YAP1 and neoplasm: Several Hippo pathway tumor suppressors, including Lats2, Mst1, and Mst2, were also slightly increased in Vgll4 mutant livers (Supplemental Fig. S3A), consistent with the well-established negative feedback whereby activation of the nuclear effector YAP leads to up-regulation of upstream tumor suppressors (Chen et al. 2015; Moroishi et al. 2015).