Expression and modulation of CD44 variant isoforms in humans

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• CD44 is a cell surface molecule with multiple isoforms generated by alternative splicing of variant exons.
• The expression and function of CD44 variant isoforms are largely unknown, with some implicated in cancer metastasis.

Purpose of the Study:

• To produce monoclonal antibodies (mAbs) against CD44 variant regions (exons 4v, 6v, 9v).
• To comprehensively analyze the expression patterns of CD44 variant isoforms in human tissues and cell types.
• To investigate the modulation of CD44 variant isoform expression by cytokines.

Main Methods:

• Immunization of mice with a fusion protein spanning CD44 variant exons 3v to 10v to generate mAbs.
• Comprehensive analysis of human tissues to determine CD44 variant isoform expression.
• Treatment of cell lines (leukocytes, myelomonocytic, epithelial) with cytokines (TNF alpha, IFN gamma) to assess expression changes.

Main Results:

• CD44 variant isoforms are widely expressed in human tissues, primarily by epithelial cells, with differential expression of exons 4v, 6v, and 9v.
• Generative cells, especially basal cells of epithelia, showed the highest variant isoform levels.
• Variant isoforms were differentially expressed on leukocytes and could be upregulated on T cells and myelomonocytic cell lines by cytokines; some epithelial cells upregulated CD44-6v upon IFN gamma treatment.

Conclusions:

• CD44 variant isoforms are expressed more broadly than previously understood.
• Expression of CD44 variant isoforms is differential across various cell types and can be modulated by specific cytokines, indicating diverse functional roles.