Recently we have shown that Shh induces expression and activity of yes-associated protein (YAP), a transcriptional co-activator that is the target of the tumor suppressive Hippo pathway, and that YAP is highly expressed in Shh-associated medulloblastomas. YAP is known to have oncogenic properties, including the ability to promote epithelial-mesenchymal transition (EMT), suppression of apoptosis, growth factor-independent proliferation, and anchorage-independent growth in soft agar (Overholtzer et al 2006). YAP is involved in the formation of numerous tumors, including glioblastomas, oral squamous-cell carcinomas, and cancers of the pancreas, lung, ovary, and cervix (Fernandez and Kenney 2010, Zeng and Hong 2008, Zhao et al 2008). However, the effects exerted by YAP are highly context-dependent, as it acts as a tumor suppressor in other malignancies, such as some breast cancers (Yuan et al 2008). Similarly, YAP activity can have pro- or anti-apoptotic effects depending on the tissue and cell context (Bertini et al 2009).