Heat shock protein 70 (Hsp70) subtype expression in neuroendocrine tissue and identification of a neuroendocrine tumour-specific Hsp70 truncation.

in Endocrine-Related Cancer
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B Zierhut Department of Medicine III, Division of Clinical Endocrinology and Metabolism, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.

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K Mechtler Department of Medicine III, Division of Clinical Endocrinology and Metabolism, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.

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W Gartner Department of Medicine III, Division of Clinical Endocrinology and Metabolism, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.

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T Daneva Department of Medicine III, Division of Clinical Endocrinology and Metabolism, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.

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W Base Department of Medicine III, Division of Clinical Endocrinology and Metabolism, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.

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M Weissel Department of Medicine III, Division of Clinical Endocrinology and Metabolism, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.

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B Niederle Department of Medicine III, Division of Clinical Endocrinology and Metabolism, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.

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L Wagner Department of Medicine III, Division of Clinical Endocrinology and Metabolism, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.

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In order to identify neuroendocrine tumour-specific protein expression, we generated monoclonal antibodies (mAbs) with a tumour-related reaction pattern using a human insulinoma as immunogen. One of the generated mAbs (mAb 1D4) exhibited striking immunoreactivity against various neuroendocrine tumours without staining pancreatic islets of Langerhans. Furthermore, mAb 1D4 immunostained a characteristic subtype of hypothalamic neurones. Using two-dimensional (2-D) gel electrophoresis, mAb 1D4 immunoblotting and mass spectrometry, heat shock protein 70 (Hsp70) isoforms were identified as the mAb 1D4-specific antigen. In hypothalamic tissue, the presence of two different Hsp70 isoforms (Hsp70-8 and Hsp70-1) was revealed by 2-D gel immunoblots and consecutive mass spectrometric peptide analysis. In contrast, insulinoma and other neuroendocrine tumours displayed solely Hsp70-8 expression. Moreover, the tumour-specific presence of an additional mAb 1D4 immunoreactive protein of 40 kDa was observed in eight out of eight tested neuroendocrine tumours. For this variant, exclusively, peptides derived from the C terminus excluding the 299 amino-terminal residues were detected. In cultured tumour-derived fibroblasts, expression of the truncated Hsp70-8 subtype was not present. In conclusion, we have demonstrated a neuroendocrine tumour-specific expression pattern of Hsp70 isoforms and identified an as yet unknown N-terminally truncated Hsp70-8 variant.

 

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