Upregulation of CYR61 by TGF-ß and YAP signaling exerts a counter-suppression of hepatocellular carcinoma
TGF-ß and Hippo signaling are two critical pathways engaged in cancer progression by regulating both oncogenes and tumor suppressors, yet how the two pathways coordinately exert their functions in the development of hepatocellular carcinoma (HCC) remains elusive.  In this study, we firstly conducted an integrated analysis of public liver cancer databases and our experimental TGF-ß target genes, identifying CYR61 as a pivotal gene relating to HCC development.  Evidence revealed that CYR61 is a direct target gene of TGF-ß in liver cancer cells. In addition, TGF-ß-stimulated Smad2/3 and the Hippo pathway downstream effectors YAP and TEAD4 can form a protein complex on the promoter of CYR61, thereby activating the promoter activity and stimulating CYR61 gene transcription in a collaborative manner.  Functionally, depletion of CYR61 enhanced TGF-ß- or YAP activation-mediated growth and migration of liver cancer cells.  Consistently, ectopic expression of CYR61 was capable of impeding TGF-ß- or YAP-induced malignant transformation of HCC cells in vitro, and attenuating HCC xenograft growth in nude mice.  Finally, Downregulation of CYR61 expression in HCC tissues than that in normal liver tissues is well associated with a bad clinical outcome in patients.  Together, these results add new evidence for the interplay between TGF-ß and Hippo signaling and unveil an important tumor suppressor function of CYR61 in liver cancer. Overall design: Two independent cell-culture replicates from the total population of HLE-Vector and HLE-CYR61 stable expression were used to generate total RNA.