hSulf1 Sulfatase promotes apoptosis of hepatocellular cancer cells by decreasing heparin-binding growth factor signaling.
OBJECTIVE
The heparin-binding growth factors fibroblast growth factor (FGF) and hepatocyte growth factor (HGF) are potent mitogens for hepatocellular carcinomas (HCCs). Heparin-binding growth factor signaling is regulated by sulfation of cell-surface heparan sulfate proteoglycans (HSPGs). We hypothesized that hSulf1, a recently described sulfatase, regulates growth signaling in HCCs.


METHODS
Expression of hSulf1 in human HCC tumors was determined by real-time PCR. Down-regulation of hSulf1 expression was investigated by analyzing loss of heterozygosity (LOH) at the hSulf1 locus and the effect of the DNA methylation inhibitor 5-aza-deoxycytidine on hSulf1 expression. The subcellular location of hSulf1 and sulfation state of cell-surface HSPGs were assessed by immunocytochemistry. FGF and HGF signaling was examined by phospho-specific immunoblot analysis. Cell growth was measured by trypan blue exclusion, and the MTT assay and apoptosis were quantitated by fluorescence microscopy.


RESULTS
hSulf1 expression was decreased in 29% of HCCs and 82% of HCC cell lines. There was LOH at the hSulf1 locus in 42% of HCCs. Treatment with 5-aza-deoxycytidine reactivated hSulf1 expression in hSulf1-negative cell lines. Low hSulf1-expressing cells showed increased sulfation of cell-surface HSPGs, enhanced FGF and HGF-mediated signaling, and increased HCC cell growth. Conversely, forced expression of hSulf1 decreased sulfation of cell-surface HSPGs and abrogated growth signaling. HCC cells with high-level hSulf1 expression were sensitive to staurosporine- or cisplatin-induced apoptosis, whereas low expressing cells were resistant. Transfection of hSulf1 into hSulf1-negative cells restored staurosporine and cisplatin sensitivity.


CONCLUSIONS
Down-regulation of hSulf1 contributes to hepatocarcinogenesis by enhancing heparin-binding growth factor signaling and resistance to apoptosis.
Lai
Jin-Ping
JP
Division of Gastroenterology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
Chien
Jeremy R
JR
Moser
David R
DR
Staub
Julie K
JK
Aderca
Ileana
I
Montoya
Damian P
DP
Matthews
Tori A
TA
Nagorney
David M
DM
Cunningham
Julie M
JM
Smith
David I
DI
Greene
Eddie L
EL
Shridhar
Viji
V
Roberts
Lewis R
LR
D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000473:pathology / Q000503:physiopathology*; D002455:Cell Division; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002945:Cisplatin / Q000494:pharmacology; D019175:DNA Methylation; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism*; D006497:Heparan Sulfate / Q000378:metabolism; D017228:Hepatocyte Growth Factor / Q000378:metabolism*; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology / Q000503:physiopathology*; D019656:Loss of Heterozygosity; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D019311:Staurosporine / Q000494:pharmacology; D013431:Sulfates / Q000378:metabolism; D015238:Sulfotransferases / Q000235:genetics / Q000378:metabolism*
D002945:Cisplatin; D016222:Fibroblast Growth Factor 2; D006497:Heparan Sulfate; D017228:Hepatocyte Growth Factor; D012333:RNA, Messenger; D019311:Staurosporine; D013431:Sulfates; D015238:Sulfotransferases; C470791:SULF1 protein, human