Specific molecular forms of GST are known to be expressed in preneoplastic cells, and have been known to participate in their resistance to drugs. GST-pi are present in most epithelial tissues of the human gastrointestinal tract. Significant amounts of the class pi GST was expressed in the majority of human tumors and human tumor cell lines. Studies have shown that GST-pi expressed highly in neoplasm and could be regarded as a tumor marker. However the immunohistochemical and the immunoelectron microscopical localization of GST-pi, in human polyps, are not clear.
A research article to be published on 14 July 2008, in the World Journal of Gastroenterology addresses this question. The study showed that the immunoreaction of GST-pi was in specific cell-type in adenoma tissues. Electron microscope immunohistochemistry revealed that between different cell types the highest intensity stain was in the columnar epithelial cells. The different density of GST-pi immunoreaction was weak in low-grade dysplasia to strong in high-grade dysplasia. There was an exception in this rule. Authors observed significant ultrastructural changes in some cases histologically characterized as mild-grade dysplasia. They found therefore immature undifferentiated cells showing a fast growing population with many free polyribosomes and enlarged nucleus and nucleoli increased in size and number, showing increased protein synthetic activity. These cases exhibited also strong GST-pi immunoreactivity similar to those of high-grade dysplasia. They found that GST-pi was located in cytoplasm and especially nucleus adjacent to nuclear membrane of colorectal dysplasia cells.
Glutathione-pi analog has recently synthesized. Clinical trials have also shown that GST-pi inhibitor induces the apoptosis in the precancerous lesions and it is expected to become a promising carcinogenesis preventive medicine in future.