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STAT3 activation is required for interleukin-6 induced transformation in tumor-promotion sensitive mouse skin
Cheng-Yong Yu1, Lihua Wang, Alexander Khaletskiy
1Laboratory of Experimental Immunology, National Cancer Institute, National Institutes of Health, Frederick, Maryland, MD 21702, USA.
Abstract:
STAT3, a member of signal transducers and activators of transcription (STATs) originally discovered as mediators in cytokine signaling pathways, plays an active role in oncogenesis. However, the function of STAT3 in signaling multistage carcinogenesis, especially in transformation of tumor-promotion sensitive epithelial cells has not been elucidated. The present study demonstrates that STAT3 is activated in interleukin-6 induced transformation in mouse skin epithelial cells. DNA binding and transcriptional activities of STAT3 were significantly increased by interleukin-6. This induced anchorage-independent transformation in tumor-promotion sensitive JB6 mouse skin P+ cells but not in the resistant variant P- cells. Two forms of dominant negative STAT3 (mutant of transcriptional domain, mF, or DNA-binding domain, mD) were stably transfected into P+ cells. Activation of STAT3 was abolished and importantly, interleukin-6 induced anchorage-independent growth was absent in both mutant STAT3 transfectants. To determine the genes targeted by STAT3, three matrix metalloproteinase proteins linked with carcinogenesis of epithelial cells were analysed. Both basal and interleukin-6 induced expression of collagenase I and stromelysin I, but not gelatinase A, were inhibited in the mutant STAT3 transfectants. Furthermore, transfection of a wild type STAT3 restored STAT3 transactivation and response to interleukin-6 induced transformation in mutant STAT3 transfectants, which up-regulated collagenase I and stromelysin I as well. Together, these results provide the first evidence that STAT3 activation is required in the progression of multistage carcinogenesis of mouse skin epithelial cells, and matrix metalloproteinases are actively involved in STAT3-mediated cell transformation.
Insights
Signal transducer and activator of transcription 3 (STAT3) activation is crucial for interleukin-6 induced transformation of mouse skin epithelial cells. STAT3 targets matrix metalloproteinases, driving multistage carcinogenesis.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Signal transducer and activator of transcription (STAT) proteins, including STAT3, are key mediators in cytokine signaling pathways and are implicated in oncogenesis.
- The specific role of STAT3 in multistage carcinogenesis, particularly in the transformation of tumor-promotion sensitive epithelial cells, remains incompletely understood.
Purpose of the Study:
- To elucidate the function of STAT3 in interleukin-6 induced transformation of mouse skin epithelial cells.
- To investigate the role of STAT3 activation in multistage carcinogenesis.
- To identify STAT3-targeted genes involved in epithelial cell transformation.
Main Methods:
- Activation of STAT3 by interleukin-6 in JB6 mouse skin epithelial cells (P+ and P- variants).
- Stable transfection of dominant-negative STAT3 mutants (mF and mD) into P+ cells to abolish STAT3 activation.
- Analysis of DNA binding and transcriptional activities of STAT3.
- Assessment of anchorage-independent growth.
- Quantification of matrix metalloproteinase (MMP) expression (collagenase I, stromelysin I, gelatinase A).
- Restoration of STAT3 activity via wild-type STAT3 transfection.
Main Results:
- Interleukin-6 significantly increased STAT3 DNA binding and transcriptional activity in P+ cells.
- STAT3 activation was essential for interleukin-6 induced anchorage-independent transformation in P+ cells, but not in P- cells.
- Dominant-negative STAT3 mutants blocked interleukin-6 induced transformation and abolished STAT3 activation.
- Basal and interleukin-6 induced expression of collagenase I and stromelysin I were inhibited in mutant STAT3 transfectants.
- Wild-type STAT3 transfection restored STAT3 activity, interleukin-6 induced transformation, and up-regulated collagenase I and stromelysin I.
Conclusions:
- STAT3 activation is a required event in the multistage carcinogenesis of mouse skin epithelial cells.
- Matrix metalloproteinases, specifically collagenase I and stromelysin I, are actively involved in STAT3-mediated cell transformation.
- This study provides the first evidence for STAT3's essential role in epithelial cell transformation during carcinogenesis.