Removal Of Glycans From Ffpe Tissue Sections Enhances Specific Binding Of Antibodies Against Glycoproteins

Immunocytochemistry (IHC) is widely used by pathologists to determine whether a biopsied sample is cancerous or not and to determine the grade level of the tumor. The diagnosis of the cancer is based on the positive staining of specific biological markers which have been determined and validated to be present in specific areas of the tissue section. In some cases, the antigen of interest can be a glycoprotein which is overexpressed in various tissues or used to differentiate between different types of malignancies. An example of such glycoproteins is CA19‐9 or sialylated Lewis (a) antigen, a tumor marker used to detect pancreatic cancer and BG8 or Lewis (y) antigen, used to differentiate epithelioid pleural (EP) mesotheliomas from pulmonary peripheral adenocarcinoma (PPA). In people with pancreatic masses, CA19‐9 can be useful in distinguishing between cancer and other diseases of the gland. BG8 is considered a positive marker for PPA and negative marker for EP mesothelioma and is used in conjunction with other panels of antibodies to distinguish PPA from EP. If the antigen of interest is potentially blocked by glycoproteins the antibody staining can give a false negative. We hypothesize that the potential problem of diminished or negative immunostaining for glycoprotein cancer markers in FFPE (formalin fixed paraffin embedded) tissue sections may be solved using a protocol that can deglycosylate the glycans “in situ” and retain the morphology of the tissue section. We used CA19‐9 and BG‐8 glycoprotein antigens as examples to demonstrate the removal of N‐linked and O‐linked glycans. By being able to “unmask” the epitope binding site to the polypeptide site chain of the glycoprotein, more accurate diagnoses can be performed by the pathologist and the correct treatment plan recommended.