led by Maria A. Blasco at the Spanish National Cancer Research Centre (CNIO) continues to make progress in unraveling the role that telomeres—the ends of chromosomes that are responsible for cellular aging as they shorten—play in cancer. The CNIO team was among the first to propose that shelterins, proteins that wrap around telomeres and act as a protective shield, might be therapeutic targets for cancer treatment. Subsequently, they found that eliminating one of these shelterins, TRF1, blocks the initiation and progression of lung cancer and glioblastoma in mouse models and prevents glioblastoma stem cells from forming secondary tumors.