Transcriptional repression of SOCS3 mediated by IL-6/STAT3 signaling via DNMT1 promotes pancreatic cancer growth and metastasis.

Abstract

BACKGROUND:

Previous studies have investigated the sustained aberrantly activated Interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) signaling pathway is crucial for pancreatic cancer growth and metastasis. Suppressor of cytokine signaling 3 (SOCS3), as a key negative feedback regulator of this signaling pathway, is usually down-regulated in various cancers. In the present study, we aim at exploring the biological function and the underlying molecular regulation mechanisms of SOCS3 in pancreatic cancer.

METHODS:

The expression of SOCS3 and other genes in pancreatic cancer was examined by Quantitative real-time PCR, western blotting and immunohistochemical staining. The interaction between pSTAT3 and DNA Methyltransferase 1 (DNMT1) was investigated by co-immunoprecipitation assay. Luciferase reporter assay was used to investigate the transcriptional regulation of pSTAT3 and DNMT1 on the SOCS3 gene. The effects of SOCS3 on the biological behavior of pancreatic cancer cells were assessed both in vitro and vivo. Furthermore, we performed a comprehensive analysis of the expression of SOCS3 in a pancreatic cancer tissue microarray (TMA) and correlated our findings with pathological parameters and outcomes of the patients.

RESULTS:

We showed that SOCS3 expression was decreased in phosphorylated STAT3 (pSTAT3)-positive tumors and was negatively correlated with pSTAT3 in pancreatic cancer cells. We also found that IL-6/STAT3 promoted SOCS3 promoter hypermethylation by increasing DNMT1 activity; silencing DNMT1 or 5-aza-2-deoxycytidine (5-AZA) treatment could reverse the down-regulation of SOCS3 mediated by IL-6. Using co-immunoprecipitation and luciferase reporter assays, we found that STAT3 recruited DNMT1 to the promoter region of SOCS3 and inhibited its transcriptional activity. Overexpression of SOCS3 significantly inhibited cell proliferation, which may be due to the increase in G1-S phase arrest; overexpression of SOCS3 also inhibited cell migration and invasion as well as tumorigenicity in nude mice. Pancreatic cancer tissue microarray analysis showed that high SOCS3 expression was a good prognostic factor and negatively correlated with tumor volume and metastasis.

CONCLUSION:

We demonstrated that activated IL-6/STAT3 signaling could induce SOCS3 methylation via DNMT1, which led to pancreatic cancer growth and metastasis. These data also provided a mechanistic link between sustained aberrantly activated IL-6/STAT3 signaling and SOCS3 down-regulation in pancreatic cancer. Thus, inhibitors of STAT3 or DNMT1 may become novel strategies for treating pancreatic cancer.

• Authors: Li Huang, Bin Hu, Jianbo Ni, Jianghong Wu, Weiliang Jiang, Congying Chen, Lijuan Yang, Yue Zeng, Rong Wan, Guoyong Hu, Xingpeng Wang
• Journal: Journal of experimental & clinical cancer research : CR (J Exp Clin Cancer Res) Vol. 35 Pg. 27 (Feb 04 2016) ISSN: 1756-9966 [Electronic] England
• PMID: 26847351 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Retracted Publication)

Chemical References

• IL6 protein, human
• Interleukin-6
• SOCS3 protein, human
• STAT3 Transcription Factor
• STAT3 protein, human
• Suppressor of Cytokine Signaling 3 Protein
• Suppressor of Cytokine Signaling Proteins
• DNA (Cytosine-5-)-Methyltransferase 1
• DNA (Cytosine-5-)-Methyltransferases
• DNMT1 protein, human
• Dnmt1 protein, mouse

Topics

• Animals
• Cell Line, Tumor
• DNA (Cytosine-5-)-Methyltransferase 1
• DNA (Cytosine-5-)-Methyltransferases (metabolism)
• DNA Methylation
• Female
• Gene Expression Regulation, Neoplastic
• Humans
• Interleukin-6 (metabolism)
• Male
• Mice
• Neoplasm Metastasis
• Neoplasm Transplantation
• Pancreatic Neoplasms (genetics, metabolism, pathology)
• STAT3 Transcription Factor (metabolism)
• Signal Transduction
• Suppressor of Cytokine Signaling 3 Protein
• Suppressor of Cytokine Signaling Proteins (genetics, metabolism)
• Transcription, Genetic