Sustained IL-6/STAT-3 Signaling in Cholangiocarcinoma Cells Due to SOCS-3 Epigenetic Silencing

Hajime Isomoto, Justin L. Mott, Shogo Kobayashi, Nathan W. Werneburg, Steve F. Bronk, Serge Haan, Gregory J. Gores

Research output: Contribution to journalArticlepeer-review

186 Scopus citations


Background & Aims: Interleukin 6 (IL-6)-mediated signal transducers and activators of transcription 3 (STAT-3) phosphorylation (activation) is aberrantly sustained in cholangiocarcinoma cells resulting in enhanced myeloid cell leukemia 1 (Mcl-1) expression and resistance to apoptosis. Because suppressor of cytokine signaling 3 (SOCS) controls the IL-6/STAT-3 signaling pathway by a classic feedback loop, the aims of this study were to examine SOCS-3 regulation in human cholangiocarcinoma. Methods: SOCS-3 expression was assessed in human cholangiocarcinoma tissue and the Mz-ChA-1 and CCLP1 human cholangiocarcinoma cell lines. Results: An inverse correlation was observed between phospho-STAT-3 and SOCS-3 protein expression in cholangiocarcinoma. In those cancers failing to express SOCS-3, extensive methylation of the SOCS-3 promoter was demonstrated in tumor but not in paired nontumor tissue. Likewise, methylation of the socs-3 promoter was also identified in 2 cholangiocarcinoma cell lines. Treatment with a demethylating agent, 5-aza-2′-deoxycytidine (DAC), restored IL-6 induction of SOCS-3, terminated the phospho-STAT-3 response, and reduced cellular levels of Mcl-1. Enforced expression of SOCS-3 also reduced IL-6 induction of phospho-STAT-3 and Mcl-1. Either DAC treatment or enforced SOCS-3 expression sensitized the cells to TRAIL-mediated apoptosis. Conclusions: SOCS-3 epigenetic silencing is responsible for sustained IL-6/STAT-3 signaling and enhanced Mcl-1 expression in cholangiocarcinoma.

Original languageEnglish (US)
Pages (from-to)384-396
Number of pages13
Issue number1
StatePublished - Jan 2007
Externally publishedYes

ASJC Scopus subject areas

  • Hepatology
  • Gastroenterology


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