6th ESACP Congress, Heidelberg, April 7-11, 1999

A019
THE QUANTITATIVE HISTOCHEMICAL INSENSITIVITY ASSAY OF G6PDH ACTIVITY IN HUMAN CANCER PATHOLOGY
Van Noorden CJF

Academic Medical Center, University of Amsterdam, Department of Cell Biology and Histology, Amsterdam, the Netherlands

G6PDH activity can be demonstrated histochemically by using a tetrazolium salt as final electron acceptor which is reduced to coloured formazan that precipitates where G6PDH activity is localized. When the reaction is performed with a special tetrazolium salt, neotetrazolium, formazan production is a proper reflection of G6PDH activity in all cell types when the reaction is performed in the absence of oxygen. In the presence of oxygen, however, formazan deposition is prevented in normal epithelium but not in carcinomas of various organs. Oxygen insensitivity of cancer cells is dependent on their high G6PDH activity, decreased superoxide dismutase levels and decreased lipid peroxidation capacity as compared with their normal counterparts. Diagnostic and prognostic values of this so-called oxygen insensitivity test were determined quantitatively in colorectal carcinogenesis using image analysis. Normal and hyperplastic epithelial cells showed oxygen sensitivity. Oxygen insensitivity was observed in half of the adenomas tested and in all carcinomas. The test proved to be a strong prognosticator for survival of patients with a carcinoma, that is better than Dukes' classification as single prognosticator. The quantitative oxygen insensitivity test was also applied to diagnose differentially chronic pancreatitis and pancreatic carcinoma. Pancreatic carcinomas were oxygen insensitive whereas normal appearing and simple hyperplastic ducts in chronic pancreatitis were, just as in normal pancreas, oxygen sensitive. Since the test was also successful in the application to cytologic specimens, the test is an excellent tool to be used for pre-operative differential diagnosis between the two pancreatic diseases as well. It is concluded that oxygen insensitivity of the histochemical assay of G6PDH activity is a valid discriminator between malignant and normal epithelial cells in both colon and pancreas. Moreover, it provides a strong prognostic prediction of survival for individual colorectal cancer patients.
References:
Van Driel et al: J Pathol 1997; 182:398-403, Van Driel and Van Noorden: J Histochem Cytochem 1999; 47:in press