CD55 is over-expressed in the tumour environment

Area of Science:

• Immunology
• Oncology
• Cell Biology

Background:

• CD55 (Complement Decay-Accelerating Factor) is a cell surface protein that regulates complement activation.
• The antigen 791Tgp72, a known target for tumor imaging and vaccines, has been identified as CD55.
• Tumor microenvironments exhibit altered protein expression, impacting therapeutic strategies.

Purpose of the Study:

• To quantify CD55 expression in the tumor environment.
• To investigate the source of CD55 in the tumor stroma.
• To evaluate CD55's potential as a therapeutic target.

Main Methods:

• Quantitative analysis of CD55 cell surface expression on tumor cells versus normal cells.
• Immunohistochemical staining of colorectal tumors to assess stromal CD55.
• Measurement of extracellular CD55 deposition by epithelial and endothelial cells.
• Assessment of CD55 expression on HUVEC cells following VEGF exposure.

Main Results:

• Tumor cells displayed a 4-100 fold increase in CD55 cell surface expression compared to normal cells.
• High CD55 expression was observed in the stroma of colorectal tumors.
• Tumor cell lines deposited extracellular CD55 proportional to cell surface expression.
• HUVEC cells produced significant extracellular CD55 despite low cell surface expression, which was further increased by VEGF.

Conclusions:

• CD55 is significantly upregulated on tumor cells and within the tumor stroma.
• Both tumor cells and associated endothelium contribute to stromal CD55.
• The elevated expression of CD55 in the tumor microenvironment supports its utility as a target for cancer imaging and immunotherapy.