H19 suppresses the growth of hepatoblastoma cells by promoting their apoptosis via the signaling pathways of miR-675/FADD and miR-138/PTK2

Background: The objective of this study was to clarify the molecular pathways involved in hepatitis B virus (HBV)-induced hepatoblastoma.
Method: The expression of factors in different signaling pathways (H19, miR-675, miR-138, protein tyrosine kinase 2 [PTK2], fas-associated death domain [FADD], hypoxia-inducible factor 1-alpha [HIFIA], focal adhesion kinase [FAK], caspase-8, and caspase-3) was compared between HBV (+) and HBV (-) groups using quantitative real-time polymerase chain reaction and Western blot analysis. Subsequently, immunohistochemistry (IHC) and TdT-mediated dUTP Nick-End Labeling (TUNEL) assays were used to verify the expression of above proteins in HBV (+) and HBV (-) groups. Computational analysis was conducted to predict the target genes of miR-675 and miR-138, whose regulatory relationships were then clarified using luciferase assays and cell transfection studies.
Result: The expression of H19, miR-675, PTK2, HIFIA, and FAK was increased in the HBV (+) group, while the expression of miR-138, FADD, caspase-8, and caspase-3 was decreased in the HBV (+) group. FADD and PTK2 were identified as target genes of miR-675 and miR-138, respectively. In addition, miR-675 was upregulated while miR-138 was downregulated by X protein (HBx).
Conclusion: In summary, the results of this study revealed the molecular pathways involved in HBV-induced hepatoblastoma. In the presence of HBV, HBX upregulated the expression of H19 through HIFIA. Consecutively, overexpressed H19 upregulated the expression of PTK2 via targeting miR-138 and downregulated the expression of FADD via targeting miR-675. Finally, increased expression of PTK2 and reduced expression of FADD both led to the inhibition of cell apoptosis, thus promoting the tumorigenesis of hepatoblastoma.