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Enhanced metastatic ability of TNF-alpha-treated malignant melanoma cells is reduced by intercellular adhesion
M E Miele1, C F Bennett, B E Miller
1Department of Pathology, Pennsylvania State University College of Medicine, Hershey 17033.
Abstract:
Treating human malignant melanoma cells with tumor necrosis factor-alpha (TNF-alpha) or interferon-gamma (IFN-gamma) causes a dose- and time-dependent increase in surface expression of ICAM-1. Increased ICAM-1 expression corresponds to greater binding of human leukocyte functional antigen-1 (CD11a/CD18)-expressing peripheral blood mononuclear cells (PBMC) to C8161 monolayers, suggesting that cytokine-treated melanoma cells would be more metastatic due to PBMC-tumor cell emboli. The purpose of this study was: (1) to test whether TNF-alpha-treated human melanoma cells are indeed more metastatic than untreated C8161 and (2) to determine whether ICAM-1 plays a role in metastasis of C8161. When surface ICAM-1 expression is upregulated, formation of lung metastases in nude mice increases 1.5- to 4-fold (P < 0.05) for human melanoma cell lines C8161, MeWo, and A375. Treatment of C8161 with ICAM-1 phosphorothioate antisense oligonucleotides using cationic lipids results in > 90% inhibition of ICAM-1 surface expression as determined by ELISA and flow cytometry. Antisense ICAM-1-treated cells form 41-64% fewer metastases than sham-treated cells. Metastasis does not increase when antisense-treated melanoma cells are exposed to TNF-alpha. However, treatment of C8161 with antisense 5-lipoxygenase (5-LO) oligonucleotides inhibits metastases 39% in Lipofectin-treated cells, but does not inhibit TNF-alpha-induced upregulation of experimental metastases. Similar experiments were performed to measure PBMC adhesion to antisense oligonucleotide-treated C8161 cells; however, TNF-alpha-inducible increase in adhesion was unaffected by ICAM-1 or 5-LO antisense oligonucleotides. These results demonstrate that ICAM-1 is involved in melanoma metastasis, but probably not at the step of PBMC adhesion to C8161 cells.
Insights
Tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) increase ICAM-1 on melanoma cells, promoting metastasis. Inhibiting ICAM-1 reduces melanoma spread in mice, suggesting ICAM-1 is a key factor in melanoma progression.
Area of Science:
- Oncology
- Immunology
- Cell Biology
Background:
- Cytokine treatment, including tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), upregulates intercellular adhesion molecule-1 (ICAM-1) on malignant melanoma cells.
- Increased ICAM-1 expression correlates with enhanced binding of peripheral blood mononuclear cells (PBMC) to melanoma cells, potentially increasing metastatic capability.
Purpose of the Study:
- To investigate if TNF-alpha-treated human melanoma cells exhibit increased metastatic potential compared to untreated cells.
- To determine the role of ICAM-1 in the metastasis of human melanoma cell line C8161.
Main Methods:
- Melanoma cell lines (C8161, MeWo, A375) were treated with cytokines, and ICAM-1 surface expression was measured.
- Nude mice were used to assess lung metastasis formation after cytokine treatment.
- ICAM-1 expression was inhibited using phosphorothioate antisense oligonucleotides delivered via cationic lipids.
- 5-lipoxygenase (5-LO) antisense oligonucleotides were used to assess their impact on metastasis.
- PBMC adhesion assays were performed on treated and untreated melanoma cells.
Main Results:
- Upregulation of surface ICAM-1 expression led to a 1.5- to 4-fold increase in lung metastases in nude mice across multiple melanoma cell lines.
- Treatment with ICAM-1 antisense oligonucleotides resulted in over 90% inhibition of ICAM-1 surface expression and reduced metastases by 41-64%.
- Inhibition of ICAM-1 prevented the TNF-alpha-induced increase in experimental metastases, while 5-LO inhibition showed a partial effect on metastasis but did not affect TNF-alpha-induced metastasis.
- PBMC adhesion to melanoma cells was not significantly affected by ICAM-1 or 5-LO antisense oligonucleotides, despite changes in ICAM-1 expression.
Conclusions:
- Intercellular adhesion molecule-1 (ICAM-1) plays a significant role in melanoma metastasis.
- The involvement of ICAM-1 in metastasis may not be directly related to the adhesion step involving peripheral blood mononuclear cells (PBMC).
- Targeting ICAM-1 presents a potential therapeutic strategy for reducing melanoma metastasis.