
<ArticleTitle>Is there loss or qualitative changes in the expression of <prot>thyroid peroxidase</prot> protein in thyroid epithelial cancer?</ArticleTitle>
<AbstractText>There is disagreement concerning the expression of <prot>thyroid peroxidase</prot> (<prot>TPO</prot>) in thyroid cancer, some studies finding qualitative as well as quantitative differences compared to normal tissue. To investigate <prot>TPO</prot> protein expression and its antigenic properties, <prot>TPO</prot> was captured from a solubilizate of thyroid microsomes by a panel of murine <prot>anti-TPO monoclonal antibodies</prot> and detected with a panel of <prot>anti-human TPO IgGkappa Fab</prot>. <prot>TPO</prot> protein expression in 30 samples of malignant thyroid tissue was compared with <prot>TPO</prot> from adjacent normal tissues. Virtual absence of <prot>TPO</prot> expression was observed in 8 cases. In the remaining 22 malignant thyroid tumours the <prot>TPO</prot> protein level varied considerably from normal to nearly absent when compared to normal thyroid tissue or tissues from patients with Graves' disease (range less than 0.5 to more than 12.5 microg mg(-1) of protein). When expressed <prot>TPO</prot> displayed similar epitopes, to that of <prot>TPO</prot> from Graves' disease tissue. The results obtained by the <prot>TPO</prot> capturing method were confirmed by SDS-PAGE and Western blot analysis with both microsomes and their solubilizates. The present results show that in about two-thirds of differentiated thyroid carcinomas, <prot>TPO</prot> protein is expressed, albeit to a more variable extent than normal; when present, <prot>TPO</prot> in malignant tissues is immunologically normal.</AbstractText>
