Aspartyl-(asparaginyl)-beta-hydroxylase regulates hepatocellular carcinoma invasiveness.
OBJECTIVE
We measured aspartyl (asparaginyl)-beta-hydroxylase (AAH) gene expression in human hepatocelluar carcinoma and surrounding uninvolved liver at both the mRNA and protein level and examined the regulation and function of this enzyme.


METHODS
Since growth of HCC is mediated by signaling through the insulin-receptor substrate, type 1 (IRS-1), we examined-if AAH is a downstream gene regulated by insulin and IGF-1 in HCC cells. In addition, IRS-1 regulation of AAH was examined in a transgenic (Tg) mouse model in which the human (h) IRS-1 gene was over-expressed in the liver, and an in vitro model in which a C-terminus truncated dominant-negative hIRS-1 cDNA (hIRS-DeltaC) was over-expressed in FOCUS HCC cells. The direct effects of AAH on motility and invasiveness were examined in AAH-transfected HepG2 cells.


RESULTS
Insulin and IGF-1 stimulation increased AAH mRNA and protein expression and motility in FOCUS and Hep-G2 cells. These effects were mediated by signaling through the Erk MAPK and PI3 kinase-Akt pathways. Over-expression of hIRS-1 resulted in high levels of AAH in Tg mouse livers, while over-expression of hIRS-DeltaC reduced AAH expression, motility, and invasiveness in FOCUS cells. Finally, over-expression of AAH significantly increased motility and invasiveness in HepG2 cells, whereas siRNA inhibition of AAH expression significantly reduced directional motility in FOCUS cells.


CONCLUSIONS
The results suggest that enhanced AAH gene activity is a common feature of human HCC and growth factor signaling through IRS-1 regulates AAH expression and increases motility and invasion of HCC cells. Therefore, AAH may represent an important target for regulating tumor growth in vivo.
de la Monte
Suzanne M
SM
Departments of Medicine and Pathology, Brown Medical School, Liver Research Center, Rhode Island Hospital, 55 Claverick Street, 4th Floor, Providence, RI 02903, USA.
Tamaki
Seishu
S
Cantarini
M Chiara
MC
Ince
Nedim
N
Wiedmann
Marcus
M
Carter
Jade J
JJ
Lahousse
Stephanie A
SA
Califano
Sophia
S
Maeda
Takashi
T
Ueno
Takato
T
D'Errico
Antonia
A
Trevisani
Franco
F
Wands
Jack R
JR
D000818:Animals; D001706:Biopsy; D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000556:secondary*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology*; D051379:Mice; D008822:Mice, Transgenic; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D010750:Phosphoproteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D007004:Hypoglycemic Agents; C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; D010750:Phosphoproteins; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D006899:Mixed Function Oxygenases; C058291:aspartic acid 2-oxoglutarate-dependent dioxygenase