Melanoma is difficult to treat once it has spread to other parts of the body such as the lungs, liver, or brain. But a new study in mice points to a way of stopping the spread in the first place. The researchers found that when a protein linked to cancer invasion was inhibited, fewer melanomas spread to the lungs. This protein—ARF6 or adenosine diphosphate ribosylation factor 6—is also involved in the spread of breast cancer and a type of brain cancer called glioblastoma. The pharmaceutical company Navigen is investigating new ARF6 inhibitors for preclinical studies.