Signaling pathway of insulin-like growth factor-II as a target of molecular therapy for hepatoblastoma.
OBJECTIVE
To address the possibility that insulin-like growth factor (IGF)-II is a growth factor and its signaling pathway so as to develop a molecular therapy for hepatoblastoma.


METHODS
Huh-6 and HepG2, human hepatoblastoma cell lines, were used. IGF-II was added to the medium deprived of serum. Western blot analysis was performed to clarify the expression of IGF-I receptor (IGF-IR). Inhibitors of IGF-IR (piclopodophyllin, PPP), phosphatidyl-inositol (PI) 3-kinase (LY294002 and Wortmannin), or mitogen-activated protein (MAP) kinase (PD98059) were added to unveil the signaling pathway of IGF-II. Cells were analyzed morphologically with hematoxylin-eosin staining to reveal the mechanism of suppression of cell proliferation.


RESULTS
IGF-II stimulated cells proliferated to 2.7 (269%+/-76%) (mean+/-SD) (Huh-6) and 2.1 (211%+/-85%) times (HepG2). IGF-IR was expressed in Huh-6 and HepG2. PPP suppressed the cell number to 44%+/-11% (Huh-6) and 39%+/-5% (HepG2). LY294002 and Wortmannin suppressed the cell number to 30%+/-5% (Huh-6), 44%+/-0.4% (HepG2), 49%+/-1.0% (Huh-6) and 46%+/-1.1% (HepG2), respectively. PD98059 suppressed the cell number to 33%+/-11% for HepG2 but not for Huh-6. When cell proliferation was prohibited, many Huh-6 and HepG2 cells were dead with pyknotic or fragmented nuclei, suggesting apoptosis.


CONCLUSIONS
IGF-II was shown to be a growth factor of hepatoblastoma via IGF-I receptor and PI3 kinase which were good candidates for target of molecular therapy.
Tomizawa
Minoru
M
Department of Medicine and Clinical Oncology, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba 260-8670, Japan. nihminor-cib@umin.ac.jp
Saisho
Hiromitsu
H
D000730:Androstadienes / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D018197:Hepatoblastoma / Q000188:drug therapy* / Q000503:physiopathology*; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology / Q000502:physiology*; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000503:physiopathology*; D009025:Morpholines / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017526:Receptor, IGF Type 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D000077191:Wortmannin
D000730:Androstadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D005419:Flavonoids; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D000077191:Wortmannin