Rosa M Pascale
University of Sassari, Italy
Title: YAP signalling deregulation and genetic susceptibility to hepatocarcinogenesis, stemness and aggressivity of liver cancer
Biography
Biography: Rosa M Pascale
Abstract
Background & Aim: Recent observations suggests, contribution of Yes-associated protein (YAP) upregulation to hepatocellular carcinoma progression (HCC). We analyzed the connection of YAP deregulation with genetic susceptibility to hepatocarcinogenesis and HCC stemness and aggressivity. Methods: HCC from F344 and BN rats are genetically susceptible and resistant to hepatocarcinogenesis, respectively; human HCC from patients with poorer prognosis (<3 years survival, after partial liver resection, HCCP) or with better outcome (>3 years survival; HCCB) were used. Gene expression was evaluated by qPCR and immunoblotting, and functional experiments were done using HepG2, Huh7, and Hep3B liver cell lines. Results: Higher upregulation of Yap and of its target CTGF was seen in F344 rat HCC than in BN HCC which was associated with highest increase in Yap-tyr357, p73 phosphorylation, and Caspase 3 cleavage in HCC from resistant BN rats. Upregulation of YAP, CTGF, 14-3-3 and YAP-14-3-3 complex, TEAD and YAP-TEAD complex reached highest values in human HCCP. In contrast, YAP-ser127 decreased with lowest values in HCCP, and YAP-tyr357, p73 phosphorylation and Caspase 3 cleavage showed highest increase in human HCCB. Stem cell markers NANOG, OCT3-4, and CD133 upregulation progressively increased from human HCCB to human HCCP and was significantly correlated to YAP and YAP-TEAD expression. Growth rate was 2.5-3 times lower, between 48 and 96 hours, in HepG2 than in Huh7 and Hep3B cells. These modifications were associated with lower YAP and NANOG, OCT3-4, and CD133 expression in HepG2 than in Huh7 and Hep3B cells at 48 hours. YAP downregulation by specific siRNA in Huh7 and HepG3 cells led to significant decrease in NANOG, OCT3-4, and CD133 expression. In contrast, sharp upregulation of stem cell markers was induced in HepG2 cells by forced YAP overexpression. Conclusions: Our results indicate: YAP signalling deregulation in HCC is under genetic control; Genetic resistance to HCC is associated with highest phosphorylation of Yap at tyr357 and p73, and highest apoptosis; YAP changes favoring YAP-14-3-3 and YAP-TEAD complexes formation, associated with cell survival, contribute to HCC aggressivity. In contrast, YAP changes favoring apoptosis, such as YAP phosphorylation at tyr357, are associated with better HCC prognosis and; YAP upregulation favors HCC stemness and aggressivity.