The prognostic value of somatostatin-receptors scintigraphy in neuroendocrine tumours.

Abstract

The 70 membrane proteins of the T lymphoblast cell line CCRF-CEM were characterized by 1.1. [35S]methionine internal radiolabeling;2.2. [125I]iodine labeling by a lactoperoxidase-mediated method;3.3. [3H]fucose internal labeling;4.4. binding to a lentil lectin adsorbant column;5.5. susceptibility to digestion with limited amounts of papain.Of the three methods of radiolabeling membrane proteins, [35S]methionine best displayed all proteins although some individual proteins were heavily iodinated or fucosylated. Thirty proteins were externally exposed as defined by susceptibility to lactoperoxidase-mediated radio-iodination and to digestion with minute amounts of papain. Thirtyfive proteins were bound to a lentil lectin absorbant column. p44 (HLA-A and -B antigens) were iodinated, fucosylated, susceptible to papain digestion and bound to the lectin column. β2-Microglobulin was iodinated and bound to the lectin column. The identifications and functions of other membrane proteins were not known. In general, proteins of high molecular weight (100 000 to 250 000 D) were more heavily radio-iodinated and fucosylated than were proteins of lower molecular weights. p95 was the most heavily fucosylated protein, p110, which had been identified only on T lymphoblasts, was fucosylated and was iodinated. p65, which was found only on the T lymphoblast line CCRF-CEM and could represent a lymphocyte subpopulation-specific molecule, was iodinated and fucosylated. p15 and p18 were equally and densely labeled with [35S]methionine but only p18 was fucosylated and it was heavily radio-iodinated. These experiments help to define the external membrane proteins of a T lymphoblast cell line in part for the selection of proteins for isolation in order to raise antisera for immunodiagnostic and functional studies.