Methylation silencing of SOCS-3 promotes cell growth and migration by enhancing JAK/STAT and FAK signalings in human hepatocellular carcinoma.
We identified that suppressor of cytokine signaling-3 (SOCS-3) gene was aberrantly methylated in its CpG island in three of 10 human hepatocellular carcinoma (HCC) cell lines. SOCS-3 RNA was undetectable in five of the 10 HCC cell lines including the three methylated cell lines, and a demethylating agent, 5-aza-2'-deoxycytidine, reactivated SOCS-3 expression in three cell lines tested. The DNA region where we found aberrant DNA methylation includes a signal transducers and activators of transcription (STAT) binding consensus sequence. When the DNA region was used as a promoter, DNA methylation markedly reduced promoter activity. SOCS-3 was also aberrantly methylated in six of 18 primary HCC samples. SOCS-3 expression was reduced in three of the three methylated and one of the three unmethylated primary samples examined. Restoration of SOCS-3 in cells lacking SOCS-3 expression suppressed STAT3 phosphorylation and cell growth. We found that IL-6 acted as a growth factor in HCC cells. Inhibition of SOCS-3 expression in cells whose growth was induced by IL-6 enhanced STAT3 phosphorylation and cell growth. In addition, AG490, a chemical JAK2 inhibitor, suppressed cell growth and downregulated STAT3 phosphorylation, but not FAK phosphorylation. We also found that SOCS-3 physically interacted with phosphorylated FAK and Elongin B in HCC cells. Restoration of SOCS-3 decreased FAK phosphorylation as well as FAK protein level. Inhibition of SOCS-3 expression increased FAK phosphorylation, resulting in enhancement of cell migration. These data indicate that SOCS-3 negatively regulates cell growth and cell motility by inhibiting Janus kinase (JAK)/STAT and FAK signalings in HCC cells. Thus, loss of SOCS-3 by the associated DNA methylation confers cells advantage in growth and migration.
Niwa
Yasuharu
Y
Department of Epigenetic Carcinogenesis, The Cancer Institute, Japanese Foundation for Cancer Research, 3-10-6, Ariake, Koto-ku, Tokyo 135-8550, Japan.
Kanda
Hiroaki
H
Shikauchi
Yuko
Y
Saiura
Akio
A
Matsubara
Kenichi
K
Kitagawa
Tomoyuki
T
Yamamoto
Junji
J
Kubo
Takahiko
T
Yoshikawa
Hirohide
H
D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D002455:Cell Division / Q000502:physiology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology*; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D020868:Gene Silencing; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008113:Liver Neoplasms / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D050794:STAT1 Transcription Factor; D015398:Signal Transduction; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
D004268:DNA-Binding Proteins; D012097:Repressor Proteins; C106644:SOCS3 protein, human; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D048031:JNK Mitogen-Activated Protein Kinases