BCL-2 AND P53 PROTEIN EXPRESSION IN FOLLICULAR LYMPHOMA

Recent studies have shown bcl-2 to be regulated by p53. Other studies have suggested an inverse relationship between p53 and bcl-2 protein e xpression in breast and colonic cancers and in a variety of subtypes o f non-Hodgkin's lymphoma. This study investigates the relationship bet ween bcl-2 and p53 protein expression and the correlation between thes e findings and the grade and cell type of follicular lymphomas accordi ng to the REAL classification. Paraffin-embedded nodal follicular lymp homas (n=37) mere subjected to bcl-2 and p53 immunohistochemistry on t issue sections using a three-step ABC system. Positive immunostaining for both oncoproteins was scored using a three-tiered scale: +, <10 pe r cent cells; ++, 10-50 per cent cells; and +++, >50 per cent cells (< 10 per cent was used as a cut-off to define negative tumours). Ninety- seven per cent (36/37) of follicular lymphomas expressed bcl-2 protein in all three grades, manifesting in the small cell (grade I) through to the large cell (grade 3). p53 protein expression showed a pattern o f increasing immunostaining with progression towards the high-grade fo llicular lymphoma: grade 1=6 per cent (1/16); grade 2=48 per cent (10/ 21); grade 3=100 per cent (6/6). Five cases comprised varying combinat ions of grades. This latter finding suggests a role for p53 mutation i n the progression!transformation of follicular lymphoma. The mechanism , however, differs from that suggested in breast and colonic cancers, since an inverse relationship between bcl-2 and p53 was not demonstrat ed in the present study. (C) 1997 by John Whey & Sons, Ltd.