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Membrane-bound regulators of complement activation in uveal melanomas. CD46, CD55, and CD59 in uveal melanomas
W R Goslings1, D J Blom, I de Waard-Siebinga
1Department of Ophthalmology, Leiden University Hospital, Netherlands.
Purpose:
To identify the presence of membrane-bound regulators of complement activation (m-RCA) on uveal melanomas and uveal melanoma cell lines and to examine their role in the inhibition of complement-mediated lysis in vitro.
Methods:
Immunohistochemistry and flow cytometric analysis with monoclonal antibodies directed against m-RCA CD46, CD55, and CD59 were applied to tissue sections of 10 uveal melanomas, three primary uveal melanoma cell lines, and one uveal melanoma metastatic cell line. A microcytotoxicity test was used for measuring antibody-dependent complement-mediated lysis.
Results:
The tissue sections and all four uveal melanoma cell lines expressed CD46, CD55, and CD59. Complement-mediated lysis in the presence of human complement was increased after partial removal of the m-RCA CD55 and CD59 with phosphatidylinositol-specific phospholipase C from the uveal melanoma cell line 92-1.
Conclusions:
These results demonstrate that CD46, CD55, and CD59 are expressed in uveal melanomas and that CD55 or CD59, or both, plays a role in resistance to complement-mediated cytotoxicity. The finding that m-RCA are expressed in uveal melanomas may have implications for the effectiveness of the anti-tumor response and in the therapeutic application of monoclonal antibodies directed against tumor-associated antigens.
Insights
Uveal melanomas express membrane-bound regulators of complement activation (m-RCA) like CD46, CD55, and CD59. These regulators, particularly CD55 and CD59, help uveal melanoma cells resist complement-mediated attack.
Area of Science:
- Immunology
- Oncology
- Ophthalmology
Background:
- Uveal melanoma is the most common primary intraocular malignancy.
- The complement system is a critical part of innate immunity that can be activated by tumors.
- Membrane-bound regulators of complement activation (m-RCA) protect host cells from complement-mediated damage.
Purpose of the Study:
- To determine the expression of m-RCA (CD46, CD55, CD59) on uveal melanomas and cell lines.
- To investigate the role of m-RCA in protecting uveal melanoma cells from complement-mediated lysis in vitro.
Main Methods:
- Immunohistochemistry and flow cytometry were used to detect CD46, CD55, and CD59 on uveal melanoma tissues and cell lines.
- Microcytotoxicity assays measured complement-mediated lysis.
- Phosphatidylinositol-specific phospholipase C was used to remove m-RCA.
Main Results:
- CD46, CD55, and CD59 were expressed on uveal melanoma tissue sections and all tested cell lines.
- Removal of CD55 and CD59 increased complement-mediated lysis of the 92-1 uveal melanoma cell line.
Conclusions:
- Uveal melanomas express CD46, CD55, and CD59.
- CD55 and/or CD59 contribute to resistance against complement-mediated cytotoxicity in uveal melanoma.
- The presence of m-RCA on uveal melanomas may impact anti-tumor immune responses and therapeutic strategies using antibodies.