Glutathione S-transferases in gastric carcinomas and in adjacent normal gastric epithelium: immunohistochemical and biochemical analyses.

Glutathione S-transferases (GSTs) are enzymes involved in the detoxification of xenobiotics and are divided into four subclasses. Alpha, Mu, Pi and Theta. Most human gastrointestinal tumors contain increased amounts of GST Pi. In order to compare data on the expression of GSTs obtained by biochemical as well as immunohistochemical methods, we characterized the presence of GST Alpha and Pi by Western blot analysis and immunohistochemistry in 22 samples of human gastric carcinoma and adjacent non-neoplastic mucosa. Biochemical analyses revealed the presence of GST Alpha and Pi in 95% and 91% of normal tissues and in 82% and 100% of tumor specimens, respectively. Immunohistochemically all cases of normal gastric tissue stained for both GST Alpha and Pi, whereas immunostaining for GST Alpha and Pi was seen in 36% and 100% of the gastric tumor specimens, respectively. No statistically significant correlation however was observed between biochemical and immunohistochemical determination of GST Alpha and Pi both in normal as well as in malignant tissue. The absence of a statistically significant correlation between biochemical and immunohistochemical determination of GST Alpha and Pi implies that a high degree of caution must be taken in interpretating data derived solely from biochemical or immunohistochemical assays.