[Immunohistochemical study of placental form of glutathione S-transferase in human brain tumors and fetal brains].

The activity of glutathione S-transferase placental form (GST-pi) was examined in 100 cases including various histologic subtypes and grading of human brain tumors and 10 cases of fetal brains by immunohistochemical studies. The 69% of cases with brain tumors were shown to be positive for GST-pi. This activity in neuroepithelial tumors tended to increase in order to tumor grading, however, medulloblastoma and primitive neuroectodermal tumor (PNET) were not immunoreactive with GST-pi. Embryonal carcinoma showed strong staining, although fetal brains were negative. The metastatic brain tumors showed the same reactivity with GST-pi as those of original carcinomas. Moreover, the difference of GST-pi activity was investigated on some brain tumors treated with or without antitumor drug, such as 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU). The 85% of recurrent cases showed strong staining with GST-pi, and GST-pi activity seemed to be increased after treated with ACNU. The present study indicated that GST-pi might be a useful marker for human brain tumor, as the same conclusion was applicable to other neoplastic lesions examined previously. It is suggested that the increased GST-pi activity with malignancy of tumor may indicate the tendency to recurrence. The presence of such activity in tumor cells may also imply their acquired multidrug resistance. Our findings suggest that the evaluation of GST-pi activity in brain tumors will offer a predictive value for eventual behavior of the tumor.