GB (guanidinobenzoatase) cell surface protease and serum inhibitors in colorectal neoplasia

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Abstract
Cell surface proteases and their inhibitors are functionally related to the invasive properties and metastatic potential of tumour cells. Epithelial cells of the colorectal mucosa possess a cell surface protease referred to as guanidino-benzoatase (GB), which is similar, if not identical, to plasminogen activator. GB exists in isoenzymatic forms, one of which is associated with epithelial cells of normal colorectal mucosa and of adenomatous polyps, whilst another isoenzymatic form is associated with colorectal adenocarcinoma cells. Normal serum contains inhibitor proteins which recognize the isoenzymatic form of GB found on normal and adenomatous polyp epithelial cells but this inhibitor does not recognize the isoenzymatic form of GB associated with adenocarcinoma cells. The fluorescent probe 9-amino-acridine locates cells possessing active GB in frozen sections of colorectal mucosa. A technique is described which enables colorectal carcinoma cells to be highlighted by fluorescence microscopy whilst normal epithelial cells are distinguished by their lack of fluorescence. This is of biological and possibly diagnostic significance.