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Updated: Aug 29, 2026
Spatial and Temporal Control of Murine Melanoma Initiation from Mutant Melanocyte Stem Cells
Published on: June 7, 2019
During human melanoma progression AP-1 binding pairs are altered with loss of c-Jun in vitro
Sun Yang1, Susan McNulty, Frank L Meyskens
1Department of Medicine, Chao Family Comprehensive Cancer Center, University of California, Irvine, Orange, CA 92868, USA.
Abstract:
We demonstrated previously that c-Jun, JunB and c-Fos RNA were dysregulated in metastatic melanoma cells compared with normal human melanocytes. The purpose of this study was to evaluate the distribution in composition of AP-1 dimers in human melanoma pathogenesis. We investigated AP-1 dimer pairing in radial growth phase-like (RGP) (w3211) and vertical growth phase-like (VGP) (w1205) human melanoma cells and metastatic cell lines (cloned from patients, c83-2c, c81-46A, A375, respectively) compared with melanocytes using electrophoretic mobility shift assay (EMSA), Western blot and transfection analyses. There are progressive variations in AP-1 composition in different melanoma cell lines compared with normal melanocytes, in which c-Jun, JunD and FosB were involved in AP-1 complexes. In w3211, c-Jun, JunD and Fra-1 were involved in AP-1 binding, while in w1205, overall AP-1 binding activity was decreased significantly and supershift binding was detected only with JunD antibodies. In metastatic c81-46A and A375 cells, only JunD was involved in AP-1 binding activity, but in a third (c83-2c) c-Jun, JunD and Fra-1 were present. Western blot evaluation detected c-Jun in melanocytes and w3211, but this component was decreased significantly or was not detectable in w1205, c81-46A and A375 cells. In contrast, JunD protein was elevated in c81-46A and c83-2c cells compared with melanocytes and RGP and VGP cell lines. Normal melanocytes and c83-2c cells (which have c-Jun involved in AP-1 binding), transfected with c-Jun antisense and treated with cisplatin, showed higher viability compared with untransfected cells, while in c81-46A cells (in which only JunD is detectable) no change in cell viability was observed following treatment with cisplatin and c-jun antisense transfection. A dominant-negative c-Jun mutant (TAM67) significantly increased the soft agar colony formation of w3211 and c83-2c cells. These results suggest that components of AP-1, especially c-Jun, may offer a new target for the prevention or treatment of human melanoma progression.
Insights
Activating Protein-1 (AP-1) dimer composition changes during melanoma progression. Targeting c-Jun in AP-1 may offer new therapeutic strategies for melanoma treatment.
Area of Science:
- Oncology
- Molecular Biology
Background:
- Activating Protein-1 (AP-1) transcription factors regulate genes involved in cell proliferation, differentiation, and survival.
- Dysregulation of AP-1 components, including c-Jun, JunB, and c-Fos, has been observed in metastatic melanoma.
Purpose of the Study:
- To investigate the dynamic changes in AP-1 dimer composition during human melanoma pathogenesis.
- To evaluate the role of specific AP-1 components in melanoma progression and potential therapeutic targeting.
Main Methods:
- Electrophoretic mobility shift assay (EMSA) to assess AP-1 DNA-binding activity.
- Western blot analysis to determine the protein levels of AP-1 family members.
- Transfection studies using antisense oligonucleotides and dominant-negative mutants to assess functional roles.
Main Results:
- AP-1 composition progressively varied across melanoma cell lines (RGP, VGP, metastatic) compared to normal melanocytes.
- c-Jun was detected in melanocytes and early-stage melanoma but decreased in advanced and metastatic cells.
- JunD levels were elevated in metastatic melanoma cells (c81-46A, c83-2c), where it was a key component of AP-1 binding.
- Cisplatin treatment combined with c-Jun antisense transfection increased viability in cells with functional c-Jun (c83-2c) but not in JunD-dominant cells (c81-46A).
- A dominant-negative c-Jun mutant enhanced colony formation in early-stage melanoma cells, suggesting c-Jun's role in proliferation.
Conclusions:
- AP-1 dimer composition undergoes significant alterations throughout melanoma progression.
- c-Jun plays a critical role in melanoma cell proliferation and survival, particularly in earlier stages.
- Targeting c-Jun represents a potential therapeutic strategy for preventing or treating human melanoma.
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