Abstract
In this study, we used immunohistochemical and biochemical analysis to show that gp200-MR6, a 200 kDa molecule that is functionally associated with the human interleukin 4 (IL-4) receptor complex, is expressed at high levels on normal breast epithelial tissues, at lower levels on in situ carcinomas, and that the expression is lost in the invasive carcinoma of the breast. Furthermore, a preliminary study showed that benign epithelial hyperplasia of the breast expresses the gp200-MR6 heterogeneously. Two populations of cells have been observed: MR6 positive and MR6 negative. Interestingly, MR6-positive cells were observed to have different morphology from those that were MR6 negative; the nuclei of the former were larger and rounded in shape, whereas the nuclei of the latter were relatively small and oval in shape. In sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting, monoclonal antibody MR6 detects the same molecular weight molecule in both normal and transformed tissue, indicating that the molecule is not a product of a truncated gene. The intensity of the gp200-MR6 bands correlates with the immunohistochemical data, indicating that the molecule is expressed at high levels in normal tissue and at lower levels in malignant tissue. These results suggest that analysis of gp200-MR6 expression may be useful in tumour grading and prognostic evaluation in breast cancer. Moreover, the molecule may be involved early in the process of tumorigenesis of the breast, in which a loss or a down-regulation of gp200-MR6 could contribute towards tumour development and progression via an effect on cell growth and differentiation.
Highlights
Dewaxed, rehydrated, paraffin-embedded breast sections were treated with trypsin and stained with monoclonal antibody (MAb) M R6 or anti-cytokeratin antibody
Snap-frozen fresh tissue sections were stalined with MAb MR6 at the same time as a control for the effectiveness of the MR6 staining
The fact that this antigcn cainnot be detected in formralin-fixed tissue samples has made it difficult to collect a larger numiiber of saim,ples of benign hyperplasia of the bre(ast, for this conditioni is usually diagnosed by chance in tissue resected for other reasons
Summary
Since the epitope detected by MAb MR6 cannot be detected in formalin-fixed paraffin-embedded tissue, fresh frozen tissue samples were used throughout this study. Extensive attempts to retrieve the gp200-MR6, applying commonly used antigen retrieval methods such as enzymatic treatment, microwaving and pressure cooking were carried out. AAM Al-Tubuly et al invasive carcinoma and eight benign hyperplasia samples) were obtained from the Departments of Medical Oncology and Histopathology, Charing Cross Hospital, London, and from the Department of Histopathology, Royal Sussex County Hospital, Brighton. Paediatric thymus samples were obtained from children undergoing cardiac surgery at Great Ormond Street Hospital, London. Samples were snap-frozen in liquid nitrogen and stored at -70°C until sectioned.
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