Gastroenterology

Gastroenterology

Volume 130, Issue 4, April 2006, Pages 1117-1128
Gastroenterology

Clinical–liver, pancreas, and biliary tract
Ubiquitous Activation of Ras and Jak/Stat Pathways in Human HCC

https://doi.org/10.1053/j.gastro.2006.01.006Get rights and content

Background & Aims: 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.

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Human Tissue Samples

Ten normal livers, 80 surgically resected HCCs and corresponding surrounding nontumor liver tissues were used. Clinicopathologic features of the patients enrolled in this study are shown in Table 1. HCCs were divided in 2 groups based on patient’s survival length: HCCs with poor prognosis (HCCp) were characterized by a shorter (<3 years) survival and HCCs with better prognosis (HCCb) by a longer (>3 years) survival following partial resection of the liver. Liver tissues were kindly provided by

Promoter Hypermethylation and LOH

The frequency of promoter methylation of Ras (RASSF1A, RASSF1C, RASSF4, NORE1A, and NORE1B) and Jak/Stat, (SOCS1, SOCS2, SOCS3, CIS, and SHP1) inhibitors was determined in a collection of 80 HCCs and matching surrounding livers (Table 1, Table 2). No promoter hypermethylation was detected in normal liver samples. No hypermethylation of the RASSF1C and NORE1B promoters was observed either in surrounding nonneoplastic or neoplastic samples. SOCS2 and SHP1 genes showed high and comparable

Discussion

In the present study, we show that uncontrolled activation of the Ras and Jak/Stat pathways is a dominant oncogenic event in human HCC. Importantly, no significant differences were detected in the frequency of Ras and Jak/Stat activation regardless of the HCC etiology or clinicopathologic features of the HCC patients, suggesting that constitutive induction of Ras and Jak/Stat pathways is essential for liver cancer development. Furthermore, the highest levels of Ras and Jak/Stat effectors were

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    Supported in part by the Intramural Research Program of the NIH, National Cancer Institute, Center for Cancer Research, Bethesda, MD.

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    Copyright © 2006 American Gastroenterological Association Institute. Published by Elsevier Inc. All rights reserved.