CD45

By Jennifer Sokolowski, MD, PhD.

By Victoria Osinski

By Jamshed Arslan Pharm.D.

CD31/PECAM-1, or platelet endothelial cell adhesion molecule 1, is a 130-kDa glycoprotein expressed on vascular and hematopoietic cells.  Depending on the cell type, CD31/PECAM-1 expression can be largely localized to cell junctions, playing a role in cell adhesion.  Aside from its role in cellular adhesion, CD31/PECAM-1 is also a large player in a variety of signaling pathways, such as angiogenesis, cell migration, leukocyte transmigration and more.  Specifically, the association and indication of angiogenesis in breast cancer is of interest, given that extensive research shows an

CD45, also known as T200 or the Leukocyte Common Antigen (LCA), is encoded by the Protein Tyrosine Phosphatase Receptor type C (PTPRC) gene. The protein is expressed exclusively on cells of the haematopoietic system, and is one of the most abundant leukocyte cell surface glycoproteins (1). Different isoforms of CD45 are found on specific lymphocyte sub-populations, and are generated by alternative splicing. (2). At least four variants of the human protein can be distinguished by electrophoresis, with molecular weights ranging from 180-220kDa (3).

CD45, also known as protein tyrosine phosphatase, receptor type, C (PTPRC), was originally known as common leukocyte antigen and is a signal transducer involved in many physiological processes such as growth and differentiation, cancer transformation, and the cell cycle. It is a transmembrane protein tyrosine phosphatase that regulates Src kinases in T- and B-cell receptor signal transduction (1).

Vimentin is a 57kDa type III intermediate filament (IF) protein that is the major cytoskeletal component of mesenchymal cells and the first to be expressed during cell differentiation. It plays a significant role in supporting and anchoring the position of the organelles in the cytosol and its dynamic nature is important for cell flexibility.  It is responsible for maintaining cell shape and cytoplasm integrity.

Immunohistochemical testing using antibody panels has a valuable role in cancer diagnosis. Some tumors, especially more malignant ones, tend to lose the appearance of the tissue of origin. However, knowing the tissue of origin assists the physician in selecting the best treatment thus a differential diagnosis is required.