Meccanismi di regolazione post-traduzionale del gene YAP nel corso dell'epatocancerogenesi

Aim:Previous studies showed that Yap1 is over-expressed in hepatocellular carcinoma(HCC). Yap phosphorylation,is the main mechanism to regulating its activation, and role on Hippo pathway. We hypothesized that modulation of Yap1 role in HCC depend on differences in its post-translational modification. We tested this hypothesis by analysing the relationship of post-translational deregulation of Yap1 in different subtypes of HCC,on prognostic bases and differences on genetic predisposition to the disease.Methods:F344 and BN rats were housed and treated according to the resistant hepatocyte protocol. Six normal livers, 20 human HCC with better (HCCB) or poorer(HCCP) prognosis, and corresponding surrounding non-tumour livers were used. HepG2, Hep3B and Huh7 cell lines were transfected with pCMV_empty vectors, pCMV6_YAP1 or Yap1 siRNA. The samples were used for genes and proteins expression studies, and additional functional experiments.Results:We observed higher expression of Yap1/CTGF axis in dysplastic nodules and HCC-chemically-induced in F344 rats, genetically susceptible to HCC. While lesion induced in BN resistant rats, do not show or show lower increase in YAP expression, compared susceptible rats. In human HCCP, levels of YAP1, CTGF, 14-3-3, and TEAD proteins,and YAP1- 14-3-3 and YAP1-TEAD complexes were higher than in HCCB. Forced YAP1 over-expression increased cell viability in HepG2, Huh7, Hep3B cells. We observed activation of cell migration and invasivity in Huh7 cells transfected with YAP1 and inhibition of cell migration and invasivity when cells were transfected withYAP1-siRNA.Conclusion:In conclusion, Yap1 post-translational modification favouring its ubiquitination and apoptosis characterize HCC with better prognosis, whereas condition favouring the formation of YAP1-TEAD complexes and cells survival are associated with aggressiveness.