Induction of hepatocyte growth factor activator gene expression under hypoxia activates the hepatocyte growth factor/c-Met system via hypoxia inducible factor-1 in pancreatic cancer.
Hepatocyte growth facor activator (HGFA) is a serine protease that converts hepatocyte growth factor (HGF) into its active form. Our previous study demonstrated that tumor-stromal interaction under hypoxia augments the aggressive invasive features of pancreatic cancer line PK8 through activated HGF/c-Met signaling. The present study investigated whether or not hypoxia increases HGFA expression in PK8 cells and promotes the processing of HGF, and leads to c-Met activation. Moreover, HGFA promoter assays were performed to define whether hypoxia inducible factor-1 alpha (HIF-1alpha) directly activates the HGFA promoter in a hypoxia-dependent fashion. As a result, hypoxia induced the HGFA mRNA and protein expression in PK8 and the elevation under hypoxia was inhibited by the transfection of HIF-1alpha siRNA, thus indicating HIF-1alpha-dependent induction of HGFA. The transfection of siRNA against HGFA to PK8 cells suppressed the conversion to the active HGF, which is secreted from fibroblast MRC5. Furthermore, the phosphorylation of c-Met and cancer invasion of PK8 cells were decreased by the transfection of HGFA siRNA under hypoxia. Using the luciferase reporter system, HIF-1alpha was shown to transactivate the HGFA promoter under hypoxia. These experiments demonstrated for the first time that HGFA is a novel HIF-1 target gene. Under hypoxia, HGFA might be overexpressed and secreted from pancreatic cancer cells, which contributes to accelerate processing of HGF from fibroblast, resulting in the activation of the c-Met pathway. HGF/HGFA/c-Met recruited between cancer-stromal fibroblasts is activated under hypoxic conditions and therefore might play a central role in the aggressive invasion of pancreatic cancer.
Kitajima
Yoshihiko
Y
Department of Surgery, Saga University Faculty of Medicine, Saga, B49-8501 Japan.
Ide
Takao
T
Ohtsuka
Takao
T
Miyazaki
Kohji
K
D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D017228:Hepatocyte Growth Factor / Q000378:metabolism*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000502:physiology*; D009361:Neoplasm Invasiveness; D010190:Pancreatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000235:genetics*
C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D034741:RNA, Small Interfering; D017228:Hepatocyte Growth Factor; C081092:HGF activator; D012697:Serine Endopeptidases