Ubiquitous activation of Ras and Jak/Stat pathways in human HCC.
OBJECTIVE
Although the natural history and pathologic characteristics of human hepatocellular carcinoma (HCC) are well documented, the molecular pathogenesis of HCC remains poorly understood. Here, we define the role for Ras and Janus kinase (Jak)/signal transducer and activator of transcription (Stat) pathways in human HCC.


METHODS
Promoter and genomic status of Ras and Jak/Stat inhibitors were assessed in 80 HCCs by methylation-specific polymerase chain reaction and microsatellite analysis. Activation of Ras and Jak/Stat signaling pathways was determined by DNA sequencing, Western blot, and immunoprecipitation analysis. Suppression of Ras and Jak/Stat pathways in HCC cell lines was evaluated by viability and apoptosis assays.


RESULTS
Activation of Ras and Jak/Stat pathways was enhanced in all HCCs when compared with nonneoplastic surrounding and normal livers coincidently with the suppression of at least 1 Ras (RASSF1A and/or NORE1A) and 2 Jak/Stat inhibitors (cytokine-inducible SH2-protein [CIS]; suppressor of cytokine signaling [SOCS]1, 2, 3; and SH2-containing phosphatases [SHP1]). HCC associated with cirrhosis showed significantly higher frequency of RASSF1A, CIS, and SOCS1 promoter methylation than HCC without cirrhosis (P < .002, P < .02, and P < .02, respectively). Furthermore, aberrant methylation of NORE1A and SOCS3 promoters was observed only in a subclass of HCC with poor survival, suggesting that inactivation of these 2 genes might be involved in HCC progression. Combined treatment of HCC cell lines with Ras and Jak/Stat inhibitors as well as with the demethylating agent zebularine induced a strong apoptotic response.


CONCLUSIONS
These data demonstrate the ubiquitous activation of Ras and Jak/Stat pathways in HCC and suggest the potential use of Ras and Jak/Stat inhibitors and demethylating agents as therapeutic modality for human liver cancer.
Calvisi
Diego F
DF
Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-4262, USA.
Ladu
Sara
S
Gorden
Alexis
A
Farina
Miriam
M
Conner
Elizabeth A
EA
Lee
Ju-Seog
JS
Factor
Valentina M
VM
Thorgeirsson
Snorri S
SS
D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D051017:Apoptosis Regulatory Proteins; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002455:Cell Division; D019175:DNA Methylation; D015536:Down-Regulation; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D019656:Loss of Heterozygosity; D008297:Male; D008875:Middle Aged; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D050791:STAT Transcription Factors / Q000378:metabolism*; D015398:Signal Transduction; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism; D014018:Tissue Distribution; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D017874:Immediate-Early Proteins; D047908:Intracellular Signaling Peptides and Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D020559:Monomeric GTP-Binding Proteins; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; D050791:STAT Transcription Factors; D050826:Suppressor of Cytokine Signaling Proteins; D025521:Tumor Suppressor Proteins; D018631:ras Proteins; C411762:RASSF1 protein, human; C454042:RASSF5 protein, human; C509249:PTPN6 protein, human