CD326 at a glance

CD326 / EpCAM is an oligomerizing 40 kDa type I transmembrane glycoprotein, serving as adhesion molecule in the basolateral membranes in most epithelial cell types. It mediates calcium-independent homotypic cell-cell adhesions.  However, it turned out CD326 has more functions and some of them affect  cancerogenesis.  Its thyroglobulin domain can inhibit cathepsins (cystein proteases) frequently produced by tumour cells. If a tumour expresses CD326, it can be protected against its own secreted cathepsins during metastasis.  Oligomerization of CD326 initiates its signaling cascade, which includes proteolytic cleavage, releasing extracellular part of the molecule, and an intracellular peptide known as EpIC, involved in initiation of gene expression with growth-promoting effects. CD326 overexpression correlates with proliferation, migration and invasiveness of tumour cells.
 
In normal tissues, CD326 is expressed in epithelial cells with exception of several specialized cell types, such as the myoepithelial cells, keratinocytes, gastric parietal cells, thymic cortical epithelial cells, and mature hepatocytes are. However, developing hepatocytes are CD326 positive, including those that appear during liver regeneration. Physiological role of CD326 in pluripotent stem cells resembles to those that have been observed in tumours, but are under not yet fully elucidated control mechanisms. Even Langerhans cells use CD326 physiologically to intercalate among keratinocytes, and later to leave that place, similarly like pathological metastatic cells do. Expression of CD326 in normal epithelia is significantly lower compared to that in tumour cells.
 

Fig. 1: Schematic drawing of CD326 (EpCAM) monomer. Extracellular side up.
 
 
The mouse monoclonal antibody 323/A3 recognizes an extracellular epitope of human CD326, and can be used for flow cytometry, Western blotting, immunocytochemistry, immunohistochemistry and immunoprecipitation. Formats:  Purified (11-582-C100), Pacific Blue™ (coming soon), FITC (1F-582-T100), Alexa Fluor® 488 (A4-582-T100), PE (1P-582-T100), APC (1A-582-T100), Alexa Fluor® 647 (A6-582-T100), PerCP-Cy™5.5 (T9-582-T100), PE-Cy™7 (T7-582-T100).
 
 
The mouse monoclonal antibody VU-1D9 recognizes an extracellular epitope of human CD326, and can be used for flow cytometry, Western blotting, immunocytochemistry, immunohistochemistry and immunoprecipitation. Formats:  Purified (11-581-C100), FITC (1F-581-T100), PE (1P-581-T100), APC (1A-581-T100), Alexa Fluor® 647 (A6-581-T100), PerCP-Cy™5.5 (T9-581-T100), PE-Cy™7 (T7-581-T100).
 
 

 
Fig. 2: Western blotting analysis of human CD326 using mouse monoclonal antibody 323/A3 on lysates of CD326-positive MCF-7 cell line and CD326-negative HEK293T/17 cell line under non-reducing and reducing conditions. 

 
Fig. 3: Separation of CD326-positive MCF-7 cells (red-filled) from CD326-negative SP2 cells (black-dashed) in flow cytometry analysis (surface staining) using mouse monoclonal antibody VU-1D9 conjugated with PE-Cy™7. 
 
Further reading:
 
Baeuerle PA and Gires O: EpCAM (CD326) finding its role in cancer. Brit. J. Cancer 2007 (96) 417-423.
 
Schmelzer E and Reid LM: EpCAM expression in normal, non-pathological tissues. Front. Biosci. 2008 (13) 3096-3100.
 
Gaiser MR et al.: Cancer-associated epithelial cell adhesion molecule (EpCAM; CD326) enables epidermal Langerhans cell motility and migration in vivo. PNAS 2012, E889-E897.
 
Dollé L et al.: EpCAM and the biology of hepatic stem/progenitor cells. Am. J. Physiol. Gastrointest. Liver Physiol. 2015; 308(4): G233-G250.
 
Thimsen V et al.: EpCAM (CD326) is differentially expressed in craniopharyngioma subtypes and Rathke´s cleft cysts. Scientific Reports 6:29731.
 
Schmelzer E et al.: Characterization of CD326-positive human hepatic stem cells. Clin. Exp. Hepatol. 2021; 7 (1): 101-110.