title: Constitutional activation of IL-6-mediated JAK/STAT pathway through hypermethylation of SOCS-1 in human gastric cancer cell line.
abstract: The interleukin-mediated Janus kinase (JAK)/STAT pathway plays a crucial role in carcinogenesis. Recently, increased STAT3 activity was found in hepatocellular carcinoma and multiple myeloma in which there was silencing of SOCS-1 (suppressor of cytokine signalling-1) by gene promoter hypermethylation. We investigated the expression level of interleukin-6 (IL-6) and SOCS-1 in gastric cancer cell lines. Expression of SOCS-1 correlated with IL-6 level in most of the cell lines, except for AGS cells in which SOCS-1 was absent despite a high level of IL-6 production. Methylation analysis by methylation-specific polymerase chain reaction and bisulphite sequencing revealed that CpG island of SOCS-1 was densely methylated in AGS cells. Demethylation treatment by 5'aza-deoxycytidine restored SOCS-1 expression and also suppressed constitutive STAT3 phosphorylation in AGS cells. Moreover, methylation of SOCS-1 was detected in 27.5% (11 of 40) of primary gastric tumours samples, 10% (one of 10) of adjacent noncancer tissues but not in any (zero of nine) normal gastric mucosa. Methylation of SOCS-1 also correlated with the loss of mRNA expression in some primary gastric cancers. In conclusion, this is the first report to demonstrate that hypermethylation of SOCS-1 led to gene silencing in gastric cancer cell line and primary tumour samples. Downregulation of SOCS-1 cooperates with IL-6 in the activation of JAK/STAT pathway in gastric cancer.
authors.affiliation: Department of Anatomical and Cellular Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, NT, Hong Kong. kfto@cuhk.edu.hk
authors.forename: K F
authors.initials: KF
authors.lastname: To
authors.forename: M W Y
authors.initials: MW
authors.lastname: Chan
authors.forename: W K
authors.initials: WK
authors.lastname: Leung
authors.forename: E K W
authors.initials: EK
authors.lastname: Ng
authors.forename: J
authors.initials: J
authors.lastname: Yu
authors.forename: A H C
authors.initials: AH
authors.lastname: Bai
authors.forename: A W I
authors.initials: AW
authors.lastname: Lo
authors.forename: S H
authors.initials: SH
authors.lastname: Chu
authors.forename: J H M
authors.initials: JH
authors.lastname: Tong
authors.forename: K W
authors.initials: KW
authors.lastname: Lo
authors.forename: J J Y
authors.initials: JJ
authors.lastname: Sung
authors.forename: F K L
authors.initials: FK
authors.lastname: Chan
mesh_terms: D002352:Carrier Proteins / Q000096:biosynthesis / Q000378:metabolism*; D002471:Cell Transformation, Neoplastic; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000494:pharmacology*; D015536:Down-Regulation; D006801:Humans; D015850:Interleukin-6 / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins; D053613:Janus Kinase 1; D011505:Protein-Tyrosine Kinases / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D012097:Repressor Proteins / Q000096:biosynthesis / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor; D013274:Stomach Neoplasms / Q000473:pathology*; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D015850:Interleukin-6; D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; C108944:SOCS1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators; D011505:Protein-Tyrosine Kinases; C507904:JAK1 protein, human; D053613:Janus Kinase 1