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Alterations in activating protein 1 composition correlate with phenotypic differentiation changes induced by
1College of Medicine, University of California-Irvine, 101 The City Drive South, Bldg. 56, Room 215, Orange, CA 92868, USA.
Abstract:
Resveratrol has demonstrated preventive and therapeutic activities in a variety of tumors. However, the mechanistic basis of its pharmacological effects on human melanoma has not been well defined. Our results demonstrated that resveratrol significantly inhibited melanoma anchorage-independent growth, and even at high doses no distinct apoptosis or cell cycle arrest was observed. It is noteworthy that c83-2c (metastatic) and wm3211 (radial growth phase) melanoma cells became more dendritic shaped with resveratrol treatment. Major histocompatibility complex (MHC) class I antigen and Fas/CD95 constitutive surface expression levels were, respectively, increased by 2.7- and 1.6-fold of control in c83-2c cells. Resveratrol reduced both activator protein-1 (AP-1) DNA binding and transcriptional activities, and supershift assay revealed that AP-1 composition was shifted from c-Jun/JunD/Fra-1 to JunD/Fra-1/Fra-2, with markedly increased JunD, Fra-1, and Fra-2 protein expression levels in the nucleus. Furthermore, we overexpressed Fra-2 in human melanoma cells by using a Fra-2 expression construct and both AP-1 transcriptional activity and 12-O-tetradecanoylphorbol-induced transcriptional transactivation were reduced significantly, whereas MHC class I antigen and Fas/CD95 levels were elevated to 2.0 and 1.8 times of control, respectively. Addition of H(2)O(2) (10 muM) partially reversed the inhibition of colony proliferation; however, no effects on either MHC class I antigen or Fas expression was evident. Although H(2)O(2) restored participation of c-Jun in AP-1 complexes, H(2)O(2) addition did not affect the induction of Fra-1 and Fra-2 by resveratrol nor the morphological changes. We propose that alterations in AP-1 transcription signaling, mediated by changes in AP-1 dimeric composition and reduced intracellular reactive oxygen species levels, substantially contribute to the phenotypic changes induced by resveratrol.
Insights
Resveratrol inhibits melanoma growth by altering activator protein-1 (AP-1) signaling, leading to dendritic cell morphology and increased Major histocompatibility complex (MHC) class I and Fas/CD95 expression. These changes occur independently of apoptosis or cell cycle arrest.
Area of Science:
- Molecular Biology
- Cancer Research
- Immunology
Background:
- Resveratrol exhibits anti-cancer properties, but its specific mechanisms in human melanoma are not fully understood.
- Melanoma progression involves complex cellular changes and immune evasion strategies.
- Activator protein-1 (AP-1) is a key transcription factor implicated in cell proliferation and survival.
Purpose of the Study:
- To elucidate the molecular mechanisms underlying resveratrol's effects on human melanoma.
- To investigate the role of AP-1 signaling in resveratrol-induced phenotypic changes in melanoma cells.
- To assess the impact of resveratrol on Major histocompatibility complex (MHC) class I and Fas/CD95 expression.
Main Methods:
- Assessed resveratrol's impact on melanoma anchorage-independent growth, apoptosis, and cell cycle.
- Analyzed changes in melanoma cell morphology, MHC class I, and Fas/CD95 expression.
- Investigated activator protein-1 (AP-1) DNA binding, transcriptional activity, and protein composition using supershift assays and Western blotting.
- Utilized Fra-2 overexpression and hydrogen peroxide (H2O2) treatment to probe signaling pathways.
Main Results:
- Resveratrol inhibited melanoma anchorage-independent growth without inducing apoptosis or cell cycle arrest.
- Melanoma cells exhibited a more dendritic morphology, with increased MHC class I and Fas/CD95 expression.
- Resveratrol reduced AP-1 DNA binding and transcriptional activity, shifting its composition towards JunD/Fra-1/Fra-2.
- Overexpression of Fra-2 mimicked resveratrol's effects on AP-1 activity and surface marker expression.
- H2O2 partially reversed proliferation inhibition but did not affect morphological or surface marker changes.
Conclusions:
- Resveratrol induces significant phenotypic changes in human melanoma cells, including altered morphology and increased expression of immune-related molecules.
- These effects are mediated by alterations in AP-1 transcription signaling, specifically changes in AP-1 dimeric composition and reduced intracellular reactive oxygen species (ROS).
- Resveratrol's impact on AP-1 signaling represents a key mechanism contributing to its anti-melanoma activities.
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