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Selective expression of FLIP in malignant melanocytic skin lesions
R R Bullani1, B Huard, I Viard-Leveugle
1Department of Dermatology, Geneva University Medical School, Switzerland.
Abstract:
FLIP (FLICE Inhibitory Protein) is a recently identified intracellular inhibitor of caspase-8 activation that potently inhibits cell death mediated by all death receptors including Fas and TRAIL. FLIP has recently been shown to favor tumor growth and immune escape in mouse tumor models. We analyzed FLIP expression by immunohistochemistry in a panel of 61 benign and malignant human melanocytic skin lesions. FLIP expression was undetectable in all but one benign melanocytic lesion (31/32, 97%). In contrast, FLIP was strongly expressed in most melanomas (24/29 = 83%). Overexpression of FLIP by transfection in a Fas- and TRAIL-sensitive human melanoma cell line rendered this cell line more resistant to death mediated by both TRAIL and FasL. Selective expression of FLIP by human melanomas may confer in vivo resistance to FasL and TRAIL, thus representing an additional mechanism by which melanoma cells escape immune destruction.
Insights
FLIP (FLICE Inhibitory Protein) is highly expressed in melanomas but not benign lesions. This protein may help melanoma cells evade immune destruction by resisting Fas and TRAIL-mediated cell death.
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- FLICE Inhibitory Protein (FLIP) is an intracellular inhibitor of caspase-8 activation.
- FLIP inhibits cell death induced by death receptors like Fas and TRAIL.
- FLIP has been implicated in promoting tumor growth and immune evasion in mouse models.
Purpose of the Study:
- To investigate FLIP expression in human melanocytic skin lesions.
- To determine if FLIP expression correlates with melanoma development.
- To assess the functional role of FLIP in melanoma cell resistance to death receptor-mediated apoptosis.
Main Methods:
- Immunohistochemistry was used to analyze FLIP expression in 61 benign and malignant melanocytic skin lesions.
- FLIP expression levels were quantified and compared between benign nevi and melanomas.
- A human melanoma cell line sensitive to Fas and TRAIL was transfected to overexpress FLIP, and its resistance to FasL and TRAIL-mediated cell death was evaluated.
Main Results:
- FLIP expression was undetectable in 97% of benign melanocytic lesions (31/32).
- Strong FLIP expression was observed in 83% of melanomas (24/29).
- Overexpression of FLIP in a melanoma cell line significantly increased resistance to FasL- and TRAIL-mediated apoptosis.
Conclusions:
- Selective FLIP expression is a hallmark of human melanoma.
- Overexpressed FLIP in melanoma cells confers resistance to death receptor-mediated apoptosis.
- FLIP may represent a crucial mechanism for melanoma immune escape by inhibiting FasL and TRAIL-induced cell death.