Constitutive activation of stat 3 oncogene product in human ovarian carcinoma cells.
OBJECTIVE
Stat 3 functions in transducing signals from the cell's surface to its nucleus and activation of gene transcription. Aberrations of Stat 3 in breast cancer have raised the possibility of its contribution to oncogenesis. Our goal was to examine ovarian cancer cell lines to determine whether Stat 3 plays a relevant role in ovarian carcinogenesis.


METHODS
Protein lysates were extracted from normal ovarian surface epithelial cells and malignant cells. Western blotting techniques were performed with phosphorylation-independent or phosphorylation-specific Stat 3 (tyrosine 705) antibody. Confirmation of Stat 3 activation was determined by a luciferase reporter driven by a promoter containing Stat 3-specific binding sites. Bcl-x(L) and cyclin D(1) were also analyzed by Western blotting.


RESULTS
MDAH 2774, OV-1063, Caov-3, and O.C. 22819 expressed high levels of phosphorylated Stat 3. In contrast, A2780 and normal ovarian surface epithelial cells had little Stat 3 phosphorylation recognized. Confirmation of persistent activation of Stat 3 activity was shown by transfection of cells with a Stat 3 luciferase reporter. Potential downstream mediators of Stat 3 including Bcl-x(L) and cyclin D(1) were also evaluated. In cells expressing activated Stat 3, high levels of both Bcl-x(L) and cyclin D(1) were detected, whereas in A2780 cells, which did not express activated Stat 3, only low levels of Bcl-x(L) and cyclin D(1) were expressed.


CONCLUSIONS
Constitutive activation of Stat 3 is present in ovarian cancer lines but not in normal ovarian surface epithelial cells. Activation of Stat 3 is a common event during oncogenic transformation upstream to both Bcl-x(L) and cyclin D(1). The relationship of this aberrancy of ovarian carcinoma harboring activated Stat 3 deserves further investigation.
Huang
M
M
Department of Obstetrics and Gynecology, University of Michigan Comprehensive Cancer Center, Ann Arbor, Michigan 48109, USA.
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D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D019938:Cyclin D1 / Q000096:biosynthesis / Q000235:genetics; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015151:Immunoblotting; D010051:Ovarian Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics; D050796:STAT3 Transcription Factor; D015398:Signal Transduction / Q000502:physiology; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein
C494811:BCL2L1 protein, human; D004268:DNA-Binding Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D051020:bcl-X Protein; D019938:Cyclin D1