THE EXPRESSION OF ALPHA-B-CRYSTALLIN IN EPITHELIAL TUMORS - A USEFUL TUMOR-MARKER

Alpha B-crystallin is a lens protein showing homology with small heat- shock proteins. We have previously demonstrated its expression in non- lenticular normal and diseased human tissues by immunostaining with a polyclonal antibody. In view of the expression seen in normal renal tu bular epithelium, we have assessed the immunoreactivity of a variety o f epithelial tumours, to determine the usefulness of alpha B-crystalli n as a specific renal tumour marker. Carcinomas arising from tissues w hich normally express alpha B-crystallin, such as cole-rectal and thyr oid carcinomas, showed a varying pattern and degree of immunoreactivit y. The most consistently positive tumours, however, with typically str ong cytoplasmic and cell membrane staining, were renal cell carcinomas , 90 per cent of which showed positive immunoreactivity. This pattern of staining, while not absolutely specific, is a useful aid to the dia gnosis of renal carcinoma. When a metastic deposit or a small biopsy i s being assessed, anti-alpha B-crystallin may be included in a panel o f antibodies, the pattern of staining of which may direct the search f or the primary site of the tumour.