Loss of protein inhibitors of activated STAT-3 expression in glioblastoma multiforme tumors: implications for STAT-3 activation and gene expression.

Abstract

PURPOSE:

STATs activate transcription in response to numerous cytokines, controlling proliferation, gene expression, and apoptosis. Aberrant activation of STAT proteins, particularly STAT-3, is implicated in the pathogenesis of many cancers, including GBM, by promoting cell cycle progression, stimulating angiogenesis, and impairing tumor immune surveillance. Little is known about the endogenous STAT inhibitors, the PIAS proteins, in human malignancies. The objective of this study was to examine the expression of STAT-3 and its negative regulator, PIAS3, in human tissue samples from control and GBM brains.

EXPERIMENTAL DESIGN:

Control and GBM human tissues were analyzed by immunoblotting and immunohistochemistry to determine the activation status of STAT-3 and expression of the PIAS3 protein. The functional consequence of PIAS3 inhibition by small interfering RNA or PIAS3 overexpression in GBM cells was determined by examining cell proliferation, STAT-3 transcriptional activity, and STAT-3 target gene expression. This was accomplished using [(3)H]TdR incorporation, STAT-3 dominant-negative constructs, reverse transcription-PCR, and immunoblotting.

RESULTS AND CONCLUSIONS:

STAT-3 activation, as assessed by tyrosine and serine phosphorylation, was elevated in GBM tissue compared with control tissue. Interestingly, we observed expression of PIAS3 in control tissue, whereas PIAS3 protein expression in GBM tissue was greatly reduced. Inhibition of PIAS3 resulted in enhanced glioblastoma cellular proliferation. Conversely, PIAS3 overexpression inhibited STAT-3 transcriptional activity, expression of STAT-3-regulated genes, and cell proliferation. We propose that the loss of PIAS3 in GBM contributes to enhanced STAT-3 transcriptional activity and subsequent cell proliferation.

• Authors: Emily C Brantley, L Burton Nabors, G Yancey Gillespie, Youn-Hee Choi, Cheryl Ann Palmer, Keith Harrison, Kevin Roarty, Etty N Benveniste
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 14 Issue 15 Pg. 4694-704 (Aug 01 2008) ISSN: 1078-0432 [Print] United States
• PMID: 18676737 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• RNA, Small Interfering
• SOCS3 protein, human
• STAT3 Transcription Factor
• STAT3 protein, human
• Suppressor of Cytokine Signaling 3 Protein
• Suppressor of Cytokine Signaling Proteins
• Tyrosine
• Serine
• Matrix Metalloproteinase 9

Topics

• Animals
• Cell Line, Tumor
• Cell Proliferation
• Gene Expression Regulation, Neoplastic
• Glioblastoma (drug therapy, metabolism)
• Humans
• Matrix Metalloproteinase 9 (metabolism)
• Phosphorylation
• RNA, Small Interfering (metabolism)
• STAT3 Transcription Factor (metabolism)
• Serine (chemistry)
• Suppressor of Cytokine Signaling 3 Protein
• Suppressor of Cytokine Signaling Proteins (metabolism)
• Transcription, Genetic
• Transcriptional Activation
• Tyrosine (chemistry)