The importance of Hippo signalling pathway in mammalian growth control is supported by reports that transgenic overexpression of YAP, or loss of Mst1/2, leads to massive hepatomegaly and rapid progression to HCC and that YAP is amplified in some tumours and may transform immortalized mammary epithelial cells in vitro [38], [46], [48], [49], [50]. The gene discussed is MST1; the disease is hepatocellular carcinoma.