Reevaluation of the 22-1-1 antibody and its putative antigen, EBAG9/RCAS1, as a tumor marker.

Abstract

BACKGROUND:

Tumor-associated antigens are appreciated as diagnostic markers, but they have also prompted tremendous efforts to develop tumor-specific immunotherapy. A previously cloned tumor-associated antigen, EBAG9, was initially defined by reactivity with the monoclonal antibody 22-1-1. Functionally, the EBAG9-encoded gene-product was believed to induce apoptosis in activated immune cells. However, using a cell-biological approach we identified EBAG9 as a Golgi-resident modulator of O-linked glycan expression, the latter product was then recognized by the 22-1-1 antibody. Secondly, EBAG9 expression was found physiologically in all murine tissues examined. This raised the question if EBAG9 is tumor-specific and mediates apoptosis itself or through O-linked glycans generated, among them the cognate 22-1-1 antigen Tn.

METHODS:

We have used immunohistochemistry to detect the expression of 22-1-1 and EBAG9 in various tissues. Correlation between expression of both antigens in cell lines was analysed by immunoblot and flow cytometry. Apoptosis was studied by using flow cytometry and Caspase-Glo 3/7 assay kit. Cellular distribution of EBAG9 was analysed by electron and confocal microscopy.

RESULTS:

Here, we compared expression of the 22-1-1 and EBAG9-defined antigens in normal and neoplastic tissues in situ. In contrast to 22-1-1 staining, EBAG9 is a ubiquitously expressed antigen in all normal and cancerous tissues. Functional studies on the role of 22-1-1 reactive material did not support any evidence for apoptosis induction. Employing electron and confocal microscopy, a refined subcellular localization of EBAG9 at the Golgi was obtained.

CONCLUSION:

We suggest that the estrogen-inducible EBAG9 gene-product and the 22-1-1 defined antigen are structurally and functionally separate antigens.

• Authors: Tatiana A Reimer, Ioannis Anagnostopoulos, Bettina Erdmann, Insa Lehmann, Harald Stein, Peter Daniel, Bernd Dörken, Armin Rehm
• Journal: BMC cancer (BMC Cancer) Vol. 5 Pg. 47 (May 17 2005) ISSN: 1471-2407 [Electronic] England
• PMID: 15904507 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• 22-1-1 antigen
• Antibodies, Monoclonal
• Antigens, Neoplasm
• Antigens, Tumor-Associated, Carbohydrate
• Antineoplastic Agents
• Biomarkers, Tumor
• EBAG9 protein, human
• Polysaccharides
• Protein Synthesis Inhibitors
• Tn antigen
• Brefeldin A
• CASP3 protein, human
• CASP7 protein, human
• Caspase 3
• Caspase 7
• Caspases
• Nocodazole

Topics

• Adenocarcinoma (metabolism)
• Antibodies, Monoclonal (chemistry, metabolism)
• Antigens, Neoplasm (biosynthesis, chemistry)
• Antigens, Tumor-Associated, Carbohydrate (chemistry)
• Antineoplastic Agents (pharmacology)
• Apoptosis
• Biomarkers, Tumor (biosynthesis)
• Brefeldin A (pharmacology)
• Carcinoma (metabolism)
• Carcinoma, Squamous Cell (metabolism)
• Caspase 3
• Caspase 7
• Caspases (biosynthesis)
• Cell Line
• Cell Line, Tumor
• Cell Nucleus (metabolism)
• Colorectal Neoplasms (metabolism)
• Flow Cytometry
• Golgi Apparatus (metabolism)
• Humans
• Immunoblotting
• Immunohistochemistry
• Immunotherapy (methods)
• Lung Neoplasms (metabolism)
• Male
• Microscopy, Confocal
• Microscopy, Electron
• Mouth Neoplasms (metabolism)
• Nocodazole (pharmacology)
• Polysaccharides (chemistry)
• Prostatic Neoplasms (metabolism)
• Protein Synthesis Inhibitors (pharmacology)
• Reverse Transcriptase Polymerase Chain Reaction
• Stomach Neoplasms (metabolism)
• Subcellular Fractions
• Tissue Distribution