Quantitative immunohistochemical analysis of the glutathione S-transferaseGSTM1: in situ phenotyping in archival material

i. GSTM1 is present in only similar to 50%, of Caucasian individuals and de ficiency of GSTM1 is associated with susceptibility to a growing number of diseases, especially cancer. Thus, a method that would allow accurate, retr ospective determination of the GSTM1 phenotype in different patient populat ions would have many applications. 2. Developed, therefore, is a quantitative, image-analysis-based immunohist ochemical technique for the analysis of GSTM1 protein in paraffin-embedded tissue samples. It was applied to the determination of the GSTM1 phenotype using liver biopsies taken from 70 patients. 3. Of the 70 cases (depending on the cut-off point), 51-54%, were deficient in GSTM1. A single 27 kD band characteristic for GSTM1 was found in seven of 16 cases analysed by Western blotting using the same GSTM1 antibody as i n the immunohistochemical analysis. There was a good correlation (r = 0.87) between the staining intensity of the GSTM1 band and the staining intensit y evaluated by immunohistochemistry. 4. It is concluded that this quantitative immunohistochemical method permit s accurate determination of the GSTM1 phenotype and is well suited for retr ospective analysis of GSTM1 expression in specific tissues In situ.