Bag-1 expression in thyroid neoplasm: its correlation with Bcl-2 expression and carcinoma dedifferentiation.

Background: Apoptosis, programmed cell death, is one of the promnent factors in the evaluation of carcinoma characteristics. It is well-known that bcl-2 and its related proteins significantly modulate apoptosis. Bag-1 is a recently identified bcl-2-related protein and is known to be linked to the biological aggressiveness of some carcinomas.

Materials And Methods: We immunohistochemically investigated bag-1 and bcl-2 expression in various thyroid neoplasms using monoclonal antibodies.

Results: High bag-1 expression was observed in 66.7% of follicular adenoma and 75.0% of follicular carcinoma, and no statistical difference was established between them. In papillary carcinoma, 60.7% were classified with high bag-1 expression, whereas only 4.5% of anaplastic (undifferentiated) carcinoma highly expressed bag-1, and the incidence was significantly lower (p < 0.0001) than in papillary and follicular carcinomas. Furthermore, in thyroid neoplasm, bag-1 expression was directly linked (p < 0.0001) to bcl-2 expression.

Conclusion: These findings suggest that bag-1 may interact with bcl-2 to play an important role in thyroid neoplasm before anaplastic transformation, and the disruption of events mediated by bag-1 and bcl-2 may be a typical characteristic of undifferentiated carcinoma.