RASSF5 links Ras and the Hippo pathway whose signaling leads to YAP degradation. YAP1 overexpression promotes cancer. Most reports point to RASSF5 suppressing cancer; however, some to promoting cancer. We propose that RASSF5 acts as an adaptor protein. RASSF5 activates MST and suppress cancer in vivo; but inhibit signaling in vitro.