Activation of Phosphatidylinositol-3′-kinase/AKT Signaling Is Essential in Hepatoblastoma Survival

• Published in: Clinical cancer research 2009-07, Vol.15 (14), p.4538-4545
• Main Authors: Hartmann, Wolfgang, Küchler, Jan, Koch, Arend, Friedrichs, Nicolaus, Waha, Anke, Endl, Elmar, Czerwitzki, Jacqueline, Metzger, Dagmar, Steiner, Susanne, Wurst, Peter, Leuschner, Ivo, von Schweinitz, Dietrich, Buettner, Reinhard, Pietsch, Torsten
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; AKT; Antineoplastic agents; Apoptosis - drug effects; Biological and medical sciences; Cell Line, Tumor; Cell Survival - drug effects; Child; Child, Preschool; Chromones - pharmacology; Cisplatin - pharmacology; Drug Synergism; Flow Cytometry; Gastroenterology. Liver. Pancreas. Abdomen; Glycogen Synthase Kinase 3 - metabolism; Glycogen Synthase Kinase 3 beta; Hepatoblastoma; Hepatoblastoma - genetics; Hepatoblastoma - metabolism; Hepatoblastoma - pathology; Humans; Immunohistochemistry; Liver. Biliary tract. Portal circulation. Exocrine pancreas; Medical sciences; Middle Aged; Morpholines - pharmacology; Mutation; Nuclear Proteins - antagonists & inhibitors; Nuclear Proteins - genetics; Other diseases. Semiology; Pharmacology. Drug treatments; Phosphorylation - drug effects; PI3K; Polymorphism, Single-Stranded Conformational; Protein Kinases - metabolism; Proto-Oncogene Proteins c-akt - metabolism; RNA Interference; Signal Transduction - drug effects; Signal Transduction - physiology; TOR Serine-Threonine Kinases; Transcription Factors - antagonists & inhibitors; Transcription Factors - genetics; Young Adult
• ISSN: 1078-0432; 1557-3265
• DOI: 10.1158/1078-0432.CCR-08-2878

Purpose: Hepatoblastoma represents the most frequent malignant liver tumor in childhood. The phosphatidylinositol-3′-kinase (PI3K)/AKT pathway is crucial in downstream signaling of multiple receptor tyrosine kinases of pathogenic importance in hepatoblastoma. Increased PI3K/AKT signaling pathway activity and activating mutations of PIK3CA , encoding a PI3K catalytic subunit, have been reported in different childhood tumors. The current study was done to analyze the role of PI3K/AKT signaling in hepatoblastoma. Experimental Design: Immunohistochemical stainings of (Ser473)-phosphorylated (p)-AKT protein, its targets p-(Ser9)-GSK-3β and p-(Ser2448)-mTOR, as well as the cell cycle regulators Cyclin D1, p27 KIP1 , and p21 CIP1 were done and the PIK3CA gene was screened for mutations. In vitro , two hepatoblastoma cell lines treated with the PI3K inhibitor LY294002 were analyzed for AKT and GSK-3β phosphorylation, cell proliferation, and apoptosis. Additionally, simultaneous treatments of hepatoblastoma with LY294002 and cytotoxic drugs were carried out. Results: Most tumors strongly expressed p-AKT, p-GSK-3β, and p-mTOR; subgroups showed significant Cyclin D1, p27 KIP1 , and p21 CIP1 expression. One hepatoblastoma carried an E545A mutation in the PIK3CA gene. In vitro , PI3K inhibition diminished hepatoblastoma cell growth being accompanied by reduced AKT and GSK-3β phosphorylation. Flow cytometry and 4', 6-diamidino-2-phenylindole stainings showed that PI3K pathway inhibition leads to a substantial increase in apoptosis and a decrease in cellular proliferation linked to reduced Cyclin D1 and increased p27 KIP1 levels. Simultaneous treatment of hepatoblastoma cell lines with LY294002 and cytotoxic drugs resulted in positive interactions. Conclusions: Our findings imply that PI3K signaling plays an essential role in growth control of hepatoblastoma and might be successfully targeted in multimodal therapeutic strategies.