EXPRESSION OF CYCLIN D1 IN MOUSE B-CELL LYMPHOMAS OF DIFFERENT HISTOLOGIC TYPES AND DIFFERENTIATION STAGES

The G1 cyclin, cyclin D1, has been implicated in the development of hu man and mouse tumors. Here we describe immunohistochemical analyses of cyclin D1 for a large panel of mouse B cell tumors. In addition, we c haracterize cyclin D1 expression in a series of cultured cell lines th at represent transformed B cells at different stages of development. I mmunohistochemical analysis showed that for low-grade lymphomas, cycli n D1 was expressed by 83% of centroblastic-centrocytic (CBCC) and 14% of small lymphocytic lymphomas (SLL). For high-grade tumors, 28% of B lymphoblastic and 23% of centroblastic tumors expressed cyclin D1, whi le all immunoblastic lymphomas were negative. Studies of RNA and prote in prepared from cultured B lineage tumors showed that cyclin D1 was e xpressed by all pre-B and most B cell tumors but not by cell lines rep resentative of late B cell differentiation or by plasma cells. Express ion of cyclin D1 in the lymphomas was not associated with alterations in the genomic structure of the Fis-1 (Bcl-1) common proviral integrat ion site or cyclin D1 itself or with cell growth activity as assessed by expression of proliferating cell nuclear antigen (PCNA). (C) 1998 P ublished by Elsevier Science Ltd.