Deleted in liver cancer 1 (DLC1), a tumor suppressor gene frequently inactivated in non-small cell lung cancer (NSCLC) and other malignancies, encodes a multidomain protein with a RhoGTPase-activating domain and a StAR-related lipid transfer (START) domain. By using immunofluorescence, DLC1 was found to colocalize with caveolin 1 (CAV-1), the principal structural component and marker of caveolae in NSCLC cell lines. The interaction between DLC1 and CAV-1 was mapped to the DLC1 START domain and was shown to be necessary for the tumor suppressor activity of DLC1. For details, see article by Du and colleagues on page 4405.