EXPRESSION OF LAZ3 BCL6 IN FOLLICULAR CENTER (FC) B-CELLS OF REACTIVELYMPH-NODES AND FC-DERIVED NON-HODGKIN LYMPHOMAS/

Chromosomal translocation resulting in abnormal expression of the LAZ3 /BCL6 gene in B cells has been implicated in the tumorigenesis of non- Hodgkin lymphoma (NHL). Therefore we studied the expression pattern of LAZ3/BCL6 by in situ hybridization with synthetic oligonucleotide pro bes in frozen tissue sections from five reactive lymph nodes and 38 B cell and non-B NHL. In addition, we investigated the expression of LAZ 3/BCL6 by Northern blot analysis on multiple human tissues. The LAZ3/B CL6 transcript was found in a variety of tissues, including skeletal m uscle, peripheral blood leukocytes, and weakly in normal lymph nodes. In the tumor samples, expression of LAZ3/BCL6 was observed in 68% of a ll B cell NHL and none of the non-B lymphomas. All cases of follicular , mixed small and large cell lymphomas showed LAZ3/BCL6 expression con fined to the neoplastic follicles. A follicular expression pattern was also found in all non-malignant reactive lymph nodes. Hence, the expr ession of LAZ3/BCL6 does not correlate to malignancy, but reflects the origin of B cells from the germinal centers.